Astro-Physics Thread-On Extension for 2.7" Focuser - Length 1.75".
This adapter threads directly into the 2.7" drawtube or the 4" to 2.7" adapter that is included with the 4" focuser. It features knife-edge baffles. The 2" adapter referred to below can be either ADA200 or ADA2003
Use with the Telecompressor for CCD Imaging: Remove the 2" adapter from the focuser drawtube, thread on the Telecompressor, then A3503 and 2" adapter . Use this 0.75" length with your SBIG ST-8/ST-10 or Finger Lakes Instruments CCD cameras with the Color Filter Wheel closely coupled to the CCD camera to provide the optimal 0.75x compression.
As an extension: Remove the 2" adapter from the focuser drawtube, thread on A3503, then thread the 2" adapter on the other side. Note, you can thread two of these extensions together or with A3504, A3502 or A1008 to form a longer tube.