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William Optics

William Optics

William Optics has built its reputation on small apochromatic astrographs that are genuinely portable, mechanically well finished and easy to bring to focus — the RedCat and Zenithstar families in particular have become default recommendations for imagers who want wide fields without a heavy mount. David Astro stocks William Optics products in Canada, shipping from Canadian inventory.

We image with these telescopes here, and can tell you where the fixed back-focus of the Petzval designs simplifies your life and where a longer focal length model would serve your targets better.

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CA$27,597.00 - CA$27,597.00
CA$27,597.00
CA$27,597.00 - CA$27,597.00
CA$27,597.00

William Optics Pleiades 181 Astrograph F/5.5 7-element with 3 ED glasses

WO-T-P-181RD

181mm Aperture, 998mm Focal Length Fast f/5.5 Focal Ratio 7-Element Optical Design with 3 Super ED Glass Elements 55mm Corrected Image Circle 4.1-...

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CA$27,597.00 - CA$27,597.00
CA$27,597.00
CA$27,597.00 - CA$27,597.00
CA$27,597.00
CA$10,653.00 - CA$12,417.00
CA$10,653.00 - CA$12,417.00
CA$10,653.00 - CA$12,417.00
CA$10,653.00

William Optics Fluorostar 156

Options available

156mm Aperture Triplet Apochromat 1217mm Focal Length (f/7.8) FPL-53 & Lanthanum Glass Elements 3.7" Rack & Pinion Focuser Thermally Stabl...

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CA$10,653.00 - CA$12,417.00
CA$10,653.00 - CA$12,417.00
CA$10,653.00 - CA$12,417.00
CA$10,653.00
William Optics Ultra-Cat 131 f/4.9 Petzval Astrograph
CA$7,449.00 - CA$7,449.00
CA$7,449.00
CA$7,449.00 - CA$7,449.00
CA$7,449.00

William Optics Ultra-Cat 131 f/4.9 Petzval Astrograph

WO-T-C-131BR

131mm Aperture 648mm Focal Length (f/4.9) 5-Element Advanced Petzval Optical Design 60mm Flat-Field Image Circle Patented WIFD Internal Focuser 13...

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CA$7,449.00 - CA$7,449.00
CA$7,449.00
CA$7,449.00 - CA$7,449.00
CA$7,449.00
CA$6,304.00 - CA$8,162.00
CA$6,304.00 - CA$8,162.00
CA$6,304.00 - CA$8,162.00
CA$6,304.00

William Optics Fluorostar 132

Options available

132mm Aperture, 910mm Focal Length (f/6.9) Air-Spaced Triplet Apochromatic Objective Premium FPL-53 Glass for Superior Color Correction Heavy-Duty...

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CA$6,304.00 - CA$8,162.00
CA$6,304.00 - CA$8,162.00
CA$6,304.00 - CA$8,162.00
CA$6,304.00
CA$5,793.00 - CA$5,793.00
CA$5,793.00
CA$5,793.00 - CA$5,793.00
CA$5,793.00

William Optics Pleiades 111 Astrograph F/4.8 7-element WIFD

WO-T-P-111BU

111mm Aperture 7-Element Astrograph 528mm Focal Length at a fast f/4.8 45mm Image Circle for Full-Frame Sensors William Optics Internal Focus Desi...

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CA$5,793.00 - CA$5,793.00
CA$5,793.00
CA$5,793.00 - CA$5,793.00
CA$5,793.00
CA$5,517.00 - CA$5,517.00
CA$5,517.00
CA$5,517.00 - CA$5,517.00
CA$5,517.00

William Optics UltraCat 108 f/4.8 WIFD

WO-T-C-108BR
1 in stock

108mm Aperture, 5-Element Advanced Petzval Optical Design Fast f/4.8 Focal Ratio with 518mm Focal Length Massive 60mm Flat-Field Image Circle Pate...

