Normalization errors after registration issues

Mmm, I think it's best for us to have a look at the data. Would you mind uploading a small subset of your data? Like 10 lights, 10 darks, etc. ?

I have uploaded 6 files each of LRGB to folder "cdp17-registration".   They are all light files (already calibrated by iTelescope before being delivered to me).

BTW the version I am running is 1.083.4, which I believe is the latest.

I appreciate you looking into this!

Charles

Ah, precalibrated. Mmm, if I'm right iTelescope also provides the calibration files seperately and raw lights. I think it will be very informative if you can get those and upload as well as this may very well be a calibration issue. This is better anyway as APP will have better calibration algorithms to use.

Hi Vincent,

I will try to get the raw lights and calibration files (I hope the raw files haven't been removed from the iTelescope FTP site yet), but it may take a few days.

In the meantime, I do see something suspicious in APP.  If I examine these files with an external FITS viewer (AvisFV), all of the files look normal, except that the "W" images (after meridian flip) are mirrored:

However, inside APP, with the image viewer the "E" images look normal, and as they do in AvisFX; but every one of the "W" images has a histogram that does not look right, and the image is all wrong (it's supposed to be monochrome, for one thing):

I am not experienced enough to know whether this indicates image issues or an APP issue, but I thought I'd bring it up as a data point.

Thanks again,

Charles

The external application shows a very stretched result, it's not possible to judge what is going on in the background there. Also if they are mono, then it seems the data has a wrong header tag maybe, does it show an RGB pattern in the fits header?

Anyway, when you have the data, please let me know and we can probably tell you what is going on. For now this does look like a data issue.

Hi Vincent,

Thanks to the excellent iTelescope support staff, the issue is resolved.  In a nutshell:

• Software bug on telescope system introduced a spurious “BAYERPAT” line in the FITS header after a meridian flip.
• This line made APP believe that the camera has a Bayer mask when in fact it does not; hence the incorrect image viewer/histogram, and the failure to integrate.
• Two workarounds were successful:

1. Use current version of APP with “no interpolation” on tab 0
2. Use older version of APP (1.078) which (apparently) does not pay attention to the BAYPERPAT line in the header

The idea that the incorrect BAYPERPAT line fooled APP is just a working theory, but in conforms with the workaround results.  In any case, this should not happen again since the iTelescope team has corrected the processing error on the telescope system.

I very much appreciate for your offer to help, but I’m glad I did not waste your time on what in fact turned out to be an image issue – as you suspected from the start.

Cordially yours,

Charles

Thanks for coming back to explain what happened Charles! That is very helpful. Glad it's figured out.

The BAYERPAT line indeed fooled APP as it does expect that tag to be correct. This was indeed introduced in a later version.

@cdp17 There is a third option: remove the BAYERPAT FITS keyword from the raw files. This is possible via the tools in the Tools tab of APP.

Wouter, thank you for drawing my attention to that feature - I wasn't aware of it!

Charles