12-bit ADUs scaled to 0-65535 in FITS file

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oopfan
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12-bit ADUs scaled to 0-65535 in FITS file

#1

Post by oopfan »

Hi Robin,

At one point in the not-so-distant past SharpCap wrote ADU Counts in the range of 0-4095 for a 12-bit camera. That's now been changed to 0-65535 by multiplying the ADU Count by 16.

This is causing a bit of a kerfuffle with my variable star endeavors at AAVSO, Everyone there uses a 16-bit CCD camera. For their software to work properly it needs ADU Counts.

There are two work-arounds that I can think of, neither are attractive. Do you remember the reason for the change?

Thanks,
Brian
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Re: 12-bit ADUs scaled to 0-65535 in FITS file

#2

Post by admin »

Hi,

actually I thought that I had been writing full 16 bit fits files for a long long time in SharpCap (some years at least). The original reason behind the choice is that for everyone like you who want their FITS files to run 0..4095, there are 20 beginners who are going to capture an image and then wonder why it is black when they load it into some other application.

The right solution is an option to choose between the two modes in SharpCap with the default set to the current mode of operation I think. I will have to think if it is a safe change to make to 3.1 or if it needs to wait to 3.2

cheers,

Robin
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Re: 12-bit ADUs scaled to 0-65535 in FITS file

#3

Post by oopfan »

Hi Robin,

You are right I was looking at a Dark image FITS file which came in less than 4095. For variable stars I think I will switch over to AltairCapture.

Thanks,
Brian
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