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Imaging Train

The imaging train is the stack of parts between the telescope's corrector and the camera sensor: adapters, spacers, a filter wheel or drawer, an off-axis guider, sometimes a rotator or tilt plate. Each part has a thickness and a thread, and together they must place the sensor at the exact distance the corrector was designed for, often within half a millimetre, and perfectly square to the optical axis.

When stars are elongated in the corners, or sharp on one side and soft on the other, the imaging train is usually the cause. This collection gathers the parts that solve it, from Baader, PrimaLuceLab, William Optics, ZWO, Player One, SVBONY, Wanderer Astro, Pegasus Astro, QHYCCD, Tele Vue and many more.

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Wanderer Astro WandererRotator Mini V2 (M54)
$399.00 USD - $399.00 USD
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Wanderer Astro WandererRotator Mini V2 - M54

Exceptionally Thin Profile to Conserve Back Focus Extremely Lightweight to Reduce Focuser Strain M54 Female Threads on Both Sides for Common Imagi...

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$399.00 USD - $399.00 USD
$399.00 USD
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$399.00 USD
Wanderer Astro WandererRotator Pro V2 (M92)
$899.00 USD - $899.00 USD
$899.00 USD
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$899.00 USD

Wanderer Astro WandererRotator Pro V2 - M92

16mm Ultra-Thin Profile Lightweight 800g Construction High-Resolution Motor Drive M92 Threaded Connections Quiet and Smooth Operation Descripti...

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$899.00 USD - $899.00 USD
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$118.00 USD
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$112.10 USD
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$112.10 USD

William Optics 120mm Saddle Handle Bar with 50mm Guiding Rings

120 mm Total Length Patented Handle and Saddle Design Mini-Vixen Dovetail Saddle Includes 50mm Guide Rings 44 mm Width Description FAQ Specific...

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$118.00 USD
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$112.10 USD
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$97.00 USD
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$92.15 USD
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$92.15 USD

William Optics 120mm Saddle Handle Bar with 50mm Guiding Rings - No Adjustments Screws

120 mm Length Integrated 50mm Guide Rings Mini-Vixen Style Top Saddle 44 mm Width Designed for Maximum Rigidity Description FAQ Specifications ...

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$97.00 USD
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$92.15 USD
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$141.00 USD
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$133.95 USD
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William Optics 243mm Saddle Handle Bar with 50mm Guiding Rings

Compatible with William Optics' slide-base guide rings Can be used to make William Optics telescopes portable Description The Wil...

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$141.00 USD
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$133.95 USD
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William Optics 30mm Flattener Adapter
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$58.00 USD
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$58.00 USD
$55.10 USD
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William Optics 30mm Flattener Adapter

30mm Optical Length Connects M80 x 0.75 to M54 x 0.75 Threads For William Optics Flat68III & Flat7A Flatteners Description FAQ Specificatio...

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$58.00 USD
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$55.10 USD
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$55.10 USD
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William Optics 4" Extender for FLT Series
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$68.00 USD
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$68.00 USD
$64.60 USD
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$64.60 USD

William Optics 4" Extender for FLT Series

Adds 67 mm of optical length to your imaging train Features M92 male and female threads for a secure connection Designed for William Optics FLT 11...

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$68.00 USD
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$64.60 USD
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$64.00 USD
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$60.80 USD
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William Optics 4" Extension Tube for FLT Series

4" extension tube designed for William Optics FLT Series Provides additional back focus for various optical setups ...

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$64.00 USD
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$60.80 USD
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$60.80 USD
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$39.00 USD
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$39.00 USD
$37.05 USD
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$37.05 USD

William Optics 48mm T-Mount for Canon

Connects M48 (2-inch) Threaded Correctors to Canon EOS Cameras Wide M48 Aperture Eliminates Vignetting on Full-Frame Sensors Adds a Precise 10.6 m...

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$39.00 USD
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$37.05 USD
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$68.00 USD
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$68.00 USD
$64.60 USD
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William Optics 48mm T-Mount for Canon EOS R Mirrorless

Connects M48-threaded correctors to Canon EOS R mirrorless cameras Wide 48mm aperture minimizes vignetting on full-frame sensors Precisely machine...

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$68.00 USD
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$68.00 USD
$64.60 USD
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$64.60 USD
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$55.00 USD
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$52.25 USD
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William Optics 48mm T-Mount for Fuji FX - Black

Connects M48-threaded correctors to Fujifilm X-mount (Fuji FX) mirrorless cameras Wide 48mm aperture minimizes vignetting on APS-C sensors Precise...

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$55.00 USD
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$52.25 USD
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$39.00 USD
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William Optics 48mm T-Mount for Nikon F

Connects M48 Accessories to Nikon F-Mount Cameras Precisely machined 8.2 mm optical length achieves exact 55mm back focus when combined with camer...

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$39.00 USD
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$37.05 USD
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$68.00 USD
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William Optics 48mm T-Mount for Nikon Z

Connects M48 accessories to Nikon Z-mount mirrorless cameras Precisely machined 38.4 mm optical length achieves about 55mm back focus when combine...

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$68.00 USD
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$68.00 USD
$64.60 USD
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$39.00 USD
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William Optics 48mm T-Mount for Pentax K - Black

Connects Pentax K-Mount Cameras to M48 Accessories Precisely machined 9.3 mm optical length achieves exact 55mm back focus when combined with came...

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$39.00 USD
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$37.05 USD
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$55.00 USD
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William Optics 48mm T-Mount for Sony E - Black

Connects Sony E-mount cameras to M48 accessories Provides a precise 36.7 mm optical length M48 (female) threads reduce vignetting on large sensors...

