Flo, a member of Young Producers, with an astrolabe by Hasan `Ali (Inv. 49861) kept in the Museum’s collection.

Flo, a member of Young Producers, discusses how we can discover the history of objects by examining their surface. 

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From Time-Turners in Harry Potter to Alethiometers in His Dark Materials, clever instruments with complex markings and shiny surfaces are great centre-pieces to stories of adventure and intrigue. I like to think that JK Rowling and Philip Pullman came to the Museum of the History of Science and were inspired by the astrolabes in the collection. And what better way to start this post than by talking about stories? I’ve chosen to talk about one particular astrolabe which has nearly eight hundred years of stories etched on its surface.

The remaining backplate of the astrolabe.

Just the backplate remains of the astrolabe (Inv. 49861) I am holding above (also pictured left). It was made in Egypt around 1282 AD. The object has an inscription saying it was made by Hasan ‘Ali in Cairo.

Astrolabes have many functions, but in short they are an instrument for solving problems relating to the positioning of the sun, moon and stars. An animation detailing the parts of an astrolabe and how it can be used to tell the time can be found on the Museum’s website.

Looking at the remaining backplate we can see that one side – the back – has various grids and inscriptions which give information to help with calculations. These calculations would use information gained by observations, which would be made using parts that are now missing. In addition to the scales on this plate, there are two tables, one is titled ‘Know the degree of the sun’ and the other is a table of Coptic Months.

A close-up of the two tables on the backplate.

However, this was much more than an ingenious scientific instrument. Each astrolabe in the Museum was almost certainly someone’s treasured possession. They were made of expensive materials and the scientific precision and artistry that went into their design and construction can’t have been cheap either. They are also, of course, beautiful. Our astrolabe is prominently signed and dated – Hasan ‘Ali wanted to be remembered as the artist.

Although only the backplate survives, the evidence is clear – this astrolabe was used extensively when it had all its parts. If you look closely, you can see the circular scrape and scratch marks where years of turning the outer parts have left their mark.

Without anything overlaying it, the backplate can’t be used for observations, and even the tables and grids inscribed on the back are just information that might as well have been written in a book. However, our astrolabe seems to have been kept and loved even when it was completely useless. Why?

Names of the zodiac houses can be seen inscribed between the almucantar lines.

When all of the other parts were lost – whether by accident or by deliberate removal – someone kept the backplate and continued to inscribe their appreciation and respect for this object into its surface. On very close inspection, it can be seen that Arabic script is scratched between the two outermost concentric circles at the centre of the backplate. These circles are almucantar lines, showing the position of the observer’s horizon at different altitudes, above which the stars are visible. The script is clearly scratched on by hand, and translates as the zodiac. This is not a useful position for the zodiac – typically it would have been inscribed around the rete, showing the (apparent) path of the sun’s movement across the sky over a year. Why would the owner need this after the other parts of the astrolabe were gone? Was it just a reminder so that it could be referred to? Or was there some other function which is now lost?

A close-up of the delicate, coin-sized fish attached to the astrolabe.

The edge of the backplate has holes that might originally have helped attach other parts. At some point, two of these holes have been used to attach delicate, coin-sized fish, made of a material that you wouldn’t normally find on an astrolabe: silver. Why are they there? Who knows? They are in line with the west and south markers that originally helped in observations (the cardinal points are the opposite way around to what we are used to today) – perhaps that has some relevance, or maybe it’s a coincidence. The northern fish rotates while the other is fixed – again, coincidental or intentional? We don’t know. Maybe they represent the zodiac symbol for Pisces – two fish, often attached with a line, though sometimes not. However, it is difficult to see any reason why Pisces alone should be represented here. Maybe – since people are people, even 800 years ago – the owner just liked fish.

The astrolabe can only give us glimpses of its probably rich and varied life – In a way the object poses more questions than it answers. Who owned it? Was it passed from hand to hand? How did it end up with the collector that eventually donated it to the Museum? We don’t know the answers to any of these questions. But I quite like that, don’t you? What is a story, after all, without mystery?