Creating Master Dark and Master Flat w/NINA & Maximdl

[GaryS]

Hi

I first captured multiple Darks and Flats(for various filters, gains, etc using NINA for the capture. I then set up Maximdl to create Master Darks and Master Flats - specifically for use with Sharpcap pre-processing. After all that effort, Sharpcap did not allow me to select any of these masters for pre-processing during live-stacking.

1. Must I only use Sharpcap to create the Master Dark and Master Flat?
2. If other applications can be used to create the masters above, what format do these need to be? I previously created them as .fits files using the above procedure but these did not work.

Thank you for any assistance on this...!
Gary

[admin]

Hi Gary,

can you give a bit more detail on not being able to select the files/files not working? Did you get an error message from SharpCap when you tried to select them? Feel free to share one or more of the created FITS files (too big to upload here I suspect, but you can share via google drive/dropbox/etc).

I would usually recommend creating your master darks/flats in SharpCap rather than other software, as it should avoid this sort of problem and also means that the processing of the master files is done in a way that is known to be compatible with the later uses of those file in SharpCap. However, compatible FITS files (16, not 32 bit) made in other applications should work.

cheers,

Robin

[GaryS]

SC simple says something like it is unable to load the selected files.

My gear is 2000 miles away so I cannot make flats and darks using the SC capture process.

I’m pretty disappointed that properly-created master dark and master flats cannot be accepted by SC. If I can’t use the pre-processing feature of SC, I really can’t use SC.

Besides 16 versus 32 bit are there other specific master frame requirements? Do .png masters work better?
Thank you
Gary

[admin]

Hi Gary,

SharpCap should be able to load 16 bit data from PNG, TIFF and FITS files. It's possible that you could get a problem if the file being loaded doesn't match the resolution of the camera in use, but then you get a different message.

I haven't encountered any significant problems loading FITS files created in other applications, but FITS is very flexible as a file format, so there could be things that aren't handled well. If you do get a chance to send me one of the files that will not load then I will investigate.

thanks,

Robin

[GaryS]

HI Robin
I tried to attach one of the files that failed to work for pre-processing. The .FITS file was rejected as having an 'invalid file extension'.
Gary

[admin]

Hi Gary,

if the file is bigger than 1Mb then it might be being rejected really for the size - I have a limit on attachment size to avoid ending up with attachments that are 10s or 100s of Mb that would then need to be backed up.

The best thing with large files (or ones the forum system rejects due to extensions) is to upload them to google drive/dropbox/onedrive and then post a public sharing link here in the forums so that I (or anyone else who is interested) can download them.

cheers,

Robin

[GaryS]

Hi Robin:
I've placed two of the masters (mDark and mFlat) that would not load for pre-processing in SC .
I hope the link below will allow you to access the files. Please let me know if there's a problem getting to them.
thank you
Gary



https://drive.google.com/drive/folders/ ... sp=sharing

[admin]

Hi Gary,

thanks for sharing - a quick look at those files reveals that they have all been saved at 32 bits per pixel format, which is currently not supported for loading into SharpCap.

I'm not sure if I should add the ability to read such files to SharpCap or not - from the technical point of view, it's certainly possible, but there would be loss of detail when loading as the image would be converted to a 16 bit format. Perhaps a notification 'image automatically reduced from 32 to 16 bits' would be sufficient warning that it was not a perfect fidelity operation?

cheers,

Robin

[GaryS]

Robin,
I apologize for being late getting back to you.
As long as the reduced, 16 bit versions will calibrate the stacking images, its all great. So, I gather that the Flats and Darks that SC prepares for us are done as 16 bit.

I just found that I can save the masters produced in Maximdl as 16 bit. If I take the ones I provided you the link to, I could try opening them in Maximdl and re-saving them as 16 bit. Seems reasonable..... but not alot of things in this world are that straight-forward. Since they don't work for their intended purpose, ie, working with SC, I have nothing to lose testing and trying I guess. I'll let you know.
Thank you for your time and help!
Gary

[admin]

Hi Gary,

converting the files in Maxim may work fine, providing that the final pixel values in the saved 16 bit FITS files haven't been shifted by the processing. That's very much going to be a 'try it and see' thing, since it's hard to know what processing other applications do as part of their standard workflow.

I also added some code to the very latest SharpCap update that allows reading of 32 bit floating point FITS images into SharpCap as long as they are 'Floating point' 32 bit (not integer 32 bit). SharpCap assumes that the files are storing pixel values in the range 0..65535 (which is the range for a 16 bit image), and will round to the nearest pixel value if the FITS file contains a fractional value. Again, that should work, but will also be a case of 'try it and see'. As mentioned previously, the safe bet is to do all processing in the same application to avoid this sort of worry!

cheers,

Robin