Jump to content


Photo

New Pyxis for Altazimuth imaging

  • Please log in to reply
11 replies to this topic

#1 Markigno

Markigno

    Messenger

  • -----
  • Posts: 431
  • Joined: 09 Jan 2010

Posted 30 August 2011 - 11:31 AM

Hy everyone, someone in another post, asked how work the pyxis as derotator field and I noticed that many people not have clear ideas about this topic. are many, many months that I'm testing a new Optec control software for the Pyxis, a camera rotor which can also work as derotator Field, and tonight I finished the last test with results amazing. This software automatically controls the step rate to apply to the derotation pyxis, drawing the necessary data for calculating, directly from the telescope, all in real time. This allows monitoring precise of the derotation of field, that allows you to take very precise images, even with very long exposure, practically free from residual derotation. The instrumentation used is composed, according to the optical train:
LX200R 12 "> Pyxis 3"> APCCD.67> AO-7> CFW8A> ST2000XM.
This configuration is useful to reach a height of 76 °, which is very respectable if considers to the impassable limit of 80 ° in height altazimuth for photography. But back to the last test tonight. The test consisted in taking an automatic sequence of 60 frames of 1 minute each in order to calculate any possible angular change between frames. The test has a logical log.file who monitored the behavior of the Pyxis during the session. I pointed the telescope to NGC7160 that in the moment starting test had a height of 61 ° or so, I activated derotator and chosen a guide star in the AO-7, calibrated and turned on all the autosequence shooting. After the first image, I have changed some parameters to guide and immediately everything worked great. I downloaded 60 images of 1 minute each and between the first and last frames, the derotation field is virtually absent and the height of NGC7160 was 71 ° when I finished the test. The Pyxis has worked better than a Swiss watch, really amazing.
I should point out that my collaboration with Optec, in the development of this project is totally free from profit of any kind. My participation was and is dictated only by the immense love I have for this wonderful hobby, Especially for astroimaging altazimuth. I try to insert a small animated gif (if the server allows it!) Comprises the second and last frame of the test, therefore 59 minutes of difference between the two frames. The frames are completely raw, so no dark, flat, without any processing, just like Mom ST2000 has pulled out.
Currently the software is not available yet (still need to finish their latest test), but I think it will soon be made available to all and I'm sure that this will be a great package for photography altazimuth.
Marco

Attached Files



#2 Kim Miau

Kim Miau

    Apollo

  • -----
  • Posts: 1264
  • Joined: 17 Jul 2006
  • Loc: Malaysia

Posted 31 August 2011 - 11:49 AM

Great! Could you show us a single long exposure as well? I wonder if there is any variation in between. Nevertheless, the result you've shown us proved the capability of what the Pyxis Rotator can do for derotating images. Thanks for your effort put into developing the algorithm.

#3 Markigno

Markigno

    Messenger

  • -----
  • Posts: 431
  • Joined: 09 Jan 2010

Posted 31 August 2011 - 07:49 PM

Hi Robin, pyxis has behaved very well throughout the duration of the test and was very constant. I already posted in another topic, an image with single shot from 10 minutes. I would try a single shot for 60 minutes, but my problem is light pollution. I live in downtown and not know what would come out with 60 minutes in luminance. it is true that I could use a filter, but to get a good result with an LX200 is crucial use adaptive optics least with 2 or 3 Hz, and with a filter in the middle, these guide rates are prohibitive. I would like to specify that algorithm and the software has been designed and developed entirely by Jordan of Optec, I did only the various tests in the field, discussing with him the various results so that he could make any changes to the software and then wich type next test to be performed.
Marco

#4 WadeH237

WadeH237

    Apollo

  • -----
  • Posts: 1358
  • Joined: 24 Feb 2007
  • Loc: Snohomish, WA

Posted 01 September 2011 - 09:58 AM

You could take a series of 10 minute exposures and then stack them without first registering them. For the purpose of tracking and rotation evaluation, this would accurately simulate a single, long exposure. I sometimes do this to evaluate flexure in my system, and it would be interesting to see here.

There's no reason to believe that derotating can't work very well. Many (most?) large "professional" observatories have been doing it for a long time because it can be impractical to equatorially mount a very large scope.

I have known of a few attempts to do this with amateur alt-az scopes, including a (non-successful) commercial product by Meade and at least one amateur attempt using a Pyxis. But for some reason, it's never caught on.

-Wade

#5 Markigno

Markigno

    Messenger

  • -----
  • Posts: 431
  • Joined: 09 Jan 2010

Posted 02 September 2011 - 03:52 AM

You could take a series of 10 minute exposures and then stack them without first registering them.

-Wade

Hi, I attack a screen shot with 60 frames stacked and combined without alignment. This has the same value of what you suggested
Marco

Attached Files



#6 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9162
  • Joined: 11 Sep 2006
  • Loc: Bolton, MA

Posted 02 September 2011 - 06:02 AM

I do not see much rotation there, how long were your individual subs?

