Meade LX-200 Startup and Shutdown

When the LX-200 is turned on in Polar mode, it assumes it is pointing at 0° declination and hour angle zero. This allows a couple different methods of parking and starting the scope:

Park by pointing the scope to an RA equal to the Local Sidereal Time and a declination of 0. Then when you startup, the scope should be pre-sync'ed. This is John Hoot's method.
Park by pointing to a position that is offset from this by a known amount. On startup, have the control software apply the correction constants.
Using one of the above methods, confirming the start-up sync by taking a quick pointing exposure.

The ASCOM Meade telescope driver uses a different method. The telescope is first switched to Land mode, then is commanded to point due south (due north in the southern hemisphere) at an elevation of zero. (Remember, in the LX-200 due south is azimuth zero). This can be done with the following code, provided by Bob Denny:

The scope can then be powered off. When it is powered up, and after it has initialized, the mode can be switched back to Polar. The scope will retain its pointing synchronization.

The 16" LX-200 has its own park command ("hP"). If possible, use it. Note that the 16" home/park position is with the forks at zero hour angle and the OTA pointing at the nonvisible celestial pole. This limits the usefulness of the home/park system in this telescope in applications where the roof won't clear the instrumental back of the telescope.

When attempting to use one of the other methods with the 16" LX-200, be aware that some firmware versions have a bug which will prevent the initialization routine from working correctly. In a typical application the scope is bedded to a known position and then turned off. When turned back on, the telescope will hunt for its home/park magnets (the hall effect sensors read magnets on the drive worms at startup). This motion is variable from startup to startup, since the position of the magnet relative to the hall effect sensor is unknown. The buggy firmware fails to take this motion into account and thus ruins the "known" position you parked into. Therefore, on power-up, you have a deviation from your "known" park position of up to a half degree.

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