Graduated dials on the axes of an equatorial mount, in right ascension and declination. Once the mount is polar aligned and set on a known star, you dial in an object’s coordinates to find it. The digital encoders of push-to systems are their modern version.
Related terms
- Right ascension
The celestial “longitude”, counted eastwards along the celestial equator from the vernal equinox point, in hours from 0h to 24h (1h = 15°). With declination it fixes a star’s position on the celestial sphere. Abbreviated RA.
- Declination
The celestial “latitude”: an object’s angle north (+) or south (−) of the celestial equator, from +90° to −90°. Vega is at +38.8°, Sirius at −16.7°. From a given latitude, declination tells you whether an object is always up, never up, or rises and sets.
- Push-to
A set of encoders on the axes of an unmotorised telescope, often a Dobsonian, linked to a handset or phone. The screen shows which way to push the tube to reach the chosen object. You keep the simplicity of a manual mount, with help to find things.
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