2021.10.10 | Bruce Waddington: De-Mystifying the PHD2 Guiding Assistant

2021.10.10 | Bruce Waddington: De-Mystifying the PHD2 Guiding Assistant

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00:13
[Music] all right go ahead hi everybody welcome back it's sunday night that means it's time for the astro imaging channel and tonight we've got a real tweet treat for us because one of the people who uh have helped developed phd2 and so many of us use phd2 bruce waddington is going to be here tonight and he's going to take us into the guiding assistant we don't inside there and he's going to show us a few things about it maybe learn how to master some of its tricks um
01:00
i played hooky last week you may or may not know i was at the okie tech star party and i spent all day since then driving home and uh so if i'm a little foggy headed this morning this evening then several of the people on the crew are going to take over for all of you who i met out at oaky tex it was wonderful seeing you and i really appreciate that you appreciate the effort that molly and eric and terry and tim and toga and wanda and rory and you
01:31
know and arno and you know how big this this is sitting at i hope i haven't forgotten anybody well one of the things that it was noted was that we've made this into a real team effort and that was really cool one of the other things i noticed though is i actually ran into a couple of people who said that they had never heard of the astro imaging channel and that is your fault yes every single one of you should be contacting every single astro imager you know and tell them to listen to watch to
02:03
sign on to the astro imaging channel every sunday night at 9 30 eastern so that that never ever happens again that i go to a star party and find out that people aren't watching um anyway we have we picked up a few more people we had some great a great time dark skies um i'm going to share my screen here because i do have to show you we go i'm so excited about all the upcoming stuff that we've got coming up um remember there's a couple of things
02:37
you can go to here one is taic shots we've got until the end of the month here for you to get your pictures of beautiful nebula the beauty of dust into arno so that arno could put them together into a movie and we were just talking that we don't have too many of them yet and then we realized oh yeah we got three weeks and you procrastinators out there are procrastinating and keeping arnold from putting together his show so get your nebula shots in so that
03:08
arnold can can put that together and thanks for doing that um we also have good word today that so far we've gotten four people who will be presenting um on the um next week uh or next month sometime in november uh we're gonna have a taic workshop the estrogen channel workshop eric calls londis's data if you haven't processed this really really really nice data you need to go check um you need to
03:38
download his files by going to this link here and you get some real nice dark files taken from a dark sky site uh and then you click on to submit the files and you send them in and we'll gonna have a discussion about how certain people processed it and what they got out of it and all that other cool stuff and you have when do you have until october 17th to do that so just a couple more weeks be to do that uh no actually that's what five days i don't i don't know it's like i've been away i don't
04:09
even know what time zone i was in most of that place um most of that now squeak okay um and of course i always like to come back up here to the to the calendar where you can see that we've got bruce tonight roger's gonna be coming in from western australia next week and he's going to tell us about how to take some nightscapes down there and we've got lots of good shows coming up for you um but you'll notice that it doesn't go on forever i did get some people volunteering from oaky text to come on and put on a show
04:40
for us so um but we we need more the hardest part of this job is making sure that we've got presentations every sunday night for you except of course for christmas new year and and halloween i think anyway that's enough for the upcoming schedule and i think we're ready to go bruce is here he's eager to tell us about everything that he knows well not everything please bruce because that might be an awful lot but if certainly the things we really need to know bruce can you go ahead and start sharing your
05:10
screen and take over did we lose bruce's audio no i don't think so he he's not audience you're not autoing yeah now you are you're fine you're good you're good we're good yeah okay don't scare me like that okay um and you can hit my name um bruce waddington one of the phd2 developers uh i think i've been at this for seven or eight years now
05:58
and um you know i've given lots and lots of phd2 presentations and probably 99 of the time i don't get through them all and in fact i think the last time andy did a presentation on taic um he wasn't able to finish it either there's just way too much material to cover usually in an hour so at alex's suggestion for this topic i wanted to really narrow it down and talk about something fairly
06:29
specific and have at least a sporting chance of getting through the whole thing so what i'm going to talk to you tonight about is the guiding assistant and give you some ideas about how this thing really works what it's trying to tell you and where the various recommendations are actually coming from um so to start uh i guess it's it's reasonable to ask why even have a guiding assistant we call this the ga that's how i'll refer
07:00
to it and the presentation and it a lot of it came from the support forums when we first started going with this stuff and we realized that you know over 99 of the problems that came to us over the forum had to do with cockpit errors or equipment errors and and now that's that's mostly mount errors or both so um you know that's an unfortunate
07:30
situation in some respects because it's frustrating to people the cockpit errors are generally easy enough to straighten out you just answer questions and encourage people to read the manual but when it comes back to difficulties with the mount um people generally don't have the tools to know you know what those problems are or even less what they can do about them and so you back away from this and you say well you know how do you really know uh how
08:02
well your mount is doing what it's supposed to do and it's kind of a touchy subject because most people uh have spent what seems like a lot of money on amount generally speaking a lot of money at least in terms of the budget that they have for the hobby and and so they buy this thing and they would really like to have an expectation that it's going gonna do what it's supposed to do and no longer be an issue and of course that's not often the case
08:32
so you say what what can you do to know whether the thing is performing well and you know you start out by believing the marketing hype and maybe you've relied on the reputation of the vendor that's probably how you decided which mount to buy in the first place and you'll probably get it and put it all together and you know you'll slew around with it and look at how well it slows and how what the accuracy is for go-to's you'll probably look at something through an eyepiece and you certainly
09:03
don't expect to see the target or the star whizzing out of the field of view and beyond that you're just going to kind of look at it and listen to it you know make sure that the gears don't sound bad when you're slewing around and maybe you'll release the clutches and kind of push it around and you know get a sense of whether things move smoothly or not and frankly you're probably going to be admiring the thing because most of us aren't exposed to mechanical devices
09:35
that have the level of precision that people are talking about with telescope mounts so this mount is going to look a whole lot more impressive than your toaster or your lawnmower or any of the other things that are a normal part of life you may in some cases decide that you want to quote hypertune the mount there are still services around i guess that do this and for the most part i think you're just kind of getting that done and hoping for the best but at the end of the day if those are
10:07
the only tools you have you still don't have a really good measure of what the mount is going to be capable of doing when it's put into a situation where you're trying to do imaging and and so what happens is you realize that you really want to measure it and probably the best measuring tool you have at hand is the guide camera so that's really what we'll be talking about here and that is how do we use the guiding assistant as a measurement tool
