Guiding Graph: Page 2 - ZWO User Forum

Guiding Graph

w7ay

Byrdsfan1948 Without pulling out my old Applied Mechanics books and doing a Free Body Diagram of the forces involved ( OCD at work ) I believe this situation is not the same as the 3 axis imbalance in DEC.

Well, you know more ME than I do. For myself, anything to do with mechanics came from Physics :-) My academic background is EE, with some influence from radio astronomy (NRAO) and some radar astronomy (Stanford). But that was a while ago, and if your handle's "1948" is the year you were born, then we are the same age :-).

When I think of it simplistically, the "third axis balance" sounds like the CG is moving around depending on where the declination axis is pointed.

But hey, for us OCD engineers (redundant phrase :-), it is "problems" like this that keeps us (at least myself) interested in technical hobbies. I ground my first parabolic mirror back around 1963 or 1964.

I believe with a quick trip to Home Depot for some threaded rod and perhaps some appropriately threaded nuts, I can easily fabricate

Yep. But you may need to be able to move the threaded rod up and down your dovetail plate too (or change the weight of the added blob). The threaded counterweight has to overcome any existing third axis issue -- and I believe -- the line from the CG of the new weight and the CG of the imbalance also has to intersect the declination axis.

The guy in the YouTube video must have done that, but did not not mention it.

Chen

Byrdsfan1948

Hi Chen Yeah 1948 is the year I was born and Byrds is my favorite Music group from the 60's. I am a lifelong musician owing to my love of that group from age 16. Actually I am impressed at how many astro photographers are also guitar players and musicians as well. Since your an EE, and from all your detailed posts, that I enjoy reading on many topics, I am well aware that you must come from a very impressive background! As such you might really enjoy yourself playing around in my home music recording studio. Amazing technology that I am sure you would love to see. Aside from my slipping musical skills I can still produce there in my studio CD's that easily rival the big studios. Unfortunately when I consider the amount of work I had to put in with some of my fellow musician friends mastering the incredibly complex software needed to do all that, I worry about this new hobby. As I see it learning how to use all my astro equipment and getting good data from it is like mastering my musical instruments. Post processing is like what I do in my studio........... And that was by far the most complex part.
I am sure I will need to experiment a bit with this new little 3rd axis project, but as we are saying it's all for fun, and in my case anyway no one is waiting to buy any of my astro pictures :-)) Al

w7ay

Byrdsfan1948 Post processing is like what I do in my studio........... And that was by far the most complex part.

Post processing software has come a very long way, Al.

Partly because I use Macintosh exclusively (I worked for 17 years [algorithms development] at Apple before I retired in 2005), astro related software was hard to come by back at the turn of the century. So much so, I had to write my own program to control the, back then, newly acquired Takahashi mount.

http://www.w7ay.net/site/Applications/cocoaTemma/Users%20Manual/index.html

However, it looks like MacOS (now macos) has turned the page among astro hobbyists since then. My latest contribution to the Mac astro hobbyist world is a true mount simulator (not just protocol simulator):

http://www.w7ay.net/site/Applications/MountSim/

Back in the dark ages, I used to stack my images manually using PhotoShop and eyeballing the layers to match the stars :-) Nowadays there are superb programs like AstroPixelProcessor that can do it all automatically. (Give it a shot if you haven't already looked at it.)

AstroPixelProcessor is very much like the ASIAIR; it takes care of the nitty gritty stuff for you behind your back. Unlike the ASIAIR however, AstroPixelProcessor also has very advanced techniques that you can set -- something the ASIAIR does not let you do.

Chen

w7ay

Byrdsfan1948

By the way, I just took a look at your picture again. It is also possible that the 3rd axis imbalance is coming from your dangling cables.

Back in the days (before the Harmonic Drive mount) when I had to critically balance my mounts, I route my cables through locations as close to the mount's axes as possible. That way, the balance does not change over the course of the night.

