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Correcteurs et réducteurs

Round stars in the corners are not a processing achievement — they are a spacing achievement. Field flatteners and reducers correct the curved focal plane and off-axis aberrations that every telescope has to some degree, and they only work when spaced to within about a millimetre of their design distance. David Astro carries field flatteners and reducers in Canada, shipping from Canadian stock.

This is the category where our back-focus calculation service saves the most frustration. Send us your telescope, camera and filters and we will specify the corrector and the exact spacers to go with it.

Filtres

$278.00 - $338.00
$278.00 - $338.00
$278.00 - $338.00
$278.00

Baader MPCC Mark III (Correcteur de Coma Polyvalent) - 2"

Options available
2 variants in stock

Correcteur de coma pour télescopes Newton, qui ne réduit ni la distance focale ni le champ image de votre télescope Grands objectifs pour des ex...

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$278.00 - $338.00
$278.00 - $338.00
$278.00 - $338.00
$278.00
Baader Planetarium Alan Gee Mark II Centering Ring for SC 9¼"
$30.00 - $30.00
$30.00
$30.00 - $30.00
$30.00

Baader Planetarium Alan Gee Mark II Centering Ring for SC 9.25"

BAA-2454410

Adapts Alan Gee II Telecompressor to larger SCTs Ensures precise optical alignment Designed for Celestron 9.25" and 11" Schmidt-Cassegrain OTAs Pr...

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$30.00 - $30.00
$30.00
$30.00 - $30.00
$30.00
Baader Planetarium Alan Gee Universal 2" Telecompressor (UAG II)
$223.00 - $223.00
$223.00
$223.00 - $223.00
$223.00

Baader Planetarium Alan Gee Universal 2" Telecompressor (UAG II)

BAA-2454405

Unique telecompressor designed for visual use with binoviewers Based on the flat-field Alan Gee design by Roland Christen of AstroPhysics Enables ...

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$223.00 - $223.00
$223.00
$223.00 - $223.00
$223.00
$281.00 - $281.00
$281.00
$281.00 - $281.00
$281.00

Baader Correcteur de Coma RCC I Rowe

BAA-2956800

Le RCC I (Rowe Coma Corrector) est un correcteur de coma de Dave Rowe avec un design Triplet Lense pour f/4 Newtons Le RCC fonctionne de f/3.5 à...

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$281.00 - $281.00
$281.00
$281.00 - $281.00
$281.00
$199.95 - $199.95
$199.95
$199.95 - $199.95
$199.95

Celestron Réducteur - Correcteur 0.63x

CEL-94175

Caractéristiques Cet accessoire combiné réducteur de focale et correcteur de champ fonctionne avec tous les télescopes Celestron 5", 6", 8", 9 1/...

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$199.95 - $199.95
$199.95
$199.95 - $199.95
$199.95
$849.00 - $849.00
$849.00
$849.00 - $849.00
$849.00

Celestron Réducteur .7x - EdgeHD 1100

CEL-94241
1 en stock

Caractéristiques L'objectif réducteur de focale EdgeHD .7x rend votre EdgeHD 1100 un F-Stop complet plus rapide que f/10, réduisant votre temps ...

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$849.00 - $849.00
$849.00
$849.00 - $849.00
$849.00
$849.00 - $849.00
$849.00
$849.00 - $849.00
$849.00

Celestron Réducteur .7x - EdgeHD 1400

CEL-94240

Caractéristiques L'objectif réducteur de focale EdgeHD .7x rend votre EdgeHD 1400 un F-Stop complet plus rapide que f/11, réduisant votre temps ...

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$849.00 - $849.00
$849.00
$849.00 - $849.00
$849.00
$419.00 - $419.00
$419.00
$419.00 - $419.00
$419.00

Celestron Réducteur .7x - EdgeHD 800

CEL-94242

Caractéristiques L'objectif réducteur de focale EdgeHD .7x rend votre EdgeHD 800 un diaphragme complet plus rapide que f/10, doublant l'expositio...

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$419.00 - $419.00
$419.00
$419.00 - $419.00
$419.00
$439.00 - $439.00
$439.00
$439.00 - $439.00
$439.00

Celestron Réducteur .7x - EdgeHD 925

CEL-94245
1 en stock

Caractéristiques L'objectif réducteur de focale EdgeHD .7x rend votre EdgeHD 9,25" un F-Stop complet plus rapide que f/10, réduisant votre temps ...

