[APML] Tak refractors, 35mm and off-axis guiding

[Alan Voetsch <alanv12952@yahoo.com>]

Hey all,

I'd like to share some of my experiences in setting up a guiding system
for my refractors. There is a standard pattern of using either a side
by side or an over/under setup. I've tried both, but after asking
dozens of questions on this list and others, I believe there may be a
better solution for some of us. Starting 3 years ago with a TV-85 and
EM-1 mount, then last Spring a GM-8, to a Tak FS-102 on a new
G-11/Gemini this last fall, I have searched for a better way, and
eventually I found it.

I want to take a minute to say that I got loads of help, advice, and
suggestions from many of you. Thanks for your patience. But the guy who
provided the key link is James Lacey. James is not a list member (APML,
those on the Losmandy group know him well), but did respond to an ad I
placed on Astromart asking for help. James has a website linked from
astromart (sponsor):
http://home1.gte.net/res0zbiw.index.html
He's got some cool stuff for Losmandy products; computer interface
cables, DC/DC convertors, Gemini control stuff, Gemini focusing
interface, etc.. He was very helpful and answered all my questions.
Eventually I asked him the right question, and he told me about the
"Feldstein adapter". If you want to know something about Losmandy
mounts, Gemini, or most anything else, James will probably know the
answer. 

Back to the Feldstein. This is an adapter that threads into the 2.7"
drawtube of Tak scopes and has 2" SCT output threads. I recently found
out that Adirondack Video has something similar, but not made by
Takahashi, so it's a bit cheaper (too late for me). Yeah, that's right!
These allow the use of SCT accessories. Some of you may know this, but
in my 4 years on this list (APML) I have never seen or heard of these
adapters. Which is why when I decided to add a refractor to my scope
arsenal I just assumed that my guiding options were: side by side or
over/under. I know some have gone their own way and have custom made
these adapters for their scope. What I didn't know is that these are
readily available at Anacortes and AVA. For $120 (Anacortes), I was
able to dispense with the following:
1. Guidescope
2. The rings that hold the guidescope to the DMM plate
3. The DMM plate
4. The DSBS plate
5. Plus, the Camera Angle Adjuster, CA35 and wide mount t-ring are
rendered redundant.

I was lucky enough to acquire a second Taurus Tracker III last month
for $175 on Astromart. I'm setting that one up on the Tak. The Taurus
itself performs the rotation function (CAA), the Feldstein sort of
takes the place of the CA35 and a regular t-ring is all you need to
mount your 35mm camera to the Taurus.

Do you understand what all this really means? All that weight, all
those multiple flexure points, GONE! The answer... A Feldstein adapter.
So simple, so hard to come by. This system is sort of second nature for
me because I've used a Taurus on my LX200s for several years. Instead
of that hulking mess on top of my mount, there is now just a single
OTA. This will save wear and tear on the servo motors, make balancing
easier, and there's just a lot less crap to haul around, assemble in
the dark, etc..

I can slso pass along this recent update: first photographic light for
this system was this last week. There was no pickoff shadow, but I
still need to nail the focus a bit better. The last 3 shots were of the
NGC1977 and M42 area. For the last one, I turned off the ST-4. The ST-4
worked beautifully with the new mount and Gemini by the way. Anyway,
that last shot was 30 minutes. I had to break out the magnifying glass
to see the star elongation. It looked every bit as good as the other
two that were guided with the ST-4. The reason I feel this is important
is because (I believe) the reason the mount did so well unguided is
that it only had a single OTA to carry. 

Those of you who have guided off-axis know that guiding off the same
light path that you're imaging, is the safest way to good photos. 

I hope some of you find this information useful. If I can help in any
way, please feel free to contact me off list.

Alan Voestch

 




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