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CA$5,517.00 - CA$5,517.00
CA$5,517.00
CA$5,517.00 - CA$5,517.00
CA$5,517.00
CA$4,965.00 - CA$4,965.00
CA$4,965.00
CA$4,965.00 - CA$4,965.00
CA$4,965.00

William Optics Fluorostar 120

Options available

120mm Aperture FPL-53 Triplet Apochromatic Optics 3.3" Rack & Pinion Focuser Built-in Camera Angle Rotator Integrated Bahtinov Mask Descrip...

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CA$4,965.00 - CA$4,965.00
CA$4,965.00
CA$4,965.00 - CA$4,965.00
CA$4,965.00
CA$3,741.00 - CA$4,137.00
CA$3,741.00 - CA$4,137.00
CA$3,741.00 - CA$4,137.00
CA$3,741.00

William Optics Cat 91 WIFD

Options available
1 variants in stock

91mm Aperture, 448mm Focal Length (f/4.9) 5-Element Advanced Petzval Optical Design 55mm Corrected Image Circle WIFD Rack & Pinion Internal Fo...

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CA$3,741.00 - CA$4,137.00
CA$3,741.00 - CA$4,137.00
CA$3,741.00 - CA$4,137.00
CA$3,741.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00

William Optics UltraCat 76 f/4.8 WIFD

WO-T-C-76BR
2 in stock

76 mm Aperture, 365 mm Focal Length (f/4.8) 5-Element Advanced Petzval Optical Design 50 mm Corrected Image Circle William Optics Internal Focusin...

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CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00

William Optics Pleiades 68 Astrograph F/3.8 7-Element WIFD

WO-T-P-68BU

68mm Aperture 7-Element Astrograph Fast f/3.8 Focal Ratio 260mm Focal Length 48mm Full-Frame Image Circle Weighs only 2.98 kg (6.57 lbs) WIFD Focu...

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CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00

William Optics Gran Turismo WIFD 81

Options available

81mm Aperture Triplet Apochromatic Refractor FPL-53 Ohara Glass for Superior Color Correction William Optics Internal Focusing Design (WIFD) Inclu...

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CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$3,033.00 - CA$3,033.00
CA$3,033.00
CA$2,877.00 - CA$3,033.00
CA$2,877.00 - CA$3,033.00
CA$2,877.00 - CA$3,033.00
CA$2,877.00

William Optics Fluorostar 91

Options available

91mm Aperture Apochromatic Triplet FPL-53 Glass for Superior Color Correction Strehl Ratio Exceeding 0.95 3.3" Dual-Speed Rack & Pinion Focuse...

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CA$2,877.00 - CA$3,033.00
CA$2,877.00 - CA$3,033.00
CA$2,877.00 - CA$3,033.00
CA$2,877.00
CA$2,013.00 - CA$2,013.00
CA$2,013.00
CA$2,013.00 - CA$2,013.00
CA$2,013.00

William Optics Redcat 71 WIFD

WO-T-C-71RDII

Apochromatic Petzval-like Optical Design WIFD (William Optics Internal Focuser Design) Integrated Bahtinov Mask in Dust Cap Included M48 Camera Ad...

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CA$2,013.00 - CA$2,013.00
CA$2,013.00
CA$2,013.00 - CA$2,013.00
CA$2,013.00
CA$1,929.00 - CA$1,929.00
CA$1,929.00
CA$1,929.00 - CA$1,929.00
CA$1,929.00

William Optics UltraCat 56 f/4.8 WIFD

WO-T-C-56BR
6 in stock

56mm Aperture, 269mm Focal Length (f/4.8) 5-Element Advanced Petzval Optical Design 50mm Image Circle for Full-Frame Sensors William Optics Intern...

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CA$1,929.00 - CA$1,929.00
CA$1,929.00
CA$1,929.00 - CA$1,929.00
CA$1,929.00
CA$1,581.00 - CA$1,581.00
CA$1,581.00
CA$1,581.00 - CA$1,581.00
CA$1,581.00

William Optics RedCat 61 WIFD

WO-T-C-61RD
1 in stock

61mm Aperture Petzval-like Astrograph Fast f/4.9 Focal Ratio WIFD (William Optics Internal Focus Design) Focuser Requires No Backfocus Calculation...

