A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2016 Dec 26, 12:56 -0800
Reference your last post, which I won’t repeat here, because it was rather long, I agree with everything you said. I was just trying to stick up for people who design chartlets. When I said ‘effectively similar to’, perhaps I should have said ‘kind of similar to’. In fact, my chartlet, which I’m working on at the moment for the astrovan, i.e. restricted to Lincolnshire, will look like a Mercator chart, work like a Mercator chart, but unfortunately won’t smell like a Mercator chart. Without a printing press and ink, I won’t be able to replicate the smell of a spanking new plotting chart straight from a drawer full of its brothers and sisters.
I want to be able to demonstrate the intercept method. So I need to be able to plot the kind of assumed positions necessary to use AP3270/HO249. That is, a whole degree of latitude and minutes of longitude to make a whole degree of LHA. I also want to include the outline shape of Lincolnshire, so that observers can get an idea just how accurate (or inaccurate) celestial can be. Therefore, I need a latitude line, 53N, and a longitude scale from about 0001.30W to 000.30E. The length of one minute of latitude on the chart will be scaled from one minute of longitude on the chartlet x secant 53.5degrees. I’ve been trying to construct this in ‘Draw’, but it’s very time consuming. I rather think I’ll end up snipping a bit out of a suitable chart and having it digitised if it’s not too pixley, a bit like below but better. That will form the top half of the sheet. On the bottom of the sheet will be a crib table for recording the relatively few values and corrections necessary for a static shot with an aircraft sextant. DaveP