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Monitoring and measuring

We are all in the gutter, but some of us are looking at the stars. {b}

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

Ladder Hill Observatory
Ladder Hill Observatory


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 page Astronomy.

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, namely variations in the earth’s magnetic field and tides:

Weather information 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. While he was there he gathered the necessary data to show that the star system Alpha Centauri is actually the closest to our own Solar System.

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, the crown commissioners{3} 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. Similarly in 1886 Rev. John Walker, writing in ‘St Helena as I saw it’, describes it as …long fallen into disuse.

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{4}, 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.

‍Longwood Observatory‍

An observatory was built in Longwood in February 1840. Longwood might seem an odd place to build a stellar observatory, given its notoriously wet climate, and so it would have been but the Longwood Observatory was constructed 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.

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){5} 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 Hutts Gate from the end of the 19th Century until the 1966 when it was replaced by the current station at Bottom Woods. The Hutts 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.

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Article: December’s Night Sky

For many years, from 1985 on Radio St Helena until his death in 2015, Stedson George published monthly in our local newspapers a description of what would be happening in our night sky that month. Choosing an example is impossible, so we have reproduced below his last contribution, from December 2014{6}

Apart from being the last month of the year, December is a very special month, since it hosts one of the most important days of the year - Natalis Solis Invistus - the Birthday of the Unconquered Sun. December 25th has been celebrated as the Sun’s Birthday for thousands of years by people in the northern hemisphere. Although the Sun reaches its furthest point south, the Tropic of Capricorn, on December 21st, its first northerly movement is not observable until around December 25th. This was a time of great rejoicing because after this date the Sun appeared a little higher in the Sky each day. So people celebrated this return of light by exchanging gifts, decorating their homes, and dancing in the streets - a custom still observed to this day, even in the Southern hemisphere. It was Pope Julius the First who proclaimed December 25th as Christmas Day in 350CE. By choosing this date as Christmas, it probably made it easier for early Christians - forced to worship in secret - to celebrate Christmas without attracting attention, since it was already a day of celebration.

December 2014 Night Sky

December is also the month of the Geminids. Earth ploughs through this stream of debris every December. The orbit of the Geminid stream resembles that of Asteroid 3200 Phaethon, which suggests that the debris came from this Asteroid. It therefore contains more rocky fragments along with dust particles so more bright meters are usually seen. Normally some 60 or more meteors can be expected at peak activity. The peak of the shower is expected to occur during the early hours of December 14th.

Because the meteors appear to radiate from the constellation Gemini they are called the Geminids. Gemini, with bright stars Castor and Pollux, rises over Flagstaff at around 11pm and will be quite high above the north eastern horizon well before dawn. Fortunately, the Moon is at Last Quarter that day, so conditions should be favourable before moonrise, if the sky is clear. So if you’re up late, or rise early on the 14th, look to the northeast for ‘shooting stars’.

As the winter constellations move to the west, the ‘summer constellation’ are rising in the east in late evening. The centre piece is Orion the Hunter with his quarry, Taurus, the Bull to the lower left. Further left is the Pleiades, or Seven Sisters.

Turning to the South two bright stars lie almost overhead. White Fomalhaut is the main star of an insignificant constellation called Piscis Austrinus (the Southern Fish). Achernar lies at the mouth of the long and straggling constellation of Eridanus (the River), Above Achernar is the constellation Phoenix and to the right of Phoenix is the constellation Grus. Below Achernar you will find the Large Magellanic Cloud - the nearest galaxy to our own Milky Way. Further to the right is the Small Magellanic Cloud.

Mars is still above the western horizon. Look for the crescent Moon above Mars on the 25th. Later in the month Jupiter will cross into the evening sky. The Moon will form a triangle with Jupiter and Regulas in Leo, the Lion, on the 11th. Look for the Moon below and to the left of the Pleiades star cluster on the evening of the 4th. Both Venus and Saturn will appear again this month. Venus will hang low in the evening sky, whilst Saturn will climb higher on the pre dawn sky. Look for the crescent Moon above and to the left of Saturn on the morning of the 19th.

Having passed directly overhead last month the Sun will reach its furthest point south, the tropic of Capricorn, on December 21st, the Summer Solstice. This marks the beginning of our Summer.

So until next month, clear sky and keep looking up
Stedson George


{a} The Historic Environment Record{b} Oscar Wilde


{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.{3} Sent out by the Crown to assess the island and make recommendations on how it could be made to pay its way.{4} 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.{5} According 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.{6} @@RepDis@@