[AZ-Observing] Re: DLSR Focusing
- From: "Jimmy Ray" <jimmy_ray@xxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Thu, 5 Jul 2007 06:56:43 -0700
In investigating "hartman masks" I came accross an article that goes into
additional methods (the star trailing looks interesting) in addition to a
mask. Here's the link
http://www.astropix.com/HTML/I_ASTROP/FOCUS/METHODS.HTM . Additionally,
another website discussed having a single triangular hole above and in
between the two round holes on the hartman mask This is supposed to allow
the user to know if focus need to be moved "in" or "out". That link was:
http://cometman.com/Mask.html.
This has been a very inlightening discussion and I'm feeling good about the
results from it. Now I need to get some (more) stuff, build some stuff and
actually get out in the back yard and try it! Thanks to everyone for the
advise that has been presented so far. Really diverse and great...(feel free
to keep adding)
Jimmy Ray
----- Original Message -----
From: "Rick Scott" <rmscott@xxxxxxx>
To: <az-observing@xxxxxxxxxxxxx>
Sent: Wednesday, July 04, 2007 23:43
Subject: [AZ-Observing] Re: DLSR Focusing
I use the Canon Right Angle Finder C along with an occulting bar that I
hold in front of the telescope to act as a rough Hartman mask. The
occulting bar can be anything, even your arm, if it's wide enough
compared to the aperture to block a significant portion of the light
path. The bar is positioned to pass through the center of the aperture
leaving a light path on either side of it. By doing this you'll see a
double image when the focus is not correct. Just focus until the
doubling disappears.
Rick Scott
Jimmy Ray wrote on 7/4/2007 11:38 AM:
I'm looking for the group's opinion on DLSR focusing when taking
astrophotos. I find that when I have the camara body mounted in prime focus
(Canon XTi to a 8" or 11" SCT) it is dificult to assess focus and to date
the results haven't been "stellar". I was looking at the Canon magifying
angle finder "C" which has 1.25x and 2.5x and runs about $180 delivered.
Other options or tricks?
Jimmy Ray
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