Noise Reduction Help Please!

[Smithynova]

Hi all, 

I've been imaging the Elephant's Trunk Nebula over the last few nights. I have stacked 9 hours of different exposure times - 180s, 300s and 600s

I included darks at each exposure time, flats and bias frames in the stack - however when I started to stretch the data in photoshop, it is horribly noisy with coloured streaks through it - I'm guessing these are hot pixels? 

Can anyone give me some advice when stacking fames of different exposure times on Deep Sky Stacker? Do I need to assign the correct dark frame to each exposure, or does DSS do this automatically (which is what I assumed)

My other images have not had these issues (some have had a few of the coloured streaks but nothing like in this stack!)

I have stretched the data very basically and I've included a crude screenshot - zoomed in on an example of the noise - but it is over most of the image. 

Other information: I'm using a ZWO ASI183MC Pro cooled to -10C with 160Gain, no binning. Scope: Redcat51, HEQ5 guided exposures with dithering using the ASIAIR Pro

 

Thanks in advance!

[wimvb]

Try more aggressive pixel rejection in dss; what you have is hot pixels and so called walking noise. For future images, increase the dither step in PHD, this will break up the pattern created by hot pixels. For a dslr ( and in my opinion also for cooled cmos), you need to dither at least 12-15 pixels in your imaging camera.

Have you tried stacking the individual exposure times, ie a stack with only 180 s exposures, one with only 300s , and one with only 600 s? It may very well be that one of the three exposure times deteriorates the whole stack.

Edited May 4, 2021 by wimvb

[PeterCPC]

AstroFlat Pro is great for removing noise.

[Ollyb]

Hi...

I’ve just imaged IC1396 with a similar setup to yours except I use an ASI1600MM Pro...

After reading various forums about calibration frames I decided not to use Bias frames and, as I keep my camera sensor permanently attached to a filter wheel, I don’t use flats. I used 18 x 420 sec exposure at 200 gain and used 20 Darks and got great results. I know you are using a OSC camera but maybe  this will help... 

Ha frames x 18 after stacking...

Edited May 12, 2021 by Ollyb

[CloudMagnet]

Dont forget Topaz DeNoise as well, bit expensive on first glance but you can do a free trial as well. Works great to remove "static" noise but I think ensuring you dither in RA and DEC will get rid of any walking noise as well.

[Ollyb]

1 hour ago, CloudMagnet said:

Dont forget Topaz DeNoise as well, bit expensive on first glance but you can do a free trial as well. Works great to remove "static" noise but I think ensuring you dither in RA and DEC will get rid of any walking noise as well.

Yes, forgot to mention Dither helps a lot with noise