Explore Scientific AR102 102mm f/6.5 Doublet Refractor Telescope

A second telescope for short weeknights, or one to set up for a line of visitors at a star party, works best when it arrives complete. The Explore Scientific AR102 (item DAR102065-02) is a 102 mm f/6.5 air-spaced achromatic doublet built to stand up to public star parties and educational outreach, and it comes with an 8x50 finder, a 99% reflective 2-inch diagonal and a two-speed 2-inch Crayford focuser, so it needs only eyepieces and a mount.

Key Features

• Optics. A crown glass lens and a flint glass lens, separated by an air space to minimize chromatic aberration, fully multi-coated, in a three-point collimation cell. It gives wide-field views of the Moon, the planets and the deep sky.
• Focuser. The two-speed 2-inch Crayford focuser has a compression ring.
• Finder. A straight-through 8x50 with a simple crosshair, on Explore Scientific's Hybrid Finder Scope Base with a quick-release bracket. On the AR102, fit the finder before the cradle ring.
• Diagonal. A dielectric-coated 2-inch diagonal, 99% reflective, with a 1.25-inch adapter; its barrel is tapered so it cannot drop out if a set screw loosens.
• Rings and dew shield. A felt-lined cradle ring with a carry handle on a 45 mm wide Vixen-style dovetail plate, and a dew shield that comes attached.

Who It's For

• Star parties and outreach. For this 663 mm focal length, Explore Scientific recommends the 52° Series 30mm (22x), 62° Series 14mm (47x) and 62° Series 5.5mm (121x) eyepieces.
• A grab-and-go refractor. The AR102 is a match for Explore Scientific's Twilight I alt-azimuth mount, rated for telescopes up to 18 lb.
• Observers deciding on glass. An achromatic doublet leaves some color around the brightest targets. The ED102 Essential puts HOYA FCD1 glass in a 102 mm triplet and costs more; our comparison of the AR102, ED102 and ED102-FCD100 sets them side by side.
• Observers who want more aperture. The AR127 gathers (127 ÷ 102)², about 1.55 times, the light at the same f/6.5.