Lot of dead pixels - Forums

Hi all. I have ZWO ASI 533 MC Pro and I can see lot of dead pixels on the image (please see attached image). I am not sure if the count of dead pixels are ok or not (suited for warranty). The pixels are in red, blue and green colors. What do you think? Is it normal to have this count of dead pixels?

They are not "dead" since they show quite clearly as colored. If they were "dead" they would be black, that is without any signal. What you have here is just hot pixels and they can be dealt with the right master dark frame and cosmetic correction afterward.

These are hot pixels, and i am assuming they are exaggerated because you used VNG debayering in Pixinsight? (VNG creates these "+" looking artifacts from hot pixels)

Anyway, calibrate with both a matching dark and a bad pixel map to get rid of most or all of them. On top of that, dithering will take care of the rest.

andrea tasselli:
They are not "dead" since they show quite clearly as colored. If they were "dead" they would be black, that is without any signal. What you have here is just hot pixels and they can be dealt with the right master dark frame and cosmetic correction afterward.

Thank you for explanation. The image is uncallibrated.

Oskari Nikkinen:
These are hot pixels, and i am assuming they are exaggerated because you used VNG debayering in Pixinsight? (VNG creates these "+" looking artifacts from hot pixels)

Anyway, calibrate with both a matching dark and a bad pixel map to get rid of most or all of them. On top of that, dithering will take care of the rest.

Thanks, the image have not been calibrated yet, just raw data. So in this case, everything is ok.

Are you dithering? When you dither, the hot pixels still appear in the subs but they are easily removed in pre-processing, as they change their position relative to the background.

In my case, I have a 294MC PRO and have lots of them, but they are rejected and do not appear in the final master thanks to dithering.

Some info here: https://nighttime-imaging.eu/docs/master/site/advanced/dithering/

Guiem.

Edit: Sorry. Didn' see that @Oskari Nikkinen already mentioned about dithering.

Are you dithering? When you dither, the hot pixels still appear in the subs but they are easily removed in pre-processing, as they change their position relative to the background.

In my case, I have a 294MC PRO and have lots of them, but they are rejected and do not appear in the final master thanks to dithering.

Some info here: https://nighttime-imaging.eu/docs/master/site/advanced/dithering/

Guiem.

Edit: Sorry. Didn' see that @Oskari Nikkinen already mentioned about dithering.

No, I did not use dithering, but I've read about it. I will use it next photo session.

Hi,
I have a camera with an IMX533C sensor, and I also have hot pixels. They disappear during preprocessing with the darks.
Clear skyes

I have a camera with an IMX533C sensor, and I also have hot pixels. They disappear during preprocessing with the darks.

If you have a sufficient number of dithered subs (50 or more) you won't have to bother with Darks for this type of sensor, since there's no amp-glow nor any dark current in excess of the Bias level. Dithering will eliminate hot pixels more reliably than Darks while giving you the ability to drop-shrink drizzle to improve the effective resolution of your OSC.

André Bremer:
If you have a sufficient number of dithered subs (50 or more) you won't have to bother with Darks for this type of sensor, since there's no amp-glow nor any dark current in excess of the Bias level. Dithering will eliminate hot pixels more reliably than Darks while giving you the ability to drop-shrink drizzle to improve the effective resolution of your OSC.

Good to know. Thanks for info.

Dither…that will resolve most of them

Completely normal.
Dithers out completely as others have said.
I remember the first time I zoomed into a dark frame and saw all the hot pixels and was shocked!
Enjoy this very capable sensor!

Jim

Using cosmetic correction with default Sigma works well in conjunction with dithering. It's not that it's required, but for some of my projects, I've had long subs and short number of frames. Cosmetic correction eliminated the hot pixels ahead of time.