Available as a bare optical tube assembly or packaged with a variety of computerized mounts, the Celestron C6 Schmidt-Cassegrain (MSRP: $459.95) fills the gap between its 5 and 8-inch brothers.
A 150mm, f/10 system, the telescope weighs just 8.6 pounds with a 6×30 finder and star diagonal attached. (It’s small enough to qualify as carry-on airplane luggage.) The standard Celestron visual back accommodates 1.25-inch accessories and a thread-on 2-inch mirror diagonal for wider field viewing.
Despite the rather large 37 percent central obstruction, the scope produces fine images and affords significant light grasp courtesy of its XLT high-transmission coatings.
Focus is achieved with the usual moving-mirror knob. It’s quite sensitive and displays a tiny bit of image shift, but the motion is smooth and progressive.
When properly collimated, the little SCT is capable of high magnifications, and it delivers impressive views of the moon, planets, and double stars.
The moon is rendered in nice contrast without a hint of false color, absolutely black shadows, and resolution of fine detail down to the theoretical limit. When compared to an f/12 Maksutov-Cassegrainian of the same aperture, the Celestron produces a brighter image with just a touch less sharpness.
The same applies when observing the planets. Mars, with a diameter of 20 arc-seconds, reveals its polar cap, limb brightenings, and many of the dark markings that define the planet at 167x. Saturn, at the same power, shows the delicate pastels of the planetary disc, the Cassini Division, and cloud belt detail.
A 4-inch Takahashi fluorite refractor produces about the same level of detail with a tad less brightness but better contrast.
Double stars are well resolved by the C-6. Epsilon Lyrae, Zeta Aquarii, and Delta Cygni are no challenge at 224x, but the large central obstruction creates a significant first diffraction ring that detracts from the aesthetics.
Deep-sky objects are surprisingly bright with the scope: M13 is resolved to the core and the Double Cluster in Perseus is nicely framed at 60x. The Starbright XLT coatings give the Celestron a clear edge in light grasp over the 6-inch Maks.
On balance, the Celestron 6 is a good choice in a relatively inexpensive, versatile telescope.
The good: Nice optics, low price, light weight
The bad: Large secondary obstruction, mediocre contrast