ASI1600MM cool Flats problem

Discussion of using SharpCap for Deep Sky Imaging
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Tommohawk
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Joined: Thu Sep 28, 2017 10:57 am

ASI1600MM cool Flats problem

Post by Tommohawk » Thu Sep 28, 2017 8:50 pm

Hi - hoping someone can help me out here!

Very pleased with my new ASI1600MM cool, but so far I've spent about 2 hours imaging lights and 20 hours trying to do flats. I'm using Sharpcap to do the 16 bit FITS lights, darks and flats, and processing in DSS. I'm letting DSS create a masterflat from 100 FITS taken just in ordinray capture mode, rather than in Flats Capture mode. The main reason is want to change as little of my basic method as possible, and thats the way I've always worked.

I could let SC do the flats and create a master, but as I understand it this will be a FITS file which I cant preview properly - FITS liberator seems to want to stretch and generally monkey around with every image I load, and I cant look at FITS on Photoshop or anytihng alse.

Couple of questions. Can I get SC to do my masterflat as a TIFF rather than as a FITS? then I could simply check it out in PS.

Or, since SC creates FITS files and creates a preview as it goes, can I load the FITS master flat which SC creates within SC to check it before stacking?

The current problem I have is that the TIFF masterflat created in DSS from 100 FITS flats taken in SC, has concentric rings. Not sure I can post an image here, but I've posted one on SGL here:

https://stargazerslounge.com/topic/3006 ... nt-3291965


Really would appreciate any thoughts!

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admin
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Re: ASI1600MM cool Flats problem

Post by admin » Thu Sep 28, 2017 9:05 pm

Hi,

Actually, I'd have thought that a master flat in SharpCap would be saved in FITS format in 16 bit mode, but it looks like it's actually saved as a PNG. From SharpCap's point of view, this is fine because I've been very careful to make sure that it can load 16 bit PNG files without loss of accuracy. Some other software silently drops 16 bit PNG files down to 8 bits when opening them, so be careful.

I have just tested PIPP and it *does* open 16 bit PNG files from SharpCap correctly and can convert them to full 16 bit FITS files, so that might be a route you can take.

You *can* load up images in SharpCap by selecting 'Test Camera 1 (Deep Sky)' and then using the 'Browse' button in the testing controls to browse for the image to display. This feature is more designed for being able to test/learn/demo features when the sky is not co-operating, so it's not tested for absolute accuracy of the displayed image.

cheers,

Robin

Tommohawk
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Joined: Thu Sep 28, 2017 10:57 am

Re: ASI1600MM cool Flats problem

Post by Tommohawk » Fri Sep 29, 2017 7:05 am

Hi Robin thanks for prompt reply.
Bit puzzled now though! If SC does save master flat as Png that might be ok, because I could then view it in Ps or whatever, and my main problem atm is not being able to view the flats properly to assess prior to registering/stacking in DSS.
That said, I dont think DSS likes png. But I splashed out on pro license yesterday and on mine it def saved the masterflat as FITS.
TBH the better option, for me anyhow, would be to be able to choose the flat format either FITS or TIFF.
I'll check out the load image idea in a bit. If I could reliably use that to check the flat that would be ok - but will it load FITS? ill check and post back.

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admin
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Re: ASI1600MM cool Flats problem

Post by admin » Fri Sep 29, 2017 7:12 am

Hmm, maybe it's the 'Preferred Still Format' setting in the options that controls it - http://docs.sharpcap.co.uk/2.9/#Preferr ... l%20Format. That could explain the difference.

cheers,

Robin

astrnmr
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Re: ASI1600MM cool Flats problem

Post by astrnmr » Fri Sep 29, 2017 7:58 pm

I always set my preferred format to FITS. Then it opens in all the programs but PS, but at least it works.

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