William Optics Fluorostar 120 Space Gray OTA — 120 mm triplet apochromatic refractor The Fluorostar 120 has a 780 mm focal length at f/6.5. William Optics specifies a 43 mm image circle.
Manufacturer model: William Optics Fluorostar 120 Space Gray OTA · Specifications checked against manufacturer data on 2026-11-03
William Optics Fluorostar 120 Space Gray OTA — 120 mm triplet apochromatic refractor
The Fluorostar 120 has a 780 mm focal length at f/6.5. William Optics specifies a 43 mm image circle.
Optics and imaging
The triplet objective can be paired with the manufacturer's listed optional field flatteners or reducers.
Focusing and adapters
3.3-inch rack-and-pinion focusing provides 95 mm travel. Connections: M92 rotator; M92 to 2-inch RotoLock; 2-inch to 1.25-inch visual back. Each corrector has its own backfocus and adjustment setting; these are listed separately in the specifications.
Dimensions and handling
Tube length is 680–850 mm; OTA weight is 7.1 kg. Manufacturer total weight is 9.45 kg.
The triplet objective uses FPL-53 glass for chromatic correction. William Optics lists a Losmandy-style mounting plate, an integrated Bahtinov mask in the lens cover, and a handle that also provides an accessory mounting point. Optional flatteners and reducers are separate optical components with their own adapter and spacing requirements.
Compatibility notes
Prime-lens telescope: corrector compatibility and spacing are model-specific.
Additional specifications
Flat7a with back extender spacing
56.41 mm backfocus; 1.41 mm adjustment
74018
Data sheet
Aperture (mm)
120
Camera adapters
M92 rotator; M92 to 2-inch RotoLock; 2-inch to 1.25-inch visual back
Camera format
Full frame and APS-C
Ed glass
Ohara FPL-53
Flat68iii spacing
65.7 mm backfocus; 10.7 mm adjustment
Focal length (mm)
780
Focal ratio
6.5
Focuser travel (mm)
95
Focuser type
3.3-inch rack-and-pinion
Image circle (mm)
43
Manufacturer listed correctors
Flat68III 1.0x; Flat7A 0.8x
Mounting plate
Losmandy-style
Optical design
Triplet apochromat
OTA weight (kg)
7.1
Total weight (kg)
9.45
Tube length (mm)
680–850
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William Optics Fluorostar 120 Space Gray OTA — 120 mm triplet apochromatic refractor The Fluorostar 120 has a 780 mm focal length at f/6.5. William Optics specifies a 43 mm image circle.
Manufacturer model: William Optics Fluorostar 120 Space Gray OTA · Specifications checked against manufacturer data on 2026-11-03
