RE: [APML] BORG Telescopes [was AP Traveler]

[Jon Kolb <jkolb@mindport.com>]

Ulrich,


> Any APML member shooting 
> with Borg scopes?
> Anyone know of web sites with photos taken with them?

As mentioned previously, Dave Kodama is doing a lot of nice work with the
100 ED set at f/6.4 and f/4.  Garth Buckles, who doesn't have a web site,
has taken some really nice shots with the 350mm f/2.8 model.

I also have the 100 ED set, but I haven't achieved good enough results to
post yet.  This is due to many factors, but chiefly my inablity to correctly
calibrate the Beattie screens I put in my Pentax 67 cameras, resulting in
bad focus on most of my shots so far.  I've recalibrated the screens, and
also just received a Mitsuboshi knife-edge focuser, which I hope to try out
this week. I expect to start getting usable images soon.  

My objective arrived out of collimation, which also caused some lost time as
I tracked down the problem.  Ted Ishikawa, the proprietor of Hutech, fixed
the problem immediately after it was discovered, shipping included.  He is
now personally testing each scope that leaves his shop, so I doubt anyone
else will have a similar experience.  Ted is possibly the most concientious
and helpful vendor I've ever dealt with, and really stands behind his
merchandise.

Since I've had the scope for a few months, I can make some additional
comments about it, even though I don't have any decent images to post yet.

I purchased the 100mm ED set, which consists of one f/6.4 objective,
focuser, and finder base, along with two tubes - one each for the 640mm and
400mm focal lengths.  The set includes a reducer/flattener for f/4 (hence
the other tube), but you need to purchase the f/6.4 field flattener
separately.  The flattener is compatible with all of the medium format
capable Borg scopes (100, 125, and 150), and threads into the Pentax 67
adapter (also purchased separately).  The reducer is only compatible with
the 100ED model, but the reducer that comes with the 125ED set is also
compatible with the 150mm model.  Either reducer threads into the focuser,
which works on all of the different scopes mentioned.  The prices are such
that you are better off buying the set with the reducer than adding the
reducer and short tube later on.  

I also purchased the necessary couplings to mount 35mm cameras to the scope
via the Pentax 67 mount.  This is definitely the way to go if you're
planning to go into medium format in the future.  The 35mm coupling threads
into the Pentax 67 mount, so there's no flexure at this point.  The Borg
35mm mount is also a "wide mount" like the Takahashi units, so there's no
"hard stop" vignetting like you would get with a standard 2" adapter and
T-ring. 

All of this stuff threads together in whatever combination you are trying
use.  The objective screws into either tube, and the massive helical focuser
goes into the finder base, which itself goes into the other end of the tube.
Two dewshields are available, the larger of which (another separate
purchase) is recommended for use at f/4 to avoid vignetting. It all goes
together very easily, although the threads are very fine and require some
care to start to avoid cross-threading.  It's all very modular.  The fully
assembled f/6.4 configuration, with Pentax 67 mount and Pentax 67 rear lens
cap on it, just fits into the length of a Pelican 1650 case, with loads of
room left over for the reducer, short tube, caps, finder, and accessories.

The big focuser takes some getting used to, but it doesn't rotate the
camera, and it has positive locks (two).  I found it to be a little stiff in
very cold weather, but not prohibitively so.  The focuser also has a
micrometer scale engraved on it, so you can get really close to critical
focus from night to night without any trouble.  The overall construction is
very good, but the tubes are very light, and should be handled with care to
avoid dents, especially to the threaded ends.  I do not recommend Parallax
114mm rings for mounting this scope.  The set I had were just too tight for
the 115mm tube, and may have contributed to poor star images in addition to
the collimation problem.  The Tak FS102 tube ring works perfectly, however.

The only complaint I have is that the thread-on dust cover is hard to start
in its threads in the dark.

Hope this helps,

Sincerely,
Jon Kolb
Adventures in Astrophotography
http://home.datawest.net/jkolb/
jkolb@mindport.com


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