TEC 0.9x Focal Reducer Corrector for APO 200 FL / 250VT The TEC FRC 0.9× combines field flattening with a 10% reduction in focal length. TEC specifies a 51 mm image circle, or a 36 × 36 mm square format, with approximately 10% corner vignetting.
Manufacturer model: TEC 0.9x Focal Reducer Corrector for APO 200 FL / 250VT · Specifications checked against manufacturer data on 2026-11-04
The TEC FRC 0.9× combines field flattening with a 10% reduction in focal length. TEC specifies a 51 mm image circle, or a 36 × 36 mm square format, with approximately 10% corner vignetting.
The current manufacturer table gives two separate spacing references for APO250VT f/8.8: “Back Focus Range” is 103 mm, while “Back Focus Real” is 100 mm. These are different mechanical references, so use the drawing and adapter that match the imaging train.
The FRC fits the Starlight Instruments FTF3545 focuser. With the named APO250VT f/8.8, applying the 0.9× factor gives a calculated 1980 mm focal length at approximately f/7.92. TEC supplies the reducer configuration for the telescope specified when ordering.
TEC describes FRC availability for all its telescope models, but the current table publishes spacing for APO250VT rather than APO200FL. The APO250 values above must not be used as an APO200 spacing specification.
TEC manufacturer documentation
Current TEC FRC table used rather than older telescope accessory prose quoting f/6.2 or 115 mm generically. Range and Real spacing columns are kept distinct. Derived focal length/ratio are arithmetic from 0.9×, not additional manufacturer measurements. ED variants must use their own adapter reference; FL spacing is not silently assigned to ED. The combined store title also names APO200FL; no exact APO200 spacing is published in the current table.
| Correction | Field flattening and focal reduction |
|---|---|
| Published image circle (mm) | 51 |
| Published square format (mm) | 36 × 36 |
| Manufacturer corner vignetting | Approximately 10% |
| Spacing table model | APO250VT f/8.8 |
| Manufacturer back focus range | 103 mm |
| Manufacturer back focus real | 100 mm |
| Derived effective focal ratio | 7.92 |
| Derived effective focal length (mm) | 1980 |
Ficha técnica
TEC 0.9x Focal Reducer Corrector for APO 200 FL / 250VT The TEC FRC 0.9× combines field flattening with a 10% reduction in focal length. TEC specifies a 51 mm image circle, or a 36 × 36 mm square format, with approximately 10% corner vignetting.
Manufacturer model: TEC 0.9x Focal Reducer Corrector for APO 200 FL / 250VT · Specifications checked against manufacturer data on 2026-11-04
