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Although most commercial telescopes will hold collimation very well once properly adjusted, always check the collimation at the same time you use a star image to evaluate the seeing, and especially if the telescope has been transported in a car and possibly shaken up on the road.įocuser Collimation. Refer to these first, and memorize the procedure so that it becomes easy to do on your own. Nearly all commercially available telescopes are provided with illustrated collimation instructions, and generic instructions are available online. The specific steps necessary to collimate a telescope vary with the telescope design and manufacturer.
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It is not normally possible to collimate the objective lenses of a refractor, or the corrector plate of a catadioptric (Schmidt Cassegrain, Maksutov Cassegrain, Maksutov Newtonian) telescope. Some of those owners paid thousands of dollars to get 1/10 wave optics, but miscollimation can reduce the image quality of a telescope to 1/2 wave or worse.Īdjustment knobs or screws are usually provided for tuning the collimation in the mirror cells of the primary and secondary mirrors of a Newtonian (Dobsonian) telescope, but only in the secondary mirror of a Schmidt Cassegrain or Maksutov Cassegrain. They are easiest to produce by moving your head from side to side while viewing a star centered in the field of a wide angle eyepiece or in a small focal ratio objective.Ĭollimation is the single most important adjustment that most observers will make in their equipment, yet many amateur telescopes are typically found to need adjustment when tested at star parties or dark sky events. These aberrations most often resemble coma or astigmatism. Miscollimation therefore produces aberrations in "on axis" or centered star images where optical images are usually flawless. Observing through a spherical symmetrical lens from an off axis position has the same optical effect as observing on axis through a distorted or asymmetrical lens. Miscollimation arises when any of the three optical axes is out of alignment with the other two (diagram, below). It is the first of two critical adjustments necessary to obtain the peak optical performance from a telescope. Telescope Optical Attributes CollimationĬollimation (pronounced kôl-ǝ-mā-shŭn) is the condition in which the three optical axes of the objective, eyepiece and observing eye are exactly aligned and coincident. Included at the end of each page is a list of Further Reading that identifies the sources used and points to additional information available online. It is one of series: previous pages explained basic optics and telescope & eyepiece combined subsequent pages discuss optical aberrations, eyepiece designs and evaluating eyepieces. This page introduces the optical principles necessary to understand the design and performance of astronomical telescope systems the telescope and eyepiece used as a visual instrument with the eye included as a third component. Astronomical optics, part 3: the astronomical imageĪstronomical Optics Part 3: The Astronomical Image