Are my FITS files junk ?

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grayb
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Joined: Mon Sep 07, 2020 9:00 pm

Are my FITS files junk ?

#1

Post by grayb »

Have upgraded my kit and so get more serious
With an ASI183MC I started with just lights and found I am getting what I now thingk are hot pixel trails using Loive Stack so then begin to trial dark image processing.
Problem
Due to various confusions in the free SC I've ended up in an odd place with aligned/stacked lights RGB FITS using Live Stack and individual dark FITS files from the separate Capture tool. DSS cant do anything with this combo - I was hoping to at least do something about amp glow. I have several nights of captutre which I've now tried to catch up the processing and found I have likely wasted all that dark sky time.
I understand SC Pro can include calibrations on the fly
Questions
Anyone know if there is any hope for me to use these dark files for any effect with any post-processing tool ? or ways to remove the hot pixel trails in the lights ?
I've googled and read many articles but anyone have any tips of how a prevent or avoid such basic beginners mistakes ?

Additional info:
DSS error
"The checked pictures are not compatible (width, height, number of colors, number of channels, only one master dark, offset and flat)."
FITS spec are the same - RAW16, binning, pixel count
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admin
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Re: Are my FITS files junk ?

#2

Post by admin »

Hi,

unfortunately it's probably not possible to correctly apply the flat/dark info you have to the saved live stack images. With enough image tweaking you could probably get past the DSS error, but that doesn't address the fundamental problem, which is as follows:

When you run live stacking, SharpCap automatically offsets (and rotates) each new frame to line it up with previous ones, making drift and rotation problems disappear. This however means that dark/flat correction has to be applied to each new frame *before* it is added to the stack - there is no way to do the correction afterwards. If you think about it, a hot pixel that is at position x=10, y=20 in each frame will get moved around in the stack due to the drift correction - that is why you see trails of bright/dark pixels in the stacked images that you want to get rid of.

Sorry that this isn't the answer you were looking for :(

For future runs, you can use the dark/flat correction in SharpCap Pro so that the corrections are applied before the frame is added to the stack. Another thing you can do (without needing the Pro version) is to use the 'Save Raw Frames' option in the Live Stacking section - that way you see the stacked image but also save the (untouched) frames for later processing in DSS etc.

cheers,

Robin
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