William Optics Apochromatic refractor AP Fluorostar 120/780 Space Gray OTA (74018)

The FluoroStar’s objective lens is a high-end, air-spaced triplet featuring premium FPL-53 ED glass from Ohara, Japan, combined with lanthanum elements. This advanced optical design ensures excellent color fidelity and image clarity, meeting the highest standards for serious astronomers.

Pair this apochromatic refractor with a quality diagonal from William Optics, and you’ll experience star views with a sharpness and detail rarely matched by other telescopes. Double stars separate cleanly, Jupiter’s bands and zones are full of detail, and Saturn’s rings look as if you’re flying right past them.

With its large, unobstructed aperture—unlike reflectors that require a secondary mirror—this telescope unlocks the full beauty of Messier objects and deep-sky targets. Anyone who looks through such a premium apochromat is sure to be captivated by the cosmos!

For astrophotography, the FluoroStar’s generous image circle ensures even illumination for full-frame cameras. Used together with the William Optics Flat7A field flattener, you’ll achieve a fast f/5.6 focal ratio. The flattener attaches securely to the focuser for stable, precise imaging.

The focuser offers smooth and precise fine adjustment, an integrated temperature display, and a wide adjustment range. It easily supports heavy astrophotography setups and can be rotated for optimal sensor positioning.

A special highlight of the latest William Optics apochromats is the innovative Bahtinov focus mask, made from optical acrylic glass with 92% transparency. Its laser-etched pattern produces a diffraction image about three times brighter than classic metal masks, making it much easier to achieve perfect focus, even on faint stars.

Specifications

Optics

• Type: Refractor (Apochromat, Triplet)

• 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; mount not 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: Space Gray (Silver)

Recommended Uses

• Astrophotography: Yes (excellent)

• Moon & Planets: Yes

• Nature Observation: No

• Nebulae & Galaxies: Yes

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

User Level

• Beginners: No

• Advanced Users: Yes

• Observatories: Yes