  We propose a sociohistorical framework for better understanding the evolution
in the use of telescopes. We define two regimes of use : a general-purpose (or
survey) one, where the telescope governs research, and a dedicated one, in
which the telescope is tailored to a specific project which includes a network
of other tools. This conceptual framework is first applied to the history of
the 80-cm telescope of Toulouse Observatory, which is initially anchored in a
general-purpose regime linked to astrometry. After a transition in the 1930s,
it is integrated in a dedicated regime centered on astrophysics. This evolution
is compared to that of a very similar instrument, the 80-cm telescope of
Marseille Observatory, which converts early on to the dedicated regime with the
Fabry-Perot interferometer around 1910, and, after a period of idleness, is
again used in the survey mode after WWII. To further validate our new concept,
we apply it to the telescopes of Washburn Observatory, of Dominion
Astrophysical Observatory and of Meudon Observatory. The uses of the different
telescopes illustrate various combinations of the two regimes, which can be
successive, simultaneous or alternating. This conceptual framework is likely to
be applicable to other fields of pure and applied science.
