×

INDI Library v1.8.9 Released (01 Mar 2021)

INDI monthly update. In addition to driver improvements, major code refactoring is in progress by @pawel-soja to modernize and improve INDI aging code.

New forum users, please go here first: indilib.org/forum/new-forum-users.html

Alt-Az mode for EQmod

  • Posts: 226
  • Thank you received: 88

Replied by geehalel on topic Alt-Az mode for EQmod

@Dirk Thanks for giving more explanations about your concerns. I don't know either why handcompiling indi in astroberry does not work, I have looked for the repo to inspect package contents, but did not find them. I may directly inspect the image, but it would be better to ask to astroberry's maintainer. If you want to help in testing, that will be mandatory anyway. I agree with your remarks concerning setup time needed when you don't have an observatory. In my backyard I can't even see Polaris, that reduces polar alignment time, just aligning on three stars and pointing inside that triangle. That's enough for my use, I don't know if that would work for faint objects.
@Federico I made an error in my previous post, after looking at the skywatcherAltAzMount driver code, the current implementation consists in speed adjustments made every seconds. It decided me to test indoor with my AZEQ5 and the CCD simulator. I have been able to track a star, take a shot and sends it to astrometry.net (Capture and Solve). It did not resolve unfortunately, the CCD image having two big circles with no stars inside it, only two or three dozens around, and a double star just in the center (I pointed Arcturus!). I must have missed something. Anyway Ekos did not complain at all with the AZEQ5 while it was tracking, Should have a try on real sky when possible.
I really believe the skywatcherAltAzMount driver is the best option for the moment. And don't understand why you would like I make two drivers in one with indi-eqmod. And don't have plans for that before at least months.
7 months 1 day ago #60011

Please Log in or Create an account to join the conversation.

  • Posts: 15
  • Thank you received: 1
Dear Jean-Luc, I will read and respond more thoroughly later today but I wanted to mention that the situation where AZ-GTI (and others) in AltAz can excel is in EAA (Electronic Assisted Astronomy). With my Nikon D5100 you can capture deep sky pics of short exposure (10-15 secs) at 1000 ISO and live-stack them and have a wonderful experience of almost-real-time seeing of objects you can't see with your eyes. As you mentioned, doing this requires somewhat precise tracking (sufficiently precise to avoid blurry images during the 10-15 secs of the exposure), although movement / rotation between pics is unimportant since the live stacking can correct it.
Jasem mentioned EAA was in the roadmap of Stellarmate. More later, thank you for your response!
7 months 1 day ago #60033

Please Log in or Create an account to join the conversation.

  • Posts: 15
  • Thank you received: 1
And to the why not use the wedge, I have it, but if I bring it I also have to bring the counterweight, which adds about 4kg to the package and also requires a more serious tripod and kind of overweights the AZ-GTI at least theoretically. In AltAz you can use AZ-GTI with minimum weight and becomes perfect for traveling. Additionally, Alt-Az doesn't require polar alignment so it can be snappier to set up.
7 months 1 day ago #60034

Please Log in or Create an account to join the conversation.

  • Posts: 82
  • Thank you received: 5

Replied by Dirk Tetzlaff on topic Alt-Az mode for EQmod

@geehalel: I can´t stress enough how thankful I am for your help and efforts !
Just posted within the astroberry section of this forum to Kaczorek, the maker of astroberry. Maybe he has some idea, what the problem is.
What makes me curious is, that the compilation of the official branch of libindi did work, apparently. At least I got a working libindi afterwards. Did I understand you correctly, that it is your assumption that the compilation of libindi does not work on the astroberry ? I have the feeling that I missed something, anybody more knowledgeable with linux would automatically do.
7 months 1 day ago #60042

Please Log in or Create an account to join the conversation.

  • Posts: 15
  • Thank you received: 1
"I don't know when does field rotation appear in altaz mode, but plate solving may also fail in altaz mode for that reason, even with a perfect smooth tracking. Or am I wrong ?"

Field rotation would not disturb pictures with an exposure so short as I was describing above (10-15 seconds)
7 months 1 day ago #60044

Please Log in or Create an account to join the conversation.

  • Posts: 226
  • Thank you received: 88

Replied by geehalel on topic Alt-Az mode for EQmod

I've played a little yesterday evening with the skywatcherAltAzMount driver. I've used the AZEQ5, 150/750 scope with a DMK41 and a 50/206 guider with a ASI120mm. Nothing aligned. Capture/solve/slew to target works great with the ASI120@206 in 4/5 iterations, but strangely with DMK41@750 it solves but does not slew at all. I suspect a problem with V4l2 devices as the laptop also has a webcam. Sync is not working, there were 3 sync points that I tried to delete, but then tracking became weird. Looking at the code, Sync is only allowed when the mount is parked. I made some images of Dumbbell @10, 30, 60 and 120 seconds to observe star drift/rotation. A silly question, I wonder if the field rotation axis is always centered with the sensor center, or is actually the scope axis. By the way I also noticed regular jumps as depicted by @Federico. I suspect the Aux encoders which are not disabled on AZEQ, and/or the tracking algorithm which updates its data every minute. Lastly I tested guiding, when calibration succeeds (I suppose RA/Az axis does not move enough at ~50° altitude using standard guiding rates), those jumps disturbed the algorithm too much (added to field rotation as the guide star was selected on an edge of the image). Guiding in AltAz mode is quite silly, however the guide tool shows the drifting graph (see the jump @45s) and almost every points are in the upper right corner (field rotation presumably, I did not make the calculations). I may use that to test Alt/Az tracking, selecting a centered star as guide star.
Thus I've learned a little more, and your posts also help me to understand what were your concerns and what you would need. As I understand it, alignment is not primordial as long as Capture/Solve/Slew is working, guiding is of no use as your setup does not have a guider, and you only really need a smooth tracking. What I have in mind as a first step is to create a new driver out of the existing indi repos, hence astroberry users may compile it without disturbing their installation. I will derive it from indi-eqmod and/or indi-skywatcherAltAzMount and then concentrate on the tracking feature. I'll keep you informed when that will be initiated and when I will need you to perform tests.
The following user(s) said Thank You: knro
6 months 4 weeks ago #60190
Attachments:

