William Optics Adjustable Flat7A Flattener/Reducer A 0.8× focal reducer and field flattener for the manufacturer's listed refractor combinations. Its optical system uses 3 elements in 3 groups.
Manufacturer model: William Optics Adjustable Flat7A Flattener/Reducer · Specifications checked against manufacturer data on 2026-11-03
A 0.8× focal reducer and field flattener for the manufacturer's listed refractor combinations. Its optical system uses 3 elements in 3 groups.
The telescope connection is M92x1; the camera connection is M48x0.75. Weight is 888.4 g. Optical length: 59.5 mm.
Backfocus varies by telescope: FLT120 with back adapter: 56.41 mm; FLT132: 69.24 mm; FLT156: 65.3 mm; GT102: 70.6 mm; GT153: 65.4 mm; ZS126: 67.76 mm. 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 | 3 |
|---|---|
| Backfocus flt120 with back adapter (mm) | 56.41 |
| Backfocus flt132 (mm) | 69.24 |
| Backfocus flt156 (mm) | 65.3 |
| Backfocus gt102 (mm) | 70.6 |
| Backfocus gt153 (mm) | 65.4 |
| Backfocus zs126 (mm) | 67.76 |
| Camera thread engagement (mm) | 4 |
| Telescope thread engagement (mm) | 6.5 |
| Adjustment flt120 with back adapter (mm) | 1.4 (product table); 1.41 (FLT120 support table) |
| Image circle flt120 with back adapter (mm) | 44.4 |
| Adjustment flt132 (mm) | 14.24 |
| Image circle flt132 (mm) | 44.4 |
| Adjustment flt156 (mm) | 10.29 |
| Image circle flt156 (mm) | 44.4 |
| Adjustment gt102 (mm) | 15.6 |
| Image circle gt102 (mm) | 44.4 |
| Adjustment gt153 (mm) | 10.41 |
| Image circle gt153 (mm) | 44.4 |
| Adjustment zs126 (mm) | 12.76 |
| Image circle zs126 (mm) | 43.4 |
| Spacing reference | Use the backfocus and adjustment setting for the named telescope and required adapter. Manufacturer model-specific values; not a universal camera spacing. |
Data sheet
William Optics Adjustable Flat7A Flattener/Reducer A 0.8× focal reducer and field flattener for the manufacturer's listed refractor combinations. Its optical system uses 3 elements in 3 groups.
Manufacturer model: William Optics Adjustable Flat7A Flattener/Reducer · Specifications checked against manufacturer data on 2026-11-03
