Erection of an equatorial mounting

A put in station is an adjustment which relates to the Télescope S equipped with a equatorial Monture. It consists in regulating the time axis of mounting to make it parallel with the axis of rotation of the Ground. This adjustment makes it possible to observe a star for long periods while following its trajectory by a simple rotation of the telescope on this time axis.

Among the many existing methods, one can distinguish three principal: approached method, based on the direct pointing of α Ursae Minoris (the pole star); the Method of Bigourdan which allows an erection with a unspecified star; and the Method of King, based on the analysis of photographs to long installation.

Generally, an erection consists in regulating on the one hand the slope time axis, and on the other hand its orientation .

Description of an equatorial mounting

See detailed article: equatorial Mounting

An equatorial mounting consists of 4 axes:
For the observation:

the time axis is that which carries the telescope, it can swivel on itself and is used to follow the Right ascension of a star
the axis of variation is at the end of the time axis, it connects this one to the tube of the telescope and makes it possible to make it rock to follow the variation

For the erection:

the axis of latitude is horizontal, it is located at the base of the time axis and makes it possible to regulate the slope of it; certain cheap mountings have a fixed slope of 40 or 45°
the axis of orientation is a vertical axis which makes it possible to make swivel the whole of mounting on the right or on the left; mounting is some times interdependent of its support, in this case it is necessary to make swivel all the support

Approximate method

The approximate adjustment of a mounting is practical for the observations of short duration. Certain German equatorial mountings are equipped with a polar sight which still facilitates this adjustment. On a mounting with fork, it requires the use of an elbow which returns the image to 90°.

First of all, the support of mounting (generally a tripod) must provide a perfectly horizontal support, and if mounting is of allemande type, it must be correctly balanced.

Adjustment at sight

To loosen the screw of the primary education horizontal axis (the axis of latitude), a graduation makes it possible to regulate it on the Latitude site of observation, then to temporarily tighten the screw
Pivoter the tube of the telescope on its axes schedule and variation to make it parallel with the time axis
Bloquer the brakes of the axes schedule and of variation
Orienter the tube of the telescope towards pole star while making swivel mounting, or the tripod if mounting is interdependent of this one, by pointing at sight in the direction of pole star

At the end of the operation, the pole star should be visible in the researcher. To obtain a better precision, one can make use of this one.

Adjustment with the researcher

The researcher allows to refine the adjustment at sight. For that, the instrument must be provided with a réticulé researcher who must be beforehand regulated to be parallel to the tube of the telescope. After a first adjustment at sight, the brakes of the axes schedule and variation must be maintained tight.

To swivel the researcher on itself so that the pilot wheels of the reticle are vertical and horizontal; to note that the image returned by the researcher is reversed right-hand side-left and haut-bas
Desserer slightly the adjustable tangent of latitude and more or less to incline the instrument to bring pole star on the horizontal brace
When the adjustment is satisfactory, definitively to tighten the screw of the axis of latitude; the adjustment obtained remains valid for any observation led later on on the same site or to the same latitude
Pivoter mounting (or the tripod) to bring pole star to the center of the reticle
Bloquer definitively the plate of mounting; in all the cases, to take care not to move the tripod

The brakes of the axes schedule and variation can be freed, the time axis is now parallel to the axis of rotation of the Earth. The rotation of the time axis follows the right ascension, and that of the axis of variation follows the variation.

The erection of mounting by this method offers a precision which generally does not exceed 2°.

See too

more precise Methods of erection:

Method of Bigourdan
Method of King

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