Plate solving for Camera Orientation

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oopfan
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Plate solving for Camera Orientation

Post by oopfan » Wed Nov 01, 2017 5:45 pm

Robin,

The other day I contacted Mr. Philippe Deverchère, the author of C2A, with two questions. The first he answered in great detail and I am thankful. The second he did not offer a reply so I am guessing that C2A is not yet capable of it.

I've attached a screenshot of a 4-frame mosaic of the Horsehead and Flame Nebulae that I am composing in C2A. Notice that each of the four frames contains a red-colored cross at the center. Also know that each frame is rotated 106 degrees.

From my experience with plate solving using SharpCap and C2A with ASCOM as the glue, I can initiate a plate solve at any time and within 30 seconds a "Field Marker" in C2A will position itself to show exactly where my scope is pointing. My plan is to make small changes to my slow motion controls and redo plate solving until the Field Marker is at the center of the mosaic frame that I wish to image that night.

The problem (if you want to call it that) is that I need to tell C2A what the camera orientation is by modifying the Field Marker definition. Fortunately I wrote some IronPython code to use the star drift method to obtain that. But with my experience using nova.astrometry.net I know that the plate solver can figure out the camera orientation by inspecting the star field, so in an ideal world I don't need my IronPython code.

It would be really nice if SharpCap could send the camera orientation angle to C2A via ASCOM. I don't know if the ASCOM protocol has a named field or property for it or if not perhaps there is an auxiliary field that could be used. And of course this would require a code modification on the C2A-side.

I thought I would plant that idea for some future version of SharpCap.

Thanks,
Brian

PS: I attached another image: an APOD from AstroBin from a few years ago by Stefan Muckenhuber. I cropped it down to the dimensions and orientation of my mosaic. What do you think? I think I might rotate it by 10 degrees clockwise. Sorry for the weird angle -- I am using Windows Paint that only allows rotation of an image by increments of 90 degrees so you need to tilt your head.
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Horsehead plan.jpg
Horsehead plan.jpg (135.79 KiB) Viewed 61 times
Horsehead envisioned.jpg
Horsehead envisioned.jpg (103.37 KiB) Viewed 61 times

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admin
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Re: Plate solving for Camera Orientation

Post by admin » Wed Nov 01, 2017 6:45 pm

Very interesting :D

I was expecting this info to be in the output of the astrometry.net engine (the solve-field script), which goes straight into the SharpCap log, but it turns out that isn't the case :(

So it turns out that we have two problems here

1) how to get the info - I presume that the plate solve must work it out, but not sure how it can be made to output it
2) the fact that there is no ASCOM way to specify rotation of the camera (this might mean that even at best there would need to be a manual step of copying the value from one app to the other).

Anyway, it might be worth you having a look at the command line params to solve-field to see if you can work out how to get the orientation - if you can get that sorted and it is compatible with what SharpCap already does I'd be happy to add the info to the log.

cheers,

Robin

ps. current solve-field output from SharpCap log

Code: Select all

Extracting sources...
simplexy: found 360 sources.
Solving...
Reading file "/tmp/796090b3-5e57-4864-a14f-d101beec2909/frame.axy"...
Field 1 did not solve (index index-4219.fits, field objects 1-10).
Field 1 did not solve (index index-4218.fits, field objects 1-10).
Field 1 did not solve (index index-4217.fits, field objects 1-10).
Field 1 did not solve (index index-4216.fits, field objects 1-10).
Field 1 did not solve (index index-4215.fits, field objects 1-10).
Field 1 did not solve (index index-4214.fits, field objects 1-10).
Field 1 did not solve (index index-4213.fits, field objects 1-10).
Field 1 did not solve (index index-4212.fits, field objects 1-10).
Field 1 did not solve (index index-4211.fits, field objects 1-10).
Field 1 did not solve (index index-4210.fits, field objects 1-10).
Field 1 did not solve (index index-4209.fits, field objects 1-10).
Field 1 did not solve (index index-4208.fits, field objects 1-10).
Field 1 did not solve (index index-4207-11.fits, field objects 1-10).
Field 1 did not solve (index index-4207-10.fits, field objects 1-10).
Field 1 did not solve (index index-4207-09.fits, field objects 1-10).
Field 1 did not solve (index index-4207-08.fits, field objects 1-10).
Field 1 did not solve (index index-4207-07.fits, field objects 1-10).
Field 1 did not solve (index index-4207-06.fits, field objects 1-10).
Field 1 did not solve (index index-4207-05.fits, field objects 1-10).
Field 1 did not solve (index index-4207-04.fits, field objects 1-10).
Field 1 did not solve (index index-4207-03.fits, field objects 1-10).
Field 1 did not solve (index index-4207-02.fits, field objects 1-10).
Field 1 did not solve (index index-4207-01.fits, field objects 1-10).
Field 1 did not solve (index index-4207-00.fits, field objects 1-10).
Field 1 did not solve (index index-4219.fits, field objects 11-20).
Field 1 did not solve (index index-4218.fits, field objects 11-20).
Field 1 did not solve (index index-4217.fits, field objects 11-20).
Field 1 did not solve (index index-4216.fits, field objects 11-20).
Field 1 did not solve (index index-4215.fits, field objects 11-20).
Field 1 did not solve (index index-4214.fits, field objects 11-20).
Field 1 did not solve (index index-4213.fits, field objects 11-20).
Field 1 did not solve (index index-4212.fits, field objects 11-20).
Field 1 did not solve (index index-4211.fits, field objects 11-20).
Field 1 did not solve (index index-4210.fits, field objects 11-20).
Field 1 did not solve (index index-4209.fits, field objects 11-20).
Field 1 did not solve (index index-4208.fits, field objects 11-20).
Field 1 did not solve (index index-4207-11.fits, field objects 11-20).
Field 1 did not solve (index index-4207-10.fits, field objects 11-20).
Field 1 did not solve (index index-4207-09.fits, field objects 11-20).
Field 1 did not solve (index index-4207-08.fits, field objects 11-20).
Field 1 did not solve (index index-4207-07.fits, field objects 11-20).
Field 1 did not solve (index index-4207-06.fits, field objects 11-20).
  log-odds ratio 167.339 (4.72476e+72), 64 match, 2 conflict, 28 distractors, 133 index.
  RA,Dec = (83.8356,-5.307), pixel scale 4.29314 arcsec/pix.
  Hit/miss: +++++++++++-+++++-++++-++-++----++++---+++++++-+-++++--+c++---+++++++-+---+-+++++--c-+++++--++(best)-c++++
Field 1: solved with index index-4207-05.fits.
Field 1 solved: writing to file /tmp/796090b3-5e57-4864-a14f-d101beec2909/frame.solved to indicate this.
Field: /tmp/796090b3-5e57-4864-a14f-d101beec2909/frame.png
Field center: (RA,Dec) = (83.84, -5.309) deg.
Field center: (RA H:M:S, Dec D:M:S) = (05:35:20.575, -05:18:32.716).
Field size: 1.55142 x 1.13939 degrees


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