NavList:

A couple of weeks ago, Ken and Alex were discussing whether it was common for navigators to observe or calculate altitudes and where this advice came from. In most cases that I have encountered involving actual navigation at sea, the altitudes were observed. And this is also what Bowditch and others recommend except in some unusual cases.

 

I have found one set of lunars tables with an explicit recommendation to calculate the altitudes instead of observing them. It's from Ward's "New Lunar Tables". In the instructions, which are dated 1823, Ward writes:

  "The most correct method of ascertaining the longitude by lunar observations, and indeed that which ought to be in general practice, is to dispense with the observations of the altitudes of the two objects, for they may be obtained with much greater accuracy by calculation than from observation."

He especially recommends this approach for an observer with no assistants.

 

I think these "nautical astronomers" (of the lunarian sort who considered themselves calculational experts) may have simply been too enamored of calculation and numerical gymnastics at the expense of efficient, error-resistant practice. I think it's obvious that Ward was way off the mark in his comments.

 

Incidentally, for the tables taxonomists, Ward's tables are in the same general category as Turner's and Thompson's (Bowditch III from 1837) which is to say that they are distilled series method, derived ultimately from Lyons' method, in which refraction and the quadratic corrections are combined together in a rather long, but relatively simple look-up table. These were popular methods.