Charles T Whitmell (1849-1919) was an Education Inspector by profession and also a member of the Leeds Astronomical Society. Nothing fascinated Whitmell so much as the observation of ‘extreme’ astronomical sights. Many of the published observations of the ‘green flash’ from the setting sun are due to him. He was also an avid observer of the young Moon. His account of a naked-eye observation of a thin lunar crescent in May 1916 makes an interesting comparison with what is thought to be the earliest feasible new moon sighting. As recently as the 1970s (and possibly well beyond) this 1916 observation was widely regarded as a naked eye record.

Charles T Whitmell

Charles T Whitmell

Whitmell reported that “from Scar­borough. in Yorkshire, about 8h p.m. (G.M.T,) on Tuesday, 2nd May 1916, the Moon was observed by Lizzie King and Nellie Collinson, two maids in the service of Mrs. Ackroyd, of 43, Westbourne Grove. I have been in correspondence with this lady, and wish to thank her for convincing evidence most courteously given. On the same evening, about 8h 15m, the crescent was also observed with the naked eye by Mrs. Willimott and her daughter, residing at Heighington in county Durham. Mrs. Willimott has also kindly replied to inquiries. We have thus the evidence of four persons. As might have been expected, atmospheric conditions were perfect …

It seemed to me exceedingly probable that a mistake of a day might have been made with regard to the observations at Scarborough and Heighington. But this was certainly not the case. Among other cir­cumstances which fixed the date as the 2nd May was the occurrence on the same night of a Zeppelin raid over Yorkshire … So far as I am aware, this Moon, 14½ hours old, is the youngest yet observed in England.”

A semi-theoretical limit to the earliest time after New Moon at which the lunar crescent can be observed was established by André Danjon (in an article published in the French magazine l’Astronomie in 1936: ‘Le Croissant Lunaire’, v.50, p.63). He derived a formula for the shortening of the cusps of the lunar cresent as its elongation (i.e. angular distance) from the sun diminished. The shortening effect was so pronounced at about 7 degrees (in geocentric terms – i.e. viewed from the centre of the Earth), that the sunlit crescent disappeared from view altogether.

At the time of the observation by the Scarborough maids (20h 00m UT), the altitude and azimuth of the Sun and Moon (as determined by the web-based almanac calculator of HM Nautical Almanac Office were:

Sun       303° 33Az, -3° 51Alt

Moon    302° 29Az, 3° 48Alt 

These are topocentric coordinates – i.e. they are the directions of the two celestial bodies as seen from a specific location on the Earth’s surface (namely, Scarborough, 0° 24′ 00″ W, 54° 17′ 00″ N).

 With a simple formula we can find the angular separation (A) of any two objects whose position is expressed in such spherical coordinates. If (a1, d1) and (a2, d2) are the two pairs of coordinates, the separation (or elongation), A, is given by:

cos A = sin d1 sin d2 + cos d1 cos d2 cos (a2-a1)

The result here is that A = 7.77 degrees. Recalculated in geocentric coordinates, the separation is approximately 8.45 degrees. In other words, pretty close to the Danjon limit of 7. 

The elongation  will not always be the same for a given age of Moon, since the orbital paths of the Earth and Moon are elliptical.

With the advent of modern imaging equipment and techniques, the crescent Moon has been photographed at much lesser elongations than the Danjon limit would suggest is possible.

For further information:

The story about Whitmell’s reporting of the 1916 observations and the significance of the Danjon limt can be read in The Astronomical Scrapbook: Skywatchers, Pioneers, and Seekers in Astronomy, by Joseph Ashbrook, Cambridge, 1984.

The Danjon limit of the first visibility of the lunar crescent, by Louay J.Fatoohi, F.Richard Stephenson and Shetha S. Al-Dargazelli (first published in the Observatory magazine) can be downloaded from the ADS website.

Astronomical Algorithms, by Jean Meeus, Willmann-Bell, 1991, pp.105-11 explains how to calculate angular separations.

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THE SEATON ROSS DIALER – William Watson (1784-1857)

