plate solve with folder camera - extract RA DEC from fits

[dmccallie]

Hi Robin,

Perhaps I missed any discussion of this, but in teaching my fellow club members how to use SharpCap (for live-stacking at our pubic observatory nights) I often send them a batch of previously captured FITS files (captured with SharpCap of course.) They can practice live-stacking and learn how to manage the histogram, using the "folder camera" - a wonderful capability.

But when using the folder camera, a "plate solve" always seems to revert to a (slow) full-sky (blind) solve, since the user is not connected to an active telescope. However, I believe that the FITS files contain the RA and DEC of the image, at least as detected at the time they were saved by SharpCap (assuming that it was connected to a scope at that time.)

Would it make sense (and be possible) to parse out the RA and DEC from the FITS header when using the folder camera (without a connected mount) and trying a plate-solve? This might also help us fine-tune the plate-solve parameters, for those images that fail to solve. (We use ASTAP.)

BTW, I notice that the ASTAP configuration now allows for additional command line parameters, but I can't find the documentation for this new feature. Can you point me to instructions on how to use it?

Thanks!

David McCallie
Astro Society of Kansas City / Powell Observatory

[admin]

Hi David,

actually I added that feature about a month ago - it applies when the 'whole sky' plate solving is in use, and it will use the RA/Dec co-ordinates from the FITS file as the starting point for the search, which usually speeds up the process a lot. It prefers to read the 'RA' and 'DEC' headers if they are present, since they are just numbers and easy to interpret, but it will try to read OBJCTRA and OBJCTDEC if necessary.

If you are using Astrotortilla/Ansvr/ASPS then this should speed up the search. It should also help with Astap as long as Astap has already worked out and stored the size of your field of view (ie you have had a successful solve already at that field of view).

The other approach to this problem is to set up SharpCap to talk to the ASCOM simulator mount (Telescope Simulator .NET). You then use the controls to 'slew' that mount to approximately the co-ordinates of your image, at which point you can use the plate solve + sync functionality which will do the quicker, 15 degree radius search.

cheers,

Robin

[admin]

Ooops, sorry, Astap command line parameters - you can add any of the parameters listed here :

https://www.hnsky.org/astap.htm#astap_command_line

SharpCap does add its own parameters, and will use its own values for -ra, -spd, -fov and -r even if you put those in the custom parameter options.

thanks,

Robin

[dmccallie]

Good!
It turns out my version 4 was out of date, so I was missing your recent additions.

Now it works, and greatly speeds up ASTAP plate-solve on "camera folder" images.

BTW, the "check for updates" menu option is misleading in that it told me there were no new automatic updates.
In fairness, it did warn me that I should also check the download site, but I had not done that.

--david

[admin]

Hi David,

check for updates is usually between 4 and 12 weeks behind what you find on the download site - I only put a new version on for auto update after it has been in use for a few weeks to make sure there are no serious new bugs in it.

Glad that the plate solving is now working well

cheers,

Robin