Description
The stunning new William Optics GTF 81APO is the new jewel of the apochromatic refractor world.
From the pristine white finish on the CNC to the elegant red beauty which has more than just good looks.
New GTF 81 features total 5-element in 2 groups design by using high-quality FPL-53 extra-low dispersion glass that reduces any secondary spectrum to an unbelievable degree,the second group of ED element (flat field corrector) is correcting the edge of flatness to the best quality (cover up to 40mm of image circle).
Optically Unbeatable
2.5” R&P Focuser
Attention to Details
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Specification
| Aperture | 81 mm |
| Focal Ratio | F/5.9 |
| Focal Length | 478 mm |
| Objective Type | Five element with FPL-53 Air Spaced (2 groups), Fully Multi-Coated, STM coatings |
| Resolving Power | 1.43 seconds of arc |
| Limiting Magnitude | 12.2 |
| Lens Shade | Retractable |
| Focuser | 2? 360° Rotating Camera-angle Adjuster, 1:10 fine focus |
| Focuser Travel Length 3.15? (80mm) | |
| 1.25? Adapter | |
| 1.25? Adapter | Brass Compression Rings |
| Field Stops | 2 Baffles |
| Tube Diameter | 90mm |
| Tube Length | 440mm Fully Retracted |
| 484mm Fully Extended | |
| Tube Weight | 3.7 kg |
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