Celestialism and logarithm tables: This page serves as the intermediate section of the logarithm method proposed on this simple self-instruction website.
Start with the Logarithme MAIN page — it forms the foundation of the “Logarithmic” menu and contains all related links. It will guide you back here when needed.
It offers the option to use logarithm tables instead of a calculator when going from a sextant observation to drawing the Line of Position (LOP) on your map.
The sole purpose of this page is to continue the concept of the estimated position and the intercept, as in the classical method using a scientific calculator, but without relying on the rule of signs (positive or negative).
The logarithmic method, on the other hand, does not use this rule: it is based on another principle — that of same name or not same name, which we will examine later.
same name / not same name
Celestialism and logarithm tables
how to calculate (L±D)
L = latitude
D = Declination
See Blank Worksheets for tables (DOWNLOAD PDF)
L and D same name
⟶ (L – D) or (D – L)
The answer must always be positive
L and D not same name
⟶ (L + D)
The answer must always be positive
Four examples with solutions of same name or not same name
L = 30° Nord; D = 12° Nord (same name)
1 ⟶ ( L – D ) = 18°
L = 13° Sud; D = 20° Sud (same name)
2 ⟶ ( D – L ) = 7°
L = 30° Nord; D = 12° Sud (not same name)
3 ⟶ ( L + D ) = 42°
L = 30° Sud; D = 12° Nord (not same name)
4 ⟶ (L + D ) = 42°
Celestialism and logarithm tables: explanation of the logarithm tables.
In addition, the purpose is to calculate the altitude of the sun (Hc) without a calculator.
In fact, the use of logarithm tables will replace multiplication with addition.
Additionally, you will find an example and two completed exercises in the main menu (see the link Alternative Approach of the Logarithm Tables at the start of this page).
The idea is to continue with the concept of the Dead Reckoning Position (DR) and the intercept, but we no longer use the Rule of Signs (positive or negative).
It will be replaced by the notion same name or not same name.
Celestialism and logarithm tables:
Method
Furthermore, in principle, we adhere to the same Marcq Saint-Hilaire method. Do not confuse it with the American HO 249 tables for aviation, which are based on different methods and are less precise.
On the other hand, these logarithm tables do not depend on time either.
Celestialism and logarithm tables: the five tables
The five tables required to obtain the calculated height (Hc) can be downloaded from the main logarithm menu page.
- Table 1: log cosine
- Table 2: log versine
- Table 3: natural cosine
- Table 4: logarithms of whole numbers
- Table 5: natural sine
