Setting circles for a Dob is something that needs some conversion calculations as you are taking the azimuth and altitude (az/alt) of the Dob to the Right Ascension and Declination (RA/DEC) so that you can track the sky. This is the computations that are done by the Digital Setting Circles (DSC) as you move the scope about and time goes by. Bob May http://nav.to/bobmay bobmay@nethere.com