M 31 - Noise

[vlazg]

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]

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]

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

[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...

[vlazg]

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]

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]

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

[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.

[Robert9]

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

[vlazg]

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

[vlazg]

1st used nebulosity and then ccdstack, same result

[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]

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

[vlazg]

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]

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]

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.