Day 10-21

On wednesday the 11th I got a chance to try measuring the altitude of a few stars. Suitable for the time sight were Alpheratz and Betelgeuse since they were close to the center of the western and eastern sky respectively, and at an altitude high enough to disregard error due to refraction.

Without anything resembling a sight on my quadrant it was pretty difficult to align it reliably with the star. I began by taking the altitude of Polaris, and it was pretty exciting to get an error of less than half a degree.

I was less lucky with Alpheratz and Betelgeuse, consistently getting errors of about 1 degree. In the end, when I used my measured values in the calculation of my geographical position, I got an error in longitude of about 7 degrees. I ended up out in the ocean, rather than on land.

The two measured altitudes, of Polaris and of another star in the western or eastern sky, as well as the accuracy of the time of observation, all contain errors. These errors are amplified when the values are used multiple times in the same calculation. I noticed that you don't need a lot of error in altitude for it to make a big difference when it comes to the calculation of longtiude.