M 31 - Noise

[vlazg (George)]

This was taken the other night
22x3min exposures, atik 383 osc, -5deg cooled
Reasonably clear, good tracking
The noise has been appearing lately in a few images
Anybody have an idea whats happening
George

[Somnium (Aidan)]

I had a similar issue with my canon 600d and I noticed in byeos that the sensor was around 50 degrees! I am not sure what camera you are using but check out the temperature and play around with the ISO

[vlazg (George)]

Originally Posted by Somnium

I had a similar issue with my canon 600d and I noticed in byeos that the sensor was around 50 degrees! I am not sure what camera you are using but check out the temperature and play around with the ISO

Oops, an atik 383 osc, cooled to minus 5 deg

[ZeroID (Brent)]

Do you dither ?
The banding effect I think can be caused by the Bayer Matrix on a OSC (or DSLR for that matter) and dithering breaks the pattern effect.
You take darks as well ?

Otherwise a dang nice picture btw...

[vlazg (George)]

Originally Posted by ZeroID

Do you dither ?
The banding effect I think can be caused by the Bayer Matrix on a OSC (or DSLR for that matter) and dithering breaks the pattern effect.
You take darks as well ?

Otherwise a dang nice picture btw...

all images were dithered, using sgpro with phd2, took darks a few weeks ago with the same parameters
disappointed with the noise, would have been a nice image otherwise

[billdan (Bill)]

Hi George,

My guess is that its probably dew, either on the lens or on the camera glass window. Check your subs one by one, probably gets worse towards the end.

Regards
Bill

[vlazg (George)]

Originally Posted by billdan

Hi George,

My guess is that its probably dew, either on the lens or on the camera glass window. Check your subs one by one, probably gets worse towards the end.

Regards
Bill

Hi Bill,thanks for the suggestion, checked the subs, no difference .Ambient Temp was 23C, so no dew was forming at the time

[Chochawker (Malcolm)]

How did you power the camera?

I saw similar effects with my 383 when powered by a battery that couldn't cope with the camera's demands.

When I moved to a beefier battery (and more recently a mains supply) that sort of thing has not come back.

[Robert9 (Robert)]

Hi George,
You don't say what program you are using for stacking. Could it be some artefact of the stacking?
Robert

[vlazg (George)]

Originally Posted by Chochawker

How did you power the camera?

I saw similar effects with my 383 when powered by a battery that couldn't cope with the camera's demands.

When I moved to a beefier battery (and more recently a mains supply) that sort of thing has not come back.

Powered separately with a 30 amp/hr deep cycle from my golf buggy, fully charged, tried that.

[vlazg (George)]

Originally Posted by Robert9

Hi George,
You don't say what program you are using for stacking. Could it be some artefact of the stacking?
Robert

1st used nebulosity and then ccdstack, same result

[Tony_ (Tony)]

Too bad about the noise - would have been much better without it.

I've reduce the noise a bit with photoshop - maybe it's a bit better?

Tony.

[vlazg (George)]

Tony, i redid it myself , best i could do before the noise starts, but i am missing detail that i think is there

[vlazg (George)]

It seems the atik 383 is very voltage sensitive
I used a converter to a constant 13.8v and the noise is gone
21 3min subs, darks taken 3/12 ago, flats
flt 110 with p flat4
sg pro,nebulosity, cs6



George

[AlexN]

Any reason you are only cooling it -5c? I used to routinely run my cd's at -20~-35c for best results.

[vlazg (George)]

Originally Posted by AlexN

Any reason you are only cooling it -5c? I used to routinely run my cd's at -20~-35c for best results.

Here in Darwin minium temperatures lately have been around 22-23 deg, so i didn't want to push it. delta is about 35 not 40 as they say.
have tried -10 but it did not seem to make much difference hence -5

[AlexN]

Ahh ok. I didn't notice you were in Darwin. I lived there years ago. I don't think it ever got to 22 when I was there. 24~25 was the lowest over night temps I saw. Where in Darwin are you? Plenty of places to get away from light pollution up there. If you don't mind the reptiles that is.

[vlazg (George)]

Originally Posted by AlexN

Ahh ok. I didn't notice you were in Darwin. I lived there years ago. I don't think it ever got to 22 when I was there. 24~25 was the lowest over night temps I saw. Where in Darwin are you? Plenty of places to get away from light pollution up there. If you don't mind the reptiles that is.

I Live in Fannie Bay but go out t a mates place out behind Humpty Doo. Reptiles aren't not too bad but the cane toads are taking over. a 6 iron keeps them at bay.

[AlexN]

I was at Larrakeyah, mind you that was back when Cullen Bay was basically a dirt patch with a marina. Haha.

Humpty Doo would be a perfect spot for a permanent observatory I think. Obviously only 6-7 months of reliable clear skies a year though.