Chen

Byrdsfan1948

Hello Chen, I just had a few moments to quickly look at those links. I've been a bit busy ( actually doing some new recordings ) in my music studio on these back to back to back cloudy evenings. I'll give them a good look tomorrow.
I did some checking on my mount. The cables are not the problem. The mount design is. I took some photos to show you but I will try to explain here. No need to add the photos here but if what I am saying is not clear, let me know, and I will send them. I removed the entire OTA assembly so I only had the mount on the tripod. The imbalance comes from the attachment assembly that holds the OTA to the mount. It is heavier on the side with the locking bolts. Actually substantially so. The bolts themselves are quite heavy, adding to the imbalance. With the OTA assembly completely removed the platform that the the Vixen plate mounts to, will not stay vertical, but rotates to the East when viewed from behind, in the direction of the side those bolts are located on. Of course it does not help that when the OTA is mounted that is the also the same side that the fine focus adjustment knob is located, adding to that imbalance. I actually have been playing around with some Free Body Diagrams trying to quantify what is actually happening in 3 dimensional space as our scopes rotate both in RA as well as DEC as we track. For example when we balance horizontally in Dec we are simply trying to find that spot where the rotational torque of one side, equals the opposite rotational torque ( around the center of the mount ) of the other side. Once found the OTA in that position is in static equilibrium. In most cases the balance is found not because both sides are perfectly equal. It is found by positioning the unequal masses, unequally distant from the center line. TORQUE M1L1=M2L2 Where MI M2 are different as are L1 L2 but their products the same. That distance from the C/L being called the moment arm. If we were at 0 degrees ( parallel to the ground ) That torque would never change no matter how we rotate the OTA. However once we introduce the angle of our latitudes we now have a different situation. At that point the OTA will no longer be rotating in a circle but depending on that angle an ellipse. That changes the actual distance from the center line as we rotate. Now add to that the additional rotation through RA and the problem becomes very complex. Bottom line is I am trying to understand how balance may change in a perfectly balanced system as we first set our balances in the home position as we then rotate our OTAs as we track. I suspect that there is a harmonic change that is a reflection of how the center of gravity of the various masses rotate, as well as their moment arms change, in 3 dimensions as we rotate around their axis as we track. Bottom line? I am unsure at this point ............. but this is a very interesting problem to try to understand. BTW as I consider this problem I also question just how valid a solution that adjustable mass was on the video we saw. It may work perfectly in that perfectly vertical position but as soon as the OTA starts rotating from perfectly central position I suspect that mass must also need to be re positioned to keep the OTA perfectly balanced. I'm sure that could be accomplished with some sort of motor and appropriate software control ( Your part of the solution :-)) ) Al

w7ay

Byrdsfan1948

Yow, who would have thunk that the 3rd axis imbalance is caused by the mount design!!

Reminds me of the Pogo comics: "We have met the enemy, and the enemy is us!"

I conjecture that if each solid subcomponent is itself balanced on all axes, then when the subcomponents are put together on bearings (RA and Declination motors in our case), the result can be balanced in all axes too. E.g., if the OTA subassembly can be balanced on all axes, then the declination axis will also balance in all axes once a single axis balance is achieved. I could be wrong... I am just visualizing it as moment arms around a pivot point.

Perhaps you can come up with some weights to balance the mount itself.

By the way, there are some premium mounts that measure the magnitude of the electrical currents through the servo motors and feed that back to the hand controller to aid balancing adjustments. So, auto-balancing is not so farfetched ("its only software" :-). Although I suspect that except for the lowest end mounts, the future of hobbyist mounts lie with Harmonic Drives, which has no balancing need.

Chen

Byrdsfan1948

Hello Chen, I figured since I took the photos I may as well send them. The top photo shows me holding the mount clamping assembly, in the vertical position. The bottom shows what happens when I let it go. It is substantially heavier on the side with the tightening knobs and it immediately rotates into the position shown, almost as if pulled by a magnet. I am certain this imbalance must have been obvious to the designers at Ioptron and they concluded that it was well within the mounts mechanical ability to compensate for. I am certain that the primary design consideration for any mount designer is that it tracks well. I doubt they obsess over our guiding graphs like we do. In the case of my mount Ioptron CEM25ec it most certainly does track very well on it's own. I have no problem getting perfectly round stars with my set up even with 5 minute unguided subs. I very much agree with you regarding the ability to measure the current draw as the mount tracks as a way understand the variations in the forces required as the mount tracks. I have found this entire conversation very interesting. As a result I will be trying to make some set up changes to my assembly. Essentially I believe given the actual complexity involved here I think think the best thing I can do would also be the easiest. I need to add enough mass to the telescope side on my OTA so that I can get the center off mass as close to the center line of the clamping assembly the hole inside the 6 Allen head screws in my picture. That would probably be the easiest way to minimize the variations on force as the mount tracks. Al

w7ay

Byrdsfan1948 I have no problem getting perfectly round stars with my set up even with 5 minute unguided subs.

