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Optical Accessories

Optical accessories are what turn one telescope into several. The same optical tube can be a wide-field imaging refractor, a high-power planetary instrument or a comfortable binocular-view visual scope depending on what you put behind it. David Astro carries a deep selection of eyepieces, diagonals, Barlows, reducers, flatteners, binoviewers and correctors in Canada, held in Canadian stock.

Our team uses this equipment on our own telescopes, so the advice you get is based on what actually works at a given focal ratio and under a given sky, not on a spec sheet. If you are deciding between two focal lengths or wondering whether a corrector will help your optic, ask us before you order.

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CA$660.00 - CA$660.00
CA$660.00
CA$660.00 - CA$660.00
CA$660.00

William Optics STC Astro Duo-Narrowband Filter

WO-YF-STC-ADN

Dual-Bandpass for H-Alpha and Oxygen-III Suppresses Urban Light Pollution Ion Beam-Assisted Deposition (IBAD) Coatings High Durability and Easy-to...

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CA$660.00 - CA$660.00
CA$660.00
CA$660.00 - CA$660.00
CA$660.00
CA$328.00 - CA$328.00
CA$328.00
CA$328.00 - CA$328.00
CA$328.00

William Optics STC Ultra Layer Astro Multispectra Filter - 48mm

WO-YF-STC-M48

48mm (M48) Filter Size Multi-Bandpass Light Pollution Suppression Passes H-α, H-β, and OIII Emission Lines Schott B270 Optical Glass Substrate STC...

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CA$328.00 - CA$328.00
CA$328.00
CA$328.00 - CA$328.00
CA$328.00
CA$215.00 - CA$215.00
CA$215.00
CA$215.00 - CA$215.00
CA$215.00

William Optics SWAN 72° 40mm Eyepiece - 2"

WO-E-SWA40
4 in stock

40mm Focal Length 72° Apparent Field of View 2" Diameter Barrel 28mm Long Eye Relief Parfocal Design Description FAQ Specifications In the Box ...

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CA$215.00 - CA$215.00
CA$215.00
CA$215.00 - CA$215.00
CA$215.00
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
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
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
CA$1,087.00 - CA$1,087.00
CA$1,087.00
CA$1,087.00 - CA$1,087.00
CA$1,087.00

William Optics x0.8 Reducer Flattener 7A

WO-P-FLAT7A

Reduces focal ratio by a factor of 0.8x Triplet lens design with 3 elements in 3 groups Corrects field curvature for full-frame sensors Designed f...

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CA$1,087.00 - CA$1,087.00
CA$1,087.00
CA$1,087.00 - CA$1,087.00
CA$1,087.00
CA$31.00 - CA$31.00
CA$31.00
CA$31.00 - CA$31.00
CA$31.00

ZWO 2.1mm 150° All-Sky Lens - For 1/3" Sensors

ZWO-LENS-2.1
4 in stock

2.1mm Focal Length 150° Field of View Optimized for 1/3" Format Sensors Functions as an All-Sky Camera Lens Standard CS-Mount Thread Descriptio...

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CA$31.00 - CA$31.00
CA$31.00
CA$31.00 - CA$31.00
CA$31.00
CA$31.00 - CA$31.00
CA$31.00
CA$31.00 - CA$31.00
CA$31.00

ZWO 2.5mm 170° All-Sky Lens - For 1/2" Sensors

ZWO-LENS-2-5
5 in stock

2.5mm Focal Length 170° All-Sky Field of View Designed for 1/2" Format Sensors CS-Mount Thread Description FAQ Specifications I...

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CA$31.00 - CA$31.00
CA$31.00
CA$31.00 - CA$31.00
CA$31.00
CA$26.00 - CA$69.00
CA$26.00 - CA$69.00
CA$26.00 - CA$69.00
CA$26.00

ZWO AR Protective Window

Options available
5 variants in stock

Protects camera sensor from dust and humidity 21mm diameter for specific ZWO camera models High-transmission Anti-Reflection (AR) coatings 1/4λ su...

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CA$26.00 - CA$69.00
CA$26.00 - CA$69.00
CA$26.00 - CA$69.00
CA$26.00
CA$209.00 - CA$209.00
CA$209.00
CA$209.00 - CA$209.00
CA$209.00

ZWO Atmospheric Dispersion Corrector

ZWO-ADC
8 in stock

Corrects atmospheric dispersion for sharper planetary images Uses two H-K9L prisms with 2° deviation angles Features 1/10 wave optical accuracy to...

