This is fairly simple, once you get the hang of it. I've made a simple scaled 'ruler' if you will, for a sextant which works on the same principle. As we cannot change the code I think that this will be the most efficient method.
It's a 'pullout' 'sextant'/ruler working very much te same as Jonz's Chrono (thanks Jonz I just adapted/copied your mod)
This is version1 (if you'd like to make changes - just shout)
I'm working on 1024x768(800) resolution I think it is, and found that with dials off I get a 60Deg elevation from sea level, which is neat. The higher res screen will come afterwards.
Here's top of the sextant - dragging it out...
Sextant referenced at sea level and a reading taken on Polaris (North Pole Star - Mouse cursor)
The scales are about 1 degree out so here goes another glass of red wine..
More later..