TeleVue TV-60is Imaging System Refractor OTA

Comments about TeleVue TV-60is Imaging System Refractor OTA:

The first thing that hits you is the mass - this scope weighs in at 7 pounds. Everything about it appears to be extra heavy duty. Fit and finish are typical Televue - I couldn't find a flaw, a scratch, or even a fingerprint. Too bad so many other manufactures can't match the raw quality that Televue puts into every one of their products.

The two speed focuser is fantastic, with no discernible backlash, image shift, or wiggle. It is only 6:1, while most other scope makers are using much higher ratios, but even at that it is super simple, and smooth, to dial in the focus with the heavy SBIG camera on the back. Two tension screws, riding against brass rings instead of digging into the drawtube, provide nice, adjustable, tension. I found that I only needed to add a tad bit of tension when I was pointing almost straight up, otherwise I ran it with no tension applied.

Being primarily an imaging scope, there is a removable field flattener included. The field flattener not only inserts about 2" into the focuser, with two set screws, but it is also threaded solidly into the end of the focuser. To use an eyepiece the field flattener must be removed. Televue provides a threaded bushing and spanner wrench to protect the internal threads of the focuser and eliminate wiggle when you go visual. The back of the field flattener has a T-ring so it attaches directly to most camera setups. No wiggle or play here.

Televue apparently realized that this would not be anyone's primary telescope, but rather a secondary item and would probably be piggybacked on a primary instrument. As such, it comes with a somewhat unique mounting system. Think of a big finder scope mount, old style with six alignment screws, and you have the idea. On the bottom of the mount, there is a dovetail clamp, making is much easier to balance the scope(s). Included is a dovetail bar that fits in this clamp, about 6" long, and has multiple 1/4-20 holes to mount on either a conventional tripod or some equatorial heads. Unfortunately Televue uses a proprietary dovetail so you may have to attach the dovetail to a mounting plate for the appropriate mount.

The scope is optimized for SLR use, so some CCD setups will require a short extension tube to reach focus or eliminate coma. The SBIG ST-8E, with color wheel, hits focus with about 1/2" travel remaining, but I get a lot of coma without an extension. 55mm is required between the back of the field flattener and the imaging surface (standard SLR distance). The SBIG setup is 42.9mm. T-thread extension tubes are available from various sources, but interestingly not from Televue, though they do have extension tubes for the 2.4" focuser on the rest of the IS line of scopes.