About this product
Part Number: T-FLT-91GD-RP33
Optical Bench Test
FLO tests all William Optics triplet refractor telescopes before dispatch.
You can be confident your telescope will, from the outset, have well figured optics, negligible false colour and spherical aberration, and no astigmatism (the bane of any optical system!).
Star shapes will be round, not triangular, oval or egg-shaped!
New for 2021 - William Optics Fluorostar / FLT 91
An Apochromatic triplet refractor for visual astronomers and astrophotographers wanting very high performance from in a midsize telescope.
The three-element optical design features a 91mm aperture using FPL-53 glass that delivers high contrast colour-free images and an impressive 0.95+ Strehl Ratio.
Thoughtful design features like the integrated saddle handle, 360º field rotator, 2" Rotolock, large focuser knob and built-in Bahtinov mask are more than just nice touches. They genuinely help make this an excellent choice for astrophotographers.
To use with the Flat6A III 0.8x Reducer / Flattener set the adjustable distance at 5.4mm for 55mm back focus. For the Flat68 III set the adjustable distance at 10mm which leaves 65mm back focus.
- 91mm FPL-53 Apochromatic Triplet Lens with 0.95+ Strehl Ratio
- 540mm, f/5.9 Focal Length
- Exquisite William Optics Fit & Finish
- Dual Speed 3.3" Rack & Pinion Focuser
- 2" Rotolock for Secure Attachment
- Bahtinov Mask Integrated into the Lens Cover
- Versatile Saddle Bar Handle for Guider / Finder Mounting
- Built-in 360º Field Rotator
- OTA Weight 4.2kg / 5.6kg with Rings / Dovetail / Accessories
- Supplied with a Soft Carry Case
The retractable dew shield features a removable lens cover, with our patented Bahtinov Mask revealed by unscrewing the face plate. The clear design allows for brighter star patterns, and precise focusing for astrophotography.
Versatile Saddle Bar
The Saddle Bar Handle, offers a solid handle with a built in dovetail chamber for use with the WO Uniguide scopes, or other Vixen style guiding/finder scopes.
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New Focuser Knob
A larger fit designed for better ergonomics.
The super smooth field rotator includes markings for every degree, and a solid thumbscrew position lock.
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Soft Carry Case
The standard package comes with a soft carry case.
Field of View Simulator
What's in the box
- FLT91 Telescope OTA
- Vixen-style Dovetail & Tube Rings
- Saddle Handle Bar
- 2" Rotolock
- Integrated Bahtinov Mask
- Soft Carry Case
|Lens Type ||Apochromatic Triplet Prime Lens |
|Focal Length ||540mm |
|Diameter ||91mm |
|Focal Ratio ||f/5.9 |
|Focuser ||Dual Speed 3.3" R&P Focuser |
|Colour ||Red | Gold | Space grey |
|Lens Material ||FPL-53 |
|Strehl Ratio ||0.95+ |
|Camera Format ||Full Frame DSLR / Mirrorless / CMOS / CCD |
|Test Report ||Zygo test report available at additional cost |
|T-Mounts Supported ||Canon EF, RF Nikon F, Z Sony E Pentax K Micro Four Thirds (M4/3) FUJI X |
|Retracted Length ||441mm without rings (485mm with rings fitted) |
|Extended Length ||510mm |
|Extension Tube Length ||40mm |
|OTA Weight ||4.165Kg |
|Total Weight ||5.575Kg |
|Extension Tube Weight ||0.105Kg |
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