Author Topic: Dark Blooms & Star Cores  (Read 1176 times)

Offline llpastro

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Dark Blooms & Star Cores
« on: 2016 August 07 17:31:00 »
When I open a raw FITS image created by Maxim and if it has blooms or saturated star cores, they are black.  See the attached screen shot.  If I open these images in other processing software, they appear normal.  If I open them in Maxim and resave as a floating point and reopen in PI, they then appear normal.

What do I need to do when downloading images from the camera using Maxim to get these to display correctly?

If I don't worry about their initial appearance and go ahead and calibrate and create masters, will they be correct?

Larry
AP 140 Refractor
SBIG ST-10XME
AP Mach 1 Mount
ATS Portable Pier
Tucson, Arizona

Offline Juan Conejero

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Re: Dark Blooms & Star Cores
« Reply #1 on: 2016 August 08 04:35:14 »
This happens because the images have been saved in 16-bit signed integer format, which is wrong. Please save raw data as unsigned 16-bit images.

Alternatively, you can enable the signed integer images store physical pixel data option in FITS Preferences. The same option can be specified as the "signed-is-physical" input format hint in tools that accept them, such as ImageCalibration.
Juan Conejero
PixInsight Development Team
http://pixinsight.com/

Offline llpastro

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Re: Dark Blooms & Star Cores
« Reply #2 on: 2016 August 08 06:39:08 »
The FITS header for this image says "BITPIX = 16 /8 unsigned int, 16 & 32 int, -32 & -64 real".  What is this telling me?

Larry
AP 140 Refractor
SBIG ST-10XME
AP Mach 1 Mount
ATS Portable Pier
Tucson, Arizona

Offline Juan Conejero

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Re: Dark Blooms & Star Cores
« Reply #3 on: 2016 August 08 11:42:11 »
This is telling you nothing, basically. It's just a generic keyword comment.

You know your image is in 16-bit signed format if BITPIX=16 and you don't have BZERO=32768.
Juan Conejero
PixInsight Development Team
http://pixinsight.com/

Offline llpastro

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Re: Dark Blooms & Star Cores
« Reply #4 on: 2016 August 08 19:54:38 »
Attached is the Maxim Dialog box for saving images from the camera.  I thought this was the correct setting, but this setting is causing the issues with the saturated blooms and star cores.  Are there other settings I need to make in Maxim to get unsigned integer?

Larry
AP 140 Refractor
SBIG ST-10XME
AP Mach 1 Mount
ATS Portable Pier
Tucson, Arizona

Offline Andres.Pozo

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Re: Dark Blooms & Star Cores
« Reply #5 on: 2016 August 09 02:03:31 »
This is one of the many reasons for deprecating FITS  ;) ;)
It is a really bad standard because it is ambiguous and each application interprets it differently.