Re: [APML] focusing question for reflectors

["Andrew Schott" <aschott@cfl.rr.com>]

Sorry in advance if this gives double posts.  I'm testing a thing with
OOootlook Ex-press and the results may be unpredictable/:-\

A low profile focuser *might* get you there since most 'store-bought' scopes
tend to have taller rack&pinion focusers.  If you're very near focus you can
gain an inch or more this way.  Another suggestion is to try a barlow lens.
It's simple, it extends the focal plane on most installations and usually
doesn't cause too much distortion.  The only problem is the apparent
magnification or "field-stretching" that it causes.  This will increase your
exposure times and reduce your field of view.  I use one a lot with my video
gear and have only occasionally used it with my film cameras due to the
darker image.  Most of my work is planetary so I've never tried to resolve
the faint fuzzies most of the members of this group are so good at.  I've
seen a variable barlow somewhere in one of the big three catalogs that I
think can be adjusted down to something less than 2X.  There may be a
manufacturer out there that makes something less powerful than that to help
you out.  I would imagine the focal plane extension varies with the power so
be advised.  A weaker one might not extend the plane far enough.

Clear skies!

Andrew Schott


----- Original Message -----
From: "m.dyer" <mr.m.dyer@worldnet.att.net>
To: "Astro-Photo (E-mail)" <astro-photo@seds.org>
Sent: Saturday, January 05, 2002 12:19 PM
Subject: [APML] focusing question for reflectors


> Hello all:)
>
> I have been trying my hand at astrophotography with an Orion SVD 6"  and
> Olympus OM 1/10 cameras.  When trying to focus using the Prime focusing
> method, it seems that I can not get the  camera far enough forward - into
> the telescope.  It comes up just short of sharp:(  I was told that I may
> have to drill new holes in the tube and move the primary mirror forward,
but
> that idea doesn't appeal to me.  Are there any other options - a low
profile
> focusing assembly, or special t-ring adapter?
>
> Thanks in advance:)
>
> Mark Dyer
>
>
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