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Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector Lens

Original price $539.00 - Original price $539.00
Original price
$539.00 - $539.00
Current price $539.00
In stock

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Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector Lens - SCTCORR-4

The Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector Lens is a versatile optical accessory designed for Schmidt-Cassegrain telescopes.

This innovative corrector lens serves a dual purpose, reducing the telescope's effective focal length by a factor of 0.63x to provide a wider field of view for astrophotography.

Simultaneously, it effectively corrects for coma aberrations, ensuring sharp and distortion-free images of celestial objects.

Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector Lens Comparison

The illustration above demonstrates the effectiveness of the SCT Corrector in enhancing off-axis spot size for a Celestron 11" SCT.

This improvement in performance holds true for telescopes of different sizes as well.

Focal Length:

The precise focal length of the reducer/telescope combination may vary slightly depending on the placement of the SCT Corrector lens within the optical path.

Typically, it will be positioned within a few millimeters of the rear threads on the telescope.

Adjusting this distance primarily impacts the focal length, with no discernible effect on optical quality.

Here are the nominal focal lengths for different sizes of Celestron SCTs*:

*Note: The SCT Corrector is also compatible and performs admirably with standard f/10 Meade SCTs.

Although exact data for the nominal designs of those telescopes is not available, the corrector is still highly effective.

Telescope Focal Length Focal Ratio
C6 1220mm f/8
C8 1450mm f/7.1
C9.25 1525mm f/6.5
C11 1760mm f/6.3
C14 2365mm f/6.7


The SCT Corrector offers a 0.63x reduction factor, although the C6 and C8, being closer to f/11 by default and having shorter backfocus, experience a slightly lesser reduction. The C14, on the other hand, is inherently f/11.

Camera Adapters:

The SCT Corrector IV boasts a nominal image circle of 27mm, suitable for most popular CCDs and DSLRs.

For larger format cameras, consider our SCT Corrector LF.

Due to the critical nature of the SCT Corrector IV's backfocus, Starizona provides a range of camera adapters for optimal performance.

Custom adapters can also be easily crafted for less common camera setups.

The nominal backfocus measures 90.3mm from the base of the threads on the camera side of the SCT Corrector IV.

For the largest compatible cameras, it's advised to maintain this within +/-2mm, while smaller format cameras may work adequately with slightly larger tolerances.

If the required adapter isn't available, we're happy to create one to ensure your setup performs at its best.

Feel free to reach out with any questions regarding configuring your camera.

Telescope Adapters:

Similar to the original SCT Corrector, the SCT Corrector IV is equipped with a 2" barrel, facilitating its compatibility with 2" visual backs or focusers.

If your telescope lacks such an adapter, we suggest considering our Virtual View rotating visual back.

This accessory enables effortless adjustments to your camera's orientation without the need to loosen any locking screws.


The front (telescope side) of the SCT Corrector IV is threaded to accept standard 2" (48mm) filters.


Features and Highlights:

  • 0.63x Focal Reduction Factor: The SCT Corrector IV reduces the telescope's effective focal length by a factor of 0.63x. This results in a wider field of view, allowing for the capture of larger portions of the night sky in a single frame.
  • 2.5x Faster Than SCT's Native f/10: With the SCT Corrector IV, your telescope operates at 2.5 times the speed of its native f/10 configuration. This means shorter exposure times and improved imaging efficiency.
  • 1.4x Faster Than Original f/7.5 SCT Corrector Design: Compared to the original f/7.5 SCT Corrector design, the SCT Corrector IV offers a 1.4x increase in speed, enhancing its performance and versatility for astrophotography.
  • 27mm Image Circle: The corrector provides a generous 27mm image circle, accommodating a wide range of popular CCDs and DSLRs, allowing for clear and detailed astrophotographs.
  • 2" Barrel Diameter: The corrector features a 2" diameter barrel, making it compatible with standard 2" visual backs and focusers, ensuring easy integration into existing telescope setups.
  • 2.5" Length Excluding Threads: Measuring at 2.5" (excluding threads), the corrector is designed to fit seamlessly into the optical path, providing optimal performance without unnecessary bulk.
  • Threaded for 48mm Filters: The corrector is threaded to accommodate 48mm filters, allowing for additional customization of your astrophotography setup.
  • SCT Corrector Top Thread: M42 x 0.75mm T-thread: This specific threading enables easy attachment to various compatible cameras and accessories, ensuring a secure and stable connection.
  • Mechanical Backfocus (Thread Shelf to Focal Plane): 90.3mm (3.56"): The corrector offers a precise mechanical backfocus of 90.3mm (3.56"), providing the necessary spacing for optimal performance in astrophotography setups.
  • Black Anodized, Machined Aluminum Housing: The corrector lens is housed in a durable and precisely crafted black anodized aluminum casing, ensuring long-lasting performance and protection.
  • Fully Multi-Coated Optics: The corrector lens features fully multi-coated optics, maximizing light transmission and minimizing reflections, resulting in enhanced image contrast and color fidelity.
  • 5-Element Optical Design with Extra-Low Dispersion (ED) Glass: The corrector employs a sophisticated 5-element optical design, including extra-low dispersion (ED) glass. This design helps to correct for optical aberrations and ensures exceptional image quality with minimal chromatic aberration.

Scott Tucker/Optical Designer thoughts on SCT Corrector:


      What's Included:

      ✓ Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector Lens

      ✓ Instructional Manual



      Focal Reduction Factor:  0.63x 
      Image circle:  27mm
      Barrel Diameter:  2" 
      Length Excluding Threads:  2.5" 
      Threaded for:  48mm filters
      SCT Corrector Top Thread:  M42 x 0.75mm T-thread
      Mechanical Backfocus (thread shelf to focal plane):  90.3mm (3.56”)
      Housing:  Black Anodized, Machined Aluminum 
      Optics:  Fully Multi-Coated


      Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector Lens Product Manual:

      Download the Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector Lens Product Manual



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