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CA$1,581.00 - CA$1,581.00
CA$1,581.00
CA$1,581.00 - CA$1,581.00
CA$1,581.00
CA$1,515.00 - CA$1,515.00
CA$1,515.00
CA$1,515.00 - CA$1,515.00
CA$1,515.00

William Optics Gran Turismo 71 APO Triplet

WO-A-F71GTII-RD

71mm Triplet Apochromatic Lens 419mm Focal Length at f/5.9 44mm Full-Frame Image Circle 2.5" Rack & Pinion Focuser OTA Weight: 2.95 kg (6.5 lb...

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CA$1,515.00 - CA$1,515.00
CA$1,515.00
CA$1,515.00 - CA$1,515.00
CA$1,515.00
CA$1,488.00 - CA$1,488.00
CA$1,488.00
CA$1,488.00 - CA$1,488.00
CA$1,488.00

William Optics Pier Mount 90

WO-YG-PM-90R

90 kg (198 lbs) Loading Capacity Lightweight 7 kg Aluminum Alloy Construction 100 mm (4") Diameter Pillar for Maximum Rigidity Includes 3/8" Adapt...

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CA$1,488.00 - CA$1,488.00
CA$1,488.00
CA$1,488.00 - CA$1,488.00
CA$1,488.00
William Optics Ultra Flat 156 (0.79x Reducer)
CA$1,474.00 - CA$1,474.00
CA$1,474.00
CA$1,474.00 - CA$1,474.00
CA$1,474.00

William Optics Ultra Flat 156 (0.79x Reducer)

WO-P-FLAT-156

Reduces focal ratio by a factor of 0.79x Designed for Medium Format, Full Frame, and APS-C sensors 3-element, 3-group optical design Requires 75.5...

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CA$1,474.00 - CA$1,474.00
CA$1,474.00
CA$1,474.00 - CA$1,474.00
CA$1,474.00
William Optics Ultra Flat 132 (0.79x Reducer)
CA$1,474.00 - CA$1,474.00
CA$1,474.00
CA$1,474.00 - CA$1,474.00
CA$1,474.00

William Optics Ultra Flat 132 (0.79x Reducer)

WO-P-FLAT-132

Reduces focal ratio by a factor of 0.79x Provides a flat field for Full Frame, APS-C, and M4/3 sensors 3-element, 3-group optical design Connects ...

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CA$1,474.00 - CA$1,474.00
CA$1,474.00
CA$1,474.00 - CA$1,474.00
CA$1,474.00
CA$1,398.00 - CA$1,515.00
CA$1,398.00 - CA$1,515.00
CA$1,398.00 - CA$1,515.00
CA$1,398.00

William Optics Zenithstar 81 WIFD Telescope

Options available

Patented William Optics Internal Focus Design (WIFD) Rigid M92 Rear Thread with M63 Adapter Included Vixen/Arca-Swiss Dual-Sided Mounting Plate In...

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CA$1,398.00 - CA$1,515.00
CA$1,398.00 - CA$1,515.00
CA$1,398.00 - CA$1,515.00
CA$1,398.00
CA$1,363.00 - CA$1,363.00
CA$1,363.00
CA$1,363.00 - CA$1,363.00
CA$1,363.00

William Optics MiniCat 51 WIFD f/3.5

WO-T-C-MINI-RD
3 in stock

51mm Aperture Diameter 178mm Focal Length f/3.5 Focal Ratio 6-Element Petzval Optical Design 43.2mm Full-Frame Image Circle WIFD Rack & Pinion...

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CA$1,363.00 - CA$1,363.00
CA$1,363.00
CA$1,363.00 - CA$1,363.00
CA$1,363.00
CA$1,225.00 - CA$1,225.00
CA$1,225.00
CA$1,225.00 - CA$1,225.00
CA$1,225.00

William Optics Redcat 51 WIFD

WO-L-RC51RDIII
1 in stock

Compact Apochromatic Refractor Petzval-like Optical Design for Flat Fields William Optics Internal Focus Design (WIFD) CNC-Machined Aluminum Body ...

