William Optics Gran Turismo 71 II The Gran Turismo 71 II is a compact 71 mm triplet apochromatic refractor with an Ohara FPL-53 objective. Its 419 mm focal length and f/5.9 focal ratio provide a wide field for deep-sky astrophotography and a portable optical tube for visual observing.
Manufacturer model: William Optics Gran Turismo 71 II · Specifications checked against manufacturer data on 2026-11-03
The Gran Turismo 71 II is a compact 71 mm triplet apochromatic refractor with an Ohara FPL-53 objective. Its 419 mm focal length and f/5.9 focal ratio provide a wide field for deep-sky astrophotography and a portable optical tube for visual observing.
William Optics specifies a 44 mm image circle and support for full-frame, APS-C and Micro Four Thirds cameras. Optional Flat GT 1.0× and Flat6AIII 0.8× correctors provide separate imaging configurations; these are accessories rather than integral elements of the triplet objective.
The 2.5-inch dual-speed rack-and-pinion focuser has 93 mm travel and supports an electronic automatic focuser. An M63 to 2-inch visual back and 2-inch to 1.25-inch adapter provide the listed visual connections.
With Flat GT, the manufacturer lists 56.6 mm backfocus using a 1.6 mm threaded spacer and removal of the front extender. With Flat6AIII, the listed backfocus is 64.1 mm with 9.1 mm adjustment. Use the spacing for the chosen corrector when assembling the camera train.
The CNC-machined aluminium tube has a retractable dew shield, a 392–470 mm length range and a 2.95 kg optical-tube weight. Its dual-sided Vixen / Arca-Swiss plate offers two mounting profiles.
William Optics manufacturer documentation
Manufacturer-published named-model content completed. Optional correctors require their individually specified adapters and backfocus settings.
| Visual connections | M63 to 2-inch visual back; 2-inch to 1.25-inch adapter |
|---|---|
| Optical tube weight (kg) | 2.95 |
| Supported camera formats | Full frame; APS-C; Micro Four Thirds |
| Optional correctors | Flat GT 1.0×; Flat6AIII 0.8× |
| Flat gt backfocus (mm) | 56.6 |
| Flat gt spacing | 1.6 mm threaded spacer; remove front extender; no additional adjustment |
| Flat gt image circle (mm) | 44 |
| Flat6aiii backfocus (mm) | 64.1 |
| Flat6aiii adjustment (mm) | 9.1 |
| Flat6aiii image circle (mm) | 44.4 |
Ficha técnica
William Optics Gran Turismo 71 II The Gran Turismo 71 II is a compact 71 mm triplet apochromatic refractor with an Ohara FPL-53 objective. Its 419 mm focal length and f/5.9 focal ratio provide a wide field for deep-sky astrophotography and a portable optical tube for visual observing.
Manufacturer model: William Optics Gran Turismo 71 II · Specifications checked against manufacturer data on 2026-11-03
