A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2014 Aug 23, 01:58 -0700
I was just messing around with my Astra in the backyard. A very large brown spider kept me company. In the absence of a nice, full moon, I was using the brighter stars to check my index error and adjust out that tiny bit of side error that I had skipped when I first received my sextant. I noticed that when I adjusted out the side error, the index error seemed to change from a consistent +1.7' to +1.0'. I had noticed the same phenomenon with my Davis plastic sextant. I assume this is a normal effect of the adjusting screws and is the reason that it is suggested one zero or check the index error as the last step. I did not zero the I.E.
Anway, I decided to try measuring some star to star distances for fun. I shot Vega-Deneb, Capella-Mirfak and Polaris-Schedar. Unfortunately, I didn't write anything down. I decided to use Stellarium to check my results as I went, even though I wasn't sure whether or not Stellarium displays the effects of refraction. But I had enough confidence in my own ability to figure it out. Once I started, I found all three measurements to be within 1.0' of what Stellarium displayed after I corrected for the +1.0' I.E. The Polaris-Schedar measurement was only 0.1' off. I used the "angle measuring" plug-in and froze the simulation at the time of each observation. I'd be interested to hear if anyone else could get the same results.