Meade LX200 instruction manual Toc 3. Precise Polar Alignment

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wedge/tripod system reads "level."

2.Set the Equatorial Wedge to your observing latitude as described in Appendix A.

3.Loosen the Dec. Lock, and rotate the telescope tube in Declination so that the telescope's Declination reads 90°. Tighten the Dec. Lock. Loosen the R.A. Lock, and rotate the Fork Arms to the 00 H.A. position (See section G. Mode Functions) and initiate the POLAR align sequence on the Keypad.

4.Using the Azimuth and Latitude controls on the Wedge, center Polaris in the field of view. Do not use the telescope's Declination or Right Ascension controls during this process.

At this point, your polar alignment is good enough for casual observations. There are times, however, when you will need to have precise polar alignment, such as when making fine astrophotographs or when using the setting circles to find new objects (see Refined Polar Alignment).

As an aside procedure, during your first use of the telescope, you should check the calibration of the Declination setting circle (see 3, Fig. 3), located at the top of the left fork arm. After performing the polar alignment procedure, center the star Polaris in the telescope field. Loosen slightly the knurled central hub of the Declination setting circle. Now turn the circle unit until it reads 89.2°, the Declination of Polaris, and then tighten down the knurled knob, avoiding any motion of the circle. Also realize, should you wish to use the manual setting circles, that the R.A. Setting Circle (10, Fig. 3) must be calibrated on the current Right Ascension of a star (see Appendix C), manually every time the telescope is set up. The R.A. Setting Circle has two sets of numbers, the inner set is for Southern hemisphere use, while the other is for Northern hemisphere use.

Once the latitude angle of the wedge has been fixed and locked-in according to the above procedure, it is not necessary to repeat this operation each time the telescope is used, unless you move a considerable distance North or South from your original observing position. (Approximately 70 miles movement in North- South observing position is equivalent to 1° in latitude change). The wedge may be detached from the field tripod and, as long as the latitude angle setting is not altered and the field tripod is leveled, it will retain the correct latitude setting when replaced on the tripod.

[ toc ] 3. Precise Polar Alignment

It should be emphasized that precise alignment of the telescope's polar axis to the celestial pole for casual visual observations is not necessary. Don't allow a time-consuming effort at lining up with the pole to interfere with your basic enjoyment of the telescope. For long-exposure photography, however, the ground rules are quite different, and precise polar alignment is not only advisable, but almost essential. Notwithstanding the precision and sophistication of the drive system supplied with the Meade LX200 telescopes, the fewer tracking corrections required during the course of a long-exposure photograph, the better. (For our purposes, "long-exposure" means any photograph of about 10 minutes duration or longer). In particular, the number of Declination corrections required is a direct function of the precision of polar alignment.

Precise polar alignment requires the use of a crosshair eyepiece. The Meade Illuminated Reticle Eyepiece is well-suited in this application, but you will want to increase the effective magnification through the use of a 2X or 3X Barlow lens. Then either follow the Refined Polar Alignment section on page 33, or follow this procedure, sometimes better known as the "Drift" method (particularly if the pole star is not visible):

1.Obtain a rough polar alignment as described earlier. Place the illuminated reticle eyepiece (or eyepiece/Barlow combination) into the eyepiece holder of the telescope.

2.Point the telescope, with the motor drive running, at a moderately bright star near where the meridian (the North-South line passing through your local zenith) and the celestial equator intersect. For best results, the star should be located within ±30 minutes in R.A. of the meridian and within ±5° of the celestial equator. (Pointing the telescope at a star that is straight up, with the Declination set to 0°, will point the telescope in the right direction.)

3.Note the extent of the star's drift in Declination (disregard drift in Right Ascension):

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