My initial frustrations with calibrating sextants caused me to come up with a variety of methods to use as a solution. The sea is too far away from me, but I do have an expanse of water nearby. This is Rutland Water, a man made reservoir. I had some success with using the horizon of the water but it meant driving a couple of miles and access was not always possible or free and there was the constant problem of fishermen not wanting to be disturbed. I eventually decided to make my own terrestrial range. Near me is a valley so I selected a suitable spot and landmark and set up a tripod to look for another target that was at zero elevation. I soon found one which I eventually measured at just over a kilometer away. I had a word with the farmers owning the targets, applied some white paint and was able to calibrate sextants to my hearts content. There were two small problems with this arrangement. Rain made life miserable and I had to use the car to get to the site.
With a view to a more comfortable and speedier calibration proceedure I decided to set up some targets on my radio tower and set up and surveyed a suitable mounting fixture in a shed which was already in use for sextant repairs. This works fine and I can always get a sextant within a few minutes from the comfort of the shed and either go out to my long range site or use some celestial object for final adjustment.
Over time I have made various items to tidy up my sextants. I usually make more than I think I need as the trouble with producing them can be best minimised by a production run, when I will spend a few days just making the same thing over and over. Sometimes because I can't get them right but in any case so I don't have to do the whole job again. Imagine the operations involved with making one bulb. Better I find, to do each operation fifty times and not visit the job again.
From time to time, and in the event of having to check calibration of a particular sextant, I will take a Meridian Transit of the Sun. I have, because of the weather, only done this in the Summer, I must see what sort of result I get in the winter. I use a surveyors tripod to hold the sextant steady and at a comfortable position. A radio controlled Alarm Clock with an easy to read digital display. and a note book and pencil. As I am still not skilled in reducing sights I use a laptop loaded with "Navigator" a really neat program available from http://www.tecepe.com.br/nav/ It can crunch all your numbers and amongst other things will supply daily pages from the Nautical Almanac. That feature alone makes it worth the purchase cost. I will take a photo of my set up next time I take a sight and in the mean time here is a view of one of the pages from my note book.
Ocasionally, I have to replace or remove bubble chamber lenses. Often I find that someone has been there first and ruined the soft alluminium ring either by stripping the slots or getting the whole ring cross threaded. Getting these rings out is not easy I discovered, even when heated to soften the shellack. I eventually came up with a device that would theoretically stop the tool from popping out of the ring slot and keep the ring at a right angle to the threaded hole.
Here is a photo of my ring removing tool.