William Optics ZenithStar ZS61 II OTA

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.

William Optics manufacturer manual

Objective and installation

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