10:38
to understand what's going on so the reason for wanting to do guiding and using the the camera and the camera sensor as a measurement tool is it's very sensitive to fine scale performance so when we identify the location of a guide star on the camera sensor that's typically going to be with an accuracy of say a tenth of a pixel it might be less than that it might be you know 0.05
11:09
pixels depending on on the setup and again depending on the image scale that's going to translate into very very small angular measurements well under an arc second in most cases so now you're talking about seeing things at a scale that are much smaller than anything you're going to typically be able to do with the naked eye or by pushing the mount around or getting some kind of a feel for how the how the mount moves
11:41
and it's interesting uh at this point to kind of step back and ask ourselves what do we really expect from this device and of course the answer is that we're gonna want to assemble all this disparate gear and all these different pieces of software and we're going to want to line it up and point it at a target and we want that guide camera to track that from horizon to horizon and for whatever pointing position in the
12:12
sky that we want to do our imaging and the accuracy that we're looking for for that sensor to move in a perfect harmony with the target is usually on the order of 5 to 15 microns now most of us don't run up against microns in the real world in normal life and so it's a little hard to know you know what does that really mean and a quick rule of thumb to calibrate it is
12:43
that a a human hair is normally between 40 and 50 microns thick so we're talking about accuracy levels that are maybe a tenth that amount so this is a lot to demand and it's no wonder really that um people run into issues with the tracking accuracy of the amount because the demands are so high whether they realize it or not so in order to put this thing to work
13:17
what we end up doing is using uh the normal guide camera guide scope assembly it doesn't matter whether it's a separate guide scope or an oag and we're gonna choose a guide star let phd two choose a guide star and we're going to measure and watch the x and y movements of that guide star centroid on the camera sensor and of course what we then have to do is immediately translate that
13:48
into the corresponding ra and dec movements now that's a translation that is just fundamental to guiding it has to happen with every guide camera exposure and it's actually a simple enough calculation it's just basically signs and cosines there's nothing to it and the point there is that that depends on the calibration that you've done in phd2 so right off the bat if we want to get
14:19
very accurate translations from x and y into r a and dec we have to be using a good calibration one that hasn't uh triggered a bunch of sanity check alerts and one in particular that doesn't have large orthogonality error well assuming that those things are all reasonably okay we can now watch the star bob around on the sensor and the only difference that in terms of what the guiding assistant is doing is that it's not issuing guide
14:51
corrections so instead of watching the star move and then pushing it back into position we just watch it and we track it and we measure how it behaves for the length of time that we want to run the guiding assistant so as with any measurement process and we probably all learned this in physics lab or somewhere along the line any measurement has uncertainty associated with it there no measurement has zero uncertainty
15:21
and we've already talked on touched on one area which is if you have a poor calibration then you're going to introduce error and uncertainty because of that another contributor that can muddy the water for these measurements is seeing effects and of course as soon as you get into imaging you realize that seeing is just kind of an ugly fact of life there's really nothing you can do about it unless you're gonna find a way to put your telescope out on
15:52
a satellite and the seeing effects come from high altitude movements in the atmosphere and for most amateurs they also come from seeing conditions right around the telescope so you have local seeing in the form of convection off of hot surfaces that are around you maybe convection from rooftops that you're imaging over as well as turbulence that's set up if you have wind blowing through
16:24
uh tall structures or trees around you those all produce the same kinds of high frequency guide star movement that we label as seeing beyond that as the guiding assistant runs it may run into various kinds of inconsistencies in your mechanical setup and by that i mean that depending on where the scope is pointing it may have more or less flexure
16:55
meaning that there are parts of that whole assembly that are going to be pulled on by gravity and are going to sag and move by tiny amounts again we're talking about here um the the mechanical behavior made may depend on imbalance a lot of mounts require a very precise balance others uh are not so demanding in that regard things like wind you get wind gusts particularly if you have a
17:27
long tube or maybe you have a dew shield on it those are going to introduce sudden movements of the guide star that don't really have anything to do with the kinds of effects that we're trying to measure and then there's just uh you know all the other ridiculous stuff that can happen uh with imaging and guiding we all have encountered these things you know maybe you're uh letting the guiding assistant run and you know it's gonna go for maybe five or ten minutes and you're kind of fidgeting
17:59
so you get up and you walk around and maybe you brush a cable that happens to go to the guide camera or maybe you're running off of a wooden deck and you walk around and the deck sags and moves a little bit uh things like that i think my favorite example here uh was a poor guy who was imaging in his backyard and he was running the guiding assistant he wanted to run it for a long time and his wife uh opened up the back door and let the dog out
18:29
and the dog came tearing out there to where he was set up and just ran headlong into one leg of his tripod and so you can imagine what that did but the stunner for me was that he didn't stop the guiding assistant run he just kept going and then he was a little upset by what kinds of results he got out of that measurement why the recommendations seem to be so wacky so that's what we think
19:00
of as garbage in garbage out you want to do as much as you can to not let this measurement process be disrupted by silly things like that so let's get to the basics of what how you want to run the guiding assistant and what you're going to get out of it and as probably most of you know we keep drumming away on this topic just like calibration the guiding assistant is going to produce the most accurate measurements
19:31
if you're pointing near deck equal zero near the celestial equator and by near i mean say within 20 degrees one side or the other of the celestial equator with the scope pointing well above the horizon so the question is why is this and the reason is that on the celestial equator the the lateral movement of the guide star in right ascension will be the largest
20:04
and that's just a consequence of the spherical geometry of the sky so a given angular error in ra tracking will produce the most visible results near dec equals zero and so from a measurement point of view the larger that uh displacement the the more accurately we're going to be able to measure it and we want the scope to be pointed well above the horizon just to reduce as much as possible
20:35
the seeing effects that you get when you're pointing down near the horizon and you're shooting low over you know hot surfaces that are that have a lot of thermal convection so the seeing is generally going to be best when you're pointing up closer to the zenith and so those are the two things that we like to see when people run the guiding assistant as well as when they do a phd2 calibration so once you're there and you start the guiding assistant then as we've said
21:06
before we're just going to rumble along and we're going to watch how that guide star moves around and we're going to be able to log and later evaluate a whole bunch of different kinds of things so we're going to see um basically all the warts associated with the native tracking of the mount and right ascension so we're going to be able to see the periodic error we're going to see other kinds of errors that are repetitive but are maybe not
21:37