#7 Markigno

Markigno

    Messenger

  • -----
  • Posts: 431
  • Joined: 09 Jan 2010

Posted 02 September 2011 - 08:43 AM

Hi Dave this are the 60 frames by 1 minute taken during test. In the screen shot posted, I combined all frames without alignment, so, if there was derotation between frames, this would be evident in the final image. I attach a screen shot of the first test I did few months ago, when the software no work very good. Here I took only 4 frames to 2 minute each. The small frame is the first in the stack (the reference) where you can already see a slight field derotation. The big image is the final combination of frames without alignment (total time 8 minutes). Here the derotation of field is very strong because it is also recorded derotation between frames. I hope I have explained well the concept .
Marco

Attached Files



#8 Gary Honis

Gary Honis

    Vendor-DSLR Mods

  • -----
  • Vendors
  • Posts: 545
  • Joined: 15 Dec 2004

Posted 09 September 2011 - 09:57 AM

Hi Marco,

Thanks for your efforts on the Pyxis unit as a derotator for Alt-Az imaging. I tested the Pyxis last year on my 20" Starmaster GOTO dob and found some field rotation was not corrected. Test results including youtube videos are posted here:

http://garyhonis.com...erPyxisMod.html

Maybe the problem I experienced was because of the Pyxis software as you found a few months ago. Are you using the original version of the Pyxis or the new "LE" version of the Pyxis? Do you know if the updated software will become available for both models of the Pyxis? When I checked the Optec web site, the "LE" version doesn't seem to have a derotator function.

#9 Markigno

Markigno

    Messenger

  • -----
  • Posts: 431
  • Joined: 09 Jan 2010

Posted 09 September 2011 - 12:35 PM

Hi Gary, I have already read, a few months ago, your very interesting report on the pyxis that you have published. The problem of derotation residual, that you highlighted in your test, is due to an uncertain operation of version 1.33. In this version you must insert your site, time, time zone, coordinates guide star etc . Therefore the software performs all the corrections basing calculations only on the initial data, "hypothesizing", where the telescope is pointed. Is there even something wrong with the old software because, for example, to run my Pyxis 3" correctly I had to enter false data, in way to obtain a height greater than 10° from the true position of the guide star in the sky. This new software, contrariwise, takes all the data from the telescope in real time, so he knows exactly where is the telescope really, at all times.
I do not know if this software will be available for the LE version. For this you should send an email to Jeff.
Marco

#10 Gary Honis

Gary Honis

    Vendor-DSLR Mods

  • -----
  • Vendors
  • Posts: 545
  • Joined: 15 Dec 2004

Posted 10 September 2011 - 08:55 AM

Thanks Marco,

I sent an email to Jeff about the new "LE" version as suggested. I was looking into the Orion SteadyStar derotator but was scared off by reports here of its mechanical quality.

#11 Jeff Dickerman

Jeff Dickerman

    Vendor - Optec, Inc.

  • -----
  • Vendors
  • Posts: 5
  • Joined: 17 Nov 2009
  • Loc: Lowell, Michigan, USA

Posted 10 September 2011 - 09:46 AM

Hi Gary,

I will reply to your email privately but I did want to help clarify a few points. First, the new software was developed and refined in collaboration with Marco. His efforts and reports have been exceptional. Jordan was tasked with developing a better approach to de-rotation at the amateur level. To accomplish this we looked closely at the professional observatories, but most of their solutions are "one off".

That is, the pros have full control and knowledge of their alt-az mount capability, adaptive optics, camera and field de-rotator and could therefore develop a specific de-rotation software for their observatory. The spherical geometry problem is very well understood so our task was to develop a de-rotation software solution that can be applied to any alt-az mount, the Pyxis rotator family, and any camera with or without an AO unit attached. As Marco has mentioned above, the AO unit will correct for many of the mechanical sins of the mount. Perhaps we'll know with further testing whether or not AO will be required for most commercial mounts. For his testing Marco was using the highest resolution Pyxis 3" with a new firmware version allowing sub-degree moves.

Our new approach takes advantage of the ASCOM platform version 6 and the ability to simply poll the telescope driver for current altitude and azimuth as well as polling current sidereal time, telescope location and elevation - all keys to successful de-rotation rate calculation.

Jordan's solution works as an ASCOM local server for both mount and rotator control. Once configured de-rotation takes place automatically upon completion of a slew making this step semi-transparent to the end user. Slew to your object and the Pyxis immediately begins de-rotating at the proper rate.

We will be posting more information on the Optec website next week with screenshots and additional details. We're pretty excited that this new solution will make longer exposure imaging with large alt-az dobs easier that ever.


Jeff Dickerman
Optec, Inc.

#12 Steven Aggas

Steven Aggas

    Viking 1

  • -----
  • Posts: 836
  • Joined: 15 Apr 2008
  • Loc: Arizona

Posted 10 August 2012 - 12:46 PM

...Our new approach takes advantage of the ASCOM platform version 6 and the ability to simply poll the telescope driver for current altitude and azimuth as well as polling current sidereal time, telescope location and elevation - all keys to successful de-rotation rate calculation.

Jordan's solution works as an ASCOM local server for both mount and rotator control. Once configured de-rotation takes place automatically upon completion of a slew making this step semi-transparent to the end user. Slew to your object and the Pyxis immediately begins de-rotating at the proper rate.

We will be posting more information on the Optec website next week with screenshots and additional details. We're pretty excited that this new solution will make longer exposure imaging with large alt-az dobs easier that ever.


Jeff Dickerman
Optec, Inc.


Hi Jeff, is this incorporated into the LE version when using ServoCAT/Argo Navis/TheSky6, "semi-transparent to the end user. Slew to your object and the Pyxis immediately begins de-rotating at the proper rate"?

Thanks, Steven






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics