SubFframeSelector didn't measure FWHM or other variables

[LarryC]

SFS always works very well, but tonight I got this error in all of my calibrated and corrected frames:

"Warning: No convergence in MRS noise evaluation routine: using k-sigma noise estimate"

And the values for most of the output variables were "0".  As far as I know I processed the light frames the same as I have done for some time. 

Anyone have any ideas what might be going wrong?


Larry

[vicent_peris]

Hi Larry,

We would need to take a look at any of those images.

Best regards,
Vicent.

[cjszoo]

Ive seen this a few times (usually when i am trying to process after being up all night).
its always when i either choose a flat instead of a dark when calibrating lights, or do something similar when calibrating my darks and flats into a master.
when i get this error, if i look at the images, they are all black with maybe a few stars.
Hope that helps.

[vicent_peris]

Yes, then there's some problem with the preprocessing. Are you working with DSLR cameras? RAW images don't have FITS headers, so you should be very sure where you put your images in the BatchPreprocessing script. If you subtract a flat images like a bias from the light, the result is a completely clipped image with the bright stars as the only remaining information. Imagine that your bias level is 1,000 ADU but, by selecting the flat as bias, you're subtracting 30,000 ADU.


Best regards,
Vicent.

[LarryC]

Vincent,

I calibrate manually and these are ASI1600 mono images. 

I'm in my office today but will look into the possibility that I accidentally used a flat or bias instead of a dark - it's possible.  If that doesn't appear to be the case, I'll post one of the images, and report back either way.

I can say that the images look good to me and no different from the images I've been collecting over the past several weeks under identical conditions and identical camera, filter and SGP settings.


Thanks,

Larry

[LarryC]

I can't find any direct evidence of what happened, but it appears I must have used a dark instead of a flat, or some such thing because the calibrated images and the corrected images were very dark with only highlights of the original image coming through on a STF stretch.  Upon reprocessing the whole set, everything looks normal. 

Thanks for the responses and help.

Larry

[vicent_peris]

Yeah, if you use a dark instead of a flat the result can be anything but the right one. Usually this kind of problems come from some mistake in the preprocessing steps. Glad you found it.


Best regards,
Vicent.