Explore Scientific ED102 102mm f/7 Triplet APO Refractor Telescope

If false color around bright stars and the Moon's limb has you looking past a 4-inch achromat, the Explore Scientific ED102 Essential (item ES-ED10207-02) keeps the 102 mm aperture and changes the glass. It is a 714 mm, f/7 air-spaced triplet with genuine HOYA FCD1 ED glass protected between two other air-spaced elements, designed for diffraction-limited, apochromatic performance.

Key Features

• Which ED102 this is. Explore Scientific's ED102 collection holds three 102 mm f/7 triplets. This Essential Series model has HOYA FCD1 glass, a 2-inch two-speed rack-and-pinion focuser and a 9.62 lb tube assembly. The ED102 FCD100 (12 lb) and the ED102 FCD100 in carbon fiber (9.5 lb) use HOYA FCD100 glass and a 2.5-inch hex focuser rated for 10 lb of imaging gear. Both cost more.
• Optics. EMD enhanced multi-layer coatings cover all optical surfaces, and the objective sits in a multi-point collimation cell, collimated in Explore Scientific's quality control department before shipping.
• Focuser and back focus. Stacked coarse and fine dials, a locking screw to hold focus and tension screws for cameras and heavy eyepieces; the focuser also rotates. Extension tubes come in the box and thread on between the focuser and the diagonal when an eyepiece or camera needs more back focus.
• Diagonal. The 99% reflective 2-inch diagonal takes 2-inch eyepieces, or 1.25-inch ones through its adapter.
• Dew shield and rings. The dew shield retracts along the tube, from 30.5 to 23.75 inches overall, and the cradle rings with carry handle sit on a Vixen-style dovetail.
• Imaging. Explore Scientific's Field Flattener f/5 to f/7 and 0.8x Focal Reducer both fit this model. The reducer turns its 714 mm at f/7 into 571 mm at f/5.6, and each needs 55 mm (±2 mm) of spacing to the camera sensor. Explore Scientific's own images of the Cygnus Wall and the Rosette Nebula were taken with an Essential Series ED102.

Who It's For

• Observers stepping up from an achromat. Our AR102 is the 102 mm f/6.5 doublet: it costs less and comes with an 8x50 finder. Our comparison of the AR102, ED102 and ED102-FCD100 sets the three side by side.
• Grab-and-go visual observers. The ED102 is a match for the Twilight I alt-azimuth mount, rated for telescopes up to 18 lb.
• Imagers starting with a DSLR or astronomy camera. The Essential Series suits both critical visual work and astrophotography; for tracking, the EXOS2-GT carries a 28 lb instrument payload for astrophotography.

Accessories & Compatibility

• Eyepieces. For this 714 mm focal length, Explore Scientific recommends the 52° Series 30mm (24x), 62° Series 14mm (51x) and 62° Series 5.5mm (130x).
• Finder. None comes in the box. The installed Hybrid Finder Scope Base accepts Explore Scientific's finder brackets and mini dovetail-type brackets.