CCD Telecompressor (CCDT67)

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Originally developed to tame the focal length of our 10" f/14.6 Mak-Cass, this telecompressor is optimized for scopes ranging from f/9 to f/18 focal ratio. The 2-element cemented design transmits close to 99% of the incoming light over the range of 420 to 700 nm. The focal length of the telecompressor optics is 305mm (12"). For refractors, the field is compressed by 0.67x. If you have a moving mirror system, the native focal ratio will increase.

This optic is not recommended for telescopes with f/ratios below about f/8-9. For faster instruments, we recommend the Photographic-Visual Telecompressor (27TVPH).

The CCDT67 design allows full corner-to-corner illumination up to an 8300 or APS-C size chip with most catadioptric telescopes. This design does not add coma to the wavefront, and thus, can be used with all flat-field and coma-free telescopes such as Maksutov-Cassegrains, Schmidt-Cassegrains, Ritchey-Chretiens and long-focal-length refractors. The inherent resolution of the telescope is not compromised when using this compressor.

Please review the exploded diagram to see how this item will fit into your imaging system. If you want a higher compression ratio, you can add one or more of the 2" Nosepiece Extension w/ 48 mm Threads (EXT48-12.7, previous part # A3703) between the CCDT67 and the nosepiece of your camera. This has the advantage of inserting the CCDT67 forward in the light cone so that in-travel requirements are reduced. Please note that as you increase compression, you decrease the size of the image circle at the focus point. At 0.67x, the CCDT67 will have a 29 mm image circle. It will not cover a full-frame size chip.

To calculate the compression factor and coverage for your particular setup, please refer to our Telecompressor Spacing, Compression Calculation and Coverage document or to the CCDT67 & 27TVPH Telecompression Graph.

  • Clear aperture is 44.5mm (1.75"), designed to screw onto our 2" Secure-Grip Nosepiece (AP16T) or any other 2" nosepiece with 48 mm threads that is designed for CCD cameras.
  • Optimized for 0.67x compression with a fully illuminated circle of 29 mm when the back spacing distance is 85 mm from the rear flange to the camera sensor is used.
  • Expect a 0.75x compression with a fully illuminated circle of 34 mm when the back spacing distance is 50 mm from the rear flange to the camera sensor.
  • Use one or two 2" Nosepiece Extensions (EXT48-12.7) to achieve the desired compression.
  • Approximately 2 inches of focuser in-travel is needed to achieve focus on the CCD chip.
  • The focal length of the CDD Telecompressor is 305mm (12").
  • Insertion depth of CCDT67 is 29.1mm (1.145").
  • Net insertion depth of 57.8 mm (2.28" when used on the AP16T nosepiece
  • There are 48 mm filter threads on the front of the CCDT67. Be sure that you have sufficient insertion depth when adding a filter. The rear of the CCDT67 has 48 mm male threads.

Diagrams and Instructions

CCD Telecompressor - exploded diagram

Astro-Physics Telecompressors - 27TVPH & CCDT67 Compression and Coverage - calculate the compression factor and coverage for your particular setup

CCDT67 and 27TVPH Telecompression Graph