Astro-Physics CCDT67 CCD Telecompressor
Originally developed to tame the focal length of our 10" f/14.6 Mak-Cass, this telecompressor will provide full coverage of the ST10E chip with 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 12". For refractors, the field is compressed by 0.67x (when using a Color Filter Wheel) . 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/9. For faster instruments, we recommend the Photographic-Visual Telecompressor (27TVPH) .
The design allows full corner-to-corner illumination of the ST-10 and ST-8300 chips 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 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, but do not use the color filter wheel, you can add one or more of the 2" Barrel Extension w/ 48mm Threads (A3703) between the CCDT67 and the nosepiece of your camera. This has the advantage of inserting the CCDT67 foward in the light cone so that in-travel (backspacing) requirements are reduced. An alternative is to use T-2 extension rings that we offer from Baader Planetarium. Threading the 15mm T-2 Extension Ring (part # BP25A) and 7.5mm Extension Ring (part # BP25C) between the CCD camera and the nosepiece. will approximate the spacing of a color filter wheel. You can also experiment with a single extension or other combinations. 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 cover the chip of the ST-10 and ST-8300. It can never cover the chip of an STL series camera or the newer large size digital SLR chips, because its clear aperture is no larger than their CCD chips.
Clear aperture is 1.75", designed to screw into our 2" Tapered Nosepiece (AP16T) or any other 2" nosepiece with 48mm threads that is designed for CCD cameras. It will not thread all the way into the nosepiece provided with SBIG cameras since the threads of that nosepiece are not deep enough.
0.67x Compression ratio for SBIG ST7/8/10 + Color Filter Wheel, when used with refractors. Fully illuminated circle: 29 mm
0.75x Compression ratio for SBIG ST7/8/10 (without Color Filter Wheel or T-2 extensions), when used with refractors. Fully illuminated circle: 34 mm
Approximately 5 inches of back focus is needed to achieve focus on the CCD chip. It will not work with the AO7.
The focal length of the CDD Telecompressor is 12" (305 mm)
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.
This image of the Ring Nebula was taken with the Astro-Physics 10" f'/14.6 Maksutov-Cassegrain and the CCD Telecompressor using an ST10E with the color filter wheel. Once you receive your CCD Telecompressor, we invite you to submit your images so that they can be featured here, all scopes will be welcome.
We highly recommend our 2" Tapered Nosepiece (AP16T) for your CCD camera. When used with the brass locking ring of most of our adapters, this unique barrel will seat your valuable CCD camera squarely and solidly into place. Even a single thumbscrew interface will be improved. Note: If you are using the older style thin 2" adapter (part # ADA2013), we suggest that you use the 2" nosepiece that came with your camera or the 2" nosepiece from Baader Planetarium (we offer as part #BP16) . The current style 2" Thin Adapter (ADA20132) works perfectly with the AP16T.