Repairing the connecting ring

Macdonnell’s refractor carries a finder telescope, which sits adjacent to the viewing end. It is used to locate a celestial object and set the position of the main telescope. The tube of the finder telescope was present when the Museum acquired the refractor, and the finder eyepiece was eventually identified in a box of parts, but the connecting ring used to join the two was missing. This ring contains adjustable crosswires that allow the astronomer to centre an object under observation in the telescope’s lens.

A new brass connecting ring was made and two new crosswires fixed in place. Originally, these ‘wires’ would have been made of spider web, but the conservation team used very fine horsehair, which was much less fragile.