Cahill Rooftop Observatory

Equipment Database - Questar

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Optical SystemMaksutov-Cassegrain
Mount TypeEquatorial, RA drive
Focal Length1300 mm
Rear Cell1.125"
Max FOV1.3°
Finder 7×15 mm
Finder FOV11.0°

We offer a 3.5-inch Questar as a light outreach telescope. This telescope is more convenient to carry than the 8-inch Celestron, but provides much better images than the Galileoscope. The Questar is also our only portable telescope with a tracking drive, making it easy to show a planet or other object to large groups of people without having to constantly adjust the telescope. Unlike other telescopes, the Questar needs to be mounted on a tall, sturdy table (much taller than shown) to bring the eyepiece up to a comfortable level; make sure you can provide one at your observing site before checking out this telescope.

The Questar's wide, one-degree field of view makes it an excellent choice for observing the Moon or large star clusters. It also provides reasonable views of the planets, although it doesn't support the magnifications needed to get most planets to look their best. We have not yet tested the Questar on nebulae or globular clusters.

The Questar's mount is a bit tricky to polar align, but fortunately even very rough alignment will be enough to keep objects in the wide field of view. The image quality is fairly good, especially with the 10×40 eyepiece. We have not done a formal test, but the Questar doesn't seem prone to serious vibrations so long as it's on a steady enough platform.