Review: TMB92SS
Thomas M. Back passed away suddenly in 2007, but he left behind some of his last telescope designs with Astronomics. Specifically, the Signature Series line still being sold by Astronomics today. As of the time I wrote this, there was still a wait list to get one. I will say it is my favorite little refractor, replacing a trusty Orion 80ED I’ve been using for the last 6 years.
The TMB92SS itself is designed with an eye towards being an imaging telescope. The end result is a short, dense telescope with a fast focal ratio that makes it easy to travel with. The focuser itself is from Starlight Instruments, which is expecting you to use some fairly heavy cameras. In short, this thing is built like a tank, and it shows. About the only thing that seems out of place is the lens shade. It slides back for travel, and only uses felt to hold it in place, so there is a bit of droop due to slack in the tolerances.It hurts the perception of quality that the rest of the telescope exudes.
Visual Quality & Focus
One issue when imaging is that your goal is to find critical focus with the telescope for imaging. When working visually, it is a little more forgiving, but since the scope is fairly fast, fine focusing is still a help here. The micro focuser, like all Feathertouch models I’ve used in the past, does an excellent job here. It can carry a good amount of weight without making it any more difficult to move the draw tube, making focusing a smooth experience, imaging or not.
Visually, the telescope is very sharp. Even when using some of my shortest focal length eyepieces, stars remained nice and tight points rather than airy disks. It’s hard to describe just how nice it is to have a telescope that does as good a job of keeping the light well focused as this one does. Yes, and 80ED can give you good views, but if it isn’t able to keep the image sharp under magnification, you lose detail. This scope has given me the best views I’ve seen of any telescope under 6”, although with the footnote that I haven’t used any of the truly cream-of-the-crop telescopes from Takahashi or Astro-Physics for any real length of time to compare. It is a definite step up from the more budget-minded telescopes out there. With optics this good, I’m tempted by the idea of binoviewers, if it wasn’t going to be horrifically expensive to double up on my existing eyepieces.
Since this is a triplet, one of the features is the lack of false color. While you can find doublets that control color very well, there is a limit to what they can do, especially in the budget category. With my 80ED, I had to fight false color pretty hard when imaging. This shot in particular, was heavily processed to try to remove false color, of which there was plenty. Another shot shows false color despite processing. Visually, the 80ED would show a little false color on some targets, making it a little harder to determine a star’s color at times. The TMB92SS in its place, showed zero false color visually. So far, it looks like the design controls false color very well.
Caveat
I have yet to actually do some serious imaging with this particular scope, and have only used it visually at this point. Even so, it is one of the sharpest refractors I’ve used. If I was using it for visual only, I probably wouldn’t plunk down the money on it unless it was my main visual telescope that I travelled with. I do plan to attempt some imaging of M42 (Orion Nebula) during the winter in order to get an idea of how well the scope itself performs imaging-wise.