Problems with flats in WBPP

dpdallolmo@aol.com

New member
Dec 26, 2019
4
0
Hello,
I am having trouble with WBPP. I am obtaining images with a ZWO ASI 2600 CMOS camera. My lights are 600 sec in duration at -10C. I have a library of darks and typically use a matching master dark (600 sec, same temp etc). I typically will use a master bias to calibrate my flats. I typically take flats (#25) after every session.
So I add my light frames and my flat frames to WBPP. I then add my master dark and master bias. I check "use master bias" and "use master dark" in the global options section. Use master flat remains unchecked.
On the flats page, I have checked "Calibrate with flat darks". Everything else on that page is defaults.
On the lights page, I use Cos Correction, Debayer, subframe weights and apply image registration. I typically do image integration after WBPP has completed.
Under Global options all are checked EXCEPT "optimize dark frames and "Use master flat".

Now is where I have a problem.
When I check the Diagnostics, I get a 2 warnings
#1) "only master bias will be used to calibrate flat frames".....This I expect as I am asking WBPP to do that

#2) "No matching master flat frame have been found to calibrate light frames"
This is my problem....I don't have a master flat frame yet it says one can't be found. What's worse is, if I run the program, flats never get "subtracted" so I see my dust motes. If I first create a master flat, then add that in place of the 25 individual flats and check "use master flat", I get the same warning...No master flat found to calibrate the light frames.
Again, if I run WBPP, my images still show the dust motes as if no flats were factored into the WBPP process.
Any Idea why WBPP does not seem to recognize either my individual flats or a master flat?
Thanks,
Dan
 

dpdallolmo@aol.com

New member
Dec 26, 2019
4
0
well I tried something something that worked. I retook my flats with my camera cooled to the same temp as the lights. The warning in WBPP no longer appears. I also retook flats for this object with the camera NOT cooled. The warning re-appeared. I suspect my flats need to be of the same temp as my subs although for the life of me, I don't understand that. This is a new camera for me and I'm still learning the ins and outs of it. I use SGP for my session management software. I don't know if flats need to be taken in the "sequence" or if they can be taken in their own sequence. I'll figure it out. Anyway....Cancel the crisis :)
 

pfile

PTeam Member
Nov 23, 2009
5,689
116
the temp shouldnt matter... i don't think any part of PI considers the temperature at all. when you run the diagnostics, what does the error say? could it be that for whatever reason there is a mismatch between the filter name for the lights and for the flats?

rob
 

dpdallolmo@aol.com

New member
Dec 26, 2019
4
0
the temp shouldnt matter... i don't think any part of PI considers the temperature at all. when you run the diagnostics, what does the error say? could it be that for whatever reason there is a mismatch between the filter name for the lights and for the flats?

rob
"No matching master flat frame have been found to calibrate light frames" This is the warning message I get when trying to use non cooled flats for calibration. I just checked the nomenclature of images to make sure they are identical except for "frame type" (i.e. lights of flats). Don't know if the nomenclature has anything to do with it being recognized as a flat for calibration. Can't I just call the image "flats" and not put in any other details such as "target name", "Exposure time", "frame #" etc??
 

fredvanner

Well-known member
Apr 17, 2019
275
43
Wells, Somerset, UK
Is it possible that your capture software is including the temperature in the image filename in a way that is being interpreted as a filter id? To check, look in your output folder, "master" subfolder. Is there a file there called something like "masterFlat-BINNING_x-FILTER_y.xisf"? If so, what are x and y?
 

ngc1535

PTeam Member
Feb 1, 2014
556
76
AdamBlockStudios.com
Oooh.. Interesting. I would think you would need to put a time in for a raw Flat. Otherwise there might be logic that it is a master flat since these files do not contain exposure time information. It would be hard for me to recreate this on my end...but would you mind loading your flats using Custom..but be certain to input an exposure time?

It just seems like something a computer programmer would do. If I have a flat..and no other information (including exposure time)...I am going to assume it is a master flat.

Just a weird guess.
-adam
 

fredvanner

Well-known member
Apr 17, 2019
275
43
Wells, Somerset, UK
I have stopped using darks with my ASI2600. I found that a 180s dark is indistinguishable from a 0.032ms bias frame - they both show a bias level of 500ADU +/- one or two ADU. The slight (noise, I assume) variation in bias level results in slight clipping of the flat / light frames when bias corrected, so I add a small pedestal (10 ADU) to flats and lights before processing. So far this has worked well.