It is not whether the stars are round. I keep reading that old saw and shake my head each time.

Lets say the guide error in each axis is Gaussian (has Normal distribution). Then by probability theory, if RA and Declinations are independent random processes, the 2D probability is Joint-Gaussian (the kernel of the probability density function looks like exp(-(x²+y²)). Guess what, this kernel is uniform with respect to the angle.

The end result is that random errors caused by autoguiding will end up with a "round" spread too.

Therefore, given independent random fluctuations between the two axes, what happens is that a round star remains a round star -- but the star is now bloated by the value that is predicted by the total RMS error that is reported by PHD2.

A 1 arc second RMS error will bloat the stars' FWHM by the predicted amount. Lets say "seeing" is independent of tracking errors, then probability theory further says that the variances of the errors add. So, lets say "seeing" bloats your star by 3 arc seconds, then the FWHM of a guiding system with 1 arc second RMS will become sqrt( 3*3 + 1+1 ) or 3.16 arc seconds. A 3 arc second RMS tracking error will cause the star to bloat by much more, a factor of sqrt(2). So, it behooves you to keep the tracking error way below 50% of the star bloat that is caused by "seeing," which you have no control.

Many of us will kill to get tighter stars. I have myself recently ordered a FOA-60Q to see if I can get a slightly sharper image across a full frame sensor under certain situations (the FOA-60Q has a large f-number and is not useful for all conditions) than my current best OTA, an FSQ-85. I promised myself that I will stop there, since there is nothing else in the amateur world with a Strehl ratio that exceeds the FOA-60Q (and especially with Takahashi's QA).

In your case, since there is a 3rd axis imbalance, sometime during the night, the graphs will be pulled toward a zero offset when the third axis imbalance diminishes. While that is happening, you will see stars trailing of the magnitude of your offset. If it is a slow process, the star trails will be small and spread over multiple frames. But what is equally likely is that the rebalancing will suddenly allow the feedback loop to have the ability to compensate, and all the star trails will occur as a large trail in a single subframe.

Chen

Byrdsfan1948

Chen thanks again !! I understand what your saying perfectly. I took the lazy way out there. Essentially I should have said round stars, and the rest of the image sharp. Or something along those lines. Of course a lot of that is due to the fact that the Ioptron cem25Ec tracks very well without guiding, and of course the focal length of my system with the 0.8 reducer flattner in place is only about 336 mm. Typically for imaging I seldom go over 3 minute subs. One reason because that is a lot of air traffic in my area, between Boston, Hartford, and New York ( I live in central CT ) and I have lost far too many 5 minute subs to that problem.
Unfortunately last night the guiding was a total mess. Just about every problem one could imagine. I started out very nicely for the first 30 minutes or so. The total error most of the time was well under 1 Arc sec, and RA and DEC adjustments around 0.6 Arc Secs. As good as it gets for me. But then suddenly everything came off the rails and guiding became a total mess. Sometimes it would go crazy after dithering, sometimes not. Sometimes it settled down quickly other times not. Sometimes it would be guiding along, seemingly with no problem, and then suddenly both RA and DEC would start to wander up off the graph. I checked all the obvious stuff at the scope and nothing seemed amiss. Balance was as normal. I know my PA was very good, and my Go To slews were dead on perfect. No wind, no clouds, the seeing was crystal clear, and as stable as it gets here. No moon etc.
As I was watching the guide page on my ASIair I could see the guide stars which would start out nicely defined, with a nice sharp peak over them, start fading until it was lost. Often the page broke up as it appeared the mount was slewing to find another star. When it did, it might restart guiding, only to have this happen all over again. Sometimes I would stop it all, pick new star myself and restart guiding, only to watch that star move, pulse by pulse, from the cross lines in the center of the box, to outside the box. As if guiding was actually doing exactly the opposite to what it is supposed to do.
Of course I tried re calibrating many times as well as tried making various up and down RA and DEC aggressiveness changes. As a last resort I tried shutting down the ASIair and restarting. No improvements.
Finally I just gave up totally frustrated at losing one of the few clear nights for imagining so far this year, to this never ending and now apparently worsening guiding problem.
I was using the ASIair FW 1.5.3 beta for a few weeks with better results than this, and this past week updated to the now current release. So far both nights since that update the guiding has been a mess. I am not sure if this is a software issue, or something else. I say that because it seems others are not having these sort of problems. While some others are. All I do know for sure is that I am using the same equipment, set up the same way as I have been from day one, and my guiding which at one point was not nearly as problematic ( FW 1.5 ) now has become my nightly show stopper.
Frankly if it were not for the fact that I need guiding to dither I would at this point stop guiding altogether. Although with all the problems I am having with the guiding, dithering isn't going to make any difference in my final stacks anyway since I'm not getting any.
I am beginning to suspect the problem could also be with my ZWO120 mini camera. The fading of the star image is very concerning. There is an update for the camera driver but it is a ZIP file and I cannot find a program on my Samsung Galaxy A tablet that can open it........... Would you know of one could look for?
I'm sure the solution to my problems are probably simple. Usually when things are this bad, the solutions are simple, and easy to find, but so far no luck. Al

