Binoviewers
I have
owned and used a TeleVue BinoVue for the past several years, and have been happy with them
in every respect. And why wouldn't I be - they were one of the
top units available (especially true when I first got them). They were designed to be a Binoviewer (rather than a
conversion) and had larger prisms, and all the newer coatings as you would expect.
They had the typical Al Nagler touch, meaning they provided excellent bright,
high contrast views.....I was happy. The only downside was the 2X
Converter needed to reach focus in my scope limited the widefield views a bit,
but even then looking through them with a pair of 16mm Naglers was awe
inspiring. Then not long ago, the bliss was shattered. I was working a trade for some other
hardware (don't you just love Astromart
?) when I came across the opportunity to trade/sell the BinoVue for one of the later model
AP/Zeiss/Baader Bino that Astro-Physics sells. This particular unit was a
bit unusual in that it had a set of replacement Lapides Adjustable Eyepiece Holders
installed (allowing independent focusing for each eye - not a big deal for me,
but an issue that my wife has to deal with). So I did the deal, and now
have a new Bino.
What do I think......well, in a nut shell - I'm surprisingly pleased! These Binos are very nice! While I am not as skilled a product evaluator
as some folks are - I noticed a difference. The edges of Mars were
suddenly more defined, sharper. Maybe the conditions have just been better since I've been using these, but I don't think so anymore.
Another advantage is that I've found I really like the option of dropping down to lower powers (I wish I hadn't gotten
rid of the 16mm Naglers now). One last benefit, I now have a better chance
of focusing the views for my wife's eyes - it is a great thing. I'll
never try to tell you that there was
"night and day" kind of a difference, but I do believe there was a noticeable improvement in
sharpness and contrast. So let's continue on, and I'll give you more of my impressions,
and some photos.
The photo above is of my "Visual Kit". A Pelican
1500 case with my bino, eyepieces, barlows, filters, diagonal and all the other
bits you might use visually. The case packs it all comfortably, and makes a nice safe travel package.
The images below show the Binoviewer - up close and
personal. These binos are sold with the diagonal, the 2" nosepiece, and a
1.25x Glasspath Compensator (there is a photo of that and its location above the
diagonal further down the page).
The black eyepiece holders are the Lapides adjustors that were added by the
previous owner.
Baader's fit
and finish of these Binoviewers is second to none, and this a very
important consideration for me. I care a lot about the look and feel of my
equipment. These binos are certainly not disappointing in that
respect.
The coatings surprised me as they didn't
appear visually like the coatings I'm familiar with. Absent is the obvious
deep green or
purple color of the coated surface like I'm used to seeing on my eyepieces,
these coatings have a slight golden green color and just seem to make the surface of the glass
disappear. You can begin
to see what I mean with the image of the Glasspath Corrector below - even under
a camera flash.
Below are two photos (top and bottom views) of the Larides
Eyepiece Holders. When I got the binos they were poorly collimated, and I
could not get the images to merge with my 9mm Naglers. I contacted Richard
Lapides and he graciously sent me up a copy of the original installation
instructions. As the instruction were in the mail, I went ahead and took
the adjusters apart (yes - I have some issues here) to figure out how to
collimate the set. It proved to be rather simple, and I had them done and
providing great views by the time Richard's instruction arrived. As it
worked out, it was great to have the instructions as there were some great tips
included about adjusting the eyepiece holders. The eyepieces are held in place by the two thumbscrews you see
in the left hand photo (non-marking brass rings are the standard - of course).
The focus adjuster ring is shown pretty clearly. The holders are a little deeper
than the originals to allow the longer (Radians/Nagler) eyepieces to fully seat
in the holder (at the expense of a small amount of back focus). These are
just a very nice, high quality addition to some already excellent Binoviewers!
I understand that there were about 70 sets of these made.......if you own one of
the Baader Binos and have a chance to pick a set of these up.....I think they
are worth it.
Rather than trying to explain the Glasspath Corrector shown
to the right, I figured it would be better to leave that to the professionals.
Roland Christen (the man behind
Astro-Physics) recently responded to a question on the
Astro-Physics User
Group on Yahoo about the advantages/disadvantages of barlows verses high
powered Glasspath Correctors. His reply offered a nice description of the
Glasspath Corrector. Here it is (with his permission):
The Glasspath corrector is used to correct the prism color and spherical
aberrations when you wish to have minimal focal length increase for wide field
as well as high power observing. It is the only unit that actually corrects for
the glass path error introduced by the prisms when they are used with short
focal ratios and higher magnification eyepieces where the prism errors would be
more pronounced. However, adding any kind of Barlow element of 1.75x or higher
will essentially eliminate the errors introduced by the prisms because the focal
ratio that the prisms now see will be very long. No glass-path correction is
needed. There is no real difference in the final result between any of the
dedicated Baader screw-in Barlows and the Barcon or Baader FFC Barlow. There are
no optical advantages to any of these schemes. Pick your method.