periodic with the with the worm gear we're going to see whatever drift might be present in ra a lot a lot of times that comes again from flexure or sagging with some of the optical elements that are on the scope and in deck we're going to see a different set of things because for deck it's a simpler problem and this is something that a lot of beginning imagers don't really realize and that is when you're just tracking the nighttime sky
22:09
the deck motor doesn't all on an equatorial telescope so that means that all of the all of these things that we like to worry about with ra with gear air and and vibration and all this other kind of stuff doesn't come into play for deck because that whole drive system is just idle so what we're going to see when we look at the errors in the deck tracking is a certain amount of drift and that's going to be predominantly because of
22:40
polar alignment error and that's going to be the secret for measuring polar alignment we'll get into that in a bit the other thing we're going to see in deck is a whole bunch of high frequency jitter in that guide star position and that's going to be the best metric that we have for the errors that are being introduced by seeing and that'll be the tool that we use for making recommendations for things like minimum moves and again i'll get into
23:12
more of that detail in a bit so all of this stuff gets logged into the normal phd2 guide logs and it can be analyzed and viewed by our log viewer tool or whatever analytical tool you'd like to use and we also in the case of backlash testing will retain results for three the three most recent guiding assistant runs and i'll show you how that works so
23:44
right up to that level this is kind of an engineering level measurement system for all the things that are going on with the gear and when we originally started with what was then not even called the guiding assistant that was all we were doing and so we kind of regurgitated all these statistical results and you know it was really propeller head stuff and we realized you know normal people are not going to be able to do anything with this
24:16
we need to find a way to aggregate it and and boil it down and produce some recommendations that they can actually take action on and translate these minutia into things that that makes sense to someone who's just trying to do some imaging and that was the goal and still is the goal of the guiding assistant uh today so when you run the guiding assistant uh this is this is the kind of output that you're going to see i'm
24:50
not going to go into any of this particular sliding detail and we'll come back to some of these other things but you know you go through a measurement process here and it wants you to let it run for two minutes or longer and the reason for that is that we have to get a solid set of statistics in order to be able to make a lot of these recommendations and in particular we want to run for two minutes to be sure that things like the drift rate has stabilized because we're going
25:22
to use that drift rate in a lot of different places to make some of the recommendations that we do if you are just trying to get a quick view on what the seeing is like um and get a sense of what the evening is going to look like you know two minutes is plenty long enough for that but if you want to um get a detailed look at what the ra tracking accuracy is of the mount maybe it's a new mount maybe you've serviced
25:53
it you're probably going to want to let the guiding assistant run a lot longer um at least one full worm period maybe two so you could be running this thing for uh you know eight to 16 to 20 minutes depending on what the worm period is so you kind of have to suit that to what you're trying to accomplish when you're running the ga now when you look at the results typically from a measurement run like this um you're going to be looking at
26:25
both r a and dec and this is typically what you're going to see on on all of my uh charts uh the red indicates right ascension you know r for red r for right ascension it's the only way i could ever remember it and then the green uh is declination so for right ascension what we see is you know kind of a typical periodic error curve here you know this isn't horrible it's you know 10 or so
26:55
arc seconds peak to peak that's not terrible and then in deck you see this steady drift rate in the green and then overlying both of those things is this high frequency jitter that i mentioned before and that's going to be coming hopefully predominantly from seeing now i say hopefully because if you've got some other kind of a mechanical problem that's causing vibration um one possibility being for example a
27:28
fan that's on the guide camera that's causing the thing to vibrate then that can kind of screw this up but normally this high frequency motion that you see in deck is due to drift and polar alignment air so when that measurement process is all done uh this is the kind of a report that that you'll get and i've uh kind of outlined some of the
27:58
key areas to focus on one is over here to the right you know we've tried to boil these measurements down to something you can do you can take action on so it's making recommendations about exposure times and values and in the case where you have chosen bruce can i ask a question while you're getting in recommendations yeah sure there was a posted question i think from one of us so if you retain three runs
28:29
are your recommendations based on the last run or the average of the three no that's a good great question uh nobody's ever asked me that it's only the last run so thanks i'm sorry go ahead no no that's a that's an excellent question really um so yes these are all numbers and results from the the just completed run and we try to put these apply buttons here so that if you are you know if you these are all recommendations there's
29:00
suggestions that you may have reasons for not wanting to do them but if you do then you just click on the apply button and we handle it for you so you don't have to go over into the advanced settings dialogue and rumble around over there and try to find the appropriate thing to set we'll do that for you so in the case where you have chosen to do measure the declination backlash and
29:30
we'll be talking quite a bit about that you'll also have this show backlash graph button and that allows you to see the graphical results of how the amount performed uh during the backlash test and as some of you know uh in the occasionally you'll get a result that said that the test failed right and that's very frustrating to people even if the test fails you can you can use this show graph
30:01
button to see what happened and i'll show you some examples of of what could happen it's usually pretty obvious why the test failed and while we're on that subject you don't have to run the declination backlash test every time in fact there's probably no reason to run it after the first few times you you've learned what your amount is like you know how much backlash it probably has and unless you've made mechanical changes
30:32
or you've made a change in the guides rate for the amount there's probably no reason to keep running the backlash test it just takes time and you can just uncheck this box over here okay so um in terms of of the reports that are being shown here there's this thing up here in the upper right which is kind of a historical curiosity when we first did the guiding assistant we were trying to figure out a way to measure to get a measure of the seeing
31:04
and when i say measure the seeing i don't mean that in the same sense as using a seeing monitor because we're talking about completely different things but we wanted to know you know how can we assess the impact of seeing on how we're doing guiding and so we started out with this stuff up in the upper right hand uh area and those of you who have used the product for a lot of years will remember this and we were using a high pass filter uh to produce these numbers and we still
31:35
do but what we found is that these numbers weren't really giving us the insight that we needed um you know they were interesting but they weren't uh always well correlated with what we would see later on in guiding and i think the problem is it's just too hard to establish the parameters for a high pass filter that's going to cover all the different configurations and operating environment that people have
32:04
so we don't actually use this for much but we haven't taken it away because what we've learned is that when we do a release and we have there um people learn how to use it and they get attached to it and sometimes they use it in ways that we hadn't anticipated and so they become very grouchy if we just arbitrarily take it away so it's still here you can do with it what you want but we no longer rely on this thing much
32:36