w7ay

Byrdsfan1948 I know my PA was very good

I don't think polar alignment (PA) is the problem... as long as the autoguiding can overcome the bias from any PA error.

What happens when PA is off is that there is a constant error (think of it as "force" if you like) that is tugging the mount in some direction. There is no real force, of course, just that the plate is moving in the RA direction at a rate that is not precisely the sidereal rate, but the plate also moves in declination.

If the PA error is large enough, the RA and/or declination error will be too large for autoguiding to compensate for. That is where you need to bump up the loop gain - which can be problematical if the gain is anywhere close to or greater than 1, at which point, the loop will oscillate.

If the autoguiding system is "strong" enough (again, using the force analogy), you will still be able to keep the guide star perfectly steady. What then happens is that over a long exposure, the plate will appear to rotate around the guide star. That's right; the rotation will not be around the center of the plate, but around the plate where the guide star is located.

But even a 1 arc minute error of deviation of the polar axis from the north celestial pole should not be a big problem with your scope's focal length, camera pixel size, and exposures of under 300 seconds. However, if you compare a plate taken an hour later, you will definitely see that the heavens have rotated with a 1 arc minute type polar error. Pretty much all auto stacking software will de-rotate the images when it stack images.

Right now, there is a bug which I believe ZWO is still trying to track down that was introduced sometime I believe between ASIAIR v1.3 and ASIAIR v1.5.0. My guiding error when using ASIAIR has pretty much doubled between last Summer and this Winter. I can imagine that with some other mounts and autoguiding settings, this doubling could cause the kind of runaway that you observed (and others have reported for quite some time now, both on this forum and on the ASIAIR Facebook page). It could be precipitated by PA error but I suspect the bug is somewhere else and polar alignment is not the root cause.

One reason because that is a lot of air traffic in my area, between Boston, Hartford, and New York ( I live in central CT ) and I have lost far too many 5 minute subs to that problem.

Hah, that's funny. I am right under the SFO-SEA air lane and when I am close to Meridian, I get a lot of airplane tracks. They go away when stacked with appropriate stacking setting (check up Google on "3-sigma clip"; yeah, that 3 sigma that we learned in college :-). The default setting in AstroPixelProcessor gets rid of them as long as you have more than a dozen subframes or so.

Chen

Byrdsfan1948

Hi Chen, I agree what I am experiencing is not a function of my PA. I will say however that while I love the PA process with the ASIair it's probably not the most precise way to do this. But at this stage of my Astro Photography career it is good enough. I also love how in the PA process by means of the plate solving the ASIair and mount end up knowing where they are pointing making it a lot easier for me to get up and imaging each night without the more involved star alignment process.
So basically at this point I am still looking at each night as a learning process. So even if it is a disaster like last night from a guiding and thus imaging POV, at least it is not a total loss.

