Off-Axis Guiders

Off-Axis guiders are almost exlusively used for tracking an image while doing long exposure photography with telescopes that have drive motors. Even a well made telescope drive has minute errors in the gear systems. As a result, when photographing an object with the high magnifications provided by a telescope, the long exposure times will render stars as short streaks unless careful corrections are made to compensate for drive errors. Off-axis guiders provide the means for either a human or a computer to watch for potential star drift and compensate for this by correcting the telescope's drive system. They are designed to go between the telescope focuser and the camera to pick off some of the light and divert it to a special eyepiece. The eyepiece generally has a lighted reticle that allows the observer to detect even the slightest drift in a selected star. More recently CCD autoguiders with computers have taken the place of the weary and sometimes bleary observer.

Guiders are usually made for use with Schmidt Cassegrain telescopes, but some are made for use on regular focusers as well. Under the heading Basic Guiders, Meade, Celestron and others make Cassegrain guiders and you can find an occasional Newtonian guider. Under the heading ofSpecial Guiders I would include the guiders by Lumicon called Easy Guiders. They include one for normal Newtonian focusers, and one for SCTs. They allow for attachment of many accessories without removing the basic guider body. Under the heading of Super Guiders I would include the Lumicon Giant Easy Guider which is the big brother of the Easy Guider designed especially for large format cameras on SCTs.

Basic Guiders	Special Guiders	Super Guiders
$50-75	$125-150	$200-250