I am pleased to report that one company has devoted their entire energy to improving binoviewing. It is almost like Denkmeier Optical picked my brain and produced units that solved the problems inherent in binoviewers from the get-go... or more specifically, the focus issue.

Furthermore, Denkemeier not only offers a standard binoviewer with the most versatile add-on options, but has recently come out with the Denkmeier II, with better coatings and optical correction.  I have put both units through their paces, and I was pleasantly surprised by both.

REPORT 1: JULY 2003 - (SEE REPORT TWO BELOW, EVEN MORE THOROUGH)
Checking both Denks (nickname) out on Mars and the Moon, I was able to see little difference in my Starmaster 14.5". Both seemed to perform as well, if not a tiny bit better on Mars than my late 1990s Televue binoviewer... BUT  a newer 2003 Televue binoviewer was just as sharp and contrasty, if not sharper (by a small margin) than both Denks. There was a hair more resolution and intraplanetary contrast on global features. Between the two Denkmeiers the differences were small. However, the Denkmeier II has individually focusing eyepiece holders which allowed for the sharpest possible view.

On deep sky the Televue, and the two Denks were evenly matched, with more work needed to sort it out. I have to exactly match magnification to make this fair. I tried numerous objects including M13, M15, and the Andromeda galaxy group.  The Denks had more vignetting unfortunately towards the edges than the Televue unit using 24mm panoptics, which produce the widest possible field size. I am going to double check this though in a variety of scopes.. others have not found this to be true.

REPORT 2: AUGUST 2003
I took the time, 4 hours to be exact, (with no coffee breaks) to really put the 3 binoviewers up against each other on a variety of objects, once again, although I found Mars and M15 to be the most fruitful. So far, I have only repeated this with the 14.5" Starmaster with the Zambuto optic... I have a 92mm apo that I am going to hit next. Oh, yes, I was using a newer 2003 Televue which might have improved coatings.

This time, I made sure to increase the magnification with the identical units (such as the Televue 2x, or the 1.3x 2" Denk OCS, or my Televue 3.8x barlow) prior to entering the binoviewer, previously I was able to match magnifications, using similar eyepieces. (I have numerous binoviewer homemade contraptions from the days when magnification was more of a challenge.) Anyway, I was surprised, because with different light path lengths, or so I thought, I thought I wouldn't get exactly the same magnification, but it looked nearly identical to me. Magnification was approx. 162, 250, and 500x on Mars, and 163x and 102x on M15. Skies were not particularly dark, with a gibbous moon rising.

Anyway, the news is that on detail on Mars (and the moon), it is quite close and I need to revisit this many times... perhaps during super steady seeing. My seeing conditions were quite good, very good, but not perfect....

All 3 units performed similarly BUT the Denkmeier 2 did repeatedly flash the most detail at me in times of steady seeing, in retrospect. In other words.. I was going round robbin with which unit was displaying the most detail (and when I say detail, I'm talking about close to the latest photographs from the likes of David Moore) - but after all was said and done... The Denkmeier 2 was the one which I had managed to catch the absolute best in retrospect. The Denk 1 and Televue were similar. Again, this is not a sure thing here, and others may have perhaps super-steady skies that may contradict the above, but the Denk 2 seemed to be a bit clearer. (BTW.. when I say "best" it is hard to tell if it was from intra-planetary contrast or better resolution, but more intricate features were discerned)

Also, I have gotten used to the single eyepiece focusers (Denk2), and found that focusing on a single dim star really made a difference, and was a big help especially with my eyes which are not 100% equal.

HOWEVER, there was a microtad more light throughput in the newer Televue unit that I was using, so that M15 resolved at various magnifications a tiny bit better than the Denk 1 or Denk 2. I don't know why. I am often in a rush, and I'm not perfect, and all this is very subjective, but I am quite the globular observer and took well over 90 minutes on this one - I have resolved M13 (hercules) for instance in very small scopes, and I don't mean the "ground sugar look" in suburban skies. (I mean, yes, individual stars in a 76mm scope) I know the thresholds and what to look for. I also used M57's 14th magnitude star to test this. On M57 I saw no difference at all between the Denk1, Denk2, and Televue in the starfield. On M15 at all magnifications, I more quickly resolved stars in the new Televue, then the Denk2 , and then the Denk1. Nevertheless, the difference from the Denk1 to the Denk2 was very little, with just a bit more difference between the Denk2 and the Televue. M15 was more quickly "richer" looking in the Televue, but I was able to get there eventually with others, it just required more off-axis viewing and time. I was hooded and everything. I will repeat this in other scopes.

REPORT 3: August 2003 - B
I tried all three binoviewers on the moon, the Denk 1, Denk 2 and 2003 Televue. This was with a refractor straight-through, and thus no barlow or optical corrector of any kind. All three were excellent, sharp in detail and deep contrast between the moon and sky. I was not using a diagonal, remember, which helps a lot with lunar-sky contrast. There was NO vignetting using 30mm ultimas on any of the binoviewers. Since 30mm ultimas yield the maximum field of view with a 1.25" eyepiece, I have concluded that previous vignetting with 24mm panoptics using optical correction in my reflector, was induced by the scope. In terms of brightness, the Denk2 , and the Televue seemed to very, very slightly offer up a purer white moon, due to a very slight amount of additional light throughput. Any differences between the Denk 2 and the Televue were too small to be meaningful and likely my imagination. In terms of detail, at low power, there was no difference noted between units.
 

MORE............

The biggest advantage of the Denkmeier binoviewers is the incredibly versatile add-on correctors. There is a corrector for just about any scope you use. On reflectors, you can utilize a 1.2-1.3X magnifier which sets a new industry standard. When I started reviewing binoviewers, it was impossible  to reach anything lower than 2.7X and reach focus in a reflector. Televue improved on that with a wonderful 2x corrector, but now Denkmeier (and also to some degree Siebert Optics) has improved on that greatly.  Although it will BARELY reach focus on some reflectors, most will do just fine. Even Harry Siebert's excellent 1.3-1.4X corrector doesn't quite give you that low a magnification in a reflector. (the Siebert unit is shorter though). On refractors, Denkmeier supplies an incredibly ingenious "screw-into-the-diagaonal" add-on which also allows for about 1.2X magnification with no major focus in-travel needed. If that weren't enough, Denkmeier offers a built-in reducer-corrector for SCT scopes.  Did I mention that Denkmeier does this in both 1.25" and 2" formats? Wow.

The binoviewer wars are heating up among my favorite units. Baader has apparently just come out with a unit that offers individual eyepiece focus. Televue has supposedly improved the coatings on their latest model, which I used in August above, and remains one of the lightest units on the market. Siebert binoviewers are constantly improving, and are a "moving target" less organized than Denkmeier as a company, but optically sophisticated. It seems that Denkmeier is taking over in a very short period of time as being the one to beat, although a few minor improvements could still be made. The individual eyepiece focusers operate smoothly, but a bit clumsily. I can't "lock" focus in place each time I swap eyepiece sets, but I have gotten used to them and they perform wonderfully.  Weight reduction would be great too, but probably impossible.

If you have multiple scopes, that traditionally were finicky with binoviewers there is no question your best bet is with Denkmeiers.

Todd Gross