Re: [APML] 35 mm Camera & Focuser

["John C. Mirtle" <spampit@shaw.ca>]

----- Original Message ----- 
From: "William R. Mattil" <wrmattil@ix.netcom.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Monday, November 24, 2003 9:09 PM
Subject: Re: [APML] 35 mm Camera & Focuser



Lumicon 2 inch Newtonian Off Axis Guider. *But* you might need something
different because at f/4 you will need the coma corrector and I am not
sure what the Vixen specifics are on theirs and how it mounts. Lumicon
has a coma corrector that threads into the bottom of the OAG. You can
<- snip ->

Bill,
    The Vixen *was* designed to be used with a guidescope - there wasn't
enough backfocus for an OAG. Most of the images you will see were done that
way, as there weren't many other options. Vixen have redesigned the scope a
bit, according to their web site. It's now green, has a bigger finder and
they have done "something" to the focuser. What that is exactly isn't clear
from the description, but it appears that they have extended the back focus
a bit or increased focuser travel. If there is 7/8" of in travel from focus,
then a Lumicon OAG would work. You just need to find one that is 60mm in
diameter......
    The Lumicon flattener is a bit of a mixed blessing. I have one that I
used at f4.5, which it was apparently optimized for. It got rid of coma all
right, but substituted massive amounts of spherical aberration. So bad, that
I could never get it focused. Even under a knife edge, it never nulled out.
It was threaded on to a Lumicon OAG for correct spacing, but in the end I
was getting better images from my f6 Newtonian. Your mileage will probably
vary, but those were my results.

John Mirtle
Calgary, Ab. Canada

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