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CA$209.00 - CA$209.00
CA$209.00
CA$209.00 - CA$209.00
CA$209.00
CA$139.00 - CA$139.00
CA$139.00
CA$139.00 - CA$139.00
CA$139.00

ZWO CH4 Methane Filter - 20nm 1.25"

ZWO-CH4
3 in stock

Reveals high-altitude detail on Jupiter and Saturn 20nm bandpass centered on the methane absorption line Standard 1.25" (31.75mm) threaded cell Re...

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CA$139.00 - CA$139.00
CA$139.00
CA$139.00 - CA$139.00
CA$139.00
CA$53.00 - CA$53.00
CA$53.00
CA$53.00 - CA$53.00
CA$53.00

ZWO CS Lens 2.8mm-12mm F1.4

ZWO-LENS-2.8-12
5 in stock

2.8mm to 12mm Zoom Focal Length Fast f/1.4 Aperture ~100° Wide Field of View Designed for 1/3" Format Sensors Standard CS-Mount Thread Descript...

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CA$53.00 - CA$53.00
CA$53.00
CA$53.00 - CA$53.00
CA$53.00
CA$139.00 - CA$239.00
CA$139.00 - CA$239.00
CA$139.00 - CA$239.00
CA$139.00

ZWO Duo-Band Filter

Options available
7 variants in stock

Passes H-Alpha (15nm) and OIII (35nm) Wavelengths Designed for One-Shot Color (OSC) Cameras 1.25" Threaded Cell Over 80% Ha & 90% OIII Transmi...

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CA$139.00 - CA$239.00
CA$139.00 - CA$239.00
CA$139.00 - CA$239.00
CA$139.00
Sold out
CA$433.00 - CA$433.00
CA$433.00
CA$433.00 - CA$433.00
CA$433.00

ZWO FF107/FF130 APO 0.7× Universal Reducer

ZWO-F107130RE

0.7x Focal Reduction Factor Designed for ZWO FF107 & FF130 APO Refractors Triplet Optical Design with 1 ED Element Standard 55mm Back Focus In...

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CA$433.00 - CA$433.00
CA$433.00
CA$433.00 - CA$433.00
CA$433.00
Sold out
Sold out
CA$279.00 - CA$279.00
CA$279.00
CA$279.00 - CA$279.00
CA$279.00

ZWO FF65 APO 0.75× Full Frame Reducer

ZWO-F65RE

Reduces FF65 APO focal ratio to f/4.8 0.75x reduction factor for wider fields of view Standard 55mm back focus from the M48 thread Integrated M48x...

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CA$279.00 - CA$279.00
CA$279.00
CA$279.00 - CA$279.00
CA$279.00
Sold out
CA$349.00 - CA$349.00
CA$349.00
CA$349.00 - CA$349.00
CA$349.00

ZWO FF80 APO 0.76× Full Frame Reducer

ZWO-F80RE
Only 1 left!

0.76x focal reduction factor Designed for the ZWO FF80-APO Refractor Triplet optical design with one ED element Standard 55 mm back focus Integrat...

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CA$349.00 - CA$349.00
CA$349.00
CA$349.00 - CA$349.00
CA$349.00
CA$17.00 - CA$21.00
CA$17.00 - CA$21.00
CA$17.00 - CA$21.00
CA$17.00

ZWO Filter Masks

Options available
5 variants in stock

Securely Mounts 36mm Unmounted Filters Compatible with All 7-Position ZWO 36mm EFWs Includes M2 Mounting Screws Prevents Internal Light Leaks D...

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CA$17.00 - CA$21.00
CA$17.00 - CA$21.00
CA$17.00 - CA$21.00
CA$17.00
CA$40.00 - CA$40.00
CA$40.00
CA$40.00 - CA$40.00
CA$40.00

ZWO IR 850nm Pass Filter – 1.25"

ZWO-850IR1-25
2 in stock

Passes Infrared Light > 850nm Dramatically Steadies Planetary Views in Poor Seeing Enables Daylight Planetary and Lunar Imaging Standard 1.25" ...

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CA$40.00 - CA$40.00
CA$40.00
CA$40.00 - CA$40.00
CA$40.00
CA$26.00 - CA$26.00
CA$26.00
CA$26.00 - CA$26.00
CA$26.00

ZWO IR-Cut Protective Window

Options available
1 variants in stock

21 mm diameter protective window for select ZWO cameras Integrated UV/IR-Cut filter maintains natural color balance 1/4 λ surface flatness preserv...

