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.
Filters
ZWO M48 Extension - 16.5mm
Adds exactly 16.5 mm of spacing to an M48 imaging train M48x0.75 male and female threads Wide 43.2 mm clear aperture prevents vignetting with full...
View full detailsZWO M48-M42 Adapter
Converts female M48x0.75 threads to female M42x0.75 T-threads Adds 0mm of optical path length to the imaging train Durable black anodized aluminum...
View full detailsZWO M54 Adapter replacing EFW
Replaces the ZWO EFW to achieve 55mm back focus with the OAG-L Adds only 15 mm of optical length to the imaging train Holds a single 2-inch mounte...
View full detailsZWO M54 Extension - 16.5mm
Optical Length: 16.5mm Connection Side 1: M54x0.75 Male Thread Connection Side 2: M54x0.75 Female Thread Material: Anodized Aluminum Descriptio...
View full detailsZWO M54 Extension - 21mm
Adds precisely 21mm of optical path length M54x0.75 male and female threads for secure connections Prevents vignetting with full-frame sensors Mac...
View full detailsZWO M54 Male to M42 Female Adapter
Thread Compatibility Durable Construction Precision Engineering Lightweight Des...
View full detailsZWO M54(M)-M48(F) Adapter - 21mm
Adds exactly 21mm of optical path length Connects M54 male threads to M48 female threads Standard 2-inch filter threading on the M48 side Black an...
View full detailsZWO M54-M48 Adapter
M54 male threads on one side, M48 female threads on the other Zero-profile design preserves critical back focus Converts larger M54 ports to the c...
View full detailsZWO M68 Sensor Tilt Plate
Corrects sensor tilt for sharp, round stars across the entire frame Adds a minimal 5 mm of optical path length to the imaging train Connects the Z...
View full detailsZWO OAG
Eliminates Differential Flexure Reduces Overall System Weight Includes 1.25" Guide Camera Holder M48 and M48 to M42 Adapters Included Spacer and H...
View full detailsZWO OAG-L
5.0 / 5.0
1 Review
Large 12mm x 12mm prism for brighter guide stars M68, M54, and M48 connection options 17.5mm thickness preserves 55mm backfocus Designed for ZWO A...
View full detailsZWO Sensor Tilt Plate - M42
Corrects sensor tilt for flat fields and sharp stars edge-to-edge Adds only 5mm of thickness to the optical path Suitable for APS-C cameras like t...
View full detailsZWO Sensor Tilt Plate - M48
Corrects Sensor Tilt: Ensures sharp stars across the entire image field by squaring the camera sensor to the optical axis. 5 mm Optical Path Lengt...
View full detailsZWO Sensor Tilt Plate - M54
Corrects sensor tilt for ZWO ASI6200, 2600, and 2400 cameras Connects compatible cameras and the M68 OAG to a 2" EFW Adds a minimal 5mm of optical...
View full detailsZWO Sony E Adapter for ASI Cameras
Connects Sony NEX (E-mount) lenses to ZWO ASI cameras Standard M42x0.75 female thread for direct camera attachment Enables wide-field astrophotogr...
View full detailsZWO T-Mount Adapter - 1.25"
5.0 / 5.0
1 Review
Connects T-threaded cameras to 1.25" focusers Standard M42x0.75 male T-threads Internally threaded for 1.25" astronomy filters Dur...
View full detailsZWO T2 Female to Female Adapter - 11mm
Adds exactly 11 mm of spacing to your imaging train Female M42x0.75 T2 threads on both sides Connects two male T-threaded components Black anodize...
View full detailsZWO T2 Male to T2 Male Adapter
Connects two female M42 T-threaded components Adds a fixed 2mm of optical path length Male-to-male M42x0.75 thread on both sides Durable black ano...
View full detailsZWO T2 Tilter II
5.0 / 5.0
1 Review
Corrects sensor tilt for sharp stars edge-to-edge Eliminates Newton's rings in H-alpha solar imaging Adds only 11 mm of back focus to the imaging ...
View full detailsZWO T2-1.25" Holder
Connects T2 (M42x0.75) Male Threads to 1.25" Barrels Non-Marring Brass Compression Ring Secure Two-Thumbscrew Locking Durable, Low-Profile Aluminu...
View full detailsParts 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.