William Optics Apochromatic refractor AP Fluorostar 120/780 Gold OTA (74017)

The FluoroStar’s objective lens features a premium air-spaced triplet design, using FPL-53 ED glass from Ohara, Japan, combined with lanthanum glass elements. This exceptionally high-quality optical system delivers outstanding color fidelity and sharpness—making it a truly top-tier instrument.

Pair this apochromatic refractor with a quality diagonal from William Optics, and you’ll enjoy stargazing with a level of clarity that few telescopes can match. Double stars split cleanly, Jupiter’s bands and zones stand out with rich detail, and Saturn’s rings appear as if you’re seeing them up close from space.

Thanks to its large, unobstructed aperture—unlike reflectors that require a secondary mirror—the FluoroStar gives you breathtaking views of Messier objects and deep-sky wonders. Anyone who experiences the view through such a high-end apochromat will be captivated by the universe!

For astrophotographers, the scope’s generous image circle ensures bright, even illumination, even for full-frame camera sensors. When combined with the William Optics Flat7A field flattener, you get a fast focal ratio of f/5.6. The flattener attaches securely to the focuser for stable imaging.

The focuser itself offers smooth and precise fine adjustment, a built-in temperature display, and a wide adjustment range. It easily supports heavy astro-imaging gear and allows rotation to perfectly position your camera sensor.

A highlight of the latest William Optics apochromats is the specially designed Bahtinov focus mask, crafted from optical acrylic glass with 92% transparency. Its laser-etched pattern generates a diffraction image that is about three times brighter than classic metal masks, making it easier to achieve precise focus—even on faint stars.

Specifications

Optics

• Type: Refractor (Apochromat, Triplet lens)

• Aperture: 120 mm

• Focal Length: 780 mm

• Focal Ratio: f/6.5

• Resolving Power: 1.15 arcseconds

• Limiting Magnitude: 12.3

• Light Gathering Power: 290× the naked eye

• Maximum Useful Magnification: 240×

Mechanical

• Tube Weight: 7.2 kg

• Tube Diameter: 126 mm

• Tube Length: 850 mm

• Carrying Length: 680 mm

• Coating: STM

Focuser

• Type: Rack and pinion, rotatable

• Eyepiece Connection: 2"

• Camera-Side Thread: T2

• Clear Aperture: 83 mm

• Fine Focusing: 1:10 gear reduction

• Focusing Travel: 95 mm

• Telescope-Side Thread: 3.3"

Mount

• Type: OTA (Optical Tube Assembly only; no mount included)

Included Accessories

• Prism Rail: Losmandy-style

• Carrying Handle: Yes

• Focusing Aid: Bahtinov focus mask

• Carry Case: Yes

• Finder Base: Vixen/Skywatcher standard

• Diagonal: Not included

General

• Series: FluoroStar

• Color: Gold

Recommended Uses

• Astrophotography: Yes (excellent)

• Moon & Planets: Yes

• Nature Observation: No

• Nebulae & Galaxies: Yes

• Solar Observation: No (only with a proper solar filter)

User Level

• Beginners: No

• Advanced Users: Yes

• Observatories: Yes