Two Images, Same Processes, Same Settings, Same Times, Different Results

[timtrice]

I'm "losing" a number of good images somehow up to registration. The attached example is a side by side comparison between two images. Both images are after the registration process. Both images look very good from step 1. I originally went debayer - calibration - registration until someone pointed out steps 1 and 2 should be reversed. So I went calibration - debayer - registration. The results are about the same.

29 images out of 30 look horrible. A couple of nights ago it was 17 out of 25. I do nothing different and of 150 subs I've gathered I can use about 100 of them. But the rest, despite being good enough for integration, do not make it through the registration process...

Temperature fluctuations are minimal, between 27 and 32. Using darks and bias, all in the same range. Flats applied to all images. They're all using the same master calibration files. They're all in the same temperature range. I see no discrepancies (images taken at 32C do make it thorugh while some also at 32C do not). So I don't think this is a problem.

[gvanhau]

Hello Timrice

I assume that you are not using the batch preprocessing script.

The correct way to go is first to calibrate , then debayer and finally register and integrate...
Have you tried to add a little amount of pedestal in the calibration process? Some times, this prevents negative values when substracting bias or darks whitch cause strange results.

If that does not resolve your issue, may be you could post the master dark, bias and flat and a couple of good and bad images to see what is happening....

Geert

[Carlos Milovic]

Something very odd is happening with your red channel. Are the images displayed correctly in the intermediate debayered images (before registration)?
Also the images look very noisy to me. Are them already calibrated? Are you sure that the orientation of the lights and masters match?

[jkmorse]

Tim,

You may be running into some FITS incompatibility issues.  I did a lot of research recently on FITS incompatibilities and this issue has been addressed time and again by PI.  Here is the results of my research into old posts on the subject:

Fixing FITS Incompatibilities
If you experience these types of incompatibilities, try the following until you hit on a solution:

First
•   Open the Format Explorer (access under “View > Explorer Windows”)
•   Double click on “FITS”
•   Make sure the top two boxes are checked
       o   “Write scaling keywords . . .”
       o   “Signed Integer images . . .”

Second
•   Where possible, particularly in the Image Calibration tool for Lights, but also with ImageIntegration when creating Master Darks and Master Bias, add the following to the “input hints” line under “Format Hints”:
       o   lower-range 0 upper-range 65535

Third
•   If the above does not work, insert the following in the “input hints” line:
       o   Signed-is-physical

Stop using input hints AFTER you have successfully saved an image after applying a PI tool; i.e, do not use input hints in ImageIntegration after successfully calibrating Light images in PI with the ImageCalibration tool (after first PI application, images are saved in proper PI format (0,1) and no longer need input hints)

For an excellent explanation of what is happening to cause this problem, check out the following threads from Juan Conejero:

http://pixinsight.com/forum/index.php?topic=3118.msg21348
http://pixinsight.com/forum/index.php?topic=3474,msg23973
http://pixinsight.com/forum/index.php?topic=3800.msg26086

Hope that helps,

Jim