Please Log in or Create an account to join the conversation.

  • Posts: 15
  • Thank you received: 1
@geehalel thank you SO MUCH for your work. Indeed, having a driver available to track correctly to be able to plate solve as a quick sync technique would be amazing. Let me know whenever there is something to test. All my very best and again, thank you. Federico
6 months 4 weeks ago #60194

Please Log in or Create an account to join the conversation.

  • Posts: 82
  • Thank you received: 5

Replied by Dirk Tetzlaff on topic Alt-Az mode for EQmod

@geehalel: you are amazing ! Many thanks, I remain excited to test !
6 months 4 weeks ago #60198

Please Log in or Create an account to join the conversation.

  • Posts: 82
  • Thank you received: 5

Replied by Dirk Tetzlaff on topic Alt-Az mode for EQmod

@geehalel: regarding your question of the field rotation axis: I guess as long as the axis of the mount and the guide scope are parallel, the center of the rotation axis should be the center of the sensor, i.e. the distance between mount axis and guide scope axis is far too small to cause any parallax as the points projected on the sensor are at infinity. Things should become more complicated, once both axes are not (perfectly) aligned: in the extreme case of the guide scope axis being perpendicular to the mount axis, there is no more rotation, only translation. In between there should be a mix between rotation and translation, i.e. the center of rotation is moved away from the center of the sensor. My understanding is, that the deviation introduced by such misalignment is what is coined "cone error". Maybe you find some hints in the logic regarding cone error correction to model this; there should also be some literature where this is being described / worked out.
Does this makes sense ?
6 months 4 weeks ago #60204

Please Log in or Create an account to join the conversation.

  • Posts: 82
  • Thank you received: 5

Replied by Dirk Tetzlaff on topic Alt-Az mode for EQmod

on second thought: as long as both axes are not perfectly aligned, the center of rotation moves rapidly away from the center of the sensor: let´s assume we have a 1.5 degree fov with our guide scope. If the alignment error between mount and guide scope axis is more than 0.75 degrees, the center of rotation is already off the sensor. I think you can calculate the center of rotation by calculating the fov of your guide scope / sensor combination and substract the deviation angle of the scope axis and mount axis in degrees. How many pixels this equates to, you can derive from the fov calculation. The direction of the deviation should be the opposite of the axis deviation in relation to the sensor orientation.
This is without guarantee. Just my understanding.
6 months 4 weeks ago #60205

Please Log in or Create an account to join the conversation.

  • Posts: 82
  • Thank you received: 5

Replied by Dirk Tetzlaff on topic Alt-Az mode for EQmod

on a third thought: I probably should have rather asked you, what you are aiming at. With my hints above, I was in "equatorial mode". In Alt-Az there is no rotational axis of the rig itself. If you want to derotate the exposures made on an alt-az mount, I think the way to go is by star pattern alignment, i.e. agnostic of any mechanical rotation calculation.
6 months 4 weeks ago #60208

Please Log in or Create an account to join the conversation.

  • Posts: 15
  • Thank you received: 1
Dear @geehalel, @knro et all,
Here's a picture I did yesterday using Stellarmate with my AZ-GTI working in ALT-AZ, Nikon D5100, and SkyWatcher 127 MAK, just one exposure of 30 seconds:

I used Synscan driver - just launched Synscan Pro app, did a one-star alignment with a star nearby the Orion nebulae, then goto Orion nebulae and alignment using Stellarmate astrometry.
Look how well defined the stars are, given that this is a somewhat long exposure and that it was in ALT-AZ, and that I only have done a one-star alignment.
I think if I repeat and align over 3 or 4 nearby stars before goto Orion, I could probably get even more dot-like stars and definition at even longer exposure times.
Of course, this opens the door wide-open to shorter exposure astrophotography, I did 10-second exposures, and then the stars were perfect dots.
This speaks volumes about how awesome the AZ-GTI is (especially given its price). This quality might not be enough for professional astrophotography (I think it might, if perfected a little) but it definitely is enough for EAA!
If only the AZ-GTI driver could do the same the Synscan Pro app do, then we would not need that app as an intermediary and we could start even faster: just turn on AZ-GTI, do alignment-sync using astrometry, boom, ready to start working.
Let me know your thoughts,
All best,
Federico
Last edit: 5 months 1 day ago by federicoparrasilva.
5 months 2 days ago #62893
Attachments:

Please Log in or Create an account to join the conversation.

Time to create page: 0.742 seconds