for the recommendations of min moves and i'll explain how that works now and then on the declination backlash measurement uh we'll this is where it'll be reported where this thing is declination backlash in this case uh it was 652 um milliseconds which is you know not bad for a commodity mount and the polar alignment down here was 3.6 arc minutes and so these are the kinds of things you're usually going to look at
33:06
when you're looking at this thing those are things you're going to pay attention to and then i'll try to give you some insight on where all this stuff comes from bruce so i've already sorry interrupt but all of a sudden we have a slew of questions that have just popped into the chat let me just go through them and you know you can at the time all right uh for provide some insights into how the recommendations are calculated uh could help us understand when we should and should not tweak them
33:37
uh i agree completely and that's what the rest of the presentation is okay so we you can handle that in a little bit with next question i find that the recommendations for backlash compensation is often higher than what it really needs to be phd then spends a few minutes dialing down the bl compensation to get to a good value sounds like a question yeah it is uh and i'll talk about that as well okay no these are no these are good questions
34:09
i you know i want to make sure we cover them if you're going to get to it we'll just we'll just let them hang the in the air yeah yeah next question i would assume deck balance affects the deck backlash if you do set up every image session the balance for each setup may be different and therefore recommend to run a deck backlash measurement each time you do a setup well you yeah the the premise is correct um the balance of the tube in deck
34:39
can definitely affect uh the backlash result i guess uh what would make more sense to me is to reassemble the scope so it has the same balance you know mark the positions so that you can restore it to its previous value it's not going to be critically dependent on on it as long as you're reasonably close but yes if you were doubtful about that you could rerun the backlash test for that reason uh and the last question i guess this is
35:12
a bit of a challenge from linda any idea why phd recommendation is higher than it needs to be what recommendation for what i'm not sure linda you want to uh clarify that on i i think linda might be talking about the backlash compensation because that relates to her earlier comment okay yeah let me let me talk about that when i cover the gory details of backlash measurement and i guess what i would say is uh for the
35:47
people that have asked those questions um let me march through the presentation before we run out of time and then if i still haven't answered those questions you know make an issue of it and and i will there's a co there's one more and then a comment let me just get to it quickly yeah is there any data from the recommendations to help adjust the hysteresis or aggressiveness or can that be done as a fine adjustment that you would do okay that comes that's an interesting
36:18
question uh because our feeling is that there's not generally any reason to be trying to fiddle with those parameters um the the way that phd2 is designed is that if the input parameters are correct meaning that the image scale the focal length the pixel size all that and if the mount is working reasonably well then the default settings on all those
36:48
guide algorithms should produce very good results but let's say that's not true then uh the best way to figure out how you might want to adjust those parameters uh is not probably with the guiding assistant it would be with normal guiding and imaging and looking at long time frames uh long windows of guiding data with the log viewer tool okay and front i'm sorry
37:19
well and just for what it's worth just an editorial comment uh you know i've been imaging for more years than i would care to say i image every clear night now uh remotely i've never adjusted any of those parameters for hysteresis or any of those things okay and ron said and i think we all agree for goodness sake let the poor guy do his talk and then ask questions so i'm uh please continue
37:49
okay i'm gonna forge ahead um but you know keep me honest and if you know if we run out of time um you can always post the questions on the on our phd2 uh google forum and i can answer them there so i'm just going to quickly cover the really easy stuff because you know these aren't things that are hard to explain and they're probably fairly obvious the exposure range you know we always make a recommendation
38:21
uh of you know try to keep your exposures in the range of you know one to three or four seconds um we actually use uh some data from the guiding assistant to know whether you can afford to go with longer versus shorter exposures what we do there is look at the steepest section of the ra tracking curve and we use that as a metric for roughly a metric for how long can you go
38:51
nra on that mount without needing to issue a guide correction and having said all that i would say that's probably one of the least accurate recommendations we make it's because we're talking about you know one brief sample in time and there's quite a bit of uncertainty associated with it and as a general rule we never recommend guide camera exposures less than a second beyond that uh you may get a recommendation that you should be in the
39:22
camera you'll see that if the image forgotten is less than half our pixel uh we prefer that it'd be a b standard uh for reasons of finding the stars uh if you are running with a calibration that generated 70 checklists we're and that's because we found a lot of beginners don't do a very good job of focusing the guide camera and start dealing with these big fuzzy polluted guide stars
40:09
and that really degrades uh the guiding performance so about all we can do there is to say well if the image scale is less than one arc second pixel and we're probably not horribly undersampling your house is watching a movie or something but your internet connection is dropping a bit okay um i'm not sure what i can do about it so i'm coming in now yeah can i disable the camera oh uh actually
41:08
hold on so it's there's a decent chance it's my connection going on okay uh you can keep talking and i'll work on it okay um so that's the that's the story on the focus recommendations and if you if we measure uh very low backlash values on the mount even historically or you told us at the time you were running the configurator that it has
41:40
absolute encoders then we'll recommend that you use low pass 2 for declination that's kind of self-explanatory i don't imagine you'll either see that or you won't it's most people don't so now let's get into the harder things and the things that people sometimes are skeptical about or don't understand and one is of the polar alignment error that we measured
42:11
and as i said that's being measured the declination drift and the thing to keep in mind about this is that there's no reason to obsess about the polar alignment error and the reason is that all that does is introduce potentially rotation of the star field uh on the main camera and as it turns out
42:41
uh the tolerances on that are generally pretty loose so drift is the easiest thing in the world to handle in guiding it's very easy to guide out so there's really no reason from our point of view to try to get microscopically fine accuracy on polar alignment that matters if you're trying to run unguided then it's got to be spot on but from our point of view normal
43:11
guiding there's no reason to spend a lot of time uh trying to get tiny values for alignment error as i mentioned before this should be done close to dec equals zero uh because at dec equals zero um the all of the drift excuse me in deck is going to be attributable to polar alignment error and again the reasons
43:44
where you might get inaccurate results or inconsistent results is the same things we talked about before calibration errors flexure seam conditions things of that nature one thing that you have to think about is if you have done a polar alignment using one of the polar alignment tools where you're pointing at the north pole you know usually you will have loosened things on the mount
44:15
and jiggered around and then re-tightened them and you have to ask yourself if you then slew 90 degrees away from that in both deck and ra are those things really going to hold tight or do you have a circumstance where it's dialed in perfectly pointing at the pole but when you move the scope around and things start happening the scope is slewing are things able to move around such that you introduce error that you had
44:46
