wsmurdoch: The first time (the 10x40) I just bandsawed, filed and sanded a jaw-shaped thingy out of black Delrin (acetal) and epoxied it to the monocular (half of a Bushnell Falcon) The pictures show my second version. This is a 7x50 made from half of an Astra binocular which I found cheap
on e-bay. I chose it because the eyepieces are of the individual focus type, thus actually attached to the monocular body rather than to a focussing gadget mounted on the hinge assembly as in most binoculars -- this was a problem with the Bushnell 10x40 rig and I had to cobble a not very satisfactory attachment of the eyepiece to the frame. In both cases the binoculars were misaligned (the two views not superimposed) so I did not have any qualms about taking them apart.
So, the mount for the 7x50 was machined from 1/4" Al plate. First bandsawed to the outer shape a bit oversize, then I bored the inner diameter, to match the mono's outer diameter at the optimal attachment point, on my chinese 7"x10" lathe. Left an ear sticking out to attach to the sextant
frame like the original. A bandsaw cut parted the circular part that goes around the mono which was then re fastened with a pair of 2-56 SHCS. I got lucky and the fit was perfect.
A lathe is nice but not necessary -- you could do the bore with a hole saw, band saw or whatever and finish it up by hand filing.
The mating part on the sextant has a triangular groove to align with a similar ridge on the original ear or tang of most sextant monoculars. I did not have this on my 1/4" plate, of course, so made do with a pair of 2-56 set screws which protrude into the alignment groove the same way that the ridge of the original part would. Seems to work.
I much prefer the 7x50 to the 10x I started with -- better field of view, higher clarity -- it is and always has been the most recommended style for marine
use. The other half is now a very useful and handy monocular independent of the sextant. Incidentally, the hinge parts
of the original binoculars were just bandsawed off -- they were an integral part of the body casting, not separate attachments -- then filed down smooth and the bare exposed Al painted over.
The clock is from 'Formotion' originally intended for motorcycles. Its a quartz movement of course and the accuracy claimed is +-2 seconds in a year. I have been checking against GMT from GPS
for about a month now and it has never been more than a second or two off. I do wish it had a date function, as I always forget whether it's tomorrow or yesterday in England
It and the hardware
store level are just stuck on with double back foam tape. Not VHB, not yet anyway as I may want to change them some day and VHB (3M's super strong stuff) just will not let go.
The LED lighting
was simple enough using Radio
. I did paint
all the solder connections with cyanoacrylate to (hopefully) mitigate corrosion
And without the need for AA batteries in the hand grip I could indulge my taste for a new one, inspired by the grip I once saw on a Hammerli (?) match pistol. Just wrapped my hand around a chunk of walnut, drew around my fingers, then bandsawed, rasped, filed, sanded, oiled, varnished ... and so on.
And if you are wondering -- didn't all this hacking about knock the sextant hopelessly out of alignment and render it useless for evermore? First part, certainly, but re-alignment is not something to be terrified of. Dutton explains it well and any fool can do it provided sufficient patience.
I hope this helps and was not overly verbose.