Page "Amateur astronomy" Paragraph 16

Setting circles are angular measurement scales that can be placed on the two main rotation axes of some telescopes.

Since the widespread adoption of digital setting circles, any classical engraved setting circle is now specifically identified as an " analog setting circle " ( ASC ).

By knowing the coordinates of an object ( usually given in equatorial coordinates ), the telescope user can use the setting circle to align the telescope in the appropriate direction before looking through its eyepiece.

A computerized setting circle is called a " digital setting circle " ( DSC ).

Although digital setting circles can be used to display a telescope's RA and Dec coordinates, they are not simply a digital read-out of what can be seen on the telescope's analog setting circles.

As with go-to telescopes, digital setting circle computers ( commercial names include Argo Navis, Sky Commander, and NGC Max ) contain databases of tens of thousands of celestial objects and projections of planet positions.