Celestron Schmidt-Cassegrain User Manual

To get the best performance from your Schmidt-Cassegrain (SCT) or EdgeHD telescope, its optics must be collimated—
properly aligned within the telescope. Your telescope was collimated at the factory when it was assembled, and its
collimation was QA-checked before it was shipped. However, if the telescope has been dropped or jarred during
transport or has undergone considerable temperature changes, it may need to be re-collimated.
You can achieve correct collimation by adjusting the tilt of the secondary mirror housed at the center of the Schmidt
corrector (see Figure 1). This is the only adjustment available to the end user and should be the only adjustment required
to bring the telescope’s optics into excellent collimation.
NOTE: Do not attempt to make adjustments to the Schmidt corrector’s orientation or positioning. Doing so will likely degrade
collimation and optical performance and may require return to Celestron to achieve proper optical alignment.
SCT & EdgeHD Collimation Guide
Optical Tube Side ViewSchmidt Corrector Side View
Optical Tube Front ViewSchmidt Corrector Front View
Secondary Mirror
Fig. 1
Schmidt Corrector Front View
Collimation Screws

Celestron Schmidt-Cassegrain Specifications

General

Optical Design	Schmidt-Cassegrain
Aperture	Varies by model
Focal Length	Varies by model
Focal Ratio	Typically f/10
Mount Type	Varies by model
Weight	Varies by model
Highest Useful Magnification	Varies by model
Lowest Useful Magnification	Varies by model
Limiting Stellar Magnitude	Varies by model
Resolution (Rayleigh)	Varies by model
Resolution (Dawes)	Varies by model
Light Gathering Power	Varies by model
Optical Tube Length	Varies by model
Optical Tube Weight	Varies by model

Summary

Checking Telescope Collimation

Collimation Setup Guide

Telescope Collimation Process

Achieving Proper Collimation

Defines proper collimation as concentric central shadow and bright inner ring with the outer ring, and uniform dark ring extinction.

Collimation Conclusion