Next message: Frank Reed: "Side error etc (Re: Beginner)"
Bill you wrote:
" The *really* nice three-arm-protractors like Alex's Soviet unit can be
dialed in to 0.1' if I
recall, so would demand input of equal precision and accuracy for optimal
results. "
An angle of 1 minute of arc is (and I do mean *IS*) a ratio of 1 to 3438
(10,800/pi to be exact). So an angle of 0.1 minutes of arc is a ratio of 1 to
about 34,000. The distance "across" the object(s) and the distance "out" to the
object(s) are in a ratio of 1 to 34,000 when the angle is 0.1 minutes of
arc. Given that, is there any chance that this tiny angle could be meaningful
in plotting with a three-arm protractor?? Assuming that the chart itself is,
let's say, one meter across, if I extend a line all the way across the chart
and shift the end-point by 1 millimeter, I'm making an angular shift of only
1/1000 or in other words about 3 minutes of arc. No horizontal angle (as
between buoys) would ever need to be measured to an accuracy better than this for
live navigation.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
