STANDARD - Survey Instrument Antique Center!

97
The Use of the Interchangeable Auxiliary Telescope
for Astronomical Observations.
Besides its ordinary use for steep sighting in mines, the interchangeable auxiliary
telescope, as described in the foregoing article, will at times be found very useful as
an astronomical instrument. It is particularly advisable in making latitude observations
by meridian altitude and in observing transits across the meridian for time. As
a rule when the prism is attached to the eye-piece of the main telescope it is not possible
with the engineer's mining transit to point the telescope at a greater angle of
elevation than about 70, consequently it would be impossible to make solar observations
at a latitude lower than 40 when the sun is at its greatest declination or observation
on Stars near the zenith. However, by attaching the prism to the auxiliary telescope
used asatop or sidetelescope, these observations may be made witheasenndthisdifficulty overcome
In making latitude observations the interchangeable auxiliary telescope should be
attached at the side and its horizontal wire is ; then, by means of the two opposing
tangent screws, made to correspond to the line of collimation of that of the main
telescope by bisecting with both telescopes some distant and well-defined object : then,
if a meridian mark is used (which is not absolutely necessary), the transit should be
set up in the meridian by the main telescope and the pointing on the sun or star may be
made with the auxiliary telescope with or without the prism, as conditions may require.
In observing transits the auxiliary telescope should be mounted on top and ranged
into line with the vertical wire of the main telescope by using the two opposing
screws as explained.
In making solar and stellar observations with the main telescope and prism attachment, the teleacope
should always be reversed through the standards with the objective down instead of up