astrograph

The term astrograph refers to a telescope designed to take astronomical photographs. The term is still commonly used for such amateur telescopes, but (digital) photography is now so ubiquitous in research/professional astronomy that its use of the term has virtually disappeared.

Some past research telescopes used photography specifically as a method to optimize astrometry research, the photographic record documenting the observation for careful calculation of the precise angles between stars (or between a star and a solar system object) and the term astrograph was often used for research telescopes designed for that type of study (e.g., the USNO Twin Astrograph). A typical design-characteristic was 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. Telescopes specifically for astrometry have also included other unusual characteristics, e.g., its entire design orientation being the measurement of one very precise coordinate, of one star at a time (e.g., its declination). Now, considerable high-precision astrometry effort is done using space observatories, and like other current research telescopes, the fact that it uses (digital) photography doesn't seem unusual enough to term it an astrograph.