Celestialism and logarithm tables

Celestialism and logarithm tables: This page serves as the intermediate section of the logarithm method proposed on this simple self-instruction website.

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.

See proposing an alternative approach to calculate your position at sea without the use of a scientific calculator, based on logarithm and azimuth tables

Celestialism and logarithm tables, text explanation of same name/not same name

SAME NAME/NOT SAME NAME is part of the logarithm method.In this part we do not use the rule of signs .

Author image: Alex Wigam

Celestialism and logarithm tables

L = latitude

D = Declination

how to calculate (L/D)

astronavigation and logarithm tables image  latitude and declination in worksheet
part of the worksheet for logarithm tables

See Blank worksheets for tables (DOWNLOAD PDF)

Author image: Raghav Veturi

Celestialism and logarithm tables:

Celestialism and logarithm tables: SAME NAME/NOT SAME NAME

L et D same name 

⟶ (L – D) or (D – L)               

The answer must always be positive

L et D not same name 

⟶ (L + D)

The answer must always be positive

Celestialism and logarithm tables:

Four examples with solution of same name / 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°

Terre-de-Bas aux Saintes W.I. Author image: Rémi Jouan

Celestialism and logarithm tables:

Explanation of the logarithms tables.

Also, the purpose is to calculate the height of the sun (Hc) without a calculator.

In fact, The use of logarithm tables will replace multiplication with addition.

Additionally, we will find an example and two exercises completed below. (the necessary pages of the tables included).

The idea is to continue with the concept of the DR position, and 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:


Furthermore, In principle, we adhere to the same Saint-Marc-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 necessary to obtain the calculated height (Hc)

  • Table 1: log cosine
  • Table 2: log versine
  • Table 3: natural cosine
  • Table 4: logarithms of whole numbers
  • Table 5: natural sine
astronavigation and logarithm tables les 5 tables de logarithm