Wholegrain .. thats the images not the bread

[toryglen-boy]

Ok, so i am just starting down the long road of imaging, and i am just getting my head around this, i am using Deep Sky Stacker to stack my images, although TBH i can see absolutely no difference from stacking 5 or 6 images, than a single shot, but that must be my n00b eye.

Ok, so i have been taking a dark for every handfull of lights, first questions is really stupid, How do i take a "dark" ? i have just been keeping the lens cap on, taking a covered shot for the exact same time as the exposures i have been taking to stack.

secondly, how do i use the dark to get rid, or at least help with thermal noise? my ISO is set to 1600 and my exposures are only 30 seconds, and i didnt think that was very long, but my god it looks sooooo grainy, but alot of this must be noise as the dark looks just as grainy, and in the same style

What settings should i change in DSS, and how do i use the dark to good effect?

There are many guides that tell you what darks do, but not how to do it through software

many thanks

:)

[dugnsuz]

Ok, so i am just starting down the long road of imaging, and i am just getting my head around this, i am using Deep Sky Stacker to stack my images, although TBH i can see absolutely no difference from stacking 5 or 6 images, than a single shot, but that must be my n00b eye.

Stacking increases the Signal to Noise ratio (S/N) so you should see increasing smoothness in the dark background with an increase in the subs you stack. You'll be able to pull much more detail out of the stacked image during processing thanks to stacking.

Ok, so i have been taking a dark for every handfull of lights, first questions is really stupid, How do i take a "dark" ? i have just been keeping the lens cap on, taking a covered shot for the exact same time as the exposures i have been taking to stack.

Spot on Duncan - now my stupid question!! Have you turned the in camera noise reduction (ICNR) function off? If not, your camera is already taking and subtracting the darks for you.

secondly, how do i use the dark to get rid, or at least help with thermal noise? my ISO is set to 1600 and my exposures are only 30 seconds, and i didnt think that was very long, but my god it looks sooooo grainy, but alot of this must be noise as the dark looks just as grainy, and in the same style

You should be able to load the darks into DSS for calibration of your light exposures.
iso1600 is a bit high to begin with. Work around 400 - 800 to begin with.
If you're only taking 30sec exps I would use the ICNR for ease of use - it will double the exp time (30sec light + 30sec dark) but save hassle loading up darks etc into DSS at this stage of your imaging career!!:P
Also turn the LCD off during imaging - when the review lights up it only adds to the thermal noise recorded by the sensor.

Doug:thumbsup:

[jjjnettie]

If you're only taking short subs, you need to use a higher ISO.
But you need to take dozens and dozens of subs so you cancel out the noise.

I've experimented with different setting eg. Taking 30 subs @ ISO 3200, 30 @ 800 and 30 @ 400. Then stacking them all together. The results are pleasing, a smoother, brighter image compared to using just a single setting.