Explore Scientific 102mm f/7 Classic White FCD100 ED Triplet Refractor

Explore Scientific 102mm f/7 Classic White FCD100 ED Triplet Apochromatic Refractor

The Explore Scientific 102mm f/7 Classic White FCD100 Triplet Refractor offers the clarity, sharpness, and color correction that only a true apochromat can deliver—at a size and weight that’s easy to manage whether you’re imaging in the backyard or observing under dark skies.

With its precision-crafted air-spaced triplet objective using Hoya FCD100 ED glass, a robust aluminum optical tube, and a rotating dual-speed 2.5" focuser, the ES102 is an ideal scope for anyone seeking portable performance for serious visual and astrophotographic use. It combines exceptional optics with mechanical durability in a traditional white finish—making it a favorite for those who value performance and aesthetics in equal measure.

The Goldilocks Refractor: Balanced Aperture, True Apochromatic Performance

The 102mm (4") aperture sits at a sweet spot for many astronomers—large enough to offer excellent light grasp and planetary resolution, yet small enough to be easily mounted, transported, and cooled. The 714mm focal length yields an f/7 focal ratio, providing a versatile mix of wide-field imaging and high-magnification capability.

At the core of the optical system is FCD100, Hoya’s premier extra-low dispersion glass—optically equivalent to Ohara’s legendary FPL-53. Paired with matched crown elements in a true air-spaced triplet configuration, the result is a system that delivers near-zero chromatic aberration. Bright stars remain tight and color-true, the Moon’s limb shows no unwanted violet fringing, and planetary details pop at high magnifications.

Every optical surface is coated with Explore Scientific’s proprietary EMD™ multilayer antireflection coatings to maximize light throughput and contrast while minimizing ghosting and stray reflections.

Traditional Strength: The Classic White Aluminum Tube

Unlike its carbon fiber sibling, the Classic White version of the ES102 uses a traditional aluminum tube and dew shield finished in a durable high-gloss enamel. While slightly heavier, this OTA retains excellent rigidity and offers time-tested performance in a variety of observing conditions.

The retractable dew shield slows the formation of dew on the objective and serves as a glare guard for daytime or light-polluted urban observing. The tube interior is fully blackened with internal baffles to block off-axis light and preserve image contrast.

Precision Focusing with a Dual-Speed Hexagonal Focuser

The included 2.5" hexagonal focuser is built for smooth, accurate, and stable performance. Designed with astrophotography in mind, it features:

• Dual-speed control with 10:1 microfine adjustment

• Oversized drawtube for full illumination of camera sensors

• Rotating focuser body for easy framing and eyepiece orientation

• Millimeter-scale graduations on the drawtube for repeatable focus positions

• Tension and lock knobs to prevent flexure or focus shift during long exposures

• 2" compression ring holder to secure accessories without marring barrels

• Two included 2" extension tubes to help dial in precise back focus

Portable and Versatile for Visual or Imaging Use

Weighing in at just under 11 lbs, the ES102 is easy to carry and easy to mount. Its size makes it compatible with a wide variety of medium-duty mounts, and its performance makes it a natural choice for:

• High-contrast planetary observing

• Lunar exploration at high magnifications

• Wide-field imaging of nebulae and star fields

• Travel and outreach events

• Visual deep sky work with rich field eyepieces

The Vixen-style dovetail is compatible with most common equatorial and alt-az mounts. The dual split mounting rings include a top stabilizer bar that doubles as a carry handle—making setup, breakdown, and transport a one-person job.

A pre-installed finder base allows easy installation of your choice of finderscope, reflex sight, or red dot.

Long-Term Warranty and Value

Each Explore Scientific 102mm Classic White Triplet is individually serial numbered and comes with a one-year limited warranty. When registered within 60 days of purchase, the scope qualifies for Explore Scientific’s Lifetime Transferable Warranty—a rare and welcome benefit that protects your investment for years to come.

Specifications

• Optical design: Air-spaced triplet apochromatic refractor

• Aperture: 102mm (4")

• Focal length: 714mm

• Focal ratio: f/7

• Glass type: Hoya FCD100 ED (FPL-53 equivalent)

• Tube construction: Aluminum with retractable dew shield

• Focuser: 2.5" dual-speed rotating hexagonal focuser

• Drawtube: Millimeter graduated, lockable

• Back focus: Two 2" extension tubes included

• Mounting rings: Dual split rings with Vixen-style dovetail

• Top handle: Stabilizer bar doubles as carry handle

• Finderscope base: Installed

• Dust cap: Slip-on metal

• OTA weight: ~10.8 lbs