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2-inch to 1-1/4-inch Precision Centering Compression Adapter (17663)

  • 6500

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.

#17663 - 2-inch to 1-1/4-inch Precision Centering Compression Adapter

The  2-inch to 1-1/4-inch Compression Adapter is our improved version of the #17662 1-1/4" adapter.  This new version features a solid brass compression ring with machined grooves to hold 1-1/4" eyepieces firmly without slippage.  A mere 1/8th turn of the upper locking ring tightens and loosens the 1-1/4" bore for easy use with gloved hands.

The #17663 offers a precision machined 2-inch outer diameter to fit into the drawtube of the TCF-S or TCF-Si focuser or any 2-inch focuser.  A dovetail cut matches the three thumbscrews on the TCF-S while the 1-1/4"  inner brass compression ring offers a non-marring alternative for 1-1/4" eyepieces and camera or instrument nosepieces.  The adapter is self-centering for any 1-1/4" eyepiece or instrument nosepiece.

The 2-inch tube features an industry standard M48x0.6mm female thread for 2-inch screw-in type filters.  Removing the lobed  locking ring (shown in red) and the brass compression ring leaves a snug-fitting T-adapter with male M42x0.75mm threads.


  • Overall Outside Diameter (locking ring):  2.20" (55.9mm)
  • Outside Diameter (main body):  1.995" (50.7mm)
  • Overall Height: 1.58" (40.2mm)
  • Clear Aperture: 1.25" (31.8mm)
  • Weight: 4.6 oz (130 g)
  • Back-focus Usage: 0.45" (11.5 mm)
  • Currently available with Red locking ring, Blue and Gold locking rings available August 2010.  Specify color when ordering.

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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