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Monitoring and measuring

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We are all in the gutter, but some of us are looking at the stars.
Oscar Wilde

Because of its location St Helena was chosen for many scientific observations

This page is in indexes: Island History, Island Place, Island Structures, Island Detail

Ladder Hill Observatory [Saint Helena Island Info:Observatories]
Ladder Hill Observatory

Below: AstronomersMagnetic Variations, Tides and WeatherLadder Hill ObservatoryLongwood ObservatoryOther Observatories


The first (recorded) person to come to St Helena specifically to make observations was Edmond Halley in 1677. Halley wanted to observe the stars of the Southern Hemisphere and chose St Helena primarily because it was, at the time, the only secure English territory south of the equator, but also because it was northerly enough for some Northern Hemisphere stars to be seen, thus linking the two hemispheres. Nevil Maskelyne and his party followed Halley in 1761 for similar reasons. Many other astronomers have chosen to make Southern Hemisphere observations from here, as listed on our Astronomy page.

Magnetic Variations, Tides and Weather

Also because of its location St Helena was popular in the 19th Century as a place to observe two phenomenon that had recently become of interest: variations in the earth’s magnetic field and tides:

  • Magnetic variation was thought to be potentially useful in establishing a ship’s position on the globe. The Earth’s magnetic field is not equal throughout the globe and it was supposed that, if the variations were charted, based on observations, and the local strength could be established, the ship’s position could be established. This had been in use by some navigators since the 16th Century and it was hoped that with more modern instruments a reliable system could be developed. Measurements made at St Helena, when compared with those taken by early Portuguese nivigators showed that the Earth’s magnetic field had shifted by some 30° in 250 years, a hitherto unknown phenomenon.

  • Tidal information was, of course, valuable to shipping, and it was hoped that a formula could be determined that would predict the tides at any given point on the planet before the area was actually visited.

Weather informtion is also of use to shipping, especially in the days of sail but even so today, which is why today we have an operating weather station on the island.

Ladder Hill Observatory

A formal observatory was commissioned by Governor Walker in the 1820s. Built at Ladder Hill{2}, next to Clifftop House just opposite the fort. Lieutenant Manuel Johnson of the St Helena Artillery was selected to take charge of it because he had showed such natural aptitude for astronomy. Indeed his ‘Catalogue of 606 principal fixed stars in the Southern Hemisphere’, based on his observations at St Helena, published by the East India Company in 1835 and awarded the Gold Medal of the Royal Astronomical Society, remains a standard work today. Curiously, Governor Walker’s motivation for setting up the observatory seems to have been to give the island’s troops something to do; looking at the stars (and other scientific activities) were better than getting drunk in the many island taverns!

The foundation stone for the observatory, which is now in the Castle, was laid on 13th September 1826, with the following inscription:

This astronomical observatory was founded in 1826 under the guidance of Alexander Walker

The observatory was completed in 1828, Johnson being in charge until he left St Helena in 1833.

Sadly when the Crown took over St Helena in 1834 sweeping cutbacks were made in island expenditure and on 29th February 1836 the observatory was closed due to its “uselessness and immense annual cost of £300{3}”, the crown commissioners{4} reporting that they had been “unable to learn its establishment had been attended with any important result to science”. Most of the instruments (deemed by the commissioners to be “of a superior description”) were sent to Canada, though the island’s Time Office did retain the clocks. The building was re-purposed as a mess hall for the fort, much to the disgust of visitor Mrs Gill who in 1878 wrote:

I say Observatory - alas! it is so no longer. Fallen from its high estate, it is now the artillery mess-room, and in the recesses formed for the shutters of the openings through which Johnson’s transit used to peep, they stow wineglasses and decanters, and under the dome they play billiards! I do not grudge the hospitable St Helena Mess their mess-room, but I do regret that so fine a site for an Observatory is vacant.

The Observatory ceased to be a mess hall when the Garrison was withdrawn in 1906 and thereafter was disused and fell into disrepair (see photo below), Philip Gosse reporting in 1938 that “half the roof has fallen in and in a few years it will be a complete ruin”. It was probably demolished in the early 1940s{5}, though a commemorative plaque was erected, initially on the site but later moved to the garden of Bleak House.

Interestingly, the last “instrument keeper”, a Mr Robert Ramage, founded one of the island’s first Friendly Societies, the Mechanics and Friendly Benefits Society in 1838.