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CA$1,225.00 - CA$1,225.00
CA$1,225.00
CA$1,225.00 - CA$1,225.00
CA$1,225.00
CA$1,161.00 - CA$1,161.00
CA$1,161.00
CA$1,161.00 - CA$1,161.00
CA$1,161.00

William Optics RC Focuser w/ Optional 0.8x RC Reducer Flattener

Options available

Provides precise focusing for Ritchey-Chrétien telescopes Includes an optional 0.8x reducer flattener for improved image quality Description...

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CA$1,161.00 - CA$1,161.00
CA$1,161.00
CA$1,161.00 - CA$1,161.00
CA$1,161.00
CA$1,161.00 - CA$1,161.00
CA$1,161.00
CA$1,161.00 - CA$1,161.00
CA$1,161.00

William Optics WO x0.72 Reducer Flattener 8

WO-P-FLAT8

Reduces focal ratio by a factor of 0.72x Corrects field curvature for full-frame sensors 3-element, 3-group optical design Connects to telescope v...

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CA$1,161.00 - CA$1,161.00
CA$1,161.00
CA$1,161.00 - CA$1,161.00
CA$1,161.00

The William Optics Range

The line divides fairly cleanly between Petzval astrographs with built-in field correction and traditional doublets and triplets that use a separate flattener.

  • RedCat and Petzval astrographs: Four-element designs with the flattener integrated, giving a flat field at a fixed back-focus with no spacing calculation required — the simplest imaging optics to set up correctly.
  • Zenithstar apochromatic refractors: Compact FPL-53 doublets from 61 mm upward, popular as first imaging telescopes and as guide or companion scopes on larger rigs.
  • GT and FLT triplet refractors: Larger apochromatic triplets for imagers who want more aperture and focal length while keeping a refractor's convenience.
  • UniGuide guide scopes: Rigid guide scopes with integrated mounting that avoids the flexure common to ring-and-bracket guide setups.
  • RotoLock and mechanical accessories: Rotating locking collars, dovetails, tube rings and Bahtinov masks designed to fit the tubes precisely.
  • Diagonals and eyepieces: Dielectric diagonals and eyepiece lines matched to the refractors for visual use.

Why Choose David Astro for William Optics

These telescopes are straightforward to use and easy to buy in the wrong focal length. That is where the advice matters.

  • Focal length matched to targets: We calculate the field of view your sensor will get on each model, so you can see whether your target actually fits before ordering.
  • Petzval back-focus supplied: The integrated designs have a fixed spacing requirement, and we provide the exact adapter list for your camera and filter setup.
  • Authorized dealer: Full manufacturer warranty with verified authenticity, handled domestically in Canada.
  • Canadian stock: Ships from Canada with no duties or brokerage fees for Canadian orders.
  • Support after first light: Help diagnosing tilt, spacing and star shape once the telescope is on the sky.

William Optics in Canada — Frequently Asked Questions

Do RedCat telescopes need a flattener?
No. The Petzval design includes field correction, so you only need to hit the specified back-focus to the camera sensor. That is one of the main reasons they are recommended to first-time imagers.
Which focal length should I choose?
It depends on your target size and sensor. Around 250 mm suits large nebulae and the Andromeda galaxy; 400 to 600 mm frames most emission nebulae well; beyond that you are into small galaxies and planetary nebulae, which also demands better guiding.
Can these work as guide scopes?
The smaller Zenithstars and the UniGuide range are commonly used this way. The key advantage of a purpose-built guide scope is rigidity — a flexing guide scope produces errors that guiding cannot correct.
Is warranty handled in Canada?
Yes. As an authorized dealer we process warranty and service claims here, without international shipping or customs paperwork.

Choosing a focal length?

Send us your camera and your target list and we will show you the framing. Canadian stock, full warranty.