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Bubble Sextant MK IX


This instrument is in a metal box with a slanted lid. Two metal latches hold the lid closed and near these there is a punched metal loop for hanging the instrument on a wall hook. On the rear of the box two more loops are attached. Also attached to the box there are the remnants of a leather strap, which is broken off at both ends where it was attached to the box. There is a white label in a metal surround on the box.

The interior of the box is lined with a grey-green rubbery/plastic material, which is badly decayed.

Inside the box there are metal supports for two long cylindrical pieces. One of these slots is occupied by board/wood cylinders.

The instruments is made of metal and has a black surface. It is roughly triangular in shape, with the sloped lid open cut open; inside, a slanted rectangular mirror is visible. On top of the instrument there is a domed transparent orange plastic window. On the front of the instrument there is a round eyepiece with a broad rubber rim, and below this a knurled knob with an arrow indicator one direction of turning, and two other buttons or switches.

On one side of the instrument there is a notched wheel, and a closed plastic cylinder mounted to one side, with a long handle or latch attached to the top. On the other side, there are a number of dials, switches and indicators, and another plastic cylinder; this one is cut with circular openings. On this side there is a white plastic sign divided into four blank sections, each with a different label.

Accession Number: 2019.ast.153

Alternative Name:

Primary Materials:

Metal: Iron Alloy, Plastics (various), Rubber


On the label on the box: “6B/151
H. H. & S. LTD (V)
SERIAL No. 4856/40 (V)

On a paper sticker stuck to the box: “Ast 59E”

Scratched into the box in large lettering: “McKAY”

Written on the box in red (crayon?): “5”

On the instrument: “A.M.
REF No. 6B/151
SERIAL No 4856/40 (V)”

On a sticker stuck below this: “UNIVERSITY OF TORONTO

On the other side of the instrument, “SERIAL No. 4856/40 (V)”

Dimensions (cm):

Box: Length = 24, Width = 20, Height = 18


The Bubble Sextant enables stellar navigation in situations where a standard sextant cannot be used as the horizon may not be level, as in an aircraft. The bubble creates an artificial horizon when the sextant is held correctly.


Poor: The box is scratched and marked across its surface and the leather handle has broken off at the base and is missing. Where tape has been affixed, a quantity of yellow glue/plastic residue remains.

The interior of the box is in poor condition: the grey-green spongey lining is dried, cracked and warped. Some of this has fallen in powdered form into the box.

The instrument is in fair condition. Its surface is in good condition with the paint/surfacing chipped off in places, particularly on the edges and protrusions. The rubber of the eyepiece is dried, cracked and extremely delicate; one piece has broken off and is loose in the box. No bubble is visible through the eyepiece. The white plastic permanent label is yellowed, dried, and warped.

Associated Instruments:


Henry Hughes & Son Ltd for the U.K. Air Ministry

Date of Manufacture: 1939-1945


The sextant was acquired by the Department of Astronomy or the David Dunlap Observatory sometime after 1945. This object was likely moved from the David Dunlap Observatory in Richmond Hill in 2008, upon the sale of the observatory. It was stored at the Department of Astronomy and Astrophysics until 2017, when it was moved to a new storage location in McLennan Physical Laboratories.

Additional Information and References:

Historical Notes: