A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2010 Mar 29, 01:11 -0700
Hello to all,
Before we could start doing any reliable and conclusive "re-processing" of this wonderful page 174 of historical ASTRONOMICAL OBSERVATIONS, should we not get first a full understanding of all the data printed ?
This is what I have been able to figure out so far, with still some (BIG) questions unanswered yet.
Your answers, confirmations, corrections are highly desirable and your comments will be highly appreciated.
1 - We are to assume that all observations are supposed to be made on board a non-moving vessel and at the very same time.
2 - We are to assume also that all given Angles are "raw data" corrected only for Instrument error. i.e. all remaining corrections remain to be performed as applicable and as follows :
2.1 - All Distances (Column 3 ) are "refracted topocentric from Limb to Limb" (if Moon + Sun)" or - as the case may be - "refracted topocentric from Star/Planet to Moon's Limb". Accordingly if we use 'conventional/classical' clearing methods we are to transform such distances into "unrefracted geocentric from Center to Center" distances in order to compare such results to Maskelyne's tabular Lunar Distances, and
2.2 - All heights (Columns 4 and 5) should be corrected for all appreciable effects and in accordance with our well known standard height reduction corrections, i.e. :
2.2.1 - Dip. WHAT IS THE HEIGHT OF EYE ? , and
2.2.2 - Refraction. I can see that Temperatures are given in Column 9 but I fail to see any values given for Atmospheric Pressure, and
2.2.3 - As applicable, Parallax and Augmented Semi-diameter.
3 - FIRST COLUMN
3.1 - It gives the dates with codes for the names of week (Sun Figure for Sunday, Moon figure for Monday, ... ).
3.2 - Dates MIGHT possibly be local dates and not Greenwhich dates. This one is fairly simple to sort out with the help of the publihsed distances.
4 - THIRD COLUMN
4.1 - The 3rd column title should be construed as "Distance from Moon's Limb from Sun's (Limb) or Star (Limb)" . Everybody agrees here ?
4.2 - At the end of each Lunar Distance given in this 3 rd column, we can read :
- either 2 " + " signs on top of one another (such as 05 Jul, 02 Aug, and several other dates), or
- only one " + " sign (such as 12 Jul, 12 Aug and several other dates), or
- one " : " sign (such as 14 Aug) , or even
- no sign at all, (such as 25 Jul, 13 and 25 Aug, and 8 Sep).
What do these codes mean ?
Obviously they must be (somewhat) related to the use of either the Moon's Near Limb or the Moon's Far Limb in case of Planetary/Stars Observations.
But ... in the case of Sun-Moon Lunars, the Moon's Near Limb is to be used (always). Accordingly such Sun-Moon Distances should then all bear the VERY SAME code. HOWEVER I can see FOUR different such codes : either 2 " + " on 09 Jul, or just one " + " on 10 Jul for example, or just nothing on 25 Jul, or even a " : " sign on 14 Aug.
SO ... What is the exact meaning of all these codes ??? Some kind of reliability scale ??? If so, where are the (required) indications about Near/Far Limb in case of Star/Planetary Lunars ?then
5 - NINTH COLUMN
Temperatures are given here in Farenheit scale. Everybody agrees here ?
6 - Apparently missing data :
6.1 - HEIGHT OF EYE. Does anybody have any clue here (Wolgang ?)
6.2 - Atmospheric Pressure. Should we go "standard" 29.92"/1013.25 HPa/Mb ?
All your answers, confirmations and corrections are highly desirable and all your comments will be highly appreciated.
Again WARMEST THANKS TO WOLFGANG !
and Best Regards to you all,
Antoine M. "Kermit" Couëtte
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