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$439.00 - $439.00
$439.00
$439.00 - $439.00
$439.00
Épuisé
$139.00 - $139.00
$139.00
$139.00 - $139.00
$139.00

David Astro 0.6x Universal Reducer - 2"

DAV-FF0.6X

55mm back focus Works with f/5 to f/7 refractors Compatible with APS-C size cameras or smaller. Accepts 2" filters Optimized for refractors with...

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$139.00 - $139.00
$139.00
$139.00 - $139.00
$139.00
Épuisé
Épuisé
$119.00 - $119.00
$119.00
$119.00 - $119.00
$119.00

David Astro 0.8x Universal Reducer - 2"

DAV-FF0.8X

55mm back focus Works with f/5 to f/7 refractors Compatible with APS-C size cameras or smaller. Accepts 2" filters Optimized for refractors with...

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$119.00 - $119.00
$119.00
$119.00 - $119.00
$119.00
Épuisé
$119.00 - $119.00
$119.00
$119.00 - $119.00
$119.00

David Astro Universal Field Flattener - 2"

DAV-FF1.0X
5 restant!

55mm back focus Works with f/5 to f/7 refractors Compatible with APS-C size cameras or smaller. Accepts 2" filters Optimized for refractors with...

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$119.00 - $119.00
$119.00
$119.00 - $119.00
$119.00
Explore Scientific 0.8x Focal Reducer
$139.99 - $139.99
$139.99
$139.99 - $139.99
$139.99

Explore Scientific 0.8x Focal Reducer

ES-FR0.8x

Reduces focal length by a factor of 0.8x for wider fields of view Engineered for refractors with focal ratios from f/5 to f/7 Provides 55mm (+/- 2...

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$139.99 - $139.99
$139.99
$139.99 - $139.99
$139.99
$399.99 - $399.99
$399.99
$399.99 - $399.99
$399.99

Explore Scientific 3" Aplanisseur de Champ / Réducteur .7x

ES-FFFR507X-00

L'aplatisseur de champ 3 pouces/réducteur focal 0,7x d'Explore Scientific est un accessoire aux multiples facettes conçu pour améliorer vos expéri...

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$399.99 - $399.99
$399.99
$399.99 - $399.99
$399.99
$449.00 - $449.00
$449.00
$449.00 - $449.00
$449.00

Lunt Aplanisseur/Réducteur .8x

LSS-CAA-RF

Le réducteur/aplatisseur de champ CAA 0,8x est un accessoire optimal pour ceux qui s'intéressent à l'astrophotographie - Parfait pour une utilisat...

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$449.00 - $449.00
$449.00
$449.00 - $449.00
$449.00
Orion Optics UK AG W-C to fit SBIG STX 16803 89dia DT- 50mm BFD 4mm adj
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG W-C to fit SBIG STX 16803 89dia DT- 50mm BFD 4mm adj

OOUK-AG-W-C-SBIG-STX

4-lens ED corrector for the AG Astrograph range Machined to fit SBIG STX 16803 89dia DT- 50mm back focal distance Individually machined to order i...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne Corr to SBIG T thread using 61mm BFD with 4mm adj
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG Wynne Corr to SBIG T thread using 61mm BFD with 4mm adj

OOUK-AG-WYNNE-CORR-SBIG-T

4-lens ED corrector for the AG Astrograph range Machined to fit SBIG T thread 61mm back focal distance Individually machined to order in the UK ...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne corrector C Mount Adaptor camera needs 18mm+-3mmBFD
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK Adaptateur monture C pour correcteur AG Wynne - Caméra avec backfocus de 18mm ±3mm

OOUK-AG-WYNNE-CORRECTOR-C-MOUNT

Adaptateur de caméra pour le correcteur AG Wynne à 4 lentilles (gamme AG Astrograph) Adaptateur monture C pour le correcteur AG Wynne Pour les cam...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne corrector fit Atlas-70mm OAG 3.5mmBFD +-4mm
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG Wynne corrector fit Atlas-70mm OAG 3.5mmBFD +-4mm

OOUK-AG-WYNNE-CORRECTOR-ATLAS-70MM

4-lens ED corrector for the AG Astrograph range Machined to fit Atlas-70mm OAG 3.5mm back focal distance Individually machined to order in the UK ...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne Corrector for Takahashi TAK72
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG Wynne Corrector for Takahashi TAK72

