William Optics ZenithStar ZS61 II OTA — 61 mm doublet apochromat This refractor provides a 360 mm focal length at f/5.9. The manufacturer lists a 45 mm image circle and optional correctors for photographic use.
Manufacturer model: William Optics ZenithStar ZS61 II OTA · Specifications checked against manufacturer data on 2026-11-03
William Optics ZenithStar ZS61 II OTA — 61 mm doublet apochromat
This refractor provides a 360 mm focal length at f/5.9. The manufacturer lists a 45 mm image circle and optional correctors for photographic use.
Focusing and camera connection
The 2-inch rack and pinion focuser provides 75 mm travel. Connections comprise M54 to 2-inch visual back; 2-inch to 1.25-inch visual back.
Field correction
Manufacturer-listed options: Flat61A 1.0x, Flat61R 0.8x. Each combination has a specific spacing and adapter arrangement; see the individual settings in the specifications. A corrector is an optional accessory.
Size and weight
Tube length is 245–315 mm and OTA weight is 2.2 kg.
The objective uses Ohara FPL-53 ED glass for colour correction. The manufacturer lists a dual-sided Vixen / Arca-Swiss dovetail for mounting. For photographic use, select the correct flattener or reducer and its specified adapters; telescope focal length and corrector spacing are separate specifications.
Compatibility notes
Prime-lens telescope: corrector compatibility and spacing are model-specific. Optional correctors are listed, not assumed included; corrector adapters may be required.
Additional specifications
Flat61a spacing
67.7 mm backfocus; 12.9 mm adjustment
Flat61r spacing
56 mm backfocus; 1 mm adjustment
67480
Datasheet
Opening (mm)
61
Camera-adapters
M54 to 2-inch visual back; 2-inch to 1.25-inch visual back
Cameraformaat
Full frame, APS-C and Micro Four Thirds
ED-glas
Ohara FPL-53
Brandpuntsafstand (mm)
360
Openingsverhouding
5.9
Focuserslag (mm)
75
Type focuser
2-inch rack and pinion
Beeldcirkel (mm)
45
Door fabrikant genoemde correctors
Flat61A 1.0x; Flat61R 0.8x
Montageplaat
Vixen / Arca-Swiss dual-sided
Optisch ontwerp
Doublet apochromat
Gewicht optische tubus (kg)
2.2
Tubuslengte (mm)
245–315
Dit product gebruikt? Deel je ervaring met andere astronomen.
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William Optics ZenithStar ZS61 II OTA — 61 mm doublet apochromat This refractor provides a 360 mm focal length at f/5.9. The manufacturer lists a 45 mm image circle and optional correctors for photographic use.
Manufacturer model: William Optics ZenithStar ZS61 II OTA · Specifications checked against manufacturer data on 2026-11-03
