astrograph

The term astrograph is used for some research telescopes designed specifically for astrometry and/or recording the precise position of solar system bodies, both of which require measurement accuracy and precision over the celestial sphere. A typical design-characteristic has been minimizing the aberrations that affect the consistency of its plate scale throughout the portion of the focal plane intended for use, so measurements across its images precisely reflect angles in the sky. In other cases, a telescope's entire design goal has been the measurement of one very precise coordinate, of one star at a time (e.g., its declination). Considerable high-precision astrometry effort is now done using space observatories, but the term astrograph is more commonly used for ground telescopes, indicating specific designs.

The term astrograph is also used for amateur telescopes designed for photography. Nearly any modern research telescope would fall within such a criteria.