Noisy image problem

[RikM]

What am I doing wrong? I know I need more subs but with the light summer sky will I just get more grey mush? The batteries on my mount motors and camera died at the same time so I took the hint and called it a night (morning). Now I can't seem to bring much out without the image going all blocky.

Stock Canon 300D on SW150P, no LPR filter or anything

ISO800

48 x 30s lights

12 x 30s darks

7 x sky flats on Av mode (came out at 1/160)

6 x dark flats (set to 1/160)

10 x bias at 1/4000

Stacked in DSS at default settings.

Attached low res. versions of DSS output stack and my best attempt at initial processing. I only have PS elements 7 for processing so the curves tool is limited. There is a colour curves tool, but you are very constrained in how much adjustment you have. I just move the sliders until the curve looks the right shape and the image looks better than before.

I would love it if someone could put me right.

Rik

[blinky]

I think the image is too noisy due to the low exposure - try for a minute or longer.

[Psychobilly]

For the relatively short exposure its a very nice image...

I'd go along with Craig.. if you can up the exposure lenght and still have good star shapes then thats probably the best the way forward...

Peter...

[RikM]

I am sure that would help get more signal but I don't have a remote so am limited to 30 seconds by the on-board camera timer. I am not sure my mount would cope for much more than 30 seconds either. I think I will try and get a timer remote.

[adamsp123]

Hi Rik, damn fine picture for the amount of subs you took, try stacking without the dark flats and bias, sometimes less is more. It is a good idea to set up a darks library, I have 30 subs in each of mine (exposure time and temp matrix) to generate a master dark I also use about 20 - 30 flats.

[brianb]

Actually, the brighter the sky, the longer the total exposure you need to get a smooth result. If you can only manage 30 sec exposures then you probably need 60 x 30 sec stacked to get the same SNR as 10 x 2 min.

You're using a DSLR. Use the LOWEST ISO setting you have - you get less noise that way, and more dynamic range too.

Sky background is better removed using the middle slider in DSS ....

.... and the orange mush will be greatly reduced by using a LPR filter ... B+W 491 "Redhancer" works quite well on sodium lamps (but of course has no effect on twilight).

Finally, if you use sigma kappa stacking, the satellite trails / aircraft lights etc. will "magically" vanish when the stacking happens.

[martin_h]

I ran your pic through Noiseware Professional to get rid of some of the noise, its got rid of a fair bit.

[RobH]

I think that's a fine image for the short subs, and you've done well bringing it out of that bright background.

When you calibrate an image, either remove bias, or flat darks from the flats, never both. You can throw the flat field calculation out by using both.

Cheers

Rob

[Psychobilly]

I think we need to make the DSS "valid" Calibration options a sticky... as it comes up every few weeks...

Just because "Maxim" does something in a particular way it doesnt mean other programs that people use all work the same

[RikM]

Thanks for all the help and nice words. I hope to get better at this in time for the dark skies. Here is my final tweak on this image and I guess it will have to do for now.

Rik