SharpCap 3.1.4477 Blind Plate Solve bug

[oopfan]

Robin,

On my slow laptop, SharpCap appears to give up after only 1 minute of trying to solve the attached star field: "M27 Plate Solve.png". If I manually invoke ASPS it takes a whopping 6 minutes to solve but it does get it right.

I acquired that image July 15, 2017 with my ASI120MC using RGB24, Gain 100, and Exposure 1 sec. (This is what I typically do after I slew to the target with my Setting Circles.) Normally I submit the image to nova.astrometry.net if I have an internet connection; if not then I use ASPS locally. As you can see there is well over a dozen stars.

I "injected" that image into SharpCap by copying the file to "C:\Program Files {x86)\SharpCap 3.1\Sample Files". I renamed it to "m42_dim.png" and then launched SharpCap and selected "Test Camera 1 (Deep Sky)". My image came up in the preview window (a good thing.) I clicked Tools -> Plate Solve. Here is the abbreviated output on the progress bar:

simplexy: found 5 sources.
Field 1 did not solve.
(about 1 minute later:) Plate Solve failed due to All Sky Plate Solver did not find a solution.

Like I mentioned, if I invoke ASPS manually it will solve it but it takes 6 minutes. (If it matters to SharpCap the image is flipped vertically with South up.)

Thanks,
Brian

PS: The forum would not accept the 500kB image file, so I converted it to JPEG.

[oopfan]

For comparison, here is an image file that SharpCap solved quickly. It is a 2-minute subframe of NGC 7331. It is good that it solved it but I don't want to have to wait two minutes in between plate solves when centering the image. I ought to be able to get a quick solution with a dozen stars with a 1 second exposure.

Is it possible to make the blind plate solver less blind by asking the user to give approximate RA and DEC? Of course he could leave those fields empty.

Thanks.

[admin]

Ok, I think the issue here isn't the not knowing the RA/Dec, more likely it's using different options for the star detection, in particular the '--sigma' option. That will lead to (for instance) the plate solver finding less (or more) stars when used from SharpCap which impacts on solve time and final output.

I think the way ahead here is

1) Something in the settings to allow you to specify the plate solve options - mostly the --sigma value
2) A way to turn off the re-goto after the plate solve from the mount GPS button - that would make the GPS button do the right thing for you.

To help you with your testing, these are the parameters that SharCap would use when doing a blind plate solve

Code: Select all

solve-field -b /etc/astrometry/backend.cfg  --sigma 50 -r --objs 100 --no-plots -N none -L 0.1 -H 20 -u degwidth -D <tmpFolder> <file to solve>

It would be interesting to compare those with your options that work.

cheers,

Robin

[oopfan]

Robin,

ASPS log files are next to useless. Wouldn't it be nice if ASPS printed out the command line when it called 'solve-field' -- but nooooo. And wouldn't it be nice if 'solve-field' printed out its arguments -- and the congregation shouts: nooooo!

I tried a last ditch effort to attach a debugger to the 'solve-field' process but my version of Visual Studio Express doesn't allow that -- thank you Mr. Gates. (I am glad I switched to Qt development.)

Without a proper debugger my only other option is to rebuild the 'solve-field' executable from the GitHub source after adding some debug statements.

Well there is another option: Uninstall ASPS, and install something better.

Sorry I can't be a better help.

[oopfan]

Robin,

I think that you are right about there being a difference in the value of 'sigma' The ASPS log file reported 400+ sources and SharpCap only reported 5.

[admin]

Hi,

You can see the command line parameters of a running process using ProcessExplorer (from Microsoft) - just hover over the process name in the list or look in the image tab in the properties.

cheers,

Robin

[oopfan]

This is what ProcessExplorer says is the command line for 'solve-field' as it was called by ASPS:

"C:\Users\Brian\AppData\Local\ASTROM~1\lib\astrometry\bin\solve-field.exe"

No arguments? Using all defaults? Or is the default to use a configuration file that ASPS created somewhere? I remember looking pretty carefully for such a thing. I cannot find any such artifact.

[oopfan]

Hmmm something is not right...
When I try to launch 'solve-field' from a command prompt, I get this:

Code: Select all

C:\Users\Brian\AppData\Local\Astrometry\bin>..\lib\astrometry\bin\solve-field.exe
ERROR: You didn't specify any files to process.
This program is part of the Astrometry.net suite.
For details, visit  http://astrometry.net .
Subversion URL svn+ssh://astrometry.net/svn/tags/tarball-0.38/astrometry/util/
Revision 16745, date 2010-11-19 20:47:53 +0000 (Fri, 19 Nov 2010).

Usage:   ../lib/astrometry/bin/solve-field [options]  [<image-file-1> <image-file-2> ...] [<xyls-file-1> <xyls-file-2> ...]

Perhaps ProcessExplorer isn't giving me full details. You sure I don't need to pay Mr. Gates?

[oopfan]

Found it:

Code: Select all

C:\Users\Brian\AppData\Local\ASTROM~1\bin\bash.exe --login -c "/usr/bin/solve-field -p -O -U none -B none -R none -M none -N none -C /temp/abort --crpix-center -z 2 --objs 100 -u arcsecperpix -L 1.8000 -H 2.0000 /temp/stars.fit > /temp/stars.log"

[oopfan]

Notice in that bash script above that there is no argument that specifies 'sigma'. So I am assuming that 'solve-field' will use a default but what is it? I'm slogging through the source code on GitHub. There isn't much documentation.

In the 'stars.axy' output file there is a hint: 'ESTSIGMA= 0.2333065'.
That estimated sigma is significantly below SharpCap's '--sigma 50'.

Like I said the ASPS log file says: 'simplexy: found 413 sources' whereas SharpCap finds only 5 sources.

Reading source code is not the best way to go about this. A better way would be to step through it with a debugger.

Robin, perhaps you could add a tab to SharpCap settings dialog for plate solving defaults?