Meade LX90-ACF Advanced Coma-Free, Инструкция по эксплуатации

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known as the “Drift” method:
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 (see
CELESTIAL COORDINATES,
page 49). 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):
a. If the star drifts South (or down), the telescope’s polar axis is pointing too far
East.
b. If the star drifts North (or up), the telescope’s polar axis is pointing too far
West.
4. Move the wedge in azimuth (horizontally) to effect the appropriate change in polar
alignment. Reposition the telescope’s East-West polar axis orientation until there is
no further North-South drift by the star. Track the star for a period of time to be
certain that its Declination drift has ceased.
5. Next, point the telescope at another moderately bright star near the Eastern
horizon, but still near the celestial equator. For best results, the star should be about
20° or 30° above the Eastern horizon and within ± 5° of the celestial equator.
6. Again note the extent of the star’s drift in Declination:
a. If the star drifts South, (or down) the telescope’s polar axis is pointing too low.
b. If the star drifts North, (or up) the telescope’s polar axis is pointing too high.
7. Use the altitude adjust control on the wedge to make appropriate changes in
altitude, based on your observations above. Again, track the star for a period of time
to be certain that Declination drift has ceased.
The above procedure results in very accurate polar alignment, and minimizes the need for
tracking corrections during astrophotography.
Periodic Error Correction (PEC) Training (Polar Alignment and R.A.
Drive Only)
If you wish to perform high-precision astrophotography, you may wish to “train” your telescope
in order to keep objects that you are imaging dead center in the telescope’s mirror during the
photographic exposure. Periodic error correction (PEC) helps to remove the slight perturbations
from center that occur due to the mechanical nature of a telescope. To perform this procedure,
you need to use a high-power reticle, such as the 9mm reticle (see
OPTIONAL ACCESSORIES
,
page 42). PEC training is only available for the R.A. drive.
Important Note: The PEC training is remembered by AutoStar ONLY when you use the “Park”
option. If you turn off the telescope without turning on the Park command, all PEC training will
be lost. See PARK, page 28.
Follow these steps:
1. Make sure that “Polar” is selected in the “Telescope: Mount” menu (“Alt/Az” is the default
setting) and the telescope is aligned in the Polar mode.
2. Choose a bright star in the South that has minimal movement and is about 30° above
the horizon
Note: If in the Southern hemisphere, pick a star in the North that is about 30° above the
horizon.
3. Look through the reticle. Use the Arrow keys to keep the star centered in the reticle
cross-hairs.
4. Select “On” when you want the telescope to turn on the Smart Drive training. A full cycle
takes about 8 minutes.
5. Press MODE to exit.
Fig. 32: Tripod set in Polar
configuration with an
optional wedge.