Re: so called new approach to design doublet APOs. ;>)

From: Tom Davis (tdavis11_at_carolina.rr.com)
Date: 11/20/04 

Date: Sat, 20 Nov 2004 16:14:32 GMT

"Mayday" <mayday@nospam.net> wrote in message
news:pnJnd.38314$IQ.32422@bignews6.bellsouth.net...
> "ValeryD" <aries@mercury.kherson.ua> wrote in message
> news:5c4a4ee7.0411200016.17aa60dd@posting.google.com...
> Where can this review be found? Thanks.
>

The reviews are in the BurgessRefractors group on Yahoo Groups. If
you can't get in, let me give you a short version here.

This scope was originally planned by Bill Burgess back in January of last
year. Due to other projects, the first light of the finished prototype
(the lenses are production, but the rest of the scope a Burgess design
with WO mechanics and Burgess mechanics) did not take place until
last week. The scope has a 92mm F/7.6 focal length on the final
production version. The one I have uses a bit fatter retaining ring, so
that the actual unvignetted aperture is 91mm (F/7.7) with a 700mm
focal length. The optical tube on mine is one that was originally intended
for a 600mm lens (the manufacturer changed the spec to improve
correction). This was just fine for me, as I have a 3.5" TeleVue extension
tube, and the shorted tube allows me to use my binoviewer without a
correction lens (meaning no magnificaton), while working just fine for
standard eyepiece use with the extension tube. Production versions
will have a longer tube (although I'm sure one could be requested with
the shorter tube if desired). The scope includes nice CNC tube rings,
a really smooth rotating William optics focuser, a William Optics
dialectric diagonal, case, and a set of Burgess eyepieces. It will also
include a 6x30 illuninated WO finder. Mine just came with a case, tube
rings and a dovetail plate to fit a Vixen GP mount.

I was immediately struck at the lack of color when I first set it up in
the daylight. The view was like that of a reflector compared to my
Orion ED80. Zero color, period, either inside or outside of focus. The
ED80 did show some be comparison (very little compared to an
achromat, but noticeable when compared to the fluorite). At night,
my first object was Vega. no color, period. The ED80 showed a
dim red first diffraction ring. Also, the star image was extremely tight,
obviously tighter than the ED80, which is no slouch. The extra 11mm
of aperture over the 80ED was readily evident. This scope showed all
deep sky objects I looked at as well as I've seen in any scope of this
size. Very nice, contrasty views. Later, Saturn showed up better than
I've ever seen it in this size scope. I showed the Cassini Division around
the full extent of the visible ring, equatorial banding, polar darkening,
and
the Crepe ring in front of the planet and more subtly in the ansae. It also
showed ring shadow as well. I could just detect the bottom of the planet
peeking out below the ring system. The view was crisp and sharp all the
way up to 350X (although it was getting a bit dim at that point). The
view in the binoviewer was really, really nice. Since Sirius was now up,
I turned the scope to it, and found again, zero color in-focus. Only a very
slight taint of color to the rings outside of focus, and I really had to
look
hard to see it.

If the main production run turns out this well, there will be a number of
happy customers. Other than the ridiculous amount of flack I have taken
over this scope, I am very happy with it. Since the first five lenses
tested
all were of excellent quality on the interferometer, and essentially of
identical quality. The liklihood that the production run of scopes (already
in process) seems to have a better than even chance of success. I
talked Bill into selling me the one he sent me for review.

Thanks, Tom Davis

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