Explore Scientific FCD100 127mm (5") ED Triplet Apochromatic Refractor OTA

Explore Scientific FCD100 127mm (5") ED Triplet Apochromatic Refractor OTA

Due to high demand and global product shortages due to the pandemic, please call for availability.

Reveal celestial wonders like the desolate beauty of the lunar terrain, the serene structure of Saturn’s rings or the brightest deep sky treasures of the Messier catalog with Explore Scientific’s 127mm FCD100 Apochromatic Refractor.

This is essentially the same scope as the ES-ED127075-03, but offering even better quality optics. We use a Hoya FCD100 element, which is very similar in characteristics to Ohara FPL-53. Relying on technological innovation, we have successfully launched the mass production of high-performance optical glass at the apex of the FCD family. Combining it with optical glass of high refractive index allows us to achieve unprecedented advanced chromatic aberration correction. Hoya FCD100 is considered the best glass ever produced by Hoya.

Having a true diffraction-limited optical design and sized to encourage spontaneous stargazing sessions, this high-quality telescope is a perfect grab-and-go instrument for exploring the skies.

Featuring an air-spaced triplet optical design that virtually eliminates chromatic aberrations, this telescope generates brilliant high-contrast images by combining genuine HOYA FCD100 extra-low dispersion (ED) glass and proprietary EMD enhanced multi-layer coatings on all optical surfaces.

In addition, this amazing scope also includes a 2.5" Hexagonal focuser with very rigid design and strong support. Up to 10 lbs of gear can be loaded onto this focuser.

ED127 Classic White f/7.5 Air Spaced Triplet with Hoya FCD100 optics and Integrated Dew Shield; 952mm focal length; 2.5" HEX Focuser; Cradle Ring with Handle and Vixen Style Dovetail Plate; Explore Finder Scope Base installed on scope; 99% Reflective 2" Diagonal. Weighs 18lbs. (Case and Finder Scope NOT Included)


127mm (5”) aperture, 952mm focal length, f/7.5 focal ratio three-lens air-spaced optical system. The optics use a center lens element of Hoya FCD100 (Dense Fluoro Crown) glass, the Hoya equivalent of FPL-53 ED (Extra-low Dispersion) glass. This ED element produces superior sharpness and color correction by minimizing the chromatic aberration, the “false” color fringing seen around bright objects when light rays pass through standard crown-and-flint doublet objectives, particularly those with apertures in the ES127 class. The result is to reduce spurious color halos and fringing to vanishingly low levels.

Enhanced Multilayer Deposition (EMD™) Coatings eliminate light scatter and maintains image contrast. Contrast is further enhanced with multiple baffles that mask and deflect unwanted stray light.

This air-spaced objective is designed for precise lens centering via adjustment screws. A heavy blow or rough shipment might require an optical recentering. Removing the dew shield will give you access to the lens centering screws in the sides of the lens cell, which you can then adjust yourself by referring to the supplied instructions. You can also send your scope to Explore Scientific’s Service Center for precision alignment. A standard service charge applies for factory realignment.


High Performance Optics demand a high precision focuser. Perfect focus is easily achieved with the standard-equipment ten-to-one, dual-speed focuser.

This is especially true when observing at high magnification or when making CCD images. With a standard focuser, you will find that a tiny nudge will throw out focus and turn your night into one of frustration. The 2.5" format reduces vignetting when imaging with larger camera sensors.

To protect against marring of accessories, the focuser and included 2" to 1.25" adapter incorporate compression rings for sure grip.

Dew Shield

The supplied fixed dew shield slows the formation of dew or frost on the lens in damp conditions to extend your observing time. It also improves the contrast, in the manner of a lens shade on a camera lens. A slip-on metal dust cap for the optical tube is standard.

Star Diagonal

The 2" dielectric diagonal provided as standard equipment includes a 1.25" eyepiece holder adapter and dust covers to protect the mirror. This diagonal incorporates a light-weight, one-piece diagonal body that securely cradles the precision polished diagonal flat mirror, insuring precision alignment. Ultra-high reflective coatings (99% reflective) composed of multiple thin layers of dielectric material delivers maximum light throughput.

Both 2" and 1.25" eyepiece holders use compression rings instead of a simple set-screw to more securely hold your valued eyepiece or imaging device, and to prevent the eyepiece or camera barrel from being scoring. You can thread standard 48mm filters into the 2" barrel or the 1.25" adapter.

Mounting rings and dovetail

The ES102 has dual split mounting rings with a dovetail plate that fits the Vixen-style dovetail slot on the head of many of the most popular medium capacity German equatorial mounts. Such mounts include the Celestron Advanced VX go-to equatorial, the Meade LXD-75 or LX-80 go-to equatorials, and the Vixen Sphinx and Great Polaris Deluxe equatorial mounts, among others. A spacer/stabilizing bar on the top of the rings provides a carrying handle that makes it easy to transport the optical tube and install it on your equatorial mount. There is a mounting shoe for an optional finderscope installed on the body of the scope.

Free Extended Warranty

Register Your Explore Scientific Telescope in Canada or the USA and receive a free Lifetime Extended Warranty.

All Explore Scientific telescopes and telescope accessories are covered under the Explore Scientific USA One Year Limited Warranty against defects with proof of purchase, but you can extend this limited warranty to the Explore STAR Transferable Extended Life of the Product Warranty by simply filling out the product registration and submitting it in within 60 days.


  • Air-spaced triplet featuring genuine HOYA™ FCD100 Extra-low Dispersion glass
  • 2.5" dual-speed focuser
  • 2" Dielectric star diagonal
  • Aluminum optical tube
  • Tube rings and Vixen style dovetail


  • Aperture: 127mm (5")
  • Focal length: 952mm (37.5")
  • Focal ratio: f/7.5
  • Lens construction: Air-spaced triplet APO, HOYA™ FCD100 low-dispersion glass
  • Optical coatings: Explore EMD
  • 2.5" Hexagonal dual-speed focuser with compression ring
  • Tube rings and dovetail, fits 44mm (1.75") dovetail saddles
  • Finderscope mounting base included
  • Camera Capable:
    • USB imagers
    • All-in-one cameras via universal digital camera adapter
    • DSLR/SLR (Requires T2 ring, 2" prime focus adapter)
    • Above cameras and adapters sold separately
  • Length without dew shield: 85cm (33.25")
  • Length with dew shield: 106cm (41.75")
  • Weight 8.2kg (18lbs)
  • Color: White with black accents
  • Explore Scientific One Year Warranty, free upgrade to Explore STAR Transferable Extended Life of the Product Warranty with registration within 60 days