This series of extensions is designed to use the robust 2.7" thread size from Astro-Physics, while providing a variety of lengths to use with Barlows, Telecompressors, and camera systems. You can use these extensions in various combinations to achieve the perfect back focus spacing for your imaging train. The re-design of these extensions includes a lip on the outer diameter to prevent the extension from being racked inside the focuser housing.
These extensions thread directly into the drawtube of the 2.7" focuser and into the 4" to 2.7" adapter (A1024), or the short version (A1024-A), which fit the 4" focuser. They feature knife-edge baffles and a flat black interior, designed to eliminate internal reflections. Accessories with 2" nosepieces can easily be attached by using the ADA2003A, ADA20132, ADA200 (discontinued), or ADA2013 (discontinued) 2" adapters with thumbscrews.
The EXT27-64.8 has a net spacing distance of 2.55" (64.8mm). This extension may be too long except for special applications.
This particular extension is also provided with Astro-Physics refractors that have the 2.7" focuser, to be used when observing straight-through without a diagonal or when imaging without a prime focus field flattener.
Thread-On Extension Sample Applications
- Achieve proper back focus spacing for your CCD camera system. It can be used in combination with other extensions and with the CCD adapters for Astro-Physics' prime focus field flatteners
- Use a combination of the extensions with the 0.75x Telecompressor (27TVPH) to achieve precise telecompression spacing. See the Exploded Diagram for placement and the Telecompressor Compression and Coverage for compression calculations
- Use with the BARADV Advanced Barlow or BPFFC and the threaded 2.7" adapter with internal 42mm thread (BH27-INT42) for the ultimate in a non-flex setup for high magnification planetary, lunar, and solar imaging