Explore Scientific ED127 127mm f/7.5 Triplet APO Refractor Telescope

Stepping up from a 102 mm refractor to 127 mm gathers (127 ÷ 102)², about 1.55 times, the light, and asks more of the mount. The Explore Scientific ED127 Essential Series is Explore Scientific's 127 mm f/7.5 air-spaced apochromatic triplet with genuine HOYA FCD1 ED glass and a push-pull front cell that adjusts for tilt and centering, so you can collimate it yourself. At Mt. Wilson Observatory, the staff mounted an ED127 on the 100-inch telescope for visitors' viewing.

Key Features

• Optics. The air-spaced triplet pairs genuine HOYA FCD1 extra-low dispersion (ED) glass with Explore Scientific's EMD enhanced multi-layer coatings on all optical surfaces, to suppress chromatic aberration.
• Collimation. Explore Scientific collimates each telescope in quality control, and a refractor's locked lens cell rarely needs more. If it does, you do not have to send it back, though Explore Scientific recommends a knowledgeable person do the work: the collimation screws sit around the front cell and take a 3 mm hex wrench. Our collimation guide covers the star test.
• Focuser. A two-speed 2-inch rack-and-pinion focuser with heavy-duty locks to hold an imaging setup, plus two extension tubes. It rotates, so you can turn it to put the knobs where you want them.
• Cradle rings with a camera handle. The handle on top is slotted for a 1/4x20 bolt to carry a DSLR piggyback, and the rings sit on a Vixen-style plate.
• Retractable dew shield. It slides back to shorten the tube from 41.75 to 33.25 inches for transport.
• In the field. Astrophotographer Chuck Ayoub imaged the Pillars of Creation in the Eagle Nebula (M16) with his ED127 and a reducer, and the ED127 worked out so well for him that it is the reason he runs two rigs.

Who It's For

• Visual observers. Targets for this model include the edge-on Sombrero Galaxy, the face-on Pinwheel Galaxy and the Moon's Hadley Rille.
• Imagers. Explore Scientific recommends its 3" Field Flattener .7x Focal Reducer for its 127 mm refractors; it comes with a threaded adapter for the 2-inch rack-and-pinion focuser. It takes the 952 mm f/7.5 to about 666 mm at f/5.25 (952 × 0.7) and needs 55 mm of back focus.
• The mount question. The tube weighs 18 lb. The EXOS2-GT PMC-Eight mount is rated for 28 lb of instrument for astrophotography and 40 lb for visual use, which leaves 10 lb of the imaging rating for camera, guide scope and accessories.
• Choosing a 127 mm or a 102 mm. The AR127 is a 127 mm f/6.5 crown-and-flint achromatic doublet that costs less and weighs 15 lb; the ED127 adds the FCD1 ED triplet. The ED102 Essential Series is 102 mm at f/7 and 9.62 lb, for a lighter mount.

Accessories & Compatibility

• Finder. The 2N1 Finder Scope Base comes installed; the finder is sold separately.
• Eyepieces. The 99% reflective 2-inch diagonal takes 2-inch eyepieces, and its 1.25-inch adapter takes the rest.
• Case. Explore Scientific designed its Soft-Sided Telescope Case especially for the ED127, with room for eyepieces and accessories.