Meade #1220 Field Derotator
Meade LX200 Series & LX400-ACF telescopes may be operated in the altazimuth mode (i.e., without polar alignment) for all visual applications and for photographic or CCD imaging exposures of up to about five minutes' duration. Most owners use their telescope in the altazimuth mode the great majority of the time. During longer photo or CCD exposures in the altazimuth mode, however, an effect called field rotation becomes evident.
Simply put, even if the telescope is perfectly guided on a central star during a long exposure, stars at the edge of the field appear to rotate about the field center during the exposure. As a result, stars away from the field center appear as small concentric arcs on the film, rather than starpoints. This effect, which in no way relates to the accuracy of the telescope's computer or internal alignment, occurs on all altazimuth-mounted telescopes, whether large observatory telescope, LX400-ACF or LX200R, and is caused by the telescope not being polar aligned.
Field rotation with an LX-200 or LX400-ACF telescope can be cured with the simple addition of an equatorial wedge; the wedge enables precise polar alignment, negating all field rotation. Alternately, the optional Meade #1220 Field De-rotater may be attached to the rear cell of any 7", 8", 10", or 12" Meade LX200-ACF or 10" or 12" LX400-ACF model, simplifying field operation of the telescope, since no wedge is required.
With the Meade #1220 De-rotater attached to the telescope's rear cell, other accessories (T-Adapter, Off-Axis Guider, etc.) can in turn be threaded to the #1220 unit.
The #1220 is easy to use! Just align the telescope as usual, using the GPS alignment procedure or one of six other available alignment procedures, and, automatically, signals are fed through one of the RS-232 ports on the telescope's control panel to the Field De-rotater, causing it to rotate at the correct speed and precisely counter the effects of altazimuth-induced field rotation. The Meade #1220 Field De-rotater is powered through connection with the RS-232 serial port.
|Attachment||Rear Cell of Your Telescope|
|Other||Update of the De-rotation : Precise and Continuous Required to Maintain Pinpoint Star Images.
Contrast Direction : Precisely Counter the Effects of Altazimuth-induced Field Rotation.