previously taken out that can happen um similarly we've seen situations where people have a tripod set up on you know on a hill or on the mud and on one leg of the tripod is you know slowly sinking into the ground those kinds of things can affect uh polar alignment air and then and here's just the math behind it not very interesting uh this isn't something that we invented
45:18
it's it's from a published uh publication um when you run the guiding assistant for long periods of time we measure the polar alignment error by breaking it up into overlapping two-minute intervals and we choose the small the best of those intervals for estimating your polar alignment error generally speaking excuse me um we think that any alignment error less
45:51
than about five arc minutes is good enough and if you're trying to guide in only one direction or you have a huge amount of debt backslash then you're probably better off with a larger alignment error that may be up as high as 10 arc minutes so i'm wondering if i can mute this just for a second and go and get a glass of water then i may maybe somebody can fill the air here and i'll be back in 30 seconds
46:25
is that okay sure um i i i want to tell you a little bit about well while bruce is getting this glass of water um some of the comments i got from people while i was visiting at oaky tex were that um that we provided a lot of good services for people through the years and that we seem to have been doing better lately with some of the content um we aren't doing the
47:00
open sessions anymore and that seemed to be popular with the few people i was talking to about this and the team approach uh right now we've got three different people who can stream the software we've also improved uh just lately tim and eric have completed a set of software that will allow us to um stream our sessions more effectively we hope we certainly hope because we're spending a lot of money on it and we can
47:31
we can uh thank you those of you who've hit the donation button through the months and years and there are some people who have made some fantastically large donations to the astro imaging channel not like well you know we ever were in this for making money but we wanted to cover our costs so we're doing that kind of stuff and we really appreciate your contributions to that but again what we need most out of you is uh passing the word to your buddies that uh there is such a resource for
48:00
them with almost 400 shows now out there and wonders wonderful spreadsheet that'll lead you to them and uh to provide presentations yes there are people like bruce who are obviously geniuses who have spent years working on this and love to share their stuff um but there are also a lot of us who are particularly geniuses like myself and um others that just have learned some stuff and they can spread the word
48:32
and uh if you want to do a presentation feel free to come on along and volunteer for that okay bruce i'm back yeah hopefully i will i'll be able to talk for a little while this is ridiculous well this is this is a real informal thing i think we mentioned that during the warm-up and well that's a very that's a very good thing yeah it's it's it's a very we're we're we're all buddies in this and it's kind of like their club meeting okay so later on you look at the comments and you say hey wait a minute we're talking about the weather for you
49:04
know stuff like that it's it happens anyway all right bruce i'm back um so let me talk about uh the how we compute these min move values uh because this is something that people are sometimes bothered about um the idea behind min moves is to avoid issuing guide corrections for errors that are really just caused by seeing you know we call that chasing the seeing
49:36
it it is a real phenomenon um the problem is that seeing fluctuations from the atmosphere cause variation on time scales of hundreds to even thousands of a second and you are simply not going to guide those out and so one of the one of the major challenges of this kind of guiding is to be able to distinguish between something is probably just a seeing
50:08
effect which you can't do anything about or something that is caused by a tracking error of some kind that that would benefit from sending a guide command and the min move value is is the most straightforward way of doing that you basically set a floor that says if i see a guide star deflection that's below that value i'm going to ignore it i'm not going to try to correct for it
50:39
and what we do as i mentioned before is we watch the high frequency movement of the star in deck knowing that the deck motor isn't running and we watch to see how those behave and use that as a metric for where we should set that seeing floor so what we actually have to do is measure all those deflections and then we have to correct for the
51:10
drift because there will be drift and then we just compute standard deviations for those tracking errors and we want to recommend a dec min move that is likely to produce something between a 10 and 20 activity level for deck guiding meaning that you should you would only be seeing deck guide corrections happening
51:39
every maybe 10 to 20 percent of the time if you're seeing guide corrections in deck that are up in you know close to 100 percent then you are chasing the c and so that's where that dec min move value comes from and then in the case of ra um we can be a little more liberal about it the the issue in deck is that on almost all geared mounts if
52:09
you change direction and declination you're going to incur some amount of delay call reversal delay or backlash that is gonna affect how well that correction um is implemented and so that's it's easy to induce oscillations in deck if you are being too aggressive about issuing deck guide corrections so that's why we're so stingy about it here and looking for a 10 or 20 activity level
52:41
not 80 or 90. now in the case of ra backlash is not an issue because even though we may be wanting to move the guide star east or west on the sensor we're not ever changing the direction of the ra drive system it's always churning to the west it all we're changing is the rate at which it's moving so we don't worry about backlash and
53:12
therefore there isn't nearly as much penalty being paid if we are too aggressive about guiding and we're starting to chase the seeing a little bit and so what we do is we generally set the radio move to be about 65 of whatever we've recommended for deck and that's why the two min move values are not the same okay the difference is that it's much you pay much more of a penalty in deck for
53:44
setting that floor too low than you do in ra and in r8 we know that there are all kinds of contributors to tracking here and mounts generally need to be guided more aggressively in ra than they are in deck and now we're up to backlash measurement which is where a lot of those questions were coming from and hopefully we'll be able to deal with this we call it backlash measurement because you know that's a term people were
54:18
familiar with technically speaking that isn't really what it is what we're measuring is a reversal delay okay and that's a measure that involves both pure backlash and if it's present some amount of stiction which is static friction or static resistance so what we can say with some considerable accuracy is that when we switch directions from
54:49
going north to going south it took a second before we saw any movement at all in deck now that might be a second worth of just pure backlash and that what we mean by that is that the gears simply aren't meshed until that one second of correction has elapsed at which point the the gears are re-engaged going in the opposite direction that's backlash stiction just means that
55:21
there's something in that axis system that is sticky it's resisting the ability of the axis to move in the opposite direction so what we're really measuring with this backlash test is this reversal delay and the whole point of doing this was not really because we wanted to help out people who were you know modifying mounts or anything it's because we wanted to implement this deck
55:53
backlash compensation feature and we needed to have a seed value an initial value that we would use for that backlash compensation amount and the the thing that i want to emphasize if nothing else is that these reversal delays are not fixed values what you're going to find is that they are usually very dependent on the pointing position
56:27
so the deck backlash that you have pointing in one part of the sky is likely to be different than what you see in a different part of the sky and this is why the fixed backlash compensation that comes in a lot of these mounts doesn't work very well you know maybe you know you're looking through an eyepiece and you're fiddling around with this and you're trying to judge when you've made the backlash go away um which is fine but it's not going to work in all positions of the sky and if you get that
