IMAGING SCIENCE by Oleg Bouevitch TOOLS OF THE TRADE Choosing an optic for deepsky astrophotography can be a challenge. But by taking several factors into account, you can select an optical system optimized for targets such as the colorful sprawling nebulosity Sharpless 2-101 in Cygnus. This deep, narrowband picture was recorded with a 10-inch f/4.6 Newtonian astrograph. All photos provided by the author. Choosing an Astrograph Here's a clever way to compare features in deep-sky imaging scopes before making a purchase. 62 APRIL 2 021 * SK Y & TELESCOPE