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Re: Maskelyne and his "able computers"
From: Frank Reed CT
Date: 2004 Sep 22, 22:31 EDT
From: Frank Reed CT
Date: 2004 Sep 22, 22:31 EDT
Regarding the calculation of the lunar distance predictions in the almanac, George H wrote:
"Then these 3-hour Moon positions were converted to declination and right
ascension"
Although they did that anyway for other tables in the almanac, it was not strictly necessary for the lunars tables and really would have made the problem more difficult. Consider especially the case of Sun-Moon lunars tables. If you stay in ecliptic coordinates, the calculation is very short since the Sun's ecliptic latitude is zero. The lunar distance, LD, is calculated from the difference in ecliptic longitude and latitude using the simple rule
cos(LD) = cos(diff_longitude)*cos(diff_latitude)
With the stars and planets, the ecliptic latitudes are low enough that certain approximations can be applied which also reduce the task of computation. Rotating to RA and Dec would lengthen the calculations quite a bit.
And wrote:
"On one occasion the computers managed to identify each other and compared
notes in secret, which led to their instant dismissal."
If I remember correctly from the Croarken article which I described earlier, those two were later re-hired by Maskelyne. Their calculational skills were too valuable to ignore despite the cheating incident.
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
"Then these 3-hour Moon positions were converted to declination and right
ascension"
Although they did that anyway for other tables in the almanac, it was not strictly necessary for the lunars tables and really would have made the problem more difficult. Consider especially the case of Sun-Moon lunars tables. If you stay in ecliptic coordinates, the calculation is very short since the Sun's ecliptic latitude is zero. The lunar distance, LD, is calculated from the difference in ecliptic longitude and latitude using the simple rule
cos(LD) = cos(diff_longitude)*cos(diff_latitude)
With the stars and planets, the ecliptic latitudes are low enough that certain approximations can be applied which also reduce the task of computation. Rotating to RA and Dec would lengthen the calculations quite a bit.
And wrote:
"On one occasion the computers managed to identify each other and compared
notes in secret, which led to their instant dismissal."
If I remember correctly from the Croarken article which I described earlier, those two were later re-hired by Maskelyne. Their calculational skills were too valuable to ignore despite the cheating incident.
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
