William Optics GTF81 81mm Apo Refractor with Built-In Flattener & DDG Focuser
This item is discontinued by the manufacturer and is no longer available.
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Availability: Item has been discontinued and is no longer available.
The stunning new William Optics Gran Turismo GTF 81 Apo is the new jewel of the apochromatic refractor world. From the pristine white finish on the CNC tube to the elegant dark red trim, this beauty has more than just good looks. This new GTF81 features a 3-element objective using high-quality FPL-53 extra-low dispersion glass that reduces any secondary spectrum to an unbelievable degree. But what makes this scope truly unique is the second optical component - a 2-element built-in ED field flattener that corrects the field, providing an excellent flat field over a 40mm image circle.
Optically Unbeatable
- Five element in two groups air-spaced objective (FPL-53) in adjustable CNC machined ultra high precision lens cell.
- Extremely sharp.
- Excellent color correction.
- Each lens is Fully Multi-Coated with a special super-high transmission coating (STM Coating) on all surfaces.
- This f/6.6 telescope is ideal for astrophotography.
2” R&P DDG Focuser
- The Digital Display Gauge - DDG - allows you to take precise focusing readings down to two decimals precision instantly.
- Extra-smooth 360 deg. rotatable 2" Rack & Pinion focuser with 1:10 dual speed: a treat to use during astrophotography. No image shifting!
- Comes with two locking screws on angled positions for heavy load applications.
- Large aluminum knob with installed thermometer and aluminum protection cover.
Finder / Guidescope Rings Included
- Includes bracket that can accommodate finders with a tube diameter of up to 60-61mmm. Perfect for adding a finderscope or guiding scope.
- Viewfinder/Guidescope shown in photos above is illustrative only and NOT included.
Simply Beautiful Finish
- Pure William Optics quality fit and finish: powder-painted white CNC-machined aluminum tube, dark red trim finish, retractable dewshield, 360 deg. rotatable R&P focuser, dewshield cap, L-shaped Vixen-style mounting base.
- Top quality anodizing.
Attention to Details
- Includes 2" & 1.25" adapter.
- Anti-marring brass compression rings.
- Carry handle with V-shape night glowing illuminator.
- 2-year warranty from WO.
Useful Resources
- Review in Jul-Aug 2013 issue of Astronomy Technology Today magazine: William Optics GTF81 Review (Non-DDG version) (PDF format, 644 KB)
- User Manual: William Optics GTF 81 (PDF format, 1.35 MB)
- Spot Diagrams: William Optics GTF 81 (PDF format, 730 KB)
The stunning new William Optics Gran Turismo GTF 81 Apo is the new jewel of the apochromatic refractor world. From the pristine white finish on the CNC tube to the elegant dark red trim, this beauty has more than just good looks. This new GTF81 features a 3-element objective using high-quality FPL-53 extra-low dispersion glass that reduces any secondary spectrum to an unbelievable degree. But what makes this scope truly unique is the second optical component - a 2-element built-in ED field flattener that corrects the field, providing an excellent flat field over a 40mm image circle.
Optically Unbeatable
- Five element in two groups air-spaced objective (FPL-53) in adjustable CNC machined ultra high precision lens cell.
- Extremely sharp.
- Excellent color correction.
- Each lens is Fully Multi-Coated with a special super-high transmission coating (STM Coating) on all surfaces.
- This f/6.6 telescope is ideal for astrophotography.
2” R&P DDG Focuser
- The Digital Display Gauge - DDG - allows you to take precise focusing readings down to two decimals precision instantly.
- Extra-smooth 360 deg. rotatable 2" Rack & Pinion focuser with 1:10 dual speed: a treat to use during astrophotography. No image shifting!
- Comes with two locking screws on angled positions for heavy load applications.
- Large aluminum knob with installed thermometer and aluminum protection cover.
Finder / Guidescope Rings Included
- Includes bracket that can accommodate finders with a tube diameter of up to 60-61mmm. Perfect for adding a finderscope or guiding scope.
- Viewfinder/Guidescope shown in photos above is illustrative only and NOT included.
Simply Beautiful Finish
- Pure William Optics quality fit and finish: powder-painted white CNC-machined aluminum tube, dark red trim finish, retractable dewshield, 360 deg. rotatable R&P focuser, dewshield cap, L-shaped Vixen-style mounting base.
