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All,
I've converted a few Davis sextants and older Astra IIIB sextants(bulb
illumination)to led illumination.
Here is what I use:
Hewlett Packard HLMP 2300-2500 series light bars.High intensity red light
only.You'll be useing the illumination at night so the red light will not
disrupt night vision as will white or clear light.
These are double led bars.Connect in series at 20 ma.Both diodes acts as a
drop resistor while on.No drop resistor used.Connected to existing switch
and the batteries(2 AA in series)internal to the handle.Replaced existing
wire with stranded Thermax 24 awg.
This gives a lot of light to read the measurement of the sextant.
On the Astra 2 2300 light bars in parrallel were used.Remove the existing
light guard remove the bulbs and wire,place one bar in each cut-out in the
guard.
On the Davis remove existing light and place as above.
More than enough light to read the instrument with.Robust in the real
world.Never had one burn out.Battery life extended compared to bulb systems.




Geoff, with conventional LED's and conventional battery voltages tehre are
many options and they are fairly simple. In fact there are a number of
places on the web that supply "LED replacements" for regular flashlight
bulbs, in the same form factor and case so they can just be dropped in as
replacements. Probably not in the tiny size found in sextants, yet.


 Good eyes and fine fingers may be needed though. If you have a
burned out Plath bulb, I could probably try converting it to a direct LED
replacement for you. The burned out bulb makes a very useful contact/mount
for the LED.

   

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