Purple and green bands--PI vs Maxim

[alanrock]

I'm using the batch preprocessing script with the same set of Bias/Dark/Flat/Lights that I'm using with the Calibration and then Stack functions in Maxim, but with PI I'm getting some very nasty background noise, which I do not get in Maxim. Other than the purple and green bands that I'm getting and which seem impossible to remove in PI, PI has done a much better job of clearing out the amp glow and removing the gradients, but these bands are just awful. Can anyone tell me what I could be doing wrong in PI? I am using all the recommended settings and am optimizing darks in PI. Obviously it's hard to compare the settings between the two products, so I'm at a loss as to what's going on. Oh, also, Maxim takes about 2 minutes to process and PI takes about 15! I don't really care how long it takes, it's just that the result is so awful. Thanks in advance for any help!

[RickS]

I wonder if the bands are there in the Maxim version but hidden by the more obvious issues?  Would be interesting to do a DBE on the Maxim version and see.  The CanonBandingReduction script might offer a fix.

Cheers,
Rick.

[alanrock]

The bands aren't there in the Maxim version. I did a DBE and they aren't there, but all the other issues are--the satellite trail, the amp glow, etc. Furthermore, there's more detail in the Maxim version as far as I can tell. The "antennae" are much more obvious in the Maxim version than the PI version.

[bulrichl]

The Maxim version (first image) seems not to be flatfield corrected.

The bands in the PI version (second image) point at a wrong calibration, namely the the handling of dark and bias frames.

Some questions concerning the workflow in PI:
1) Do the bands show up in the light frames?
2) Do the bands show up in the calibrated light frames?
3) Did you use the dark subframes or a pre-built MasterDark in the batch preprocessing script?
4) If a pre-built MasterDark was used: how did you make the MasterDark?
5) Did you also try darks with the same exposure time as the lights and NO dark frame optimization?

It might be important as well, which camera was used (looks like an OSC camera with Panasonic or Sony sensor).

Bernd

[alanrock]

The Maxim version (first image) seems not to be flatfield corrected.
I agree, although the option _is_ selected in Maxim

The bands in the PI version (second image) point at a wrong calibration, namely the the handling of dark and bias frames.


Some questions concerning the workflow in PI:
1) Do the bands show up in the light frames?
No
2) Do the bands show up in the calibrated light frames?
No
3) Did you use the dark subframes or a pre-built MasterDark in the batch preprocessing script?
Dark subframes
4) If a pre-built MasterDark was used: how did you make the MasterDark?
5) Did you also try darks with the same exposure time as the lights and NO dark frame optimization?
I just did and have attached the resulting image. It looks way better, although the amp glow is evident now, but that's not really a deal breaker in this image. Interestingly, the darks and the lights are the same exposure length (although the total exposure time is different between the darks and lights.)

It might be important as well, which camera was used (looks like an OSC camera with Panasonic or Sony sensor).
Yes, it's an OSC. ZWO ASI183MC Pro

[bulrichl]

OK, as expected  the calibration settings strongly influence the outcome.

One additional question:
Which setting was used for 'Optimization threshold' in the 'Darks' tab? Did you leave the default of 3.0 or did you use a different setting?

However, I have no explanation for the appearance of the bands when 'Dark frame optimization' is checked. My camera is a OSC CMOS camera as well (ASI294MC). I tried both, 'Dark frame optimization' enabled (with the default optimization threshold 3.0) and not enabled. In no case I had such colored bands in the integration image. (I do not use the script, but the process 'ImageCalibration'.)

In my case, the amplifier glow was corrected better without dark frame otpimization. This is the expected result. For me it's very strange that you are experiencing just the opposite.

I guess you will have to try different calibration settings and compare which one makes the best result for your camera. Perhaps my guide https://pixinsight.com/forum/index.php?topic=11968.0 might be helpful therefor.

Bernd

[alanrock]

Bernd,
I didn't make any changes to the Optimization threshold setting; I go with the defaults unless told otherwise.
Particularly frustrating for me is how difficult it is with PI to do easy things. For example, if I just want to quickly stack some images that I've taken, forgetting about darks, flats, bias etc., it's at least a two (tedious) step operation in PI. In Maxim, I click on the Stack button, I choose my files and my star alignment method from the same dialog box, and then I click "go". Using 20+images 40MB each, the entire process takes 5 minutes tops. This is at least a 30 minute process in PI! I know, I know, "PI was not made to be user friendly", but seriously!