FITS vs. TIFF

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SteveSD
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FITS vs. TIFF

Post by SteveSD »

In SC you can stack and output using the default FITS format. You also have the option of saving individual frames as TIFF, JPG, etc. If you save as FITS you can open the stack with Deep Sky Stacker in a few seconds and then proceed to Photoshop or whatever. If you use DSS to open TIFFs -it's a long process. I recently tried Sequator and discovered that it won't open FITS files at all but it will open TIFFS very quickly. FITS files are tiny compared to even one TIFF that would be part of a stack. They must have way more detail in them so one would think they would be better to use. Can someone enhance my understanding of this? How can the 2 vastly different file sizes have equivalent data in them and which approach is to be preferred/

Thanks so much for your input.

Steve
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Re: FITS vs. TIFF

Post by admin »

Hi Steve,

the two file formats serve quite different purposes – TIFF is very much an imaging format (and quite an old one too). If you're planning on opening the images in a generic image editor program then this is one of the better choices. FITS is a scientific data format – as you noticed applications geared towards Astro imaging may well be better at dealing with this format than with TIFF.

SharpCap does have an option in the settings to add compression to TIFF files. Unfortunately the downside of this is that some processing applications don't have the necessary code to read the compressed TIFF files - worth testing that before long capture session.

FITS is probably the place to start for Astro imaging – if you need to convert to another format then you can do this fairly easily in bulk using applications like PIPP.

Cheers, Robin
SteveSD
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Re: FITS vs. TIFF

Post by SteveSD »

So let's say you've live stacked in Sharpcap and you've set the program to output FITS. When I open the FITS file in Deep Sky Stacker I don't see the stack I just see one image. There is a setting in SC to save individual raw frames and it does that in TIFFs. Since you have a choice to set the output for a few different formats my expectation was that if you set the output as TIFF it saves individual frames as TIFFs and if you set the output for FITS it saves the individual frames as FITS. Is that a misunderstanding on my part or am I doing something wrong?
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Re: FITS vs. TIFF

Post by admin »

Hi Steve,

my expectation would be that the raw frames would get saved in the format you have selected in the 'Capture Format' control for the camera (or in the format selected as the default still format in the first page of the settings if 'Capture Format' is set to a video file format).

cheers,

Robin

PS. It used to be different, so make sure your SharpCap is up to date
Eyeroll1952
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Re: FITS vs. TIFF

Post by Eyeroll1952 »

Hi,

I am new to SC and have an issue that seems related. If I capture images in SC, save as TIFFs, and then stack in DSS I get very weird images when I open in Photoshop - see second picture. The M51 galaxy is completely buried in "clouds."

If I instead capture images in SC but save as FITS and then stack in DSS the problem disappears - see first picture. I am happy working with FITS files but am wondering whether this is normal behavior or not? BTW, the TIFF issue is repeatable on multiple nights.

FYI, I am using Win10 on a newish Dell XPS and capturing with a ZWO ASI2600 camera.

Cheers,

Paul
Attachments
M51 saved as FITS.jpg
M51 saved as FITS.jpg (47.21 KiB) Viewed 177 times
Weird stacked TIFF2.jpg
Weird stacked TIFF2.jpg (23.12 KiB) Viewed 177 times
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Re: FITS vs. TIFF

Post by admin »

Hi,

the images you are saving are RAW images with the colour information contained in the fine grid pattern you will see if you zoom in to the pixel level. In order to process these images properly, they need to be debayered to extract the colour information, but DSS will only do this when loading FITS data, not TIFF. The presence of the grid pattern without it being properly dealt with causes the rather interesting effect that you see.

You can use a different application (for example PIPP - Planetary Imaging Pre Processor) to debayer any existing FITS files you have before stacking the debayered versions in DSS - that way you should get a good image.

Robin
Eyeroll1952
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Re: FITS vs. TIFF

Post by Eyeroll1952 »

Thanks Robin, now life makes sense again. It was always a bit unclear to me how DSS dealt with debayering (or not).

Paul
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