Check the listing for details. Celestron #93515 Single Axis Motor Drive Corrector for Telescope EQ2 Equator. Condition: New. Listed at 101.69 USD. Celestron #93515 Single Axis Motor Drive Corrector for Telescope EQ2 Equator Product Dimensions: 12.7 x 10.2 x 7.6 cm ; 839 g Shipping Weight: 1.1 Kg Item model number: 93515 OPERATION This motor drive allows tracking of celestial objects at the speed of the earth's rotation rate. The hand controller can be used as a correction for long exposure photographs. For the motor drive to properly compensate for the earth's rotation, your telescope mount must be polar-aligned and the altitude axis set to your local latitude. Under these conditions, no adjustment of the declination axis should be necessary for astrophotography. You will only need the R.A. motor drive. When the power is on and all buttons on the control box are depressed, the motor drive will automatically rotate at the correct speed to compensate for the rotation of the earth. Its rotation speed matches the earth's rotation rate for stars to appear stationary in telescope eyepiece.