Flat images not showing

[Peter]

I have been good and uploaded the latest greatest update of Pixinsight, but when uploading my herd Neumann flats to pixinsight I just see a black frame. I can open the image in photo gallery, canon's own image preview software but not on the Pix? The green border appears to show image selected but just the black frame. The images are still CR2 as unable to as mentioned view the images for any form of quality control. Just as an aside, does anyone else use a Gerd Neumann flat field panel? If so should they be as red as they are and in various histograms the red is furthur along the x axis than the blue and green which seem perfectly matched. In effect two questions for the price of one message...lovely

[NGC7789]

You need to apply STF to your linear flat. Color cast in the flat should not matter as long as all the channels are properly exposed.

[Peter]

Yes I have tried STF, 24 bit lookup, histogram transformation, autostretch and extended autostretch to no avail as the image remains black. However I have found if I use the rescale button then a image does appear but I still do not understand the problem with the other processes and why they do not work. Equally I am not understanding how rescaling brings up the image but I guess that is for furthur study. No the problem is that none of the raw flat images are being processed by STF and all its kin but thank you for the reply. The additinal jpeg image is a saved Canon Digital Photo Professional stretch and shows the problem I am having so moderators et al what is wrong?

[Peter]

As per usual it seems that if a user has a problem with a processing step he or she needs to figure it out for themselves. With that knowledge certified I have spent some time finding an answer and it seems increasing exposure of my flats to 2 seconds has placated Pixinsight and it is happy to oblige in showing my flats once more. 

[Astrocava]

Perhaps your flats are underexposed, 1/250s seems very short duration for me. If your exposure is very short you can freeze electroluminescence vibration of the panel as is shown in your image with that banding. Try to get the peak of the histogram of your flats between 0.5 and 0.66.  Hope this helps.

Have fun!

Sergio

[Peter]

Hi Sergio, The 1/250s exposures are admitedly too short and the banding you describe is noticeable. The reason for sucha short exposure was in part using a Gerd Neumann panel which is meant for slower optics and longer focal length scopes. The reason for my post was to try to understand why PixInsight would not show the image while other image software programs had no trouble. The read out for the image was also a little strange as it gave readings of 0.0000 for both the blue and green channels! I know my image is reddish but certainly not pure red in structure. Anyway, as noted above I shoot at 1.8 seconds for my flats after placing 6 sheets of white printing paper in front of the light panel. I can work on these images now but never did find out why the original sets never displayed properly or why there were no readings for blue and green. Other readings from the other imaging software gave a high reading in red that was twice the readings for the blue and green. So while the mystery still stands now I am using the longer exposure flats without problems so again thank you for the assistance and information...Cheers