Image of the day

From the
ATWB Customer Gallery


My Account

New to Astromart?

Register an account...

Need Help?

Comparing the Tele Vue 12mm Radian

Posted by Patrick Anway   10/27/2004 12:00AM

I am fortunate to live under dark skies. And though the natural beauty of the upper peninsula of Michigan has nurtured a tourist "Mecca", those skies are preserved by long winters of snowfalls approaching 200 inches and one of the largest population of flying insects. Thus many visit, yet few choose to reside in the area.

With 15 years of experience and mag-6 skies you might think that my interest would migrate toward mining the faint smudges noted in obscure catalogues that few amateurs would be familiar with, but you'd be wrong. I love "doubles" and I'm not ashamed of it. Mind you, I don't ignore the globs, nebulae or distant galaxies that beckon to every amateur; I do have an observatory at home and a pier mounted C11 that satisfies my occasional cravings for such treasures, but when I think of new equipment or accessories, my prejudice shows and my mind immediately zeros in on anything that might enhance my "double star" infatuation.

Thus with so much appearing in print over the past couple of years about Televue Radians, I decided to take the plunge. I ordered three : the 8mm, 12mm and 18mm. This review will focus in on the 12mm, but the same thoughts would be relevant to the other two.

The contestants:

To get a good "feel" for the performance of the 12mm, I compared it alongside a couple of other 12mm's that I own; a 12.5mm Vixen ortho and a 12.5mm Celestron Ultima.

Here are the statistics *:

Eye Relief---20mm---9mm------9mm

* All statistics taken from the manufacturer's website.

The physical appearance of the Radian is quite nice. It's hefty, weighing in at ½ lb., with a "fit & finish" that is typical of all Televue products and no doubt behind the user loyalty that these products have mustered. It comes with a very unique "sliding" body that adjusts the eyecup's height so that when you position your eye against it, you are taking in the entire field. If you have ever used eyepieces with this much eye relief and particularly if you don't wear eyeglasses, you can appreciate that it is sometimes difficult to know just where to position your eye; this eliminates that problem. I had heard mixed reviews about this feature, but I found myself in the "I like it" group.

As Al Nagler noted on his website, the Radians are aimed toward eyeglass wearers and thus the 20mm eye relief; however, for a non-eyeglass wearer like me, the 9mm eye relief in both the Ultima and the Ortho was plenty and a good amount for easy positioning of the eye, so at this focal length the extra 11mm's of eye relief in the Radian is nice, but not necessary. (I would expect that when you get to focal lengths of "5mm and below", the 20mm of eye relief would make a big difference.)

To run the eyepieces through their paces, I used my Zeiss AS100/1000 refractor. Though an achromat it is virtually free of secondary color and is very well corrected. Coupled with each eyepiece it yielded about 80X; with each eyepiece and a 2.4X Vernonscope dakin barlow about 200X.

The conditions:

I waited for a day with relatively high humidity and the resulting light haze that stills the air. From experience, I've found that this type of day is often followed by a steady night and I was not disappointed.

A quarter moon bathed the night sky in light (the effect enhanced by the haze), but it was cloudless and no dew problems were noticed. About 80° F.

The targets:

The moon was hard to ignore and is always a good contrast test, so it became my first target. At 80X all three eyepieces showed equal contrast and sharpness along the terminator. The Ortho did appear to present a brighter view, yet it was a very slight difference. I nudged the scope over to include the limb in the view and saw no induced color in any of the three, even laterally as I allowed the limb to float toward the edge of the view.

With the barlow in place I scanned the region of the crater Clavius at 200X. Try as I might to discover an advantage in one eyepiece, I found little difference in the views they offered. After switching between the eyepieces for some time, I could find no evident winner. Each showed Clavius-J clearly; as well as the ridges running north from the Clavius-C. In fact, each time I thought I had discovered a bit more detail, switching eyepieces brought the same result in it's competitor; again, no striking difference. Even in off-axis sharpness the Ultima and Ortho matched very closely the Radian and if there was any difference at all, it was at best - subtle.

There was of course, one area where the Radian struts it's stuff and that was in AFOV. With out a doubt the 60° AFOV of the Radian was a lot of fun on the moon, giving more of that "in orbit" feeling. But the surprising thing, at least to me, was that Radian gave an amazing sharp-to-the-edge, undistorted view, which I have found lacking in other "wide field" eyepieces I've looked through. Though the Ortho and the Ultima also do well in this area, the Radian did it across a 10 to almost 20 degree wider field. I now saw why these eyepieces had earned their reputation.

Enthused by the finding so far, and despite washed out skies, my second target had to be a double. After all, the reason I had decided to give these eyepieces a try was the lure of: the sharpness of an Ortho in a "wide-field" eyepiece. For a "double-star enthusiast this would be "sugar-coated candy".

For a "star-hopper" like me, used to a dark sky with lots of guide posts, a washed-out heavens would pose a challenge. I opted for an easy double to locate; Epsilon Lyrae. The "double-double", as it is called, is a popular double for testing optics and I have examined it many times. It would make a nice target for the 12mm's because both pairs would fit into the same field of view.

I tried each eyepiece with the dakin at 200X. Each component of the "double-double" were split cleanly; with both pairs sharing the field - a striking view. All three 12mm's gave equal splits, but the radian once again gave a more pleasing view with the greater AFOV and I also noticed at this point that the sky background in the Radian seemed slightly darker. The wider view provided by the Radian showed the multiple system more "in context" with a spattering of background pinpoint diamonds surrounding the twin pairs; wow!


As a double star observer, I have always looked at the Ortho as the eyepiece of choice. Beside a full set of Vixen's, I own two Zeiss orthos that show outstanding contrast and I still believe that these eyepieces make wonderful tools for such work. I was pleased to see how well they held up to the more elaborate designs of the modern offerings such as the Ultimas and Radians. Though in comparison to the Ultimas and particularly now the Radians, they do give that "tunnel" vision feeling.

Todd Gross once said that his "favorite series of mid-priced eyepieces is the Ultima series" and as an owner of seven of them, I would have to agree that they are hard to beat for the price. They also matched well, the sharpness and contrast of the much higher priced Radians. They remain my workhorse eyepieces and I can recommend them highly.

The Radians are in my opinion, amazing. They are an engineering wonder, in the fact that such a well contrasted eyepiece, with a sharp-to-the-edge 60° AFOV, can come in a 1.25" package of reasonable weight. They are the closest thing to a "wide-field" ortho as you can come; a double-star enthusiast's dream. Though I will no doubt continue to use my orthos for double star work, the Radians will get lots of use also, particularly for those picturesque binaries.

Click here for more about the 12mm Radian. -Ed.