Like virtually everyone else the WiFi issue with the ASIair Pro was at one point my biggest problem. I couldn't get more than 10 feet from the unit with losing my connection. Over the last couple of months and after many attempts I have finally resolved that problem. While it is not the perfect solution for everybody, I now connect my ASIair Pro directly to my home network router via a 50 foot Ethernet cat 7 cable. I connect my Samsung Galaxy tab wirelessly to my home network where the ASIair network then appears. That usually works great but sometime the image downloads can still take a while......... Last night I was able to complete the connection totally via Ethernet Cable after buying an adapter to connect and Ethernet cable from my home router to my Tablet via it's USB c connector. BINGO!!!!! My downloads ( star trails and all 😀 ) were virtually instantaneous! As I said not a solution for everyone, but it works great in my case.

I guess my point is that as long as I can solve one problem each night it's not a complete waste.

Yes I have to believe that there is a bug in the ZWO software that has yet to be understood. There are just too many examples of problems like mine. As I said the fact is that with FW 1.5, the guiding for me was going fairly smoothly. Obviously I don't have your experience going back further. Weird issues started showing up in 1.5.1 and so far with 1.5.3 the problems seem to show a very unstable program only getting worse. The funny part here is the Beta version of 1.5.3 wasn't nearly as problematic as the officially released version.

I think it's probably time for me to see if I can move away from the ASIair at least for guiding. To that end I have tried adding Bluestacks to my Windows computer so I can load the ASIAir app there ( at this point that is yet another problem just trying to get Bluestacks to download that app ) and then see if it is possible for me to guide using PHD2 while using the ASIair for everything else?

I must admit this has been far more challenging to set up than my music studio!!! But I will not let it beat me!! And as long as there are very knowledgeable people like you around who are so willing to help out I'm sure it won't!! :-) Al

w7ay

Byrdsfan1948 I will say however that while I love the PA process with the ASIair it's probably not the most precise way to do this.

On the contrary, it is quite precise. It is leaps and bounds better than using a polar scope, and still way better than things like PoleMaster, that uses the human to plate solve in the 21st century :-). The only thing that equals it is very long term drift alignment, if you have the patience for it. (I used to feed the mosquitos [not intentionally] when drift aligning with PHD2 :-).

I have measured ASIAIR's polar alignment using my MountSim program that I had linked earlier. MountSim draws stars from the Hipparcos catalog, and I use the Sämundsson formula to simulate atmospheric refraction.

If you start with the OTA at declination 90º (well, I only go to 89.5º to avoid any secant errors, just in case), the ASIAIR polar alignment produces consistent results that is within about 12 arc seconds (thats arc seconds, not arc minutes) of the pole, as defined in MountSim.

With real world "seeing" fluctuations, it won't be as accurate. But the problem comes from nature, and not from the ASAIR implementation. I don't know how many asterisms ASIAIR uses for plate solving, but if they use multiple asterisms, even "seeing" becomes a non problem.

If you use a declination angle that is lower than 0.5 degrees from the pole (ASIAIR allows up to about 30 degrees in declination from the pole), the alignment error is larger. At 30º from the pole in declination, it is somewhat more more than 2 arc minutes off, if memory serves.

Chen

Byrdsfan1948

Hello Chen, OK great to know !!! Again perhaps I could have phrased myself better. Without question the ASIair Pro PA process has been far more accurate than anything I was able to attain using the absurdly difficult to use, built in polar scope on my Ioptron CEM25EC mount. Whoever designed that could use a few good lessons in ergonomics.
My concern about the ASIair PA process is that I can quickly zero in to a total alignment error of under 2 minutes, but from that point or so on, the process can get a bit frustrating. The fine tuning adjustments needed, and the ASIair refresh delay, often lead to me chasing the target circle all over the place. BTW this is another disappointment with my Ioptron CEM25C. The hardware used for this simply was not designed with the kind of precision needed to reliably make those very fine adjustments. Essentially at this point it becomes a game of tag as I try to zero in better. I have gotten to under 20 Arc seconds but that was more luck than anything else. Last night I quit at 30 Arc Secs.