56:58
amount too high by even a small amount you're going to introduce oscillation in the deck guiding and it will never stabilize i mean you're just cooked so that's why we tell people to not use the firmware deck backlash compensation features okay they just don't work well for guiding so you say well why should this should it matter where the scope is pointing
57:29
and there's several reasons um one of the more common ones is simply uneven gearware so if you've had the mount for quite a number of years maybe you're not even the original owner the wear on the gears is going to depend on where the scope has been operated so in my case i do most of my imaging probably between i don't know minus 10 degrees deck and 40 degrees deck
58:01
okay so probably 85 percent of the time that the scope is moving around it's in that band but that means when i slow up to a higher deck you know i'm going to image m81 or m82 or something i'm now in a part of that deck gear system that isn't nearly as warm okay it's much more it's much closer to the way it was when it was originally built and therefore the mesh is different therefore the
58:31
amount of backlash is different it's also true that none of these gears can be perfectly machined so to some extent they're going to be slightly eccentric they're not perfectly round so again depending on where you are in that mesh pattern between the two gears that the amount of gap between the gears is going to be slightly different and that means the backlash will be slightly different
59:02
and as one of the questioners pointed out earlier it can also depend on the balance so if the if the scope is not well balanced on the deck axis it may be harder to get the mount to move north versus south or the other way around depending on how it's imbalanced and this is one reason why we always advise people to try to get good balance around deck and if you're you know
59:33
disassembling and reassembling the scope each night then you really want to get that balance as close as you can get it without having it turn into a big science project when you're trying to get it going and what this what this looks like from a phd2 point of view is it looks like static resistance you know we're pushing on this thing we're trying to overcome this impedance to get the axis moving in the other direction and it's just not going anywhere it's it's like it's stuck
01:00:05
for a few milliseconds and then it lets go and in some cases over reacts and i'll show you some examples of that so again if you if there is actually a source of resistance on the axis it might be sticky grease it might be some kind of crud that's in there again that's going to affect some parts of the gear system in some positions versus others so major lesson here the one we learned the
01:00:37
reason we implemented this adaptive backlash compensation feature is because we learned that it cannot be a constant value and i haven't forgotten about the other questions related to this i i'm gonna come back to them um so let me explain how this works and and it you know this thing is i guess kind of uh i don't know it's a little controversial in some circles but it's really it's the
01:01:08
simplest possible test what we do is we lock on a guide star and we choose a big guide pulse size typically 500 milliseconds that's a half a second that's a long guide pulse and we want to aggressively clear whatever backlash is currently on the axis we don't have any way of knowing how much is going to be there and we do that by issuing these big pulses and we want to see three consecutive
01:01:40
moves with that guide star moving more than four pixels and we don't allow any directional changes all right which sounds like it should be an incredibly easy thing to do but you would be surprised it sometimes takes a lot of guide pulses to meet this criterion once we're happy that we have really cleared that north backlash now we keep moving north and we're gonna do it
01:02:10
for a long time either eight seconds or one and a half times the amount of the backlash that we just spent time clearing so we're going to generally run that star a long way north okay that's 8 seconds you know at 500 milliseconds per pulse that's going to move it a long way and by the time we're done moving there we can be really confident that
01:02:41
the deck gear system is fully engaged in the north direction then we turn it around and we don't do any of that backlash clearing we simply issue the same number of moves to the south same number same guide pulse size so obviously if you had a perfect mount with zero backlash that would take you right back to the point where we started the north moves
01:03:13
not the backlash clearing moves but the north moves so that would be this third bullet item that's the starting point for the north test and with a perfect mount issuing the same number of moves to the south would take you right back to that starting point and what we do then is we correct again for the deck drift because this takes time to do it's taken at least 16 seconds depending on the polar alignment error
01:03:44
that means that the guide star will have drifted a little bit during that 16 seconds so we have to factor that out and then we have to try to decide when has the mount started moving south in a consistent way okay and i'll show you what this means graphically so here's a case where this is a pretty clean mount all right and what we always show you this is this is the graph that you see
01:04:15
when you push the button that says show the black backlash graph okay so this stuff over here to the left those are the north moves after the north backlash has been cleared so it's chugging along boom boom boom boom nice and consistent nicely evenly spaced and you get this slope and that's the rate at which the axis is turning then we take this top point and we start over okay we move it over here and now this white line
01:04:46
shows what would happen with a perfect mount okay so obviously you start at this point and you march right back down to the original starting point same slope same spacing same everything now in this example this is a mount with a pretty small amount of backlash but what you see is there's a flat spot up here okay so we issued that first 500 millisecond pulse to the south and nothing happened
01:05:18
okay then we issued another 500 millisecond pulse and and it started to move but it isn't moving at the same rate that it is over here and then we do another 500 millisecond pulse and bang we're back in business okay so if we measure the size of that flat spot up there that's going to give us an estimate for the backlash or the reversal delay
01:05:48
so that's all we're doing all right you could do the same thing yourself uh you know with pencil and paper and manual guide pulses if that's what you were inclined to do now here's an example of a not so good male and unfortunately i can't show you this with the same graph because i had to go back and find historical examples from the few thousand logs that we've got hanging around but here it's the same idea the red lines where the north moves
01:06:18
and the green points where the south moves well this thing basically never really got going i mean it isn't just it isn't purely a flat spot the the rate of south movement never approached the rate of north movement so this is a case where we're going to say the test failed and the reason is how could you possibly choose a backlash compensation amount that was going to correct for this kind
01:06:49
of a problem now looking at this the likelihood is that this is all some kind of static resistance it could have been that the mount was that the scope was horribly imbalanced it could be that there's something really stiff or fouled up this doesn't really look like pure deck backlash to me but this would be an example this is a real world example of a case where we say the test failed here's one that's even
01:07:22
harder to figure you know you notice that in the north moves only space there's kind of jiggering you know stair step function and then you get up here to the top and you have a flat spot you know that looks like maybe one two three four maybe that's for two seconds it's it's not doing anything at all but then you get this straggling you know south behavior over here
01:07:52
and you know this frankly is just a mess you can't do deck backlash compensation if this is how the mount is going to respond this is a mechanical problem i think in this case what it turned out to be is that the whole gear system was tightened up so much that it was kind of a minor miracle that the thing would move at all so these are the kinds of things that you have to deal with mechanically there's nothing that can be done in the software that's going to just make this
