About 3 years ago I examined one of Siebert Optics first production
binoviewers.  Although a solid product with good optical quality there were
a number of areas for improvement.  It would appear that in the interim
virtually all of these areas of improvement have been met.  Not all, but most.

The clear apertures are still in the 22-23mm
area, but virtually everything else has been improved.  Mechanically the
unit is excellent, with smooth inter-ocular adjustment and quick easy change
barlow.  You can go from a refractor or Dob to using it without the barlow
in an SCT by a VERY simple shaft replacement.  The barlow shaft slides out easily
and is quickly replaced by a non-barlowed shaft, although the 1.7x barlow
can be used in an SCT for extra magnification.  The 1.7x magnification gives
a nice low magnification and seems to improve the optical quality of the
eyepieces used.    So my best views through the units in some of my faster
scopes were with the barlow in place.  The eyepieces that Siebert Optics
supplied (19mm Ultras) were good solid eyepieces, but would not replace my
19mm Panoptics, although both had a comparible apparent fov.  This is not to
say that the 19mm's were not good and sharp, but did not have quite as good
sharpness at the outer edge on my relatively  fast refractors and
Newtonians. These may be sharper to the field's edge in longer focal
distance scopes, but by and large for the asking price they would not be a
disappointment.

In action, The Siebert binoviewers work much like the Televue binoviewers except
images are inverted. The binoviewers did exhibit more "color" than the Televue binoviewers..
but contrast on the planets seemed a micro-tad better. No out of field reflections could be noticed on these bright
objects which means that the Siebert units must be well baffled.

Now for the potential for deepsky, the Televue units outperformed the
Siebert units by a slim margin here also.  The Televue x2 corrector has a
small edge on the Siebert 1.7x barlow, but this does not rule the Siebert's
out for deepsky by any means.    Televue's edge here was small and the
Siebert units gave very nice views on most DSO's.   But considering the price differential
the budget conscious astronomer should very well consider these for more
than just planets.  It's deepsky potential is considerable.  His price at
the time of posting this is $449-$469 and can be seen at
www.SiebertOptics.com.

Here are a list of other things that have been improved:

1)  Initially the unit had a 2.4x barlow.  It is now 1.7x and is near
parfocal with single eyepieces.  The barlow is more cleverly designed than
most others.  I wish more had a quick integration feature to their barlow
like this one.  A lot of thought has gone into the design of this barlow
method and the barlow also acts as an image erector in Newtonians so your
view when using the barlow will match what you see when looking at a star
map, although this will not be the case in an SCT or refractor. The diagonal
will cause the image to be upsidedown, but correct left to right.  But in an
SCT simply removing the barlow will give an image orientation equal to a
single eyepiece.

2)  The plumbing fixture look that was once commonly mentioned is now gone.
It has been replaced with fine finish stainless steel.  Also to save weight
it appears as though Delrin was used at what appeared to be non-critical
areas.  The binos weighed 1lb 2ozs with the non-barlowed shaft.  Nice for
delicately balanced instruments.  1lb 4ozs when using the barlow.

3)  The eyepiece holders are a fine application of Delrin.  It gave a very
snug fit and fine friction properties to any eyepiece used with it.  The
eyepieces never felt unstable or appear to shift in colimation.  But I am
sure most would agree that the self-centering eyepiece holders that mark
better binoviewers seem to get much better results than the old thumbknob
setups, which seem to have colimation problems.  No colimation problems
could be perceived with any eyepiece combinations I used in the Siebert
unit.

All in all, I am very impressed with what Siebert Optics has achieved in the
last 3 years.  They started out with a good unit and with some needed
improvements - Now they have wiped out nearly all the negatives that were attached to the
early units.  What we are left with is a unit that I have become fond of and
would highly recommend to anyone. Although I slightly prefer the Televues, I would probably
buy these over the Televue because of the price/performance value had these been available
5 years ago.

Todd

SPECIAL NOTE 3/03: Harry has developed an unbelievably versatile 1.35X adapter / corrector that will also work on
the Televue binoviewers. It is excellent and only requires 1/4" of in-travel.