- Top quality anodizing.
Attention to Details
- Includes 2" & 1.25" adapter.
- Anti-marring brass compression rings.
- Carry handle with V-shape night glowing illuminator.
- 2-year warranty from WO.
| Manufacturer | William Optics |
|---|
| Aperture | 81 mm |
| Focal Ratio | F/6.6 |
| Focal Length | 535 mm |
| Objective Type | Five element with FPL-53 Air Spaced (2 groups), Fully Multi-Coated, STM coatings |
| Resolving Power | 1.43" |
| Limiting Magnitude | 12.2 |
| Lens Shade | Retractable |
| DDG Focuser | 2" 360° Rotating Camera-angle Adjuster 1:10 fine focus Focuser Travel Length 3.15" (80mm) 1.25" Adapter |
| L-type Mount | L Bracket |
| Field Stops | Knife-Edge Baffles |
| Tube Diameter | 90mm |
| Tube Length | 440mm Fully Retracted 484mm Fully Extended |
| Tube Weight | 8.1 lbs. (3.7 kg) |
Availability: Item has been discontinued and is no longer available.
The stunning new William Optics Gran Turismo GTF 81 Apo is the new jewel of the apochromatic refractor world. From the pristine white finish on the CNC tube to the elegant dark red trim, this beauty has more than just good looks. This new GTF81 features a 3-element objective using high-quality FPL-53 extra-low dispersion glass that reduces any secondary spectrum to an unbelievable degree. But what makes this scope truly unique is the second optical component - a 2-element built-in ED field flattener that corrects the field, providing an excellent flat field over a 40mm image circle.
Optically Unbeatable
- Five element in two groups air-spaced objective (FPL-53) in adjustable CNC machined ultra high precision lens cell.
- Extremely sharp.
- Excellent color correction.
- Each lens is Fully Multi-Coated with a special super-high transmission coating (STM Coating) on all surfaces.
- This f/6.6 telescope is ideal for astrophotography.
2” R&P DDG Focuser
- The Digital Display Gauge - DDG - allows you to take precise focusing readings down to two decimals precision instantly.
- Extra-smooth 360 deg. rotatable 2" Rack & Pinion focuser with 1:10 dual speed: a treat to use during astrophotography. No image shifting!
- Comes with two locking screws on angled positions for heavy load applications.
- Large aluminum knob with installed thermometer and aluminum protection cover.
Finder / Guidescope Rings Included
- Includes bracket that can accommodate finders with a tube diameter of up to 60-61mmm. Perfect for adding a finderscope or guiding scope.
- Viewfinder/Guidescope shown in photos above is illustrative only and NOT included.
Simply Beautiful Finish
- Pure William Optics quality fit and finish: powder-painted white CNC-machined aluminum tube, dark red trim finish, retractable dewshield, 360 deg. rotatable R&P focuser, dewshield cap, L-shaped Vixen-style mounting base.
- Top quality anodizing.
Attention to Details
- Includes 2" & 1.25" adapter.
- Anti-marring brass compression rings.
- Carry handle with V-shape night glowing illuminator.
- 2-year warranty from WO.
Useful Resources
- Review in Jul-Aug 2013 issue of Astronomy Technology Today magazine: William Optics GTF81 Review (Non-DDG version) (PDF format, 644 KB)
- User Manual: William Optics GTF 81 (PDF format, 1.35 MB)
- Spot Diagrams: William Optics GTF 81 (PDF format, 730 KB)
| Manufacturer | William Optics |
|---|
| Aperture | 81 mm |
| Focal Ratio | F/6.6 |
| Focal Length | 535 mm |
| Objective Type | Five element with FPL-53 Air Spaced (2 groups), Fully Multi-Coated, STM coatings |
| Resolving Power | 1.43" |
| Limiting Magnitude | 12.2 |
| Lens Shade | Retractable |
| DDG Focuser | 2" 360° Rotating Camera-angle Adjuster 1:10 fine focus Focuser Travel Length 3.15" (80mm) 1.25" Adapter |
| L-type Mount | L Bracket |
| Field Stops | Knife-Edge Baffles |
| Tube Diameter | 90mm |
| Tube Length | 440mm Fully Retracted 484mm Fully Extended |
| Tube Weight | 8.1 lbs. (3.7 kg) |