SharpCap and All Sky Plate Solver

[Menno555]

For plate solving I use All Sky Plate Solver (ASPS) in SharpCap and that works great and very fast.

But there is something that I don't understand: when I use SC to plate solve a individual FITS, using the Folder Camera, that plate solving works fine.
But when I use ASPS directly, that same FITS can not be solved, there is no solution? I use the same focal length that I did put into SC, the same astrometry is used, and so on.
So how come that the combi SC/ASPS does work but only ASPS not?

Menno

[admin]

Hi Menno,

check what parameters are being used in ASPS when you use it directly - you can compare these with the ones SharpCap uses, which are recorded in the SharpCap log. In particular, the sigma parameter which determines star detection may be the cause. SharpCap will also read the RA/Dec co-ordinates in a FITS file when using the folder monitor camera and use those as the starting point for the search when plate solving, which may be helping.

cheers,

Robin

[Menno555]

Hi Robin

It's no biggie. It's just curious that ASPS itself will not solve any FITS I give it. Yet that same FITS will solve fine and fast in SC and also solves very fast on astrometry.net. And to make it weirder: when I make a JPG of that FITS, then ASPS just solves fine. Go figure.
And as I understand it, SC will save a plate solve first as PNG and then ASPS will solve it, right?
Ah well, no matter. It works in SC and that's the main thing

Menno

[admin]

Hi,

SharpCap definitely does convert to PNG, maybe it is the conversion to 8 bit that is helping - in some cases throwing away the fine detail in pixel values can help star detection...

cheers,

Robin

[BucketDave]

I'm having a problem getting SharpCap to plate-solve at all.

As my starting point, I've taken some CR2 images from my Canon 1100d DSLR and converted them to 8 bit JPG files using RawTherapee. The images are :
1) M51, taken through an 8" ACF (FL~2032mm)
2) NGC6888, taken through an 8" ACF (FL~2032mm)
3) M86, taken through a 300mm camera lens
4) NGC7000, taken through a 300mm camera lens

All four solve using ASPS and defining the nominal focal length and pixel size (5.19um)
However, almost none of the images will solve when I import them into SharpCap. Those that do have "do not use FL" selected in the settings.

1) M51, 14s in ASPS, 60s in SC
2) NGC6888, 44s in ASPS, FAILED in SC (in this context, FAILED means > 4 minutes)
3) M86, 12s in ASPS, 16s in SC
4) NGC7000, 24s in ASPS, FAILED in SC

So starting with the same image, SharpCap always takes longer to reach the solution than ASPS (if it gets there at all). Now ASPS knows the approximate focal length and pixel size whereas SC knows nothing except what may be embedded in the image file.

Defining FL in SC doesn't seem to be helping.

Now, my images were taken without my mini-PC being connected to the mount, so the images contain no information on approximate RA or DEC (current mount is a Star Adventurer). Surely it would help SharpCap if, in the plate-solver settings, we users could also input the approximate RA and DEC of the image (and an error margin)? This might speed things up for users who aren't using computer controlled mounts.

Regards

Dave Cundy

[admin]

Hi Dave,

essentially the main use of plate solving in SharpCap is to reposition the mount in one way or another to get the right target in view. The case for plate solving image files is much less obvious, since even if you do get correct plate solve information on a loaded image file, what do you then do with that information in SharpCap? Not much except in the 'Goto Image' functionality.

That being said, if the loaded image file is in FITS format and contains RA/Dec co-ordinate info then SharpCap will pass that info onto the plate solving engine as a location hint, which is kind of what you are talking about.

cheers,

Robin