NavList:

I have been using the Anti-Spoof app to refine my sextant work.  Over time I have discovered several variables in shooting that I hadn't realized were so important.  I shoot usually from a spot at Rye Harbor on the NH coast, primaily because it is one of the few places I can see a south facing horizon, as well as to the east, generally.  

Yesterday I went down there and shot 19 Sun altitudes, taking particular care to get the temp/pressure right, the index error correct (recently determined the over/under sun tangent method), and height of eye.   On this board several years ago I posted a question about height of eye taken from a land position and found out I have to pay attention to tides.  Here the range is 9 feet or so, so I have to note the tide and make the adjustment for that as well.  

After all that, I graphed the results and two things surprised me.  That there was so much variability in my individual sights, despite paying particularly close attention.  Getting the "exact altitude" is harder than it looks!   But the other thing that I concluded was that I Anti-spoof is a great tool for helping hone shooting skills.  The averaged line looks like a good fit overall.  Is it?  

Jim Rives

43N 71W