William Optics Flat73A Flattener for ZenithStar 73 A 1.0× field flattener that preserves the telescope's native focal length for the manufacturer's listed refractor combinations. Its optical system uses 2 elements in 2 groups.
Manufacturer model: William Optics Flat73A Flattener for ZenithStar 73 · Specifications checked against manufacturer data on 2026-11-03
A 1.0× field flattener that preserves the telescope's native focal length for the manufacturer's listed refractor combinations. Its optical system uses 2 elements in 2 groups.
The telescope connection is M63x1; the camera connection is M48x0.75. Weight is 328.8 g. 39.5 mm flattener plus 26 mm rotator/adapter.
For ZenithStar 73: 66.2 mm backfocus, with 11.4 mm adjustment and a 43 mm image circle. Use the listed front or rear adapter where specified; backfocus and mechanical adjustment are different measurements.
William Optics manufacturer specification and compatibility chart
Spacing and mechanical fit require exact interfaces and reference surfaces. Named standards do not establish every system combination.
| Optical groups | 2 |
|---|---|
| Backfocus (mm) | 66.2 |
| Adjust distance (mm) | 11.4 |
| Camera thread engagement (mm) | 4 |
| Telescope thread engagement (mm) | 6 |
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William Optics Flat73A Flattener for ZenithStar 73 A 1.0× field flattener that preserves the telescope's native focal length for the manufacturer's listed refractor combinations. Its optical system uses 2 elements in 2 groups.
Manufacturer model: William Optics Flat73A Flattener for ZenithStar 73 · Specifications checked against manufacturer data on 2026-11-03
