NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lewis and Clark lunars: more 1803 Almanac data
From: Frank Reed CT
Date: 2004 Apr 16, 16:44 EDT
From: Frank Reed CT
Date: 2004 Apr 16, 16:44 EDT
Ken M wrote:
"If we consider the two series with Aldebaran (A and C in your original message) as one series, then a least-squares fit gives an apparent motion of the moon of 0.239°/hr. The almanac data shows that the moon had an apparent motion with respect to Aldebaran of 0.534°/hr during that interval."
The rate in the almanac data is geocentric. You would have to calculate the apparent topocentric rate incorporating changing parallax and refraction in order to compare against the observed rate.
And:
"It's pretty hard to misidentify either Aldebaran or Rigel."
Although I don't think one can reach the conclusion that they misidentified their star *yet*, it is a real possibility. For anyone trained in celestial navigation in the past 75 years identifying the stars is part of the game. But back then it wasn't. Stars were rarely used by navigators in the 19th century *except* the nine lunars stars. Bowditch and other navigation manuals included little charts and descriptions for these stars and no others. Certainly many people learned the constellations for their own amusement, but those who did not would have a tough time picking out the right stars until they accumulated some serious experience.
Frank E. Reed
[ ] Mystic, Connecticut
[X] Chicago, Illinois
"If we consider the two series with Aldebaran (A and C in your original message) as one series, then a least-squares fit gives an apparent motion of the moon of 0.239°/hr. The almanac data shows that the moon had an apparent motion with respect to Aldebaran of 0.534°/hr during that interval."
The rate in the almanac data is geocentric. You would have to calculate the apparent topocentric rate incorporating changing parallax and refraction in order to compare against the observed rate.
And:
"It's pretty hard to misidentify either Aldebaran or Rigel."
Although I don't think one can reach the conclusion that they misidentified their star *yet*, it is a real possibility. For anyone trained in celestial navigation in the past 75 years identifying the stars is part of the game. But back then it wasn't. Stars were rarely used by navigators in the 19th century *except* the nine lunars stars. Bowditch and other navigation manuals included little charts and descriptions for these stars and no others. Certainly many people learned the constellations for their own amusement, but those who did not would have a tough time picking out the right stars until they accumulated some serious experience.
Frank E. Reed
[ ] Mystic, Connecticut
[X] Chicago, Illinois
