NavList:

   

Reply

George H, you wrote:
"The moment of LAN is  delayed by 15.3 (tan lat - tan dec) * v where v is the
Southerly component of  the speed in knots."

That adds needless complication to an otherwise  extremely simple procedure.

And:
"It's worthwhile estimating in  advance what this correction is going to be,
and in which direction, because  what the observer is looking to measure is
the centre-of-symmetry of his plot  of observed altitude. His observation
period ought to be 20 to 30 minutes  before and after that moment of maximum
altitude."

Note that this  adjustment is totally unnecessary using the simple procedure
that I outlined  previously.

And:
"The whole object of the exercise is to discover the  moment of noon. So how
does the observer know how many minutes each plotted  point is away from
noon in order to calculate that adjustment?"

It  makes no difference. Whatever point in time is picked as the "zero"
point, where  no adjustment for northing/southing is made, will be the time of the
fix. Being  able to label the fix as "noon" is not terribly important but it
is nicely  traditional. The real time on it, of course, is a moment of  GMT.

"However, it looks to me as if an error in
that initial  presumption of noon would give rise to an error in the deduced
maximum  altitude, and so in the latitude. Perhaps Frank will comment."

Nope. No  error. See above. By the way, perhaps George could consider
addressing people in  the second person. Thanks in advance.

-FER
42.0N 87.7W, or 41.4N  72.1W.
www.HistoricalAtlas.com/lunars

   

Reply