OOUK-AG-WYNNE-CORRECTOR-TAK72-35MM

Custom-designed AG Wynne corrector for the Takahashi TAK72 Engineered for a 35mm back focus distance (BFD) Provides +4mm of fine adjustment for se...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne corrector to fit 2.005" FLI using 40mm BFD with 4mm adj
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG Wynne corrector to fit 2.005" FLI using 40mm BFD with 4mm adj

OOUK-AG-WYNNE-CORRECTOR-2-005

4-lens ED corrector for the AG Astrograph range Machined to fit 2.005" FLI 40mm back focal distance Individually machined to order in the UK De...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne corrector to fit 2.55" FLI using 50mm +-4mm
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG Wynne corrector to fit 2.55" FLI using 50mm +-4mm

OOUK-AG-WYNNE-CORRECTOR-2-55

4-lens ED corrector for the AG Astrograph range Machined to fit 2.55" FLI Custom back focal distance to order Individually machined to order in th...

Afficher tous les détails
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne corrector to fit 3" FLI using 35mm BFD with 4mm adj
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG Wynne corrector to fit 3" FLI using 35mm BFD with 4mm adj

OOUK-AG-WYNNE-CORRECTOR-3-FLI

4-lens ED corrector for the AG Astrograph range Machined to fit 3" FLI 35mm back focal distance Individually machined to order in the UK Descri...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29
Orion Optics UK AG Wynne corrector to fit Atlas to 3" MOAG using 7mm BFD
$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Orion Optics UK AG Wynne corrector to fit Atlas to 3" MOAG using 7mm BFD

OOUK-AG-WYNNE-CORRECTOR-ATLAS-3

4-lens ED corrector for the AG Astrograph range Machined to fit Atlas to 3" MOAG 7mm back focal distance Individually machined to order in the UK ...

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$297.29 - $297.29
$297.29
$297.29 - $297.29
$297.29

Flatteners, Reducers and Coma Correctors

Each type solves a different optical problem, and using the wrong one degrades the field instead of correcting it.

  • Field flatteners: Correct focal plane curvature without changing focal length, so framing stays the same and only corner star shape improves.
  • Focal reducers: Flatten and shorten focal length, typically to 0.8x or 0.7x, widening the field and increasing the effective focal ratio for shorter exposures.
  • Coma correctors: For Newtonian reflectors, correcting the comet-shaped off-axis stars inherent to a parabolic mirror, essential below about f/6.
  • SCT reducer-correctors: Typically 0.63x units for Schmidt-Cassegrains, which both widen the field and considerably reduce exposure times at long focal lengths.
  • Telescope-specific versus universal: A corrector designed for your exact tube will outperform a universal one, particularly at the corners of large sensors.
  • Back-focus specification: Every corrector has a design distance from its rear surface to the sensor, commonly 55 mm. Missing it produces elongated corner stars pointing either inward or outward.

Why Choose David Astro for Field Flatteners and Reducers

A corrector is one of the few products where the accessory list matters as much as the product itself.

  • Back-focus calculated and spacers supplied: We provide the full component list including fine shims, and account for the focal shift your filter glass introduces.
  • Star shape diagnosis: If your corners are wrong, the direction of elongation tells us whether you are over- or under-spaced. Send us a corner crop and we will tell you which way to move.
  • Telescope-matched selection: We identify the corrector designed for your specific tube rather than defaulting to a universal unit that will underperform on a large sensor.
  • Authorized dealer: Genuine correctors with full manufacturer warranty, held in stock for fast domestic shipping.
  • Ships from Canada: No duties or brokerage fees for Canadian customers.

Field Flatteners and Reducers in Canada — Frequently Asked Questions

How precise does back-focus have to be?
Within about one millimetre for most correctors, and tighter at fast focal ratios. That is why filter thickness matters — a 3 mm filter shifts focus by roughly 1 mm, which is the entire tolerance.
My corner stars are elongated. Am I over or under spaced?
Stars elongated radially, pointing away from centre, generally indicate too much spacing. Tangentially elongated stars generally indicate too little. Send us a corner crop and we will confirm and give you a number.
Flattener or reducer?
Use a flattener if your framing is already right and only the corners are wrong. Use a reducer if you also want a wider field and shorter exposures, accepting that your image scale drops.
Will a universal corrector work on my telescope?
Sometimes acceptably, but a corrector matched to your specific tube will correct better at the edges, especially with an APS-C or larger sensor. Tell us your tube and we will check what exists for it.

Chasing corner stars?

Send us your imaging train and a corner crop. We will calculate the spacing and specify the parts. Held in Canada, shipped fast.