Quote:
Originally Posted by xelasnave
Chris
I think there is a problem called field rotation.
Alex
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Thanks Alex,
Yes, that's clearly a problem, and I had just edited my post to mention that, (before reading yours - believe it or not
) because I'd left it out originally ...doh...
But there's always a period of time before the effect of field rotation cuts in. I can take simple exposures on a tripod for up to 20secs without losing star shape. Once I use a scope the time drops dramatically, but I can still get clear shots. I'm imagining that I could possibly take a whole row of short shots, realign them to correct the rotation, and then stack them. But I may be way off the mark! I've never tried stacking, so I may have a completely wrong idea about what it can achieve.
There's a site that I have visited before which explains the field rotation issue very clearly. They say that it rules out "long exposure" photography, but it left me unclear as to how long is "long"
I suppose it depends on the telescope. I guess I'm just going to have to try it out and see.
http://www.astronomyasylum.com/teles...stutorial.html
I'd like to know how the guy in that video did it though.
EDIT: He says
"Programs used were, Deepskystacker to stack the images & StarTools to process the images. Because of field rotation I am limited to around 60s depending on position of DSO. The mount is not modified in any way."
60 secs sounds like an age to me. Is his location so much more favourable than mine as far as the general effects of field rotation go? I know that it makes a big difference how far out from the centre of rotation an object is... but 60 seconds sounds like a long time. I guess I'll just have to give it a go...