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Failed to plate solve the Orion Nebula heart at long FL

ZWO ASIAIR Plus Plate Solving M42 Messier Objects Emission Nebula
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Rostokko avatar
Rostokko avatar
This past night one of the steps in my plan was unable to plate solve (goto) a framing of the Orion Nebula core.
It was an attempt at capturing the core at 1450mm FL; I understand the underlying challenges in plate solving that. But this is the first subject which failed so consistently, no matter the exposure time I tried, or the plate solving algorithm (the traditional or the "new" one). Other closeups like the Horsehead or Cone nebulae worked perfectly fine.
For the record, I was shooting Ha NB, with a 294mm.
I happened to wake up and check on the plan execution just in that timeframe, and I could see the framing was quite close to the intended target, and there were indeed only a few visible stars in the auto-stretched image; the bright Orion core was, well, very bright… As mentioned, I did try a few different combinations, but nothing helped. Eventually I reverted to a different target and let that modified plan go.
I suppose the main problem here is how bright the core of the subject is in conjunction with the limited field of view. Short of using the wider FOV of a guidescope for doing just plate solving during goto, or just giving up on a long FL closeup of Orion, do you have any other suggestions?
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Stephen Jones avatar
Stephen Jones avatar
GDay  I  could not plate solve my SW250 PDS, OAG-L, 174 mm guide scope and 2600 mono.   Its 1200mm but with the paracorr its 1380mm.  Had me stumped.  Easy solution with no problems now… was to set the main scope to 0 guide scope set to 1380mm (as iIm using an OAG )and let the Asiair  work out your main scope.  May work for you as well
Rostokko avatar
Rostokko avatar
Stephen Jones:
GDay  I  could not plate solve my SW250 PDS, OAG-L, 174 mm guide scope and 2600 mono.   Its 1200mm but with the paracorr its 1380mm.  Had me stumped.  Easy solution with no problems now... was to set the main scope to 0 guide scope set to 1380mm (as iIm using an OAG )and let the Asiair  work out your main scope.  May work for you as well

So you basically used the 174mm through the OAG to plate solve, right? I suppose that may work if the guide camera is lucky enough to capture a few good/key stars. Worth a try.
Thanks!
Stephen Jones avatar
Stephen Jones avatar
The Asiair will work if you enter a zero for your main.  It does require the guide scope mm to be entered.  You can do it at start up or whilst everything is up and running.  I just enter a zero and even without a polar alignment send to a decent star and it will configure it self.  After I sent it to a star and hit the solve button to sync the mount, I ha
ve even entered zero again for a test, and it did a polar align without a problem.  The Asiair just works it out.  Great piece of gear to play with.
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Rostokko avatar
Rostokko avatar
To "close" the loop on this.
The method proposed by @Stephen Jones didn't work for me; it still failed to platesolve.
So, I proceeded with a plan I devised yesterday:
  • I added the 60/240mm guidescope to my C8/OAG setup, not for guiding but for plate solving M42 (I typically use that guidescope only in the Hyperstar configuration)
  • I already had a set of "Mac-based" macros (Keyboard Maestro) which manage shooting a few heavily "tree constrained" targets in these nights (M42, Horsehead and Cone - I have about one hour for each of them, a bit more for Cone which is higher).
    • The macros run on a Mac where the AsiAir app is open; they basically deal with stopping and starting AsiAir plans at very specific times by simulating mouse and keyboard interactions. AsiAir itself doesn't offer the ability to deal with precise time-based plan start times (I know, I know - I should move to nina; but I won't, at least for the time being).
  • I modified the "M42" macro to actually stop the running plan, switch the main camera to the guidescope, goto m42, switch back to the actual imaging camera and start Autorun (because unfortunately AsiAir's plans ignore your "don't auto-center" setting and try to auto-center/platesolve anyway; Autorun doesn't care)
  • I also had to disable the automatic focusing procedure to not start at the beginning of Autorun - because that too doesn't work well with that bright target, and manually turn on guiding (because Autorun doesn't do that for you...)
  • That worked well, shooting 70 minutes of 120s exposures of M42
  • At the end of those 70 minutes, the next macro took over and switched to the next phase of the plan - which doesn't need messing with the guidescope, phew...

It did take some careful testing/simulation yesterday evening before starting the first part of the nightly plan, but it did work well for me. Now it needs to do that for quite a few more clear nights before I have enough signal across at least Ha and Oiii to work with.
I posted this just because I expect that a similar approach, maybe targeted at solving different challenges, is a useful tool to have in your pockets.
Stephen Jones avatar
Stephen Jones avatar
Good to see you arrived at a solution…not the easiest but at least you can image.