Watson’s 12-foot diameter sundial on a cottage in Main Street, Seaton Ross

Watson’s 12-foot diameter sundial on a cottage in Main Street, Seaton Ross

William Watson was born into a farming family in the tiny Yorkshire village of Seaton Ross on 17th May 1784. William, along with all of his seven brothers in due course became a farmer in his own right. His three sisters, also, by marriage, entered into the same activity. In his later life William admitted that he had been “ne’re a Week out of Seaton”. He cannot have had anything but the most elementary education, yet this did not stop him acquiring some unusual skills. Alongside his farming activities, he managed to become a most accomplished surveyor and cartographer and was responsible for producing a number of accurate plans of villages, towns and landed estates in the Vale of York. He also learned how to design and set up sundials. An ability which he advertised in a piece of verse:
  I am a Farmer, which I tell,
  I also know Surveying well,
  Dials I’ve made many sorts,
  At School I did not learn these arts,
  Astronomer some do me call,
The original name of his house had been Common farm, but the farm became so ornamented with sundials that it gained the name Dial Hall. Not only did he make sundials for his own use, he eventually started to make a business of it. Dials by Watson began to appear on other build-ings.
He was fond of expressing his thoughts in – it must be said – rather mediocre verse. Hence,
  If any Person wants a Dial,
  Apply to me I’ll make a trial,
  I now can make for any man,
  Upon a much improved Plan,
  Five Guineas is the price of one,
  And each mile distant Half a Crown.
I assume that this advertising jingle is derived from his early dialling career and represents the price of a pretty limited range of product sizes. Perhaps the solar timepiece above the local church porch is the sort of thing he had in mind. Surely the price cannot have been intended to cover some of his later ‘monster’ productions.  The modern visitor to Seaton Ross cannot help being astonished by the Watson sundial, which adorns the entire façade of one house on the high street. This dial (pictured) is reputed to be the largest vertical sundial in Britain.
Watson was anxious to share his skills and, in due course, wrote a book on his passion: Dialling Diagrams with explanations, published in Pocklington by John Forth (2nd edition, 1854).

“At this Church I so often with pleasure did call, that I made a Sun Dial upon the Church wall” -Watson’s 1825 dial above the local church porch

“At this Church I so often with
pleasure did call,
that I made a Sun Dial upon the
Church wall”
-Watson’s 1825 dial above the
local church porch

For further information, refer to An Early Yorkshire Land Surveyor: William Watson of Seaton Ross, A.Harris, The Yorkshire Archaeological Journal, Volume 45 (1973), pp.149-157.
Note: the 12-foot Seaton Ross sundial is at OS map ref. SE776419

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In James Ferguson’s celebrated book, Astronomy Explained Upon Sir Isaac Newton’s Principles (1778), there is a table for the Equation of Time. It gives figures for how much a clock should be faster or slower than the Sun at different times of the year. Ferguson says that the table is ‘by Mr Smeaton’.
John Smeaton

John Smeaton

This is John Smeaton (1724-92), who is justly famed for the design and construction of the third Eddystone Lighthouse. Many of his great engineering works – mills, harbours, bridges and waterways – are still in use today. Smeaton was the archetypal civil engineer, as opposed to the previous mainly military engineers.

So, how did it come to pass that an arcane astronomical table should be provided by a civil engineer?
Although Smeaton’s later professional life was dominated by the civil engineering works for which he is still honoured, his election to the Royal Society at the age of 28 preceded any of these works and was the result of his earlier role as a maker of ‘philosophical instruments’. Throughout his life his ‘leisure’ hours were dominated by an intense interest in astronomical matters. Indeed, such matters were the only things allowed to occasionally impinge upon his engineering work. His daughter, Mary, recounted that “his time was governed by a method as invariable as inviolable: for professional studies were never broken in upon by any one; and these (with the exception of stated astronomical observations) wholly ingrossed the forenoon”.
John Smeaton was born at Austhorpe Lodge, in Whitkirk, East Leeds, on 8th June 1724 and lived there for much of his life. Unfortunately, the Lodge was demolished in the 1930s. Here we would have seen the the tower that he built, on top of which he made his astronomical observations. One floor lower was the design office for his professional work and at the base of the tower was the workshop, where many of his experiments were conducted and his instruments were fabricated.
Austhorpe Lodge

Austhorpe Lodge

Smeaton’s father had a legal practice in Leeds, but from an early age John seemed to drawn more to the profession of his grandfather, who had been a watchmaker of some renown in York. Already, by the time he left Leeds Grammar School at the age of 16 he had his own workshop. A distant cousin, visiting John two years later, reported that “in the year 1742, I spent a month at his father’s house, and being intended myself for mechanical employment, a few years younger than he was, I could not but view his works with astonishment; he forged his iron and steel, and melted his metal; he had tools of every sort … He had made a Lathe, by which he cut a perpetual screw in brass, a thing little known at that day, and which I believe was the invention of Mr Henry Hindley, of York …. Mr Hindley was a man of the most communicative disposition, a great lover of Mechanics, and of the most fertile genius. Mr Smeaton soon be-came acquainted with him, and they spent many a night at Mr Hindley’s house till day light, conversing on those subjects.”
The prominence given to the perpetual screw, mentioned in this account, perhaps owes something to Smeaton’s own estimation of its importance. This screw was essentially a precision worm gear for the careful adjustment of setting circles and arcs on astronomical instruments so as to achieve accurate measurements. The screw had an ‘hour-glass’ – rather than cylindrical – shape, which was calculated to reduce any play (or ‘drunkenness’) in the gearing. Its manufacture required a sophisticated dividing engine and Smeaton rightly saw such devices as being crucial for the advancement of astronomy.
Not long after his first acquaintance with Hindley, the young Smeaton was sent to London to commence a legal educa-tion – perhaps by parents who were becoming alarmed at their son’s bent for mechanical matters rather than more gentlemanly occupations. Within two years he returned, persuaded that legal circles were not for him. Whilst in London, however, he had met and formed crucial friendships with Benjamin Wilson and other Royal Society members and he continued a correspondence with them which frequently dealt with astronomy. Soon he resolved to make a profession out of building scientific instruments. This was to be a lifelong passion. By the age of 23 he had built his own telescope and had become, in his own estimation ‘quite an artist’ at grinding and polishing lenses.
In 1748, aged 26, with parental blessing, he departed once more for London to start his instrument building career. The first product of this endeavour was a vacuum pump that ended up being used (by Wilson and others) in electrical discharge experiments.
One of the next fruits of his industry was a marine compass (developed in collaboration with Dr Knight). Smeaton submitted a paper on this to the Royal Society in July 1750. Other high quality instruments followed – including a telescope for John Ellicott and a precision lathe for William Matthews. Around this time he also began his pioneering experiments on the power of water and wind. All in all, it was clear that, as well as being a formidable instrument builder, Smeaton was a first class scientist. In December 1752, he was proposed by Lord Charles Cavendish for membership of the Royal Society and in March 1753, with the support of James Short, William Watson, and others, he was duly elected.
Blue plaque near the Royal Armouries, Leeds

