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This is a small rectangular wooden box, unpainted except partly along the lid and one side in black. The lid lifts off. In the box, there are three slots cut into the wooden base. Two of these slots contain circular metal components. These consist of a circular metal rim 2.3cm in diameter with a hole 1.1cm in diameter in the centre. In this hole (although only surviving on the piece in the centre of the box) there is a pair of very thin filaments that cross at right angles in the centre of the circle. A tiny knurled knob allows adjustment of the filaments.

The components are held in place when the box lid is closed by a block of wood fixed to the lid of the box covered in a layer of green felt.

Accession Number: 2019.ast.203

Alternative Name: Crosswires for telescope

Primary Materials:

Wood, Metal: Copper Alloy (?), Glass? (filaments)


Handwritten on the lid of the box: In ink: “22”

In pencil: “Crosswires for viewing telescope 74″

Dimensions (cm):

Box: Length = 11, Width = 7.3, Height = 4.5


Crosswires are fitted to the eyepiece of a telescope and can be used in conjunction with an eyepiece to mark a precise point in the field of view. These appear to have been used with the 74″ David Dunlap Observatory telescope.


Good: The box is in good condition, although dirty from use. One of the crosswires is missing. One is broken, its filaments missing. The central crosswire is intact. The metal of the surrounds of the crosswires is dulled.

Associated Instruments:

Manufacturer: Hilger?

Date of Manufacture: Early-Mid 20th Century


From the time of its use, this object was kept at the David Dunlap Observatory until 2009 when upon the sale of the Observatory it was moved to the University of Toronto’s Department of Astronomy & Astrophysics at the St George Campus. In 2017 it was moved to a new storage location in McLennan Physical Laboratories.

Additional Information and References:

Historical Notes: