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Meade® Smart DriveTM

Permanent Periodic Error Correction(PPEC) for Meade LX200GPS Telescopes

Included as standard equipment with all Meade LX200GPSSchmidt-Cassegrain telescopes, and with the #1664 and#1697 drive systems of Meade apochromatic refractors (p.56) as well, the Smart Drive permits a professional level ofdrive-rate precision. No longer are large worm gearsystems required, whensmaller gears coupled toSmart Drive software canachieve periodic errors of 5arc secs or less—an observ-atory standard of precision.

All worm/worm-gear com-binations, no matter howwell made, have minorinaccuracies that manifestthemselves as periodicerrors in the telescopetracking rate, with the perioddependent on the worm’srate of rotation. To programthe Smart Drive, theobserver guides on an object visually, making correctionswith the handbox controller. The software then remembersthese keystrokes, stores them in memory, and in the futureautomatically compensates for the periodic errors of thegear system.

Smart Drive user programming is stored in the telescope’scomputer memory forever, independently of any powersource, unlike other periodic error correctors that must bereprogrammed each time you use the system. The SmartDrive can be erased, updated, or even averaged with futureprogrammings at the user’s option.

The significant value of the Smart Drive is immediatelyappreciated during long-exposure astrophotography, wherethe resultant low periodic error of the system enablesrelaxed guiding with a minimum of handbox corrections. InCCD imaging, where 2- to 3-minute exposures of deep-space objects are often all that is required for stunningresults, the Smart Drive often permits imaging without anyguiding requirements at all.

Smart Drive programming isdone through the telescope’shand controller.

Meade® Model 1220 Field De-rotaterfor Meade LX200GPS Telescopes

Meade LX200GPS telescopes may be operated in thealtazimuth mode (i.e., without polar alignment) for all visualapplications and for photographic or CCD imagingexposures of up to about five minutes’ duration. MostLX200GPS owners usetheir telescope in thealtazimuth mode the greatmajority of the time.During longer photo orCCD exposures in thealtazimuth mode, how-ever, an effect called fieldrotation becomes evident.

Simply put, even if thetelescope is perfectlyguided on a central starduring a long exposure,stars at the edge of thefield appear to rotateabout the field centerduring the exposure. As aresult, stars away from thefield center appear assmall concentric arcs onthe film, rather than star-points. This effect, whichin no way relates to theaccuracy of the telescope’s computer or internal alignment,occurs on all altazimuth-mounted telescopes, whether largeobservatory telescope or LX200GPS, and is caused by thetelescope not being polar aligned.

Field rotation with an LX200GPS (or with their predecessorLX200 models) can be cured with the simple addition of anequatorial wedge (see, e.g., p. 18, 29, or 39); the wedgeenables precise polar alignment, negating all field rotation.Alternately, the optional #1220 Field De-rotater may beattached to the rear cell of any 7", 8", 10", or 12" MeadeLX200 or LX200GPS model, simplifying field operation ofthe telescope, since no wedge is required. With the #1220De-rotater attached to the telescope’s rear cell, otheraccessories (T-Adapter, Off-Axis Guider, etc.) can in turnbe threaded to the #1220 unit.

The #1220 is easy to use! Just align the LX200GPStelescope as usual, using the GPS alignment procedure orone of six other available alignment procedures, and,automatically, signals are fed through one of the RS-232ports on the LX200GPS control panel to the Field De-rotater, causing it to rotate at the correct speed andprecisely counter the effects of altazimuth-induced fieldrotation. The #1220 Field De-rotater is powered throughconnection with the RS-232 serial port.

Meade #1220 Field De-rotater(arrow), shown with #62 T-Adapterand 35mm camera body attached toa Meade 10" LX200GPS, ready forlong-exposure astrophotography.

The Smart Drive is a tremendous aid in obtaining high-quality,long-exposure images, such as this 2-hour exposure of theSpiral Galaxy (M81) in Ursa Major by Philip Perkins.