Meade #1222 Field De-Rotator, for 16" LX200 & LX200GPS Models
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• Placed atop the Supergiant Field Tripod, the 16" LX200GPS-SMT operates in the altazimuth mode with the tracking and pointing accuracies previously described. For visual observing, or for CCD imaging or astrophotography not exceeding four to five minutes duration, no additional equipment is required.
• During longer periods of imaging or photography, however, field rotation, an effect inherent to any altazimuth-mounted telescope, becomes apparent. The result of such field rotation during photography or imaging is to cause stars at the outer edge of the field to appear to rotate relative to the centrally-located star, even if the exposure is perfectly guided.
• This effect can be cancelled completely and precisely by adding the optional Meade #1222 Field De-rotater which attaches to the rear cell of the telescope and plugs into a special connector on the control panel. Digital data fed from the telescope's microprocessor to the field de-rotator permit precise and continuous update of the de-rotation required to maintain pinpoint star images throughout the field.
• The field derotator integrates with your scope's Autostar II computer for imaging in the altazimuth mode. The Autostar calculates the amount of field rotation during an altazimuth photograph, based on the region of the sky being imaged.
• It then automatically rotates the field derotator and its attached camera in the opposite direction by the precise amount needed to compensate for the field rotation.
• Should exceptional pinpoint accuracy be needed for very critical imaging or scientific measurement purposes, however, you might want to consider going with an equatorially mounted 16" scope and training its PPEC system rather than using a field derotator on analtazimuth mount.