What are the pros and cons of adding aftermarket collimating screws to my Schmidt-Cassegrain telescope (SCT)?

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	What are the pros and cons of adding aftermarket collimating screws to my Schmidt-Cassegrain telescope (SCT)?

Answer Celestron’s SCTs have a trio of either button head Allen screws or Philips screws on the outside of the secondary mirror cell. These screws are used to collimate the scope by slightly changing the tilt of the secondary relative to the optical axis of the scope.

Because SCTs do need to be collimated and because these screws require a tool to turn, many people have replaced the factory collimation screws with knurled or knobbed screws.

The pros of collimation screw replacement: tool-less and easier to re-collimate your scope in the dark and singlehanded.

The cons: the scope becomes decollimated more easily, since the screws generally turn with less effort than the factory screws. Dust covers and tube caps may not fit in place as the knobs stick out significantly farther than the low-profile factory screws. Possible damage to the secondary mirror support by replacing screws with those having the wrong threading. It’s also possible to drop the secondary into the tube by not properly removing the original screws.

NOTE: Using aftermarket screws may void your Celestron warranty.

Article Details

Article ID:

2215

Created On:

May 06 2009 04:21 PM