01:08:24
go away so let's come back to the question of why can these measurements start out too high and you know the the basic reason is that the place that you did the measurement could be different than the place where you started guiding in which case all you've proven is that the again that the backlash depends on where you're pointing and that's why this thing has to be
01:08:56
adapted so when we when we do the backlash compensation we always are looking at to see the results of whatever guide pulse we've issued and we're very aggressive about reducing it because if we don't reduce it very quickly then you get into this oscillation mode and nobody wants to sit there and watch this thing just oscillate for you know two or three minutes so we're aggressive about
01:09:26
decreasing it and generally speaking what you'll see is that it stabilizes fairly quickly you know usually within you know maybe five or six uh camera cycles you know it will still maybe be irritating to you but it will stabilize and then you're back in business um we generally don't want to use compensation pulses that are more than
01:09:56
about three seconds all right and the reason for that is that that's good if it's taking you three seconds just to clear the backlash in deck that's allowing the ra axis to basically run unguided for long periods of time three seconds plus whatever the exposure time is and most mounts that have this much deck backlash are also going to have somewhat inaccurate tracking and they're going to
01:10:28
suffer if the ra is not guided more aggressively than that so that's why the the backlash test won't recommend backlash compensation values that are greater than about three seconds if if you're stuck in that circumstance obviously the best answer is to get a mechanical improvement uh and improve the gear mesh or eliminate the stiction if you can on the axis one quick fix is to use faster guide
01:11:00
speeds so generally speaking we recommend that people run the mount guide speed up close to 1x sidereal some mounts i guess don't handle that very well but i think most of them do and and that reduces this reversal delay by linearly okay so if you measure a reversal delay and you're using a 0.5 x sidereal track guide speed that if you double the guide
01:11:31
speed you have the reversal delay all right it also can help clear some kinds of static resistance and it's generally a good thing to try if you're really hesitant to open up the drive system and try to fiddle around with the mechanics and if all else fails you can do unidirectional guiding in deck meaning you guide only north or only south in which case you don't get into these reversal situations and therefore the
01:12:04
deck backlash basically doesn't matter anymore and you know people are reluctant to do this they feel like it's just giving up or something but really a lot of experienced imagers choose to run this way anyway simply so they don't even have to think about backlash issues and i image this way for years and years and you can get very good imaging results i i really don't think people should be quite so hesitant to give it a try if they're
01:12:36
dealing with a mount that has these kinds of problems so i think that's probably the end of it and hopefully i answered those questions and hopefully i haven't run over my time allotment and i guess if there's any other questions or you want to re-ask them now would be a good or time uh you i think you might have answered
01:13:07
me just read through them can inmo be used to keep ra and dec error about the same making rounder stars yes this is an interesting question and i i'm somewhat embarrassed to say it but um i had a circumstance where i could make the deck guiding on my mount arbitrarily good but i couldn't achieve the same improvements
01:13:41
in ra and so what i would do is intentionally degrade the deck guiding a little bit until those ra and deck numbers came back into line and it worked fine all right obviously it's not a perfect outcome but it was a lot better than dealing with elongated stars all the time so yes you can you can tinker around with the deckman move you can make it be intentionally a little bit too small
01:14:13
if you're trying to bring it more in line with ra and not have um elongated stars so that's a good question well there was another follow-up to that to piggyback on the same question yeah let me see if i can get this right a general recommendation of figures pa backlash min mailloid max ra deck etc would be nice partic point do we need to start to tweak these values
01:14:44
okay there's no reason to ever tweak the max ra and the max deck because those are those are huge numbers those are two and a half second guide pulses and you have to understand the max deck value or the max deck and max ra values have no effect at all on normal guiding they're only there to kind of be a safety net for some kind of a tracking disaster
01:15:16
where the mount has just you know gone off into the weeds for some reason and you don't want to try to guide that out but you know there's really no reason to fiddle with those things um as i said the the things that you want to adjust in the guiding parameters are the min move values because the seeing can change you know from hour to hour and and that those are good things to adjust and in the if you're using the right ascension
01:15:46
predictive peck algorithm it's good to fine-tune some of those parameters uh once you've analyzed the frequency spectrum of of the r of the ra system and you know that you want to lock on a particular frequency for peck but the other uh guiding parameters um nine times out of ten they're gonna be just fine right out of the box so uh paul actually asked he says that
01:16:19
his graph only shows uh five points north and south how does he get more sample points there's been a couple of comments in the chat but uh what's your answer to that the the answer to that is this is the this is the one case where it's you may need to choose a guide star yourself and what you want to do is choose a single guide star that's going to give you plenty of room for moving
01:16:49
the mount north and not having it run off the off the sensor and you just have to figure out which way north is when you're looking at it you know you're probably going to have to choose a star that's up well off center and and away from any of the any of the margins of the sensor i'm looking to it alex did i miss any questions here yeah we've got a we've got some that that i haven't seen have been covered uh let me flip back there the ernie i think it was
01:17:25
um in your experience what is a large declination backlash error i would say anything over well anything over two seconds i would consider to be large um earlier you re you would refer to 625 milliseconds as pretty good for the kinds of amounts we have yeah that's i mean that's maybe i was being uh too critical there
01:17:57
you know 600 700 800 milliseconds is going to be fine um because that's not really delaying the guide cadence much and it's going to be well handled by the backlash compensation feature so basically anything from a second or lower i would say is is fine we'll be able to handle it nicely you know one second to two seconds you know you're kind of in a middle ground there where maybe you want to try to achieve some improvements anything over two seconds i would say it
01:18:29
would be worth trying to figure out why the amount is doing that and see if you can get it fixed sometimes it's it's really simple sometimes it's a matter of just changing the mesh on the deck gear system to reduce it okay um steve seguir sigerian asked the question that i was dealing with on a project that i've got to build a real portable mount but uh are just are some cameras just guide cameras are some of them just like not very good for guiding
01:19:02
well i mean what would what would what would it mean to be not very good um what what makes a good guide camera bruce well how about we rephrase the question okay what what should i look for in a guide camera well some of the things are are kind of hardware oriented and probably fairly obvious you want to have a high degree of sensitivity on the sensor you want it to be a monochrome guide camera
01:19:32
you would like to presumably have as large a sensor as you can so you've got a sizeable field of view that's more important if you're going to be using it on an off-axis guider so those are kind of the basics i think the part that people don't think about don't pay any attention to is the quality of the software so um an excellent guide camera for me is one that i don't have to fiddle around with i don't have to keep reinstalling
