GTLS used in Sestrel and Morin hand bearing compasses
Two examples of fine and effective use of tritium: the Sestrel handbearing compass, and the Opti-compas.
How is the tritium used, and; is it replaceable?
The Sestrel Handbearing compass:
For good reason the design hasn't changed in 70 years. The first decades they had C-batteries in the wooden handle and an incanbulb, later they got GTLS-capsule for lighting. The compass is still available, called ' Radiant ' from SIRS in the UK.
The tritium capsulee is mounted below the transparant compass card. The bearing is read from the prism, hold at arm-length from the eye. At that distance, the view in the prism is filled completely with the vial, and the contrasting lettering from the compass card. The tritium capsule can be replaced, it is accessable, clamped to a stem under the compass card. Compass-makers can supply or replace the capsule. Pictured example, is readable at night but would benefit replacement.
Very very few puck compasses have GTLS nowadays due to 'green' marketing and regulations. The Opti-compas was introduced in the seventys or eighties by compass maker Morin (France) and was also sold by Offshore Instruments (UK) named Mini-Compass.
All puck-style compasses nowadays are copy-cats from the early Morin one. The newer models often have an added prism in the design to enable reading the bearing from the top also, and mostly use GITD for lighting. (E.g. Plastimo Iris, Axium 2, Miron-2000, Vion Mini, Weems and Plath)
The old GTLS. Compass makers can still supply the light.
The original light was glued with a clear silicon glue. It looks like glass encapsulated paint, 3x9x1mm. The white holder would fit a 3x8 tube. The cilinder shaped void is 6mm deep and 11mm in diameter.
Got a betalight from www.beta-master.com, made a slot, mounted trit with hotmelt-glue, so its reversabel and can be replaced in 8 years or so.
Light from the GTLS underneath the compass card is read through the prism. Ready for another decade of use.
Mounted for form and function a sheet of glow-in-the-dark underneath.