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Originally Posted by JohnH
Especially from a static Tripod. You have had some tips already - stacking copied images will not get you any signal/noise advantage stacking more images will, also taking longer images will, however you are then constrained by lack of tracking and a desire to see stars as points not trails. You can use this "rule of thumb" formula to calculate the max exposure without noticeable trails
700/F where F is the focal length so here it is 700/50 = 14s
This is for stars at the celestial equator though and stars closer to the pole appear to move more slowly you can use 1000/F at 50 Degrees S, even more closer to the pole.
So take a set of images based around 20s in + and -5s steps use the greatest ISO you can (1600 on a 350D?) and shoot in JPEG to start with, once you are happy with the image and focus switch to RAW and take a set of 10 to 20. Convert to TIFs for registax - and reduce to 1024x768 or so for initial sorting/processing (faster than working at full scale). If you do not have the ability to go over 30s you will need to get a cable release (highly recomended).
You might also try stopping the lens down a little - now this sounds silly when you want as much light as possible but it will reduce the any distortions due to the lens, try going down a 1/2 - 1 stop, a UV filter will help reduce the blue halos (CA).
That's enough for now I think, and welcome to IIS !!!
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Hi John,
This is exactly what I wanted someone to post -- so that I can learn.
I have taken your points on board and will employ them the next time I get out in the field.
Thank you!
Regards,
Humayun