The Synta Technology Corporation 90mm Maksutov telescope (MSRP: starting at $199) is a very portable, low-cost telescope that excels on solar system objects and can be used directly as a camera lens.
Pros: Good optics, compact, versatile
Cons: Photographically slow for imaging faint objects
The telescope is available as the Celestron, Orion, and Sky-Watcher brands, each offering various accessory packages. In the astronomical versions (spotting scope versions are also available), you can get the optical tube alone, or buy it with a variety of mounting options. It will come with two eyepieces, a star diagonal, and either a 6×30 finderscope or a red-dot finder. These fit the same mounting shoe, so are interchangeable.
The f/13.9 optical system is the Gregory-Maksutov configuration (secondary mirror is a silvered spot on the back of the corrector meniscus) and you focus with a knob that moves the primary mirror. There is a minuscule amount of backlash in the focuser, but no perceptible mirror “flop” if you track across the meridian.
The port in rear cell has an M44.5×1.0 thread onto which is fitted a standard 1.25-inch visual back for astronomical accessories. The visual back has a photographic T-thread (M42×0.75) so that you can directly mount any compatible camera and use the telescope as a 1250 mm lens.
The latest incarnations of the telescope have a standard Vixen-Sky-Watcher dovetail, which also has 1/4-inch Whitworth photographic thread, so you can mount it on a photographic tripod or any of the numerous mounts that take the dovetail.
The supplied eyepieces are of acceptable quality, but if you really want this little gem to shine, try a better eyepiece. I use Orthoscopic eyepieces with mine and they are quite stunning. The telescope snaps to a very crisp focus, and has excellent stray light control, making details on the moon or bright planets crisp and well-defined. It also excels on the brighter double stars; for example, in good seeing you can easily split the double-double (Epsilon Lyrae), which has separations of 2.6 and 2.3 arcseconds.
Extended deep sky objects are less suited. You can, for example, see the core of the Andromeda Galaxy (M31), see the Ring Nebula (M57) as a ring, and even begin to resolve some stars in The Great Hercules Cluster (M13) but they are dim and not very impressive. You can’t beat the laws of physics.
The meniscus corrector is unprotected at the front of the tube, so it doubles as a very sensitive dew-detector. Consequently, either a dew shield or a heated dew strap must be your first additional accessory.
The only other thing to be aware of is that this optical configuration is very sensitive to miscollimation, but the good news is that it doesn’t easily lose collimation once it is set. I set mine more than a decade ago, and it’s still good.
At only 9 inches (228 mm) long and weighing only 3 pounds (1.4 kg), this is an ideal travel scope.