Seen from the wharf, 19th C [Saint Helena Island Info:Observatories]
Seen from the wharf, 19thC

Situation with Clifftop House, 1860s [Saint Helena Island Info:Observatories]
Situation with Clifftop House, 1860s

Obervatory in disuse {1}, early 20th C? [Saint Helena Island Info:Observatories]
Obervatory in disuse{1}, early 20thC?

Longwood Observatory

An observatory was built in Longwood in February 1840. Longwood might seem an odd place to build a stellar observatory, given it’s notoriously wet climate, and so it would have been but the Longwood Obseratory was constucted to observe magnetic variations, not stars.

St Helena was chosen “as approximate to the point of least intensity of magnetic force on the globe”; Longwood was chosen because it has deep soil, thus reducing the effects of the rock on the magnetic readings.

The observatory also made meteorological observations. Activities continued there until 1849 when the equipment was dismantled and the building later became a hotel and is now St. Mark’s Church Hall. The church hall is still sometimes referred to as ‘Sabine’s Observatory’.

In charge of the observatory was Lieutenant-Colonel Edward Sabine, and in 1847 Sabine published ‘Observations made at the Magnetic and Meteorological Observatory at St Helena’ in several volumes. Apart from precise detailed descriptions of the instruments used, the majority of this work consists of around 600 pages of data tables for each year. In our layman’s opinion this may be the least interesting work in the history of literature, and hence we have not included it as a download, but if you really must read it (why?) it can be found on the Internet. We have included its two images below.

Sketch of the Longwood Observatory [Saint Helena Island Info:Observatories]
Sketch of the Longwood Observatory{a}

Longwood Observatory plans [Saint Helena Island Info:Observatories]
Longwood Observatory plans{a}

Longwood Observatory (St. Mark’s Church Hall), 1974 [Saint Helena Island Info:Observatories]
Longwood Observatory (St. Mark’s Church Hall), 1974

Other Observatories

There was also an observatory in Jamestown, located at Palm Villa, built by astronomer Johann Encke (Governor Janisch’s grandfather). It appears on the right in the old family photograph (below){6} and it is apparent from the visible telescope that this was a stellar, rather than a magnetic observatory (though it might have been both). We do not know when it was constructed or dismantled but the photograph is dated 1862.

There was a weather station at Hutt’s Gate from the end of the 19th Century until the 1966 when it was replaced by the current station at Bottom Woods. The Hutt’s Gate station replaced an earlier one at Oakbank (from 1902).

A ‘Dark Sky Observatory’ has been proposed as a possible feature if the SHELCO ‘Wirebird Hills’ resort complex is built at Broad Bottom, Blue Hill.

Finally the 1903 photograph (below), enigmatically captioned on the original print “‘Longitudes’ - a visit from the Cape Observatory” seems to show some sort of small telescope with operator. Not a grand building like the one at Ladder Hill we can see that it was little more than a tin shed, braced against the wind and presumably with some kind of removable roof to keep the rain off the instruments. We assume this was a temporary construction but have no idea where it was located.

Palm Villa, Jamestown, 1860s [Saint Helena Island Info:Observatories]
Palm Villa, Jamestown, 1860s

Temporary Observatory, 1903 [Saint Helena Island Info:Observatories]
Temporary Observatory, 1903

closinghumourimage [Saint Helena Island Info:Observatories]

Laugh at funny observatories humour - LOL [Saint Helena Island Info:Observatories]


{a} ‘Observations made at the Magnetic and Meteorological Observatory at St Helena’, Lieutenant-Colonel Edward Sabine, 1847.


{1} Note the failed roof to the east.

{2} A note in ‘Extracts from the records’ (Janisch, 1885) suggests the building might not have been new. The minute, from 24th October 1823, includes: “There can scarcely be a better situation than Ladder Hill for an Observatory and there is a building there (a tower) which at no great expense can be fitted up for the purpose”. However we believe this was a reference to the Round Tower, close to where the observatory was actually built but not part of it.


{4} Sent out by the Crown to assess the island and make recommendations on how it could be made to pay its way.

{5} It was still standing when the Viceroy of India visited in 1939 - it appears in the photographs - but does not appear in a 1943-4 photo set, so seems to have been demolished before 1943.

{6} Acoording to the description written on the original print this is the family of Governor Janisch. It is possible that the boy sitting on the step is actually a young Governor Janisch himself.


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