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CA$26.00 - CA$26.00
CA$26.00
CA$26.00 - CA$26.00
CA$26.00
CA$207.00 - CA$419.00
CA$207.00 - CA$419.00
CA$207.00 - CA$419.00
CA$207.00

ZWO LRGB Optimized Filters

Options available
3 variants in stock

1.25" (31.75mm) Threaded Filter Set Greater than 92% Transmission at Passband Balanced 1:1:1 RGB Exposure Weighting 1/4 Wavefront Polished Optical...

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CA$207.00 - CA$419.00
CA$207.00 - CA$419.00
CA$207.00 - CA$419.00
CA$207.00
CA$517.00 - CA$979.00
CA$517.00 - CA$979.00
CA$517.00 - CA$979.00
CA$517.00

ZWO Narrowband Filter Set - 7nm H-alpha, OIII & SII

Options available
1 variants in stock

Includes 1.25" H-alpha, OIII, and SII filters 7nm bandpass for high-contrast imaging Ideal for creating "Hubble Palette" images Fine-optically pol...

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CA$517.00 - CA$979.00
CA$517.00 - CA$979.00
CA$517.00 - CA$979.00
CA$517.00
CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00

ZWO Narrowband H-alpha Filter - 7nm

Options available

Isolates Hydrogen-Alpha light at a 7nm bandpass Standard 1.25" threaded metal cell Blocks light pollution and moonlight for extreme contrast Multi...

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CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00
CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00

ZWO Narrowband OIII Filter - 7nm

Options available
2 variants in stock

7nm Bandpass at OIII Emission Line Isolates Planetary Nebulae and Supernova Remnants Standard 1.25" Threaded Filter Cell 1/4 Wave Optical Substrat...

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CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00 - CA$349.00
CA$181.00

Choosing Optical Accessories That Match Your Telescope

Every accessory in this collection modifies the light cone before it reaches your eye or sensor. The right choice depends almost entirely on your telescope's focal ratio, focal length and back-focus budget.

  • Eyepieces: Focal length sets magnification against your telescope's focal length; apparent field and eye relief determine how comfortable that magnification is to use.
  • Diagonals: Dielectric mirrors typically exceed 99% reflectivity; prisms can outperform them at f/10 and slower on planetary targets but introduce chromatic effects in fast refractors.
  • Barlow lenses and extenders: Multiply focal length for planetary work and push the focal plane outward, which is often the cheapest fix for a scope that will not reach focus with a diagonal.
  • Field flatteners and reducers: Correct field curvature and coma across large sensors; each has a fixed back-focus that must be hit precisely.
  • Binoviewers: Two-eye viewing that dramatically improves perceived detail on the Moon and planets, at the cost of significant added optical path.
  • Finders and reflex sights: Acquisition optics — the accessory most often skipped and most often missed.

Why Choose David Astro for Optical Accessories

Optics are easy to buy badly. A well-reviewed eyepiece can still be the wrong eyepiece for your focal ratio, exit pupil or sky.

  • Focal length guidance: We help you build a spaced eyepiece set rather than three focal lengths that overlap, and we calculate exit pupil against your aperture and typical seeing.
  • Corrector matching: We confirm that a flattener or reducer is designed for your telescope's focal ratio before you buy, since a mismatched corrector degrades a field rather than fixing it.
  • Authorized dealer: Full manufacturer warranty and verified authenticity on everything we list.
  • Canadian stock: In-stock optics ship from Canada, with no surprise duties or brokerage fees for Canadian customers.
  • Service and support after the sale: In-house diagnostics if something is not performing as expected.

Optical Accessories in Canada — Frequently Asked Questions

Will a premium eyepiece improve a modest telescope?
Usually yes at the edges of the field, especially in fast telescopes below f/6 where simpler designs struggle. On the axis at f/10, the difference between a good eyepiece and a premium one is much smaller.
How do I know if I need a flattener or a reducer?
A flattener corrects curvature at the same focal length. A reducer also shortens focal length, widening the field and speeding the system. If your stars are elongated only in the corners, you need a flattener; if you also want more field, a reducer.
Do binoviewers work in every telescope?
They add roughly 100 mm or more of optical path, so most refractors need a corrector or a Barlow-style element to reach focus. Schmidt-Cassegrains generally accommodate them without modification.
Is everything shipped domestically?
Yes. Anything shown as in stock is held in Canada and ships without customs delays for Canadian orders.

Match the accessory to the optic

Tell us your telescope and what you want to see, and we will recommend the right combination. Ships from Canada.