2-inch to Standard SCT thread Adapter (17665)
2-inch to Standard SCT thread Adapter (17665)
2-inch to Standard SCT thread Adapter (17665)
2-inch to Standard SCT thread Adapter (17665)


2-inch to Standard SCT thread Adapter (17665)

Regular price
$ 55.00
Sale price
$ 55.00
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.

#17665 - 2-inch to Standard SCT thread Adapter.

The 2-inch to SCT thread Adapter is our original secure fit adapter for 2" x 24tpi  SCT male telescope thread.  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 #17665 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.

With a heavy wall and astronomy industry standard SCT-thread, the #17665 is both rugged and easy to use.  The long SCT thread will screw into any adapter or receiver including most any SCT accessory, the Celestron f/6.3 telecompressor body, many filter wheels, and a several camera faceplates. 

A word of caution, however, some SCT female threaded filter wheels will not allow the full 0.4" of thread to be screwed into the filter wheel body without obstructing the filter wheel.  Contact Optec for an optional retaining ring to limit the in-travel of the male SCT threads.

The wide flange on the 2-inch to SCT thread adapter features a machined brass registration screw to exactly match the notch on all TCF-S focusers.  This allows easy rotational alignment each time the #17665 is removed and re-inserted into the 2-inch drawtube making it especially suited as a 2-inch camera nosepiece.  No more fumbling in the dark to re-align your camera or accessory.  Simply slide the 2-inch nosepiece into the focuser drawtube, rotate until the brass screw drops into place, and lock down the thumbscrews.   The brass registration screw can be easily removed when using a non-Optec focuser.


  • Overall Outside Diameter:  2.38" (60mm)
  • Outside Diameter (main body):  1.995" (50.7mm)
  • Overall Height: 1.80" (45.5mm)
  • Height of SCT-threads:  0.400"  (10.0mm)
  • Clear Aperture: 1.70" (43.3mm)
  • Weight: 2.4 oz (70 g)
  • Back-focus Usage: 0.25" (6.4 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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