›

WBPP not seperating out Flat Darks by Exposure time.

Mike Freeberg
in PixInsight
I was using WBPP to calibrate some images and I noticed that when I load in my flat darks for LRGB it puts them all in the same group.  I have attached a screenshot  to show what is happening.  When I load  the calibration flats , it behaves as I suspect and puts the flats in different groups according to exposure time(Seen screen shot).  When I load the Image darks it also seperates them into correct grouping.  If I look at the calibration of the flats it uses the 1.85 sec for the calibration of all the different flats, I have attached a screen shot of the calibration of the 0.43 sec flat and it uses the 1.85 sec flat dark. 

This seems to be a new behavior and I am not sure what is wrong.  I have looked at the fit headers for all the flat darks , and they all show "Dark Frame" for IMAGETYPE and EXPTIME looks correct for each flat dark.  Does anyone have any ideas what is going on. 

Thanks Mike



Comments

  • BlockHeadBlockHead
    There is a dark frame exposure tolerance. (when you are in the Darks tab, your first picture you will see the option to the right.)
    The default is 10 seconds I believe. If you want to have exact matching of darks you would lower the exposure tolerance... you probably need to set it to the minimum (0.1).

    BUT- you should ask yourself if this is reasonable. 
    Your dark for flats are very short.

    1. If you have a reasonable sensor/camera then these are just bias frames and you should put these in as biases..and in the future expose at the minimum time for biases and these will calibrate your flats of any short exposure time (even if they are different).

    2. If you have silly camera where the matching darks for flats are required (ones with an amp glow)- your flats should probably be at least 2 seconds in duration...and the matching darks the same. This will avoid some other well-known issues.

    I explain all of this in my WBPP series. 

    -the Blockhead

  • Mike Freeberg
    Thanks Adam,  That took care of the problem.  I figured it was something simple that I was overlooking.  I have a CMOS camera that does have amp glow that is the main reason why I am using flat darks.  I will look at increasing the time for the flats. 

    Thanks Again Adam,

    Mike
Sign In or Register to comment.