DSLR imaging: delay between exposures

[Black Knight]

Hi all,

I've noticed a fair bit of noise in my DSLR images (800 ISO). I'm wondering if this is caused by too short a delay (currently around 15 seconds) between exposures. At the moment I am using 30 second exposures, but aim to squeeze a little more out of my setup if at all possible.

So what sort of delay should I be using?

Thanks

[Vega]

I do 300 sec exposures (guided) and never touch the delay... I leave it on the default 10 seconds (using ImagesPlus). However, I always take darks to remove noise.

Cheers

[Black Knight]

300 seconds? Wow! Well maybe my problem lies elsewhere then. If you can do 5 mins on a 400D then I guess I ought to be able to do 30 seconds on a 500D!

I always take darks as well as bias frames. My camera isn't modded - would that make a difference?

[lukebl]

I wouldn't have thought modding has any effect on noise.

How many darks are you taking (do lots), and are they of the same exposure as the lights? And what stacking software do you use? Registax?

[Black Knight]

At the moment I have been taking 10 darks, all under the exact same conditions as the light frames (ISO, temp, focus, delay between exposures etc), except the telescope cap is on

I stack in DSS.

[themos]

The longer your sub, the cleaner it will look (until you start saturating the pixels, of course).

[jgs001]

I only leave 10 second gaps, and haven't really noticed much of an issue.

[Black Knight]

I'll try longer subs then. On my setup though, it is a battle against star trailing

[Uranium235]

I go for 30 second gaps between exposures, it gives the CMOS a bit of a rest before the next image - and it gives you time to cancel the shoot if things arent to your liking.

[dph1nm]

I've noticed a fair bit of noise in my DSLR images (800 ISO). I'm wondering if this is caused by too short a delay (currently around 15 seconds) between exposures. At the moment I am using 30 second exposures, but aim to squeeze a little more out of my setup if at all possible.

I very much doubt it. My Canon1000D has virtually zero dark current in 30secs (I never use darks), so I can't see how a rest would help. The read noise is very low as well, so this shouldn't make it look noisy. If might if you have a bright sky though? Or simply not enough subs?

NigelM

[Black Knight]

From what I've learned, I think it's probably not enough / or long enough subs. For my last two targets I only ended up with around 20-30 odd subs after the rest were discarded.

[Keiran]

I was told to do atleast half to the amount of lights you take, unless under 40 then match them... But the more you do the better.

I might be wrong, so correct me if i am

[dph1nm]

From what I've learned, I think it's probably not enough / or long enough subs. For my last two targets I only ended up with around 20-30 odd subs after the rest were discarded

Well here is M57 with a 1000D from two nights ago taken though an 8.5" Newtonian - 22x30sec frames, combined in DSS using 20 bias frames but no darks. I have deliberately stretched it so you can see the noise levels relative to the objects. This is using a LP filter, which will have cut the noise in the red channel a bit, but you shouldn't be doing any worse than this with the 500D.

NigelM