Explore Scientific FCD100 Series 127mm f/7.5 Triplet APO Refractor - Aluminum with 2.5" HEX Focuser

127mm FCD100 Triplet Optics: Apochromatic Views at f/7.5

At the heart of this refractor is a 127mm air-spaced triplet objective featuring genuine HOYA FCD100 glass. This extra-low dispersion (ED) element virtually eliminates chromatic aberration, resulting in images free of false color and purple fringing around bright stars and planetary limbs. Combined with Explore Scientific's EMD enhanced multi-layer coatings, the optical system delivers maximum light transmission for brilliant, true-to-life views.

The f/7.5 focal ratio provides a versatile balance, offering enough magnification for fine details on Jupiter's cloud bands and Saturn's rings while remaining wide enough to frame many deep-sky targets. Stars resolve to sharp, pinpoint dots against a dark sky, revealing subtle structures in nebulae and galaxies that lesser optics would smear.

2.5" HEX Focuser: A Smooth and Stable Imaging Platform

The telescope includes a rigid 2.5" hexagonal rack-and-pinion focuser designed to prevent flexure and slippage, even with heavy camera setups. This design offers greater stability than conventional Crayford focusers, ensuring your imaging train remains securely aligned throughout a long exposure. The smooth, precise motion allows for critical focus adjustments necessary for high-resolution planetary imaging and sharp deep-sky astrophotography.

The 127mm Tube Assembly: Integrated for Field Use

The aluminum optical tube is engineered for both durability and portability. It incorporates several features designed for practical use in the field, minimizing setup time and improving your observing sessions.

• Retractable Dew Shield: An integrated dew shield slides forward to prevent moisture from forming on the objective lens and blocks stray light from degrading image contrast.
• Cradle Rings & Handle: The included cradle ring assembly provides a secure mounting point and features a top-mounted handle, making the 127mm optical tube easy to carry and mount.
• Vixen-Style Dovetail: A standard V-style dovetail plate ensures compatibility with a wide range of common astronomical mounts right out of the box.

FCD100 vs. FPL-53 Glass: The Apochromatic Difference

In the world of apochromatic refractors, two glass types stand out for their exceptional color correction: Ohara FPL-53 and HOYA FCD100. Both are elite extra-low dispersion glasses that allow optical designers to bring the entire visual spectrum to a single, sharp focus point. Choosing between them is less about one being superior and more about the specific optical design it enables.

By using FCD100 in this 127mm triplet, Explore Scientific achieves a level of apochromatic correction that produces textbook-perfect star images and neutral color rendition. For an observer, this means the highest possible contrast and sharpness that the 127mm aperture can deliver, uncompromised by distracting chromatic aberration.