2-inch to 3"x24tpi Male Thread Adapter (17666)
2-inch to 3"x24tpi Male Thread Adapter (17666)
2-inch to 3"x24tpi Male Thread Adapter (17666)


2-inch to 3"x24tpi Male Thread Adapter (17666)

Regular price
$ 95.00
Sale price
$ 95.00
Unit price

This item is out of stock but you can place an order now and we’ll ship when it becomes available.


Adapters for 2-inch Focuser Drawtubes

2-inch O.D. Adapters to fit the TCF-S and other 2-inch focusers.

Each of our 2-inch Drawtube adapters are machined to tight tolerances for a smooth, snug fit into the TCF-S and TCF-Si 2-inch focuser drawtubes. A dovetail cut directly matches the thumbscrews on the TCF-S for a secure fit.  By tightening the thumbscrews, the adapter is drawn tightly into the focuser's drawtube.

These 2-inch drawtube adapters will usually fit very well into other manufacturer's focusers as well.   Contact Optec for any 2-inch drawtube adapter not listed here.

#17666 - 2-inch to 3"x24tpi male  thread Adapter.

The 2-inch to 3-inch thread adapter was developed to easily adapt the Apogee and SBIG cameras and filters wheels for the TCF-S focuser.

By holding tight tolerances (+/- 0.003") Optec has achieved a slip-fit that is second-to-none.  When used with the TCF-S focuser, the #17666 with its  precision machined dovetail cut exactly matches the three thumbscrews on the focuser's  drawtube.  By tightening the thumbscrews, the dovetail is drawn tighter to the face of the drawtube completely eliminating flexure.

A word of caution, however, the FLI cameras and filter wheels featuring a 3-inch x 24tpi thread are slightly larger (3.005").  Be certain the #17666 2-inch nosepiece fits snugly into the FLI camera or filter wheel before installing into the TCF-S focuser.  Additionally, the FLI filter wheels allow only 0.100" of thread to extend into the filter wheel body without obstructing the moving filter carousel.


  • Overall Outside Diameter:  3.2" (81mm)
  • Outside Diameter (drawtube body):  1.995" (50.7mm)
  • Overall Height: 2.32" (59mm)
  • Height of 3x24 threads:  0.22"  (5.6mm)
  • Clear Aperture: 1.80" (45.7mm)
  • Weight: 3.0 oz (85 g)
  • Back-focus Usage: 0.10" (2.75 mm)

Compatible with:

  • TCF-S or TCF-Si focuser,
  • TCF-S3 or TCF-S3i focuser with #17804 3-inch to 2-inch reducer,
  • Any manufacturer's 2-inch focuser or receiver.

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