Using Setting Circles, Calculating Power | Meade 114 EQ-DS instruction

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•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 are visible through the Meade 114 EQ-DS.

USING SETTING CIRCLES

Setting circles of the polar aligned equatorial mount can facilitate the location of faint celestial objects not easily found by direct visual observation. To use the setting circles, follow this procedure:

•Use a star chart or star atlas, and look up the celestial coordinates, Right Ascension and Declination (R.A. and Dec.), of an easy-to-find bright star that is within the general vicinity of the faint object you wish to locate.

•Center the determined bright star in the telescope’s field of view.

•Manually turn the R.A. setting circle (27, Fig. 1c) to read the R.A. of the object now in the telescope’s eyepiece.

•The setting circles are now calibrated (the Dec. setting circle (28, Fig. 1c) is factory calibrated). To locate a nearby faint object using the setting circles determine the faint object’s celestial coordinates from a star chart, and move the telescope in R.A. and Declination until the setting circles read the R.A. and Dec. of the object you are attempting to locate. If the above procedure has been carefully performed, the faint object will now be in the field of a low power eyepiece.

•The R.A. Setting Circle must be manually re-calibrated on the current Right Ascension of a star every time the telescope is set up, and reset to the centered object’s R.A. coordinate before moving to a new R.A. coordinate setting. The R.A. Setting Circle has two sets of numbers, the inner set is for Southern hemisphere use while the outer set of numbers (the set closest to the R.A. gear), is for use by observers located North of the Earth’s equator (e.g., in North America).

CALCULATING POWER

The power, or magnification of the telescope depends on two optical characteristics: the focal length of the main telescope and the focal length of the eyepiece used during a particular observation. For example, the focal length of the Meade 114 EQ-DS telescope is fixed at 1000mm. To calculate the power in use with a particular eyepiece, divide the focal length of the eyepiece into the focal length of the main telescope. For example, using the H 25mm eyepiece supplied with the Meade 114 EQ-DS, the power is calculated as follows:

Power = 1000mm ÷ 25mm = 40X

The supplied 3X Barlow lens triples the power of each eyepiece. Insert the 3X Barlow lens into the the eyepiece holder (17, Fig. 1b), followed by the eyepiece, and secure by tightening the respective thumbscrews. For example, the 25mm (40X) eyepiece, when used with the 3X Barlow Lens, yields 120X.

The letter “H” refers to the “Hyguens” optical design, which yields corrected images. The optical design has no bearing on the power of the eyepiece.

Meade Instruments manufactures several types of eyepiece designs that are available for your telescope. The type of eyepiece (“MA” Modified Achromatic, “SP” Super Plössl, etc.) has no bearing on magnifying power but does affect such optical characteristics as field of view, flatness of field, eye relief, and color correction.

The maximum practical magnification is determined by the nature of the object being observed and, most importantly, by the prevailing atmospheric conditions. Under very steady atmospheric “seeing,” the Meade 114 EQ-DS may be used at powers up to about 225x on astronomical objects. Generally, however, lower powers of perhaps 75x to 175x will present the best images consistent with high image resolution. When unsteady air conditions prevail (as witnessed by rapid “twinkling” of the stars), extremely high-power eyepieces result in poor magnification, where the object detail observed is actually reduced by the excessive power.