Speaking of last night, my guiding was a bit better than the night before but still so problem filled that it is essentially useless at this point. I added two pictures. As you can see in one the guiding is going along just fine then just like that it's off the rails............... Once again last night the seeing was perfect. As I think I've mentioned more and more I wonder about my guide camera. As I have said I know ZWO has a FW update for it and it sounds like that update is meant to deal with some of the issues I believe I am having. I am trying to find what program I need to add to my Samsung Tablet so I can unzip the files I have downloaded. If I can do that then I will certainly update that FW and see if it helps at all.
HAHA but adding insult to injury........ I needed to preform a Meridian Flip. I watched holding my breath. The ASIair and my mount preformed it perfectly!! I mean flawlessly! It even after the flip found a guide star, re-calibrated then after setteling started the photos again....... Only to a few shots latter come off the rails lose that star and stop guiding again!!!
Al

w7ay

Byrdsfan1948 Whoever designed that could use a few good lessons in ergonomics.

Hi Al, one of the better polar scope reticules are the ones from the Takahashi EM mounts. Their scale is still too small, and back in the dark ages, I used to mount a camera at the exit pupil of the polar scope so that I have a large image on a laptop to use for adjustments (and also to avoid straining my neck with my latitude).

Unfortunately, may hobbyist products (including astrophotography) are designed by people who themselves have never practiced the hobby, or are neophytes themselves, picking up the hobby after being assigned the task of implementing the design.

Byrdsfan1948 The fine tuning adjustments needed, and the ASIair refresh delay, often lead to me chasing the target circle all over the place.

That is the biggest flaw in the ASIAIR paradigm -- their copying of Apple's easy to use GUI methodology, but without the careful consideration of said GUI.

The graphical interface of the PA process is the prime example. The problem with the ASIAIR polar alignment display is that the scale of the graphics changes! As you get closer to the target, the drawing scale suddenly changes making you think that the error has suddenly jumped higher. It is pure absurdity (as with the scale of the guide graph suddenly changing; ZWO simply does not trust the user in choosing the correct display scales). The same GUI problem are everywhere else too.

I personally ignore the polar alignment graphics completely; never even look at them. Instead, I focus on the altitude and azimuth error numbers and little green errors on the top right of the screen. Just tweak the altitude and azimuth bolts to reduce those numbers. If this numbers jump around, the problem is with the mount. The difficult alt-az adjustment caused RainbowAstro to issue a replacement base, but less scrupulous manufactures just don't seem to care about improving them. I know many people who added their own teflon sheets etc to make the azimuth adjustment of their mounts smoother.

Byrdsfan1948 I have gotten to under 20 Arc seconds but that was more luck than anything else. Last night I quit at 30 Arc Secs.

For what its worth, 30 arc seconds is well good enough for the plate scale (focal length and camera resolution) that you use.

I have been able to get within 2 arc seconds with my RST-135 within 4 minute from scratch (random tripod position), and under 2 minutes from night to night with my semi-permanent tri-pier and mount situated outdoors (I only remove the OTA and guide scope when I am done for the night).

Byrdsfan1948 Only to a few shots latter come off the rails lose that star and stop guiding again!!!

Yep, that is the guiding bug that people complained about the most, and not fixed yet. Plus they are on Chinese New Year's holidays at the moment, so who knows when a fix is forthcoming. With some mounts, don't know about yours, the bug is ASIAIR mistaking the slew rate (usually between 1x sidereal and 512x sidereal) for the guiding rate (usually between 0.1x sidereal and 1x sidereal). If you mount suffers the same bug, open up that small GOTO sub-window and drag the slew rate slider down to 1x to reduce the problem. When you calibrate, set the guide rate in the mount GUI to 0.9x. For many mounts, this (0.9x vs 1x) error is small enough to make things work sufficiently (but to us real engineers, not great).

Chen

Byrdsfan1948

Hello Chen, Thanks again for all your suggestions. FWIW I have been using that 1X Slew rate adjusted by that GOTO slider for quite a while now. I saw a comment quite some time ago now from ZWO regarding that. I can't honestly say however If I have seen any real difference. I currently have my guide rate in the mount set to 0.5 so I will try your suggestion of 0.9 next chance I get.

