Meade LX90GPS instruction manual Lining Up with the Celestial Pole, Equatorial Wedge

Fig. 30: Section of Right Ascension Setting Circle.

Fig. 31: Section of Declination Setting Circle.

Fig. 32a: Equatorial Wedge.

Fig. 32b: LX90 mounted on an equatorial wedge.

Fig. 32c: The Ultrawedge is available for the 10" and 12" models.

Note that the R.A. circle is double-indexed (i.e., there are two series of numbers running in opposite directions around the circumference of the R.A. circle). The upper series of numbers (increasing counterclockwise) applies to observers located in the Earth’s Northern Hemisphere; the lower series of numbers (increasing clockwise) applies to observers located in the Earth’s Southern Hemisphere.

To use the setting circles to locate an object not easily found by direct visual observa- tion:

With the telescope aligned to the Celestial Pole, first look up the celestial coordinates (R.A. and Dec.) of the object in a star atlas. Then loosen the R.A. lock and turn the telescope to read the correct R.A. of the desired object; lock the R.A. lock onto the object. Next, turn the telescope in Declination to read the correct Declination of the object. If the procedure has been followed carefully, and if the telescope was well-aligned with the pole, the desired object should now be in the telescopic field of a low-power eyepiece.

If you do not immediately see the object you are seeking, try searching the adjacent sky area. Keep in mind that, with the 26mm eyepiece, the field of view of the LX90 is about 0.5°. Because of its much wider field, the viewfinder may be of significant assistance in locating and centering objects, after the setting circles have been used to locate the approximate position of the object.

Pinpoint application of the setting circles requires that the telescope be precisely aligned with the pole. See LINING UP WITH THE CELESTIAL POLE, page 52

EQUATORIAL WEDGE

An optional equatorial wedge allows a more precise Polar alignment. Polar alignment allows you to take longer exposure photographs with your LX90.

The LX90 requires an adapter to attach the equatorial wedge to the tripod. See the instruction sheet supplied with the wedge for installation.

Equatorial Wedge

The equatorial wedge permits use in an astronomical, or “equatorial,” mode. The wedge fits onto the field tripod.

NOTE: The Meade equatorial wedge is designed solely for use in conjunction with the Meade field tripod. The wedge should never be used without the field tripod (e.g., by placing the wedge alone on a table top and then mounting the telescope on the wedge – the wedge may become seriously imbalanced, to the point where the telescope may actually tip over.

Included features:

•Attachment of the wedge to the field tripod by means of only one manual knob.

•Quick azimuth adjustment by loosening the manual knob as described above.

•Bubble level for rapid tripod/wedge leveling.

•Etched latitude scale for fast adjustment of the latitude angle.

Lining Up with the Celestial Pole

Objects in the sky appear to revolve around the celestial pole. (Actually, celestial objects are essentially “fixed.” Their apparent motion is caused by the Earth’s rotation). During any 24 hour period, stars make one complete revolution about the pole, making concentric circles with the pole at the center. By lining up the telescope’s polar axis with the North Celestial Pole (or for observers located in Earth’s Southern Hemisphere, with the South Celestial Pole), astronomical objects may be followed, or tracked, simply by moving the telescope about one axis, the polar axis. This tracking may be accomplished automatically with the LX90 electric motor drive.

If the telescope is reasonably well aligned with the pole, very little use of the telescope’s Declination slow motion control is necessary. Virtually all of the required telescope tracking will be in Right Ascension. (If the telescope were perfectly aligned with the pole, no Declination tracking of celestial objects would be required.) For the purposes of casual telescopic observations, lining up the telescope’s polar axis to within a degree or two of the pole is more than sufficient: With this level of pointing accuracy, the telescope’s motor drive will track accu- rately and keep objects in the telescopic field of view for perhaps 20 to 30 minutes.

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