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How to Use a Meade F6.3 Focal Reducer

The Meade F6.3 focal reducer is a telescope accessory offered by Meade Instruments Corporation, a U.S. manufacturer of telescopes and other optical products.

The principal application of Meade focal reducers is astro-imaging through Meade or Celestron Schmidt-Cassegrain telescopes (SCTs.) A focal reducer compresses the light cone exiting the telescope, thereby converting a standard F10 SCT to F6.3. As a result, exposure time is shortened for any camera because more light is concentrated per unit area. The field of view seen by an electronic charge-coupled device (CCD ) camera is effectively increased since more of the field fits on the CCD chip. A focal reducer also increases the size of the visual field in a Schmidt-Cassegrain scope, but magnification is reduced.

Things You'll Need

Camera T-adapter
T-ring specific to the camera brand

Instructions

Astro-Imaging Application
- 1
  Remove the protective cap from the primary mirror cell at the rear of the telescope. Thread the focal reducer onto the cell and tighten it firmly, taking care not to touch the lenses.
  
  The male thread on the exit end of the focal reducer matches the thread on the rear of the telescope, so other accessories can simply thread onto it.
- 2
  Thread the T-adapter onto the focal reducer, then thread the T-ring onto the T-adapter.
- 3
  Thread the exit end of the T-ring onto the camera. Note that the T-ring must be specific to the camera brand and that some digital cameras may require additional accessories. For example, a camera without a threaded lens requires attachment devices specific to the camera.
- 4
  Check to be sure all connections are tight. The telescope is now ready for astro-imaging.
Visual Application
- 5
  Thread the telescope's eyepiece holder onto the focal reducer and tighten it firmly.
- 6
  Insert an eyepiece into the eyepiece holder and tighten the thumbscrew. The telescope is now ready for visual observing.
- 7
  Note that the telescope magnification produced with any eyepiece will be reduced to 63 percent and the diameter of the visual field will be increased by about the same amount.
- 8
  Refocus the telescope; this may require considerable movement of the focuser because the telescope's focal ratio was changed from F10 to F6.3.

Astronomy