Look at all the "stars" (Hot Pixels)

[Buzzard75]

Last night was the first time I'd used my ZWO ASI178MC for anything other than planetary, lunar or solar imaging. As should be expected, it went terribly. I had to throw out 2/3 of my images due to wind vibration. On top of that, I had so many hot pixels, you'd think you were looking at a field of stars. See below. Ignore the lights in the right hand corners. I don't think I had the lens cover on quite right so there might have been a bit of light bleed. In any case, this is a 120 second dark frame. I know it was hot out last night and this is an uncooled camera, but I have less hot pixels on my DSLR that is a few years old than I do on this camera that basically came straight from the manufacturer a few months ago. I was able to use these dark frames and get rid of them on the processed image, but I just don't feel that it should be quite this bad even for an uncooled camera. Be sure to actually open the file as it doesn't seem to display properly in the preview. Is this normal?

 

Edited June 29, 2019 by Buzzard75

[geordie85]

I'm assuming this is an uncooled camera? If so then yes this is normal. 

Also that's not light leakage, that's amp glow. 

[Buzzard75]

Thanks, Geordie! Yes, it is an uncooled camera. As I said it was quite warm last night. The sensor was at 31C. It just looked excessive. I might have to hold this camera back specifically for planetary or solar work and get a cooled camera. I plan to get one eventually, just hadn't planned on doing it just yet.

[Davey-T]

Wouldn't worry about it my cooled to minus 20C  8300 cameras have just as many hot pixels as that, a bad pixel map will remove them.

Dave

[vlaiv]

Quite normal, even cooled will have plenty of "hot" pixels - these are not really that hot - they are above average but most of them are no where near saturation, so dark subtraction works well.

On my cooled 178 - I have couple of pixels that go "hot" even on -20C and 2 minute exposures - these you can't calibrate out, but like pointed bad pixel map helps there.

[Buzzard75]

Thanks for the info, all!

[Xplode]

Make sure to dither and the hot pixels will be removed easily.
If you use darks for an uncooled camera make sure they are taken at a lower temperature than the lights, that way they will remove some of the dark noise, but probably not all.

If the darks are taken at a warmer temperature they will also remove some signal.

[Buzzard75]

6 hours ago, Xplode said:

Make sure to dither and the hot pixels will be removed easily.
If you use darks for an uncooled camera make sure they are taken at a lower temperature than the lights, that way they will remove some of the dark noise, but probably not all.

If the darks are taken at a warmer temperature they will also remove some signal.

It's the iOptron SkyGuider Pro and is simply an RA clockwork drive. It's not a true equatorial mount and it's not being driven by a PC, so I can't really dither. In the end, the photo turned out much better than expected. Using the darks removed all the hot pixels on the lights. I expected to see hot pixels in the data, I just hadn't expected to see quite so many.

Darks were taken subsequently from the lights so they were roughly the same temperature, at least within a degree.