Author Topic: Strange Cross Hatch Pattern  (Read 300 times)

Offline kerrywaz1

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Strange Cross Hatch Pattern
« on: 2019 January 21 18:51:31 »
Hello All,

I have an Ha image that is a combination of 70 Ha frames dark subtracted and calibrated using a superbias generated from 55 bias frames. The image has a strange cross hatched weave pattern that appears in the lower signal areas of the image. Attached is the image stretched with the STF Autostretch boosted  tool.

Anyone know what is causing this or if I am ding something wrong with the bias subtraction?

Thanks,
Kerry
Deep Sky Instruments RC14C
FLI PL16803 w/MOAG + StarlightXpress Ultrastar
Pyxis 3"
Astro Physics AP1200
Tak FSQ-106EDXII
Apogee Alta F16M
Hap Griffin modified Canon EOS 5D Mark II
PixInsight, MaxIm DL, PhotoShop CS5

Offline pfile

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Re: Strange Cross Hatch Pattern
« Reply #1 on: 2019 January 21 19:48:18 »
i sometimes see this kind of thing in narrowband exposures when i don't use flats - in fact the crosshatch pattern is visible in my flats... is this a camera with a kodak sensor?

rob

Offline kerrywaz1

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Re: Strange Cross Hatch Pattern
« Reply #2 on: 2019 January 21 20:40:49 »
Yup - a KAF-16803 sensor.

I used flats. The round artifacts in the image are lens flares from the moon or bright stars.

--- Kerry
 
Deep Sky Instruments RC14C
FLI PL16803 w/MOAG + StarlightXpress Ultrastar
Pyxis 3"
Astro Physics AP1200
Tak FSQ-106EDXII
Apogee Alta F16M
Hap Griffin modified Canon EOS 5D Mark II
PixInsight, MaxIm DL, PhotoShop CS5

Offline pfile

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Re: Strange Cross Hatch Pattern
« Reply #3 on: 2019 January 21 21:56:38 »
oh - have never seen a flare like that before, thought it was no flats...

maybe it is worth trying with a regular master bias instead of a superbias.

rob

Offline GregW

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Re: Strange Cross Hatch Pattern
« Reply #4 on: 2019 January 21 22:30:30 »
debayer correctly?
Objects in the mirror are farther than they appear