Location by celestial navigation

Enjoy exploring this page location by celestial navigation, BUT ONLY AFTER COMPLETING the foundational La Rochelle exercise.

The main goal of these exercises is to calculate and understand how to calculate the line of position with the sun in daytime.

“La Rochelle”is the first in a series of eight identical exercises, each named after a major city in the world near the simulated sextant observations.

This page focuses on the Rotterdam exercise. You can find the others on the Celestial Course page.

While the La Rochelle exercise is for free, the answers for the remaining exercises can be bought in the store.

The accuracy of your estimated Dead Reckoning (D.R.) position directly influences the size of your intercept. If your D.R. position is well-estimated, your intercept will be minimal.

Conversely, if you haven’t observed the sun for several days, experienced varied weather conditions, and your intercept exceeds 30 minutes, it is advisable to reset and begin a new with a new Dead Reckoning position, as illustrated in the accompanying image below.

Location by celestial navigation, image of line of position with intercept more then 30 miles
If the intercept exceeds 30 miles, restart the calculation all over again from the closest point from dead reckoning position to the calculated line of position(new dead reckoning position). See image

Firstly, on this page Rotterdam you will find all the sextant sun sight observations required after taking a sun sight at sea off the coast of Rotterdam

The Euromast in winter Rotterdam (2015) author: AgainErick

Location by celestial navigation: start of the exercise Rotterdam

Location by celestial navigation Rotterdam, image calculator

print/download PDF worksheet or copy by hand


First part of the sheet of the sun sight observations

Location by celestial navigation Rotterdam worksheet with red entries

Firstly, start manually completing the red entries on this page.


Location by celestial navigation

Time UT and Date

Location by celestial navigation, image watch

DAY = Saturday; DATE = 11/06/2022; UT Time = 08:54:01


sextant height (Hs)

Location by celestial navigation Rotterdam image sextant height

lower limb


index error

Location by celestial navigation Rotterdam image sextant index error

Non adjustable error

Location by celestial navigation  Rotterdam inspection certificat of a sextant

eye height

Location by celestial navigation Rotterdam eye height picture

Dead reckoning position:

Latitude (L) :

52° 08′ North

Longitude (G) :

003° 54′ East


daily page

nautical almanac

Location by celestial navigation, image nautical almanac
11 june 2022

Also this daily page has been downloaded on the nauticalalmanac.it website with the kind permission of its author Capt. Roberto Iori




Hvanney lighthouse Bjorn.thorvaldsson.is

Location by celestial navigation Rotterdam:

The sea off the coast of Rotterdam

Indeed, the sea off the coast of Rotterdam, historically, has been part of the North Sea, a body of water that connects the Atlantic Ocean to Northwestern Europe.

In fact, in the 16th century, Rotterdam, a major port city in the Netherlands, played a significant role in maritime trade and commerce. The city’s strategic location facilitated trade routes and contributed to the economic growth of the region during the Age of Exploration.

The waters off the coast of Rotterdam would have been bustling with sailing vessels engaged in international trade, transporting goods such as spices, textiles, and raw materials.

The maritime activities during this period laid the foundation for Rotterdam’s future as one of the world’s largest and busiest ports. The sea off Rotterdam’s coast, like many other maritime regions, witnessed the dynamics of exploration, trade, and cultural exchange during this historical era.