How did an Italian astrolabe end up on the New Zealand passport?

A few years ago I enjoyed a blog post in which National Maritime Museum curator Rebekah Higgitt wrote about the "navigation" theme of the new New Zealand passport design.  Higgitt discussed the use of John Harrison's H1 clock as an illustration in the passport.  She also noted that the description on the New Zealand government website mentioned an astrolabe, which piqued my interest.  I tried to find out more, but the website didn't include pictures, and none of my Kiwi friends had new-style passports.

So I forgot about it... - until last week when a friend of mine was talking about the designs that have been proposed to replace the current NZ flag.  I took the opportunity to ask to see his passport, and bingo! Here it is:

I was intrigued by the distinctive design and decided to see if I could find similar astrolabes in any published museum collections.  It didn't take me very long to track down this one:

Image courtesy of Museum of the History of Science, University of Oxford

This is astrolabe 50257 at the Museum of the History of Science in Oxford.  You don't have to be an expert to spot the similarities.  But the question is, are those similarities remarkable? How unusual is this design?

To answer that question, let's go back to basics for a moment.  The similarity you notice - the dark pattern of rings, heart shape and so on - is the rete of the astrolabe.  It was made by cutting holes in a sheet of brass, so that it resembles a net (that's what rete means in Latin) or, as Chaucer thought, a spider's web.  It sits inside the mater of the astrolabe, and rotates around that big pin in the middle.  Each of the pointers on the rete marks a star, making the rete a moving star map, able to simulate the daily (apparent) motion of the heavens around the earth.

This overall layout, with the rete turning above a plate engraved with a grid of coordinates and a horizon for a particular latitude, is by far the most common form of an astrolabe.  The basic concept goes back to Ptolemy in the 2nd century CE, and the instrument had this settled form, with the mater, interchangeable plates for various latitudes, the rete and rule (which also moves, as you can see from its differing position in the two pictures above), by the time John Philoponus wrote a description of it in the early 6th century.

But that still left a lot of flexibility for individual designers and craftsmen.  They could choose which stars to include on their rete, but more noticeably, the supporting brass "net" could be almost any shape, as long as it included that smallish eccentric (off-centre) circle which is the ecliptic, mapping the Sun's annual progress through the zodiac.  Craftsmen expressed their flair through ingenious designs - a favourite trick, as you can see here, was to make the rete symmetrical, even though the stars obviously weren't.

As far as I know, this particular design of rete is unique.  Luckily the astrolabe itself has the name of its designer on the back: Giovanni Domenico Fecioli of Trento, in the far north of Italy.  We also have the name of the man who commissioned it: Giulio Cesare Luchino, of Bologna.  The latitude of Bologna is 44° 30', which matches the astrolabe's single latitude plate.  It's dated 1558, just when the popularity of astrolabes in Europe was at its peak.

Image courtesy Museum of the History of Science, Oxford

In technical terms there's nothing particularly remarkable about this astrolabe, but the design is an attractive one.  The illusion of interlocking circles at the bottom of the rete was a popular motif in that period - compare, for example, this one by the prolific Arsenius workshop in Louvain.  Arsenius was famous for his tulip-shaped designs (can you see the tulip?), and Fecioli's rete doesn't quite match the delicacy of Arsenius's intricate brasswork, but it's still beautiful, and I'm sure it was much prized (and proudly displayed) by Luchino.

I have no idea why the New Zealand government chose a Fecioli astrolabe as an illustration for their passports.  But it's worth saying a few words about the place of this instrument in the overall design scheme.

Here's what their website says about it:

The passport’s new design evolved from the concept of navigation and our evolution from a place of discovery, to a place of destination and follows the journeys of the earliest explorers of New Zealand through to the journeys made by Kiwis today. Themes of arrival and departure, navigation and time are represented figuratively and metaphorically throughout the passport.

And about pages 20-21 specifically:

The astrolabe and chart – the astrolabe is an astronomical instrument used by astronomers, navigators, and astrologers. Its many uses included: locating and predicting the positions of the sun, moon, planets and stars; determining local time using local longitude and vice-versa; surveying and triangulation. 

Of course the theme of navigation is perfect for a passport.  But the astrolabe's place in that theme is less certain.  It was a multifunctional compendium of astronomical and astrological functions, not particularly suited to use at sea.  It's true that the mariner's astrolabe was a popular navigational device (I made and tested one for a previous blog post), but that was a quite different instrument.  It's certainly highly unlikely that Fecioli's beautiful piece ever went offshore.

Even if it had, it could never have been used to determine longitude (or to predict the positions of the Moon or planets).  The relationship between longitude and time was well known in the age of the astrolabe, and astrolabes could certainly be used to find local time.  But longitude is a relative measurement (these days we measure it east or west of Greenwich); if you want to go from local time to local longitude, you also need to know the time at the reference point (e.g. Greenwich) from which you're measuring longitude.  Local time was easy to find, but when Fecioli made his astrolabe, a reliable, robust method of keeping