01:20:06
drivers or working around buggy drivers or finding out that you know the camera that i have that model is no longer supported those are the kinds of things that will bite you um and they're not really hardware specification things okay so you want something that works reliably um yes yeah okay arak chan wants to ask a question about um um that
01:20:39
well what he says is i think a general recommendation of figures fuller alignment backlash motion minimum motions aggression max ray deck etc would be nice particularly at what point do we need to start to tweak and i don't i'm not sure or not but i think you're asking uh can we just go with the defaults and how do we know when the defaults aren't working for us okay well the answer is yes you should
01:21:10
go with the defaults the defaults are tuned to the image scale that you're using that's why there's different phd2 configurations for different setups so when you run that new profile wizard by the time it's done it has already issued it's already made the best recommendations that we know how to for all those guiding parameters it then the issue is if you think that
01:21:41
your guiding is still not up to snuff the worst thing you can do is start turning knobs and fiddling around with guiding parameters because you're probably just going to make it worse and you're not going to learn anything in the process so what you should do unfortunately is collect those logs and learn how to analyze them and and we can help you do that on the forum i mean we look at i don't know five or six or 700 logs a year
01:22:13
and you could be one of them and i will say that i can't even remember the last time that i analyzed somebody's guiding and ended up telling them that they needed to change the hysteresis value or aggressiveness what i usually do is tell them put it back work because the problem that you're having has nothing to do with guiding the problem is in the mount and so you have to understand
01:22:44
what the shortcomings are with the mount first in order to know what to do with the guiding to be able to mitigate those problems okay is there a single button that will restore all the defaults for any given configuration there are two single buttons if you go into uh the advanced settings into the uh algorithms tab maybe a place you haven't been before
01:23:15
you will find there's there's a there's a column there for ra and a column for deck and you each has reset buttons okay so if you reset it then it restores all those guiding parameters so for those people like me that have been messing around with it for a while and kind of lost track of where i should be i should i should just go back and reset everything and start over again that would be my recommendation yeah okay
01:23:46
all right eric i i think i've gone through the questions uh folks if are there any other questions you see out there well there's a question that just came up i'm not sure what the question is but i'll read it uh can you recommend anything for us asi air people uh no i can't you made a decision just to go with asi air and that means you're gonna go with asi air and it's a good decision
01:24:19
if you got what you wanted so go for it bruce i do want to take a second to say that um i want to thank you and others who are working on phd for i mean there's an incredible amount of amazing stuff happening under the hood even more than i realized and the fact that this software is available for free to us and that their support on the forums is really incredible and uh without guiding i think the majority of us wouldn't be able to get as good of images as we get and phd just makes it
01:24:51
push your dummy easy how many how many people actually work on putting this thing together what's your what's your development team look like bruce uh it's pretty small uh andy and i are really the ones that do uh almost all the development work san diego colossal right yeah uh and he you know he's been pulled away from it a little bit more of the last year and a half or so just because of other obligations but he's not going
01:25:23
away he'll he'll be back but yeah he and i do most of the development work he still handles all the builds we have a community of guys who do more work on the unix-based platforms and we have you know a hopefully growing number of people uh that help out on the support forum um to answer questions and try to help people who are really struggling yeah that's it but it's just such a that it is the community effort putting
01:25:54
out what is let's face it largely the standard among amateur uh imagers uh it's just a community of people that got together to do that it's quite a quite a statement yes and what we've found is that you know even though andy and i are the ones that do most of the development work people will come forward with a particular implementation or a particular idea and you know we'll be enthusiastic about it and and get that into the product and then they move on and do other things that's
01:26:26
what happened with the predictive periodic error correction which truly is a rocket science project it was the basis for a phd thesis um by the the guy who did the work it's a brilliant piece of work um and he worked on that for you know over a year and then uh you know got his phd and moved on and we've been everly ever grateful since since he did it bruce you could stop uh your
01:26:57
presentation if you'd like and just yeah and just uh quit screen sharing then yeah quit quit the screen share and then we can see you well seeing me not might not be any great treat well here here we go so yeah i warned you i think people like to see the the people who are behind the software that we use every night [Music] and and just just to draw a fine point to that when you were saying
01:27:27
that uh well i um what was it a micron is like 40 or 50 human hairs and i'm thinking that what's that what's the human hair uh yeah you know you could you might be able to get you can get in touch with somebody and get one maybe yeah maybe [Laughter] anyway look at this right who's talking and i did tell you that this is a rather informal group we have here on youtube
01:28:01
so okay um where are we eric are we good we good on the questions no i think we're good to go okay uh we'd love to have you back on some other things you've got to explain to us about phd although it's for dummies we should just be able to press here and make it work well we try you know it is amazing what it can do i mean it really is amazing um but we're gonna we're gonna call it and
01:28:31
invite you back someday uh when you get something else some other chunk of it that you want to explain to us i could i could use some help getting what you know what the advanced things say why why i opt for this why i opt for that there's a thousand things we could do yeah one of them would probably be multi-star guiding because that's the latest each latest big feature that we've implemented and i you know i think people are probably curious about how that works we did get one last minute question
01:29:00
about using uh can you use pempro with phd2 um yes uh but you but pempro basically just creates uh the periodic error curve and uploads it to the mount so you don't use empro while you're guiding but for most mounts unfortunately not all of them but for most mounts if you get a good pe correction curve programmed into the mount that benefits guiding it just makes
01:29:31
guiding easier that's good to know so there's kind of a divide in the in the community on whether uh whether periodic error correction fights guiding or whether they work together yes and unfortunately that depends on how the pe was implemented by the mount vendor okay some of them do a really good job and it always helps others of them uh have done a really poor job and then so that can sometimes lead to
01:30:02
really bad results interesting bruce it would probably be a good idea um if you posted a link to this program because i am sure that there are a lot of people out there using your guiding assistant that could use the information that you just presented to people okay yeah we can do that you can do that yeah okay um we could go on for a while because we're just really appreciative of all the work you do okay no problem happy to do it okay but we we we like to keep the shows in where are we down to 61 yeah we're
01:30:37
starting to lose them don't go away yeah we haven't left anyway time to go to good times time to go to bed good night everybody and we'll see you next week when we're all right thanks guys we're going to go down under next week and see some wide field astro imaging with um all right with the groom okay okay bye-bye you

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