Author Topic: Hot Pixels  (Read 1841 times)

Offline ronk01

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Hot Pixels
« on: 2014 November 03 14:54:40 »
Dear PixInsight Experts,
Every so often people like me (non engineer, non scientist, non math wizard) "lose the formula". In my case the problem is that "all of a sudden" I have lots of hot pixels after doing the image integration process.

I normally acquire images with Maxim (latest version) or SkyX with camera add-on. Usually this is 8 to 10 subs of 300 to 600 seconds each. This is done with a OSC SBIG ST-4000CXM camera.

My normal processing step is to import the "raw" images into Maxim and to calibrate, measure quality, and auto star match the images. If I tell Maxim to combine those images (sigma clip) the hot pixels disappear. (But most of the time the color saturation is not that great).

I used to take the calibrated and color-converted images and do an image integration process in PixInsight (and then do more processing). I used to get processed images that did not have a lot of hot pixels but now I do. Taking the calibrated and color-converted images through the PixInsight star alignment and then the integration process still gets me lots of hot pixels. I also tried cosmetic correction but did not get anything better.

Can someone provide me the "magic" combination of integration parameters that works best in eliminating hot pixels?

regards,

Ron K.


Offline Alejandro Tombolini

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Re: Hot Pixels
« Reply #1 on: 2014 November 03 15:21:35 »
Hi Ron, most of the hot pixels should have been eliminated during the calibration routine. maybe you can try calibrating the image with BPP and see if the result is as you expect. Follow the BPP videos with the default parameters to obtain a reference  integration. If there are hot pixels, open Blink tool for inspection of the _c images.
Saludos, Alejandro

Offline Geoff

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Re: Hot Pixels
« Reply #2 on: 2014 November 03 15:57:27 »
Hi Ron. Do you dither your acquisition frames? Cosmetic correction and dithered frames should pretty much eliminate hot pixels.
Geoff
« Last Edit: 2014 November 04 12:03:11 by Geoff »
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Offline ronk01

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Re: Hot Pixels
« Reply #3 on: 2014 November 04 05:56:24 »
Yes I dither. 2 pixels.

It is still strange that the Maxim calibration routines (dark and bias only) do not remove the hot pixels but their combination routine (process/stack/combine with sigma clip selected) does indeed remove the hot pixels. I will however try the Batch pre-processing routines. Thanks for the guidance.
regards,

Offline vicent_peris

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Re: Hot Pixels
« Reply #4 on: 2014 November 04 06:21:07 »
Hi Ron,

My advice is to make always a much larger dithering to better reject all the hot pixels and maybe some strange artifact.


Best regards,
Vicent.