Author Topic: Help me with a kind of centered color gradient in all RGB's  (Read 250 times)

Offline Thomas

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Hello,

since some time I noticed some kind of "centered color gradient" in all my RGB's (greenish in center, reddish around) which I don't understand because I use this equipment since years without a this effect. This is seen in now in al RBG's doesn't matter in which sky region or climatically conditions. (see attached pic, just calibrated and basic stretch)

OFC This has nothing to do with PI but since here are a lot of experienced specialists maybe someone knows what could cause this.



What changed in my setup since I noticed this behavior was:

- I installed my setup on a dark sky remote place.
- I had to do an "anti-banding" Firmware update on my QSI 683 camera / Astrodon filter.
- I cleaned the front lens of my Tak FSQ 106ED with Baader optical wonder Cleaning Fluid.
(I am not making any of this responsible, it is just for information)


What I have tried so far.

-I made fresh BIAS/ DARKS / Flats library , tried it with 2 different flat field panels , and tried it with different flat ADU values : ~ 23.000 / ~ 35.700
- Even if I calibrate the RGB's without flat's the "centered color gradient" is visible.

Info:
I am doing RGB at 1:1:1 exposure length at -20°C
I activate a dew heater if humidity goes above a certain level. (> 80% RH)
I doubt it's  caused from light pollution since all RGB's showing a "centered color gradient".

PS: Primarily I am not asking how to solve this with a tool like DBE or others (though it could be a pain) , I just want to figure out what is causing this since I didn't had this in the past with the same equipment.

Any help is welcome.

« Last Edit: 2018 May 01 18:19:29 by Thomas »

Offline Barry-Wilson

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Hi Thomas.

I've just read your post and am having a think about your issue but wanted to let you know straightaway that I too have had to update the firmware of the QSI683 I have at my home observatory due to a banding issue.  I bought the 683 secondhand last year and hadn't imaged with it a lot, instead using my first QSI683 which is now at e-Eye.  I updated the firmware in March 2018, created new bias, darks and flats and my images have calibrated well with no banding and certainly no central colour gradient like you are seeing.

I'll have a think and email you.

CS!

Barry
10Micron GM1000HPS; QSI683wsg8; FSQ106, FSQ85, WO132FLT
My images: https://barrywilson.smugmug.com/

Offline Thomas

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Hi Barry,

thanks for the replay. I sent you a mail :-)

Thomas