Note:  Do not rely on this information. It is very old.


Finder is a small telescope ranged parallel to every large one for the purpose of locating that portion of the field of view which it is desired to examine. The larger instrument takes in a smaller area, and therefore would require much moving about to locate an object. Beet by pointing the finder at this object, the telescope must also be directed towards it, for the two are kept parallel to each other. As the finder and the telescope are concentric, when the object viewed is at the centre of the finder (marked by intersecting lines), it must be within the field of view of the telescope.