In a separate post, Roland also offered some thoughts about the new Baader Mark V
Bino, and some thoughts about eyepiece focal length selection when using
Binoviewers. While information on the new Mark V doesn't apply to the
older unit shown here, I found the information (especially his perspectives on
eyepiece selection) to be very interesting,
as I find most of what Roland chooses to share, and thought you might like to
read it also. The original post can be seen by following
this link.
I've added the content of that post below (with Roland's permission) for those
folks who are interested in the subject and don't want to join the forum:
Hi all,
I see that everyone is nervous about the new Binos from Baader and how the
diopter adjustment works, and whether the eyepieces rotate or not.
In my opinion, whether the eyepieces rotate or not is a non-issue. I have tested
just about every eyepiece that I would use in a Binoviewer, rotated them by hand
and found them to be well centered, well enough that I saw no image shift. Nevertheless, if you do have some ultra-cheap eyepieces that are not centered,
or very short focus eyepieces (more on that below), you will run into other
issues anyhow. One of them is, how will you know which way the eyepiece
is rotated to begin with whenever you insert them into the bino at night when
you can't see which way they are facing? Second question is, are you always sure
to insert eyepiece A into the left channel and eyepiece B into the right
channel? This makes a difference if they are cheap, off center and have
slightly different focal lengths.
The way Baader designed the new eyecups, he tried to get the lowest profile
eyecups so that you don't run into the problem of not enough back focus. These
new eyecups achieve the goal of diopter adjustment and positive locking while
keeping the eyepiece exactly centered with no more eyecup height than before. Do
the eyepieces rotate when you turn the diopter? That depends how you do it. The
eyepieces sit inside a non-rotating sleeve, and if you turn the upper diopter
adjusting barrel, while keeping slight tension on the click-lock mechanism with
your other thumb, the eyepiece will slowly move outward without rotating. Is
this really necessary? Not in my opinion. If you don't hold the bottom
part with your thumb, the eyepiece might or might not turn a bit, depending how
loose it sits in its barrel.
The eyepiece holders are not easily removed and have been precisely collimated
at the factory. It is not recommended that you take them apart to replace them
with other barrels, or try to collimate them yourself. It would take some heavy
hammer blows to change the collimation, so please no hammers.
The coatings are new and have been optimized for visual, because this is after
all a strictly visual device. As such, the coatings have a null in the
yellow-green to give the highest possible transmission. The beam splitter uses a
dielectric coating which is also more efficient, but does introduce some
polarization. This is not an issue for any night use, but may make one image a
tad brighter than the other under certain daytime lighting conditions where the
light is polarized. I have looked through them in the daytime and found no
effect that I could see myself. They look just like my original Zeiss versions.
Recommended eyepieces. I have no particular eyepiece recommendations as to type,
except to say that the longer focal length eyepieces are going to give you the
best view. To explain a bit further, if you want high power, it is better to
produce this before the prism set than afterwards. The rewards are many,
including longer eyerelief, less sensitivity to tiny miscollimations and much
lower amounts of optical aberrations due to the long prism path itself. If you
have a fast scope, F7, F6, F5 or even shorter, it makes no sense to use 5mm, 4mm
or 3mm eyepieces to get up to planetary powers. You will magnify not only all
the prism aberrations, but also any image offsets that might be in the eyepiece
barrels or the prisms themselves. You may have trouble merging the image. Even
if you could adjust the collimation precisely by moving the eyecups
around, the next time you insert the eyepieces, they won't be in the exact same
orientation and all your collimation efforts will be for naught.
My rule of thumb for any Binoviewer is to use focal lengths no shorter than
10mm, preferably 12mm for high power viewing. Insert a Barlow element ahead of
the Bino to achieve a long focal length. This will narrow the beam considerably
over prime focus, with the result that the active area for each object beam will
occupy only a tiny portion of the prism faces. This will really cut down on
aberrations in the optical path. This applies to every Binoviewer out there.
While the Baader prism are top notch, and better in my opinion than any others,
they are not perfect. They will, however produce a perfect Airy disc when used
with a Barlow ahead of the optical path. If you are looking for that last 2% for
those subtle Mars features, think long eyepiece, long F-ratio, and you will
dazzle them.
Roland Christen
Finally, Roland posted a couple of basic guidelines for using
Binoviewers (of any brand) that seem to some it all up (again with his
permission):
Here is a rule of thumb:
1) For optimum planetary contrast, limit your power to 40x per inch of aperture.
This will result in an exit pupil of .67mm. Below that size exit pupil, floaters
in the eye become a problem.
2) Limit your eyepiece focal length to 10mm or higher. Shorter than that will
result in magnifying Bino prism defects as well as positional errors that can
cause merging problems.
Obviously, people may still use higher powers for planetary studies and throw
short focus eyepieces into their Binos and claim super performance. The above
are general guidelines and can vary from one individual to the other. Some
people don't have floater problems, some people have no problem merging images,
etc.
Roland Christen
