Graphical Display of Periodic Errors

 

	date (yy/mm/dd)	exp. time (min/sec)	CCD / telescope	Mount	Remarks
Celestron 8 fork mount	00/09/29	150 x 2 sec	Starlight SX C8 + Focal reducer @ f /5.6	original Celestron 8 (orange) fork mount (build 1982) before azimuth correction	periodic error ± 30 arcsec period about 5 ½ min maximum unguided exposure time about 60 sec ( 1 out of 5)
Celestron 8 fork mount	00/10/07	250 x 2 sec	Starlight SX C8 + Focal reducer @ f /5.6	original Celestron 8 (orange) fork mount (build 1982) after azimuth correction	periodic error ± 30 arcsec period about 5 ½ min maximum unguided exposure time about 60 sec ( 1 out of 5)
Losmandy CG 11	00/10/19	165 x 2 sec	Starlight SX C8 + Focal reducer @ f /5.6	Losmandy CG 11 before azimuth correction	periodic error ± 3...6 arcsec period about 30 ... 40 sec maximum unguided exposure time about 10 sec ( 1 out of 10)

The deviation of the declination from a straight line is produced by the seeing which is always in the same order of 1 ... 2 arcsec for this short exposures.

The slope of the declination line is a measure for the misalignement of the polar axis in azimuth (the images were taken near the meridian).

The overall slope of the right ascension line is a measure for the incorrect speed of the mount. This is a special problem with the Celestron 8 fork mount with its modified Tuthill drive corrector (enlarged scope of minimal [about 20 Hz] and maximal [about 100 Hz] correction speed). The correct speed of 50 Hz can only be set by a potenziometer(?, regulator) without a notch(?) while observing the beat of a LED. When it shines with constant light you have reached 50 Hz.