Stacking photos and darks

[batema]

Sometimes when looking at the iformation provided on some of the photos I see a number of shots have been stacked however there might be 10 sec with 30 sec and 60 sec shots stacked. Is there a benefit in stacking different timed shots of the same image???? Also If you shoot 10 shots of something how many darks should you take?? We have not built anything yet to allow us to take flats however we have a connon 400d that comes up with the self cleaning sensor. Do we need to take flats?? Thanks Mark.

[Alchemy]

bit harsh when no one helps.....

benefit of stacking different times- not usually stacked in one hit although some have used photoshops hdr facility to do this, a better way is to stack times similar together and then mask together in photoshop for images like m42 which have huge brightness difference accross the subject.

if i shot 10 shots id want 4-5 darks

for flats just stick a white t shirt tight over your scope and point at a patch of sky straight up just before sun comes up, turn it into grey by desaturating vwoila flat feild.

flat fields are not mandatory but will improve your deepsky images. and to some degree help remove dust donut type flaws.

[theodog]

As per Alchemy

Remember darks should be taken at the same temp and exp time, so take them as frequently as time allows -every 4-5 shots maybe.

I (sometimes) do flats using the evening sky. I don't remove or change the camera orientation after taking the flats.

I don't trust anything "automatic" and would rather have some imput, so I would still do flats. It doesn't hurt to learn and practise this technique.:)

[Terry B]

Flats are important to fix dust and also to even out vignetting. It is very easy yo do with a digital camera. I do then at the end of my session after I have parked the scope and turned the mount off. I put a T shirt over the front of the scope, turn the lights on in the nearby room and aim the scope at the lights by releasing the clutches. I take 7 frames with the camera set to auto. Each one is about 1 sec exposures. It doesn't really matter as long as they are not too long to need dark frames. Then average the frames in your favorite processing software.