2.7" Thread-On Extensions for Astro-Physics Focusers and Accessories (A3502-A, A3503-A, A3504-A, A3505, A3506, A1008-A)

 May 31, 2021 - Part # changed to more clearly describe its function. Refer to the chart below. 

This series of extensions is designed to utilize the robust 2.7" Astro-Physics thread size, while providing a variety of lengths for use with barlows, telecompressors and camera systems. These extensions can be used in various combinations to achieve the perfect spacing distance for your system.

These extensions thread directly into the drawtube of the 2.7" focuser and into the 4" to 2.7" Adapter (A1024), or its shorter version (A1024-A), which fit the 4" focuser. They feature knife-edge baffles and an interior that is painted flat black 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.

Thread-on Extension with the following applications:

• Achieve proper spacing requirements for your CCD camera system - it can be used in combination with other extensions and with the CCD Adapters for our Prime Focus Field Flatteners.
• Use a combination of the extensions with the 0.75x Telecompressor (27TVPH) to obtain precise telecompression spacing. Reference the Exploded Diagram for placement and see Telecompressor Compression and Coverage for detailed compression calculations.
• Use with the BARADV or BPFFC and the BH27-INT42 Barlow Holder System with its Internal T-thread System for the ultimate in a rigid, non-flexing setup for high magnification planetary / lunar / solar imaging. See: A3511 System Chart

The re-design of these extensions include a lip on the outer diameter to prevent the extension from being racked inside the focuser housing.

EXT27-15.2 (formerly A3505) 2.7" Thread-on Extension This extension has a net spacing distance of 0.60" (15.2 mm).

EXT27-19.1 (formerly A3503-A) 2.7" Thread-on Extension This extension has a net spacing distance of 0.75" (19.1 mm).

EXT27-22.9 (formerly A3506) 2.7" Thread-on Extension This extension has a net spacing distance of 0.90" (22.9 mm).

EXT27-31.8 (formerly A3504-A) 2.7" Thread-on Extension This extension has a net spacing distance of 1.25" (31.8 mm).

EXT27-44.5 (formerly A3502-A) 2.7" Thread-on Extension This extension has a net spacing distance of 1.75" (44.5 mm).

EXT27-64.8  (formerly A1008-A) 2.7" Thread-on Extension This extension is provided with Astro-Physics refractors that have the 2.7" focuser. It is for use when observing straight-through without a diagonal or when imaging without a prime focus field flattener. [Note that this extension may be too long except for special applications.] This extension has a net spacing distance of 2.55" (64.8 mm).

You may prefer a sturdier cover than the included plastic plug.  Astro-Physics also offers an optional aluminum cover that will accommodate this part, depending on your storage needs.  Please review the information regarding the Threaded Cover for AP 2.7" Drawtubes and Accessories with 2.7" Female Threads (A1005).  This part can also accommodate the Threaded Cover for AP 2.7" Field Flatteners and Accessories with 2.7" Male Threads (A1225). More information can be found on our Accessory Reference Chart for 2.7" Threaded Covers.