Hi Robin,
In the last release (6.2.2) of DeepSkyStacker I added support for using the WCS information from the FITS headers for determining offsets and rotation for image stacking.
I recently had a report of images created by Sharpcap where the WCS information in the headers resulted in mis-registration of the stacked images.
Disabling the use of the WCS data in DSS resulted in the images being registered and stacked correctly.
SharpCap v4.1.14310.0
WCS information in FITS headers
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*** Please do not post license keys - please report any problems with licensing to 'admin' by private message ***
Please include the following details in any bug report:
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[If SharpCap crashes, please send the bug report when prompted instead of including the log]
WCS information in FITS headers
Clear skies, David
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Re: WCS information in FITS headers
Hi David,
oooh, this is a can of worms... I did a lot of work on this a while back as I had had reports of similar issues. My initial plan was to check the information created by other plate solving engines like Astap and Astrotortilla and then make sure SharpCap matched those. That didn't work out because they didn't all agree (part of which came down to not always agreeing about which way is positive in image pixel space, particularly for the Y direction).
So, one part of the problem is that it may depend on what plate solving engine has been selected by the user in SharpCap.
On another tack, you are mentioning that DSS is using this for registration purposes... In what sense are you using this data? For offsets/rotations between frames? That would definitely be a problem because SharpCap is not necessarily writing the plate solving info for a specific frame into the headers, it is writing the most recent plate solving info it has. That means that the data is likely to be the same from frame to frame during a capture, even if the view is drifting - unless the user plate solves manually at some point during the capture process, which would bring the 'latest' data right up to date.
cheers,
Robin
oooh, this is a can of worms... I did a lot of work on this a while back as I had had reports of similar issues. My initial plan was to check the information created by other plate solving engines like Astap and Astrotortilla and then make sure SharpCap matched those. That didn't work out because they didn't all agree (part of which came down to not always agreeing about which way is positive in image pixel space, particularly for the Y direction).
So, one part of the problem is that it may depend on what plate solving engine has been selected by the user in SharpCap.
On another tack, you are mentioning that DSS is using this for registration purposes... In what sense are you using this data? For offsets/rotations between frames? That would definitely be a problem because SharpCap is not necessarily writing the plate solving info for a specific frame into the headers, it is writing the most recent plate solving info it has. That means that the data is likely to be the same from frame to frame during a capture, even if the view is drifting - unless the user plate solves manually at some point during the capture process, which would bring the 'latest' data right up to date.
cheers,
Robin
Re: WCS information in FITS headers
Oh dear - DeepSkyStacker makes the (not unreasonable IMHO) assumption that the capture software is plate solving every frame. If even one light frame in an image set lacks WCS data, then DeepSkyStacker falls back to registering frames the "hard way".
If you aren't plate-solving every frame, but instead are inserting the WCS data for the first image in a set (for example) into all light frames, than that has to be a bug (doesn't it?).
Is there any way to force Sharpcap to plate-solve every light frame?
David
If you aren't plate-solving every frame, but instead are inserting the WCS data for the first image in a set (for example) into all light frames, than that has to be a bug (doesn't it?).
Is there any way to force Sharpcap to plate-solve every light frame?
David
Clear skies, David