08-12-2010, 07:06 AM
[quote name='popo' timestamp='1281565868' post='1694']
Even at 30 seconds at those focal lengths I would expect some trailing if you're not using a tracking mount.
[/quote]
Yes, that is definately the case ... a little depending on the region of the sky you are
pointing at, but generally .... yes.
With an 85mm you get blurred stars with exposuretimes longer than 4-8secs ... startrails
form from roughly 30sec onwards ... so, with an 135mm you need a shorter time
(something like 2secs or less) or you need to mount the camera on a telescope
and use the telescope as a tracking system.
Even at 30 seconds at those focal lengths I would expect some trailing if you're not using a tracking mount.
[/quote]
Yes, that is definately the case ... a little depending on the region of the sky you are
pointing at, but generally .... yes.
With an 85mm you get blurred stars with exposuretimes longer than 4-8secs ... startrails
form from roughly 30sec onwards ... so, with an 135mm you need a shorter time
(something like 2secs or less) or you need to mount the camera on a telescope
and use the telescope as a tracking system.