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Frank Reed

''We can predict where the planets will be on the celestial sphere (relative to each other) for centuries into the future, but we cannot predict exactly what time it will be when each of those planets will cross some specific local observer's meridian''

Unless '' Je suis dans les patates'', a basic astrolabe can do that.

''You mentioned putting your lines of position and a fix on a "Mercator grid". It's not really "Mercator". The only grid required is "locally conformal" or 'longitude space scaled by cos(latitude) at the center of the grid. ''

I draw a rectangle of 1 degree of Lat (any latitude) vertically  and 1 degree of Long. horizontally.  If Long unit (grid)   = 1 , Latitude unit (grid) will always be secant of Lat.
We might be saying the same thing here.

''—FER''
(signed in my traditional style for a little inside joke... do "you" see it?)

What is this  ''little inside joke'' ? 
Thank you

''the least squares fix calculation in the back of the Nautical Almanac included since the late 1980s! ''

Would you believe that I have only a 1980 version..😢 If it is legal, could someone put this article here. I read a lot lately about this and I found something strange :
for example, on a 4 stars fix spread on a 20 minutes period, they don't seem to carry all the sights to the same time of one specific star , DR updated with course and speed of the ship.
If this is not done, of course, the fix will be a large triangle, especially at 25 knots...

Merci beaucoup pour votre temps ''Frank''😎