Enclosed above is another guiding example from last night. In this case it's the RA that came off the rails. It could just as easily been the DEC, or in other cases, both. Again last night I did have a reasonably long period of very acceptable guiding, but once the problems started, they persisted. It didn't matter where or what the target, or how many times I re calibrated. To me that suggests that whatever this problem is, it is not hardware related, or at least if it is the hardware, it is only a part of the problem. To me clearly this is some sort of software, or compatibility problem with my equipment, and the ASIair Pro.
My experiment last night was to connect my guide camera differently. Originally I had it connected directly from the ZWO120mini to the ASIair Pro. A month or so ago after seeing how others were connected I changed that so I connected the guide camera a USB 2 port on my main ZWO183MC camera. That camera is then connected via USB3 to a USB3 port on the ASIair.
Last night I reverted to my original connection method connecting the guide camera directly to one of the two ASIair USB3 ports. The bottom line was, I didn't see any difference.
I am now wondering about my Samsung Galaxy A Tablet? It didn't dawn on me until this morning that I could try to use my Apple 12 Iphone in place of that tablet at least as my next experiment. I already had loaded the ASIair app on my Iphone but I have never tried running my system from my Iphone.
This morning I tried connecting my Iphone and my system and it immediately connected perfectly with no issues. I tried some commands and the mount responded properly. So next clear night I will try using my Iphone just as an experiment to see it my system plays any differently with that, than it may be doing with my Samsung.
Also perhaps I may be able to download and INSTALL that latest 120mini driver onto my Iphone. So far I have only been unable to download that file onto my Samsung Tablet, but have been unable to open it to install.
If the Iphone makes a difference then perhaps that means I should get an Apple tablet. If it does not, then my next idea might be to delete the ASIair App and then reinstall it.
As a fellow engineer I am sure you can appreciate why it is necessary to try to resolve issues like this by changing only variable at a time........... Any thoughts about my ideas here? Al

 Beyond that I

w7ay

Byrdsfan1948 I am now wondering about my Samsung Galaxy A Tablet?

Autoguiding is done autonomously inside the ASIAIR (Raspberry Pi), Al. Your tablet is simply displaying the results; it is not part of the feedback loop. The lag time is too great (and with the ASIAIR WiFi, too unstable) that you will get overshoots exactly like what you are seeing, but it will happen all the time, instead of creeping up on you.

The next time you have the wild oscillations, instead of rebooting the ASIAIR, could you please try this? First stop autoguiding (red stop sign), go over to the Guide Setup and disconnect the guide camera. Wait half a minute and reconnect it back. Unfortunately, at this point, I think that ASIAIR will also make you recalibrate guiding. Then resume autoguiding to see if the problem goes away. If it does then we will have some concrete evidence that it is the guide camera process that is the culprit (binary chop to find the bug :-).

I have for some time been suspecting that there is something bad that happened to their guide camera interface since the frame rate of my PHD2 log has become more erratic in the past few ASIAIR releases. If the frame rate stutters, and your mount has enough backlash, we will see the oscillatory behavior; albeit I don't know if the PHD2 itself compensates for the non-constant sampling times.

I haven't myself experience large errors like what you are seeing, with my mount. I am assuming that your aggressiveness settings are already below 0.5, right?

When all else fail, try this:

Use the plate solve and GOTO as usual to get to your target. Then, disconnect ASIAIR's Telescope Setup from your mount and instead select "On-Camera ST4." You would also need an 1-to-1 RJ11 cable to go between the guide camera's RJ-11 and your mount's ST-4 input.

Then go through the guide calibration process.

This then bypasses the pulse guiding. Check back on my post in the past 2 mounts, I had described how pulse guiding through the mount protocol works (ASIAIR uses slew commands to generate the pulses). If there is any lag time in the ASIAIR mount interface (USB serial port), it can also cause the overshoots that you observed.

If ST-4 guiding is clean, then the error is in their USB driver (I will send an email to the ZWO developers to ask them to check the lag time too -- some guy might have thought that mount control does not need high priority, but it actually needs very high priority to do pulse guiding properly, since the guide pulse lengths are done with software timing. ST-4 does not use the USB serial protocol and will not suffer this lag -- (but it may suffer some other lag, ha ha).

Chen

RonM

I’ve been following this thread for awhile now. I have the same mount (cem25es) as you, same balance issue and same guiding issue. I use an Apple iPad and Apple iPhone same problem guiding on both. Just wanted to let you know you’re not the only one having guiding problems.

Ron

Byrdsfan1948

Welcome to the conversation Ron. Please feel free to add any or your experiences or ideas. Al

Byrdsfan1948

OK thanks again Chen. I'll copy these ideas and give them a chance next clear night. That unfortunately maybe a while however, since we are again digging out from almost another foot of snow. Which means a lot of digging to get to where I typically set up my mount :-).