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$55.00 USD
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$52.25 USD
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$148.00 USD - $178.00 USD
$148.00 USD
$140.60 USD - $169.10 USD
$140.60 USD - $169.10 USD
$140.60 USD

William Optics 50mm Guiding Scope

50mm Aperture Doublet Lens 200mm Focal Length f/4.0 Focal Ratio 1.25" RotoLock Eyepiece Holder Total Weight: 0.42 kg / 0.93 lbs Description FAQ...

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$148.00 USD - $178.00 USD
$148.00 USD
$140.60 USD - $169.10 USD
$140.60 USD - $169.10 USD
$140.60 USD
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William Optics 54mm Flattener Extender for GT81 WIFD
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$68.00 USD
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$68.00 USD
$64.60 USD
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$64.60 USD

William Optics 54mm Flattener Extender for GT81 WIFD

Provides a precise 54mm of optical length Connects the FLAT68III flattener to M48 imaging trains Designed specifically for the William Optics Gran...

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$68.00 USD
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$68.00 USD
$64.60 USD
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$64.60 USD
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$129.00 USD
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$129.00 USD
$122.55 USD
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William Optics Camera Angle Rotator for 2.5" M63 Focuser

Adds 360° of smooth camera rotation Designed for William Optics 2.5" focusers Secure M63 male and female threads Maintains optical alignment durin...

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$129.00 USD
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$129.00 USD
$122.55 USD
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$388.00 USD
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$388.00 USD
$369.00 USD
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$369.00 USD

William Optics Elite Drawer OAG Kit

Integrates Off-Axis Guider and Filter Drawer 37.5 mm Optical Length Supports M48, M54, and M68 Connections Magnetic M48 Filter Holder 336 g (11.85...

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$388.00 USD
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$369.00 USD
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$64.00 USD
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$64.00 USD
$60.80 USD
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$60.80 USD

William Optics Flat4 Draw Tube Adapter for FLT (Gold) for 2012-2016 Models

Securely connects the Flat4 Field Flattener to the draw tube Designed for William Optics FLT 98, 110, 132, and 152 models Compatible with telescop...

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$64.00 USD
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$64.00 USD
$60.80 USD
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$64.00 USD
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$60.80 USD

William Optics Flat4 Draw Tube Adapter for GT102, FLT 132 - Black for 3" V-Power Focuser

Connects William Optics Flat4 Flattener to Draw Tube Designed for 2017 William Optics V-Power telescopes Compatible with V-Power 102 & 132 (20...

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$64.00 USD
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$64.00 USD
$60.80 USD
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$64.00 USD
$64.00 USD - $64.00 USD
$64.00 USD
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William Optics Flat4 Draw Tube Adapter for GT102, FLT 132 - Blue for 3" V-power Focuser

Connects Flat4 Flattener to the V-Power Focuser Compatible with William Optics GT102 & FLT 132 Engineered for 2017 Telescope Models Secure Thr...

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$64.00 USD
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$64.00 USD
$60.80 USD
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$398.00 USD - $438.00 USD
$398.00 USD
$378.10 USD - $416.10 USD
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$378.10 USD

William Optics GuideStar 61

FPL53 ED Air-Spaced Doublet Lens Dual-Purpose Guide Scope and Imaging Telescope Draw-Tube (Push-Pull) Focuser Rotating Lens Assembly for Fine Focu...

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$398.00 USD - $438.00 USD
$398.00 USD
$378.10 USD - $416.10 USD
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$60.00 USD
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$57.00 USD
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William Optics Image Plane Tilt Adjuster

Designed for the first-generation William Optics RedCat 51 (V1) astrograph Corrects image plane tilt for perfectly round stars across the frame Ad...

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$60.00 USD
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$60.00 USD
$57.00 USD
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$57.00 USD
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Parts of the Imaging Train

  • Thread adapters and spacers: Convert between M42, M48, M54, M68 and SCT threads and set the distance. See T-rings, spacers and thread adapters.
  • Off-axis guiders: Pick off a guide star in front of the sensor, eliminating flexure between guide scope and main telescope. See off-axis guiders and guide scopes.
  • Rotators: Turn the camera to frame the target without loosening anything. Motorized rotators make framing repeatable across nights.
  • Tilt adjusters: Push-pull plates that square the sensor to the light path. See rotators and tilt adjusters.

Back-Focus in Practice

  • Start with the number: Most flatteners need 55 mm from their thread to the sensor. Some need 56.2, 63 or something else entirely. Check your corrector.
  • Count everything: Camera internal distance, filter wheel or drawer, OAG, adapters and spacers.
  • Add for filters: A filter adds about one third of its thickness. A 2 mm filter needs about 0.7 mm more spacing.
  • Prefer threads to compression: Threaded connections hold squareness much better than 2-inch nosepieces with thumb screws.

We Plan Your Train for You

  • Spacing sheet: Send us your corrector, camera and accessories. We return the list of parts and the exact distances.
  • Diagnosis: Send a raw frame and we will tell you whether the spacing is too long, too short or tilted.

Imaging Train: Frequently Asked Questions

How do I know if my back-focus is wrong?

Stars stretched radially in all corners point to spacing too short or too long. Stars that are good on one side only point to tilt.

Can I use a 2-inch nosepiece for imaging?

It works, but threaded connections are stiffer and more square. For larger sensors, go threaded.

Need a back-focus plan?

Send us your telescope, corrector and camera. We will list every part and distance.