NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Table on Davis Quadrant
From: Nicolàs de Hilster
Date: 2007 Sep 22, 09:47 +0200
From: Nicolàs de Hilster
Date: 2007 Sep 22, 09:47 +0200
Dear group,
last week I got in contact with an owner of a Davis Quadrant. On the back of the large arc the following table is inscribed:
In simplified form we could change this into:
The table lacks an entry for 0.00, which would most probably have read L=100 and D=0. The figures in columns L and D can also be calculated using simple math:
L=COS(a*b)*100
D=SIN(a*b)*100
In above formulae 'a' stands for the value in the first column (so 0.25, 0.50, 0.75 etc) and 'b' is a constant. Using the least squares method I was able to calculate 'b' as 11.266, so the formulae used were:
L=COS(a*11.266)*100
D=SIN(a*11.266)*100
Question that remains is: what use was this table to a navigator?
Anyone any idea?
best regards,
Nicolàs
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
last week I got in contact with an owner of a Davis Quadrant. On the back of the large arc the following table is inscribed:
|
L |
D |
|
L |
D |
|
L |
D |
|
L |
D |
¼ |
100 |
5 |
1¼ |
97 |
24 |
2¼ |
90 |
43 |
3¼ |
80 |
60 |
½ |
99 |
10 |
1½ |
96 |
29 |
2½ |
88 |
47 |
3½ |
77 |
63 |
¾ |
99 |
15 |
1¾ |
94 |
34 |
2¾ |
86 |
51 |
3¾ |
74 |
67 |
1 |
98 |
20 |
2 |
92 |
38 |
3 |
83 |
56 |
4 |
71 |
71 |
In simplified form we could change this into:
L | D | |
0.25 | 100 | 5 |
0.50 | 99 | 10 |
0.75 | 99 | 15 |
1.00 | 98 | 20 |
1.25 | 97 | 24 |
1.50 | 96 | 29 |
1.75 | 94 | 34 |
2.00 | 92 | 38 |
2.25 | 90 | 43 |
2.50 | 88 | 47 |
2.75 | 86 | 51 |
3.00 | 83 | 56 |
3.25 | 80 | 60 |
3.50 | 77 | 63 |
3.75 | 74 | 67 |
4.00 | 71 | 71 |
The table lacks an entry for 0.00, which would most probably have read L=100 and D=0. The figures in columns L and D can also be calculated using simple math:
L=COS(a*b)*100
D=SIN(a*b)*100
In above formulae 'a' stands for the value in the first column (so 0.25, 0.50, 0.75 etc) and 'b' is a constant. Using the least squares method I was able to calculate 'b' as 11.266, so the formulae used were:
L=COS(a*11.266)*100
D=SIN(a*11.266)*100
Question that remains is: what use was this table to a navigator?
Anyone any idea?
best regards,
Nicolàs
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---