FYI the last two observing nights I had my ASIair either connected via a Cat 7 Ethernet cable to my home WiFi router, and my Tablet connected to the ASIair via wifi to my home network where the ASiair then shows up. This has proven to be a very strong and reliable connection that for me has totally eliminated the short WiFi range problem of the ASIair.......... Or, I have also had my Tablet directly connected with an Ehternet cable ( Cat 7) using an Ethernet/USB3 connector to the same router as my ASIair. Essentially hard wired from the ASIair to Tablet. In that case the connection Tablet to the ASIair is lightning fast and my down loads are virtually instantaneous. So if this is what you mean by lag time, and unstable ASIair WiFi, I think I have both those problems well beaten.

I have tried all sorts of aggressiveness settings from 0.9 to 0.3. In fact last night during one of the wild oscillation events I did reduce the settings to 0.3. It did seem to bring things temporarily under better control, but then the wild oscillations reoccurred. I think we are both concluding that certainly there is something very wrong somewhere with the ASIair software either in the ASIair itself, or maybe the guide camera. Perhaps both? The frequent Star Lost message ( for no obvious reason ) is very concerning to me that somehow the guide camera is part of the problem. As I have previously mentioned I often see very large variations in the guide star brightness from what we would say is normal for guiding, and a nice sharp peak, to it totally fading away. No clouds or other obstructions are the cause. In those cases I often see the what looks like the camera starting to search around slewing to find a new star to guide on. Obviously I get the star trails in one of the pictures I have shown above.
What I suppose still is a mystery to me however is if there is a software or camera problem why is it that so many others report no problems at all? Al
In any case as usual your being very helpful and I will give your thoughts here a try. Thanks Al

w7ay

Byrdsfan1948 FYI the last two observing nights I had my ASIair either connected via a Cat 7 Ethernet cable to my home WiFi router, and my Tablet connected to the ASIair via wifi to my home network where the ASiair then shows up. This has proven to be a very strong and reliable connection that for me has totally eliminated the short WiFi range problem of the ASIair..........

Yep, all that should work well.

My own setup is a Mortar tri-pier and RainbowAstro mount that are left outdoors under a couple of dry bags when not in use (I only remove my main OTA and guide scope from the dual-saddle plate on my mount). At the base of the tri-pier is a waterproof box that includes an ASIAIR Pro and an eero mesh router. Effectively, that ASIAIR is directly connected to my home network. 12V feeds the box from the house.

For what its worth, the ASIAIR will connect directly to an iPad through a Lightning-to-Ethernet adapter (older iPads) or a USB-C-to-Ethernet adapter (newer iPads) by setting the network setup in iOS to use Ethernet instead of WiFi. Absolutely blazing speeds. I do not drive to remote locations, but if I did, directly connecting an iPad to ASIAIR would be my preference.

What I suppose still is a mystery to me however is if there is a software or camera problem why is it that so many others report no problems at all?

Well, lots of people probably fall into my category; we can get within a factor of 2 of PHD2 (with single star tracking) and while not ideal, produces acceptable star sizes, and we just leave it at that. The better mounts have less backlash (the RainbowAstro and Hobym harmonic drive mounts (both Korean) have virtually no backlash), and a small backlash might be what makes the difference.

You are definitely not alone, though. If you read the Facebook ASIAIR pages, you will find lots of people with a problem of mounts just taking off by themselves while autoguiding (and lost stars too, even when they are visible on the screen). And like spotting cockroaches, if there are a couple of people bothering to report a problem, there must be many more who don't, and may have given up on ASIAIR and went to use N.I.N.A., StellarMate or INDIGO Sky.

Many months ago, I had sent the ZWO folks a heads up that the DONUTS multi-star tracking was available in the open sourced INDIGO framework. DONUTS was published in professional circles at about the 2013 time frame I think -- the variance of "seeing" error halves each time you double the number of stars used. Now, PHD2 has its own multi-star tracker (under Beta), so ZWO lost the chance to get a leg up on PHD2. Instead, the tracking in ASIAIR appears to be a factor of 2 worse than single star PHD2; so there is now a factor of 4 in tracking performance between what you can get from PHD2 and what you can get from ASIAIR.

Chen

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