Author Topic: Image calibration. Tests run  (Read 1590 times)

Offline bianry

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Image calibration. Tests run
« on: 2014 February 25 12:53:10 »
I have run same 17 frames 5 times with the ImageCalibrator.

Every time I get same result.
About half gets the ** Warning: No correlation between the master dark and target frames (channel 0).

Code: [Select]
ImageCalibration: Global context

Loading master calibration frames:
Loading calibration frame image:
C:/Users/mats/Desktop/Astrofoto/NGC_5033/master_bias.fit
Reading FITS: 16-bit integers, 1 channel(s), 3072x2048 pixels: done
* Subtracting pedestal keyword 'PEDESTAL': -100.0000 DN
Loading calibration frame image:
C:/Users/mats/Desktop/Astrofoto/NGC_5033/master_dark.fit
Reading FITS: 16-bit integers, 1 channel(s), 3072x2048 pixels: done
* Subtracting pedestal keyword 'PEDESTAL': -100.0000 DN
Loading calibration frame image:
C:/Users/mats/Desktop/Astrofoto/NGC_5033/master_flat.fit
Reading FITS: 16-bit integers, 1 channel(s), 3072x2048 pixels: done
* Subtracting pedestal keyword 'PEDESTAL': -100.0000 DN

Calibrating target frame 1 of 17
Loading target frame:
C:/Users/mats/Desktop/Astrofoto/NGC_5033/test/T21-bianry-NGC5033-20140222-023844-Luminance-BIN1-E-180-001.fit
Reading FITS: 16-bit integers, 1 channel(s), 3072x2048 pixels: done

Calibrating target frame 2 of 17
Loading target frame:
C:/Users/mats/Desktop/Astrofoto/NGC_5033/test/T21-bianry-NGC5033-20140222-024202-Luminance-BIN1-E-180-002.fit
Reading FITS: 16-bit integers, 1 channel(s), 3072x2048 pixels: done

Writing output file: C:/Users/mats/Desktop/Astrofoto/NGC_5033/test/T21-bianry-NGC5033-20140222-023844-Luminance-BIN1-E-180-001_c.fit
Dark scaling factors:
k0 = 0.000
** Warning: No correlation between the master dark and target frames (channel 0).
Gaussian noise estimates:
s0 = 3.317e-004, n0 = 0.876 (MRS)
** Warning: Overwriting already existing file.
Writing FITS image: 32-bit floating point, 1 channel(s), 3072x2048 pixels: done

Writing output file: C:/Users/mats/Desktop/Astrofoto/NGC_5033/test/T21-bianry-NGC5033-20140222-024202-Luminance-BIN1-E-180-002_c.fit
Dark scaling factors:
k0 = 0.018
Gaussian noise estimates:
s0 = 3.269e-004, n0 = 0.870 (MRS)
** Warning: Overwriting already existing file.
Writing FITS image: 32-bit floating point, 1 channel(s), 3072x2048 pixels: done

File ....-001.fit always fails and ...-002.fit always passes.

https://www.dropbox.com/s/um2nsg4jy8sdkq2/master_dark.fit
https://www.dropbox.com/s/b8hy75zo7oo2y60/T21-bianry-NGC5033-20140222-023844-Luminance-BIN1-E-180-001.fit
https://www.dropbox.com/s/rlyzh7wr4id8a52/T21-bianry-NGC5033-20140222-024202-Luminance-BIN1-E-180-002.fit

If someone smarter than me could take a look and inform me what the problem is. Is it the light frame(s) or the dark?

Any help appreciated.

Mats

Offline julianr

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Re: Image calibration. Tests run
« Reply #1 on: 2014 June 24 04:24:15 »
Did you get this sorted, same thing is happening with me - not sure why at all

Offline bitli

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Re: Image calibration. Tests run
« Reply #2 on: 2014 June 26 04:13:04 »
Hi,
You may want to look at http://pixinsight.com/forum/index.php?topic=7149.msg48225#msg48225
I think I wrote an explanation there, but I am not sure (I cannot read it right now). And it may not be clear.
Somehow your darks are not related to your lights for some reason. 
Check that your darks are correct:
  • Especially almost no pixel at zero!
  • Blink your dark and image - you should see some hot pixels at the same spot on the dark and on the background area of the image. Otherwise you have a problem of orientation or just plain wrong dark
[li]Make sure you use the proper CFA parameter if you use CFA (DSLR)
[/li][/list]
You may have make a mistake calibrating your dark or reading them.
Or your camera is so good or preprocess the image (if DSLR) or the the exposure time was so short (seconds) that the dark is useless.

You may hide the message by not using dark optimization, but then you likely degrade your image with your darks!

-- bitli