M57 with DSI

Pete Lawrence wrote:
On Fri, 10 Dec 2004 18:36:29 +0000, Tim Auton
wrote:

Out of curiosity Pete, how do you focus?
[snip]
Depends what's up and about Tim. I have used DSLRfocus in the past.
It's a good program and works with a number of DSLR cameras to help
you achieve focus. It's pretty cheap too and the author, Chris
Venter, is a really friendly chap.

Sadly Windows only and I have a Mac laptop. OS X and Apple hardware is
lovely, but not particularly well supported for amateur astro work
(IRAF is a touch heavyweight for a few snaps of the moon!).

Perhaps I'll write something if Canon update their SDK to support the
20D and approve me as a developer.

I move the scope to a bright object and focus it through the camera's
viewfinder. I make a number of passes through the focal plane so I
get a feel for where the focus is. Once I've done this, I apprach the
focus from one direction (out to in - i.e. shortening the focusser)
and stop it short of the focal point. I then proceed to take short
exposures of faint stars, displaying and max zooming the results. I
tweak the focusser in by a very small amount (and I mean small -
sometimes it doesn't even feel like the focusser has moved!) and keep
checking the star sizes.

That's pretty much how I'm doing it, but in a marginally less refined
way. OK, I just twiddle the knob till it looks about right


Tim
--
This is not my signature.