RE: [APML] Refractor recommendation

["Dave Dockery" <dave.dockery@zianet.com>]

Greg,
I really appreciate you taking the time to put together the well thought
out and informative reply.
Santa is bringing a Losmandy plate and rings for Christmas.  I've been
using a six point mount from Ken's Rings and Things for my ST-80 and I
really want to step up to the dovetail system for my new refractor.  I
already have Losmandy counterweights and have been very happy with them.
(2D is the way to go...)
I've dealt with the SCT mirror flop issue using a carriage bolt and
nylon spacers in the shipping bolt hole and it seems to work pretty
well.  When I auto-guide using the LX200 at 1600mm, I'm thinking that
the piggybacked refractor @ around 500mm should have nice tight stars,
as long as I'm using a rigid mounting scheme.
I've been meaning to tune up my wedge and drives but haven't yet.  I
have a pretty good PEC Cal and my backlash compensation is on but at a
pretty large value and there's still a slight shift when I change
directions.  A tune up would probably help that. 
Thanks again, Greg.
Dave


-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org] On
Behalf Of Greg Hartke
Sent: Saturday, December 14, 2002 7:16 AM
To: Astrophotography Mail List
Subject: RE: [APML] Refractor recommendation


BTW, Dave, did you read Dave Novoselsky's review of the 76 ED on
cloudynights (http://www.cloudynights.com/reviews/borg76ed.htm)? He's a
very
experienced visual observer and always worth a read. I'm very optimistic
about the performance I can expect from mine. Besides, it's always a
*lot*
easier to do AP through a refractor than through an SCT. It'll provide a
pleasant contrast.

When assessing costs, don't forget things like mounting plates, etc. The
Borg rings can use a Losmandy universal dovetail which runs something
like
$75, not to mention the blocks you'll need to mount to the LX-200.
(Check
with Scott Losmandy directly if you're uncertain what you'll need.)
You'll
also want a finder of some sort. (I ordered a unit power reflex sight
from
Orion for mine.) Also keep in mind that you'll need a counterweight set
to
piggyback any scope on your LX-200. Like most, I recommend the Losmandy
2-D
CW set that you can mount under the OTA of the LX-200. I have that and
it's
excellent, though I don't use it anymore since I switched to an MI-250
mount.

Hmm. This didn't occur to me before but the Borg mounting rings will be
useless for your purposes. (I bought the rings because I'll have the
scope
on a side-by-side mounting plate with a guidescope occupying the other
dovetail.) In your case, you'd actually need something like a set of
Losmandy guidescope rings mounted on a dovetail atop the OTA because
you'll
want to adjust the pointing of the Borg relative to the SCT pointing. If
it
were me, I'm not sure I'd want to mar the finish of an expensive OTA
with
the three-point Delrin tipped adjustment screws of the rings. Others do
it,
though, and it may not bother you.

Another issue to consider is how well it will work to piggyback a
refractor
of this focal length on your SCT. The flexure in the optical train of
the
SCT could potentially lead to problems. I've shot at 200 mm piggybacked
on
my LX-200 with no trouble (make sure you secure the primary through the
shipping bolt hole!) but the 76 ED will be closer to 500 mm focal length
and
I'm not positive you can expect nice round star images from a long
exposure
with this set up. It's worth thinking about this potential problem.

BTW, the Meade SuperWedge works excellently with about $30 in parts and
a
little sweat equity used to add bearings to the adjustors and to replace
the
azimuth dog (which engages the tang on the field tripod to do the
azimuth
adjustment) with a more rigid home made unit. These minor mods result in
virtually zero backlash and extremely easy (two finger!) adjustment. The
only remaining backlash comes from some flexure in the tang on the
tripod
(it's very minor) and there's not much you can do about that. Polar
alignment becomes a joy after you've made these mods.

The LX-200 is a very capable system for beginning and intermediate AP if
you
know how to keep the drives working properly. If you don't know about
the
Meade Advanced Product Users Group, you should check out their web site
(www.mapug.com) for advice on (for example) combating and removing
backlash
and retrograde motion. If you keep things tweaked and train your PEC
well,
the LX-200 system works quite well.

Good luck!

Regards,

Greg


-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On
Behalf Of Dave Dockery
Sent: Saturday, December 14, 2002 12:03 AM
To: astro-photo@seds.org
Subject: RE: [APML] Refractor recommendation


Hi Greg,
I was wondering about the Borg.  Sounds like another great option since
I'm
shooting 35mm and I've seen some of Dave's work.
Sorry about the weather but you know it's only because you bought the
new
scope.
Thanks for the help,
Dave


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