Blue plaque near the Royal Armouries, Leeds

Smeaton’s career now turned decisively to engineering. He put his hand to the design of water-mills, masonry bridges and drainage schemes. His scientific approach to these commissions – at once both analytical and experimental – made its mark with other fellows of the Royal Society. So much so, that when the lighthouse on the Eddystone Rock was destroyed by a storm in 1755, the President of the Royal Society (Lord Macclesfield) advised the owners that Smeaton – an engineer with no previous experience of lighthouse construction – was the ideal man to take charge of the design and building of a new one!
By October 1759 the new lighthouse – the third on the Eddystone Rock – was permanently operating and ultimately it became the archetypal symbol of civil engineering in Britain, featuring on the crest of the Institution of Civil Engineers. It also forms the centrepiece of the Smeaton memorial at Whitkirk Parish Church (see photograph).
Around 1760 Smeaton, his wife Ann, and their baby daughter moved back to Austhorpe Lodge in Leeds and set about its renovation.
The demand for Smeaton’s engineering skills continued to escalate and inevitably took up most of his time, but astronomical interests were not neglected.
In the May of 1768 two papers of Smeaton on astronomical topics were read to meetings of the Royal Society: The first concerned the gravitational influence of the Moon upon the Earth and its effect on apparent planetary positions at different stages of the lunar month; The second was on a method of accurately determining the position of a celestial body, using a transit telescope, even though the body was far away from the meridian.
On 4th June 1769, the day after he missed seeing the transit of Venus, due to clouds, Smeaton made careful measurements of a partial solar eclipse (magnitude 0.576) from his Austhorpe observatory, using a Dollond refractor and a micrometer.
Although he personally didn’t witness the Venus transit, Smeaton still managed to contribute to the international observing effort, for it was he who had designed the portable observatories for the purpose taken to Tahiti by Captain Cook and to Hudson’s Bay by William Wales and Joseph Dymond. Smeaton also designed fixed astronomical observatories for several sites in the UK: including Thorley Hall (Matthew Raper) and Deptford (Alexander Aubert). The current observatory in the Yorkshire Museum Gardens in York too is reputed to have been designed by him.
From Austhorpe, John Smeaton maintained regular correspondence with his scientific friends, including the Reverend John Michell of Thornhill, about twenty kilometres away, whom he sometimes visited. Michell is credited with first envisioning the existence of ‘black holes’ and with devising the experimental apparatus which allowed Cavendish to ‘weigh’ the Earth. Michell was also an ambitious telescope constructor and in this he received much encouragement from Smeaton, who visited his workshop and on occasion stayed at his house.
In the late 1780s Smeaton submitted further papers to the Royal Society on astronomical matters, the first being a masterly survey of the history of the graduation of scales on observing instruments. This formed the introduction to a detailed description of the method invented by his deceased friend, Henry Hindley.
The next paper concerned observations of Mercury at greatest elongation that Smeaton had made in the autumn of 1786, using an equatorial micrometer of his own design and construction. This was followed by a report describing a patented improvement (a ‘quadrant of altitude’) that he had devised for the celestial globe and how it could be used to solve problems of positional astronomy.
Memorial tablet at Whitkirk Church

Memorial tablet at Whitkirk Church

John Smeaton died on 28 October 1792, six weeks after having a stroke as he walked through his beloved garden at Austhorpe. according to his daughter, “He always apprehended the stroke, as it was hereditary in his family; he dreaded it only as it gave the melancholy possibility of out-living his faculties, or the power of doing good: to use his own words, ‘lingering over the dregs, after the spirit had evaporated!'”. Thankfully, however, his memory and intellect during his final weeks seemed to have been spared. “He would sometimes complain of his own slowness (as he called it) of apprehension, and then would excuse it with a smile, saying, ‘It could not be otherwise, the shadow must lengthen , as the sun went down!’ There was no slowness in fact to lament; for he was as ready at calculations, and as perspicuous in explanation, as at any former period….. The body gradually sunk, but the mind shone to the last.'”
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