Meade 60EQ-D instruction manual Calculating Power, Maintenance

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The number of fascinating objects visible through your Infinity refractor is limited only by your own motivation. Astronomical software, or a good star atlas (see “Meade Star Charts” in OPTIONAL ACCESSORIES, page 11) will assist you in locating many interesting celestial objects. These objects include:

•Cloud belts across the surface of the planet Jupiter.

•The 4 major satellites of Jupiter, visible in revolution about the planet, with the satellite positions changing each night.

•Saturn and its famous ring system, as well as several satellites of Saturn, much fainter than the major satellites of Jupiter.

•The Moon: A veritable treasury of craters, mountain ranges and fault lines. The best contrast for viewing the Moon is during its crescent phase. The contrast during the full Moon phase is low due to the angle of illumination.

•Deep-Space: Nebulae, galaxies, multiple star systems, star clusters— hundreds of such objects can be located through the Polaris 60EQ-D.

•Terrestrial Objects: Your Polaris refractor may also be used for the observation of land subjects. In this case, note that the diagonal mirror results in an image which is reversed left-for-right, but which is correctly oriented up-and-down. For a fully corrected image, the #927 Erect Image Prism system is required. (See “OPTIONAL ACCESSORIES”). Terrestrial observations should almost always be made using a low power eyepiece for bright, sharp images. Land objects will not normally accept higher powers because the telescope is being used through the thickest part of the Earth’s atmosphere, unlike astronomical observations made by pointing the telescope up through the atmosphere.

CALCULATING POWER

The power, or magnification, at which a telescope is operating is determined by 2 factors: the optical, or focal, length of the telescope’s objective lens and the focal length of the eyepiece. The focal length of the Polaris 60EQ-D is 900mm. To compute power, divide the focal length of the eyepiece into the focal length of the objective lens. The resulting quotient is the magnifying power of the telescope when used with the eyepiece in question. For example, the 25mm eyepiece yields, with the Polaris 60EQ-D, a power of:

Power = 900mm ÷ 25mm = 36X

The letter “H” refers to the “Huygens” optical design which yields well corrected images with refracting telescopes. The optical design of the eyepiece has no bearing on power, however.

The Barlow lens serves to increase the power of each eyepiece. Insert the 3X Barlow lens into the telescope focuser first, followed by the diagonal prism and eyepiece, secure by tightening the respective thumbscrews. For example, the 25mm (36X) eyepiece, when used in conjunction with the 3X Barlow Lens, yields 108X.

A few words of wisdom about power. While the theoretical power or magnification of a telescope is virtually limitless, there are, however, practical limits imposed by the Earth’s atmosphere as to what can be seen well at a given power. The most often useful higher magnification with any 60mm diameter telescope is in the range of 80 to 120 power. The general rule to follow with any telescope, regarding power: only use as much magnification as supports a steady, well-defined image. This often varies with the stability of the air being viewed through and is one reason why having various eyepieces is highly desirable. Higher powers are no guaranty of better images; in fact, the opposite is often true. Also, keep in mind, that land viewing and wide-field, deep-space observation are, generally, low power applications of your telescope.

MAINTENANCE

As with any quality optical instrument, lens surfaces should be cleaned as infrequently as possible. A little dust on the surface of the objective (front) lens causes negligible degradation of image quality and should not be considered reason to “clean” the lens. When lens cleaning does become necessary, use a camel’s hair brush or compressed air blown gently to remove dust. Wipe only with a soft, clean cloth, applying as little pressure as possible to avoid scratching glass surfaces. Note: remove the dew shield/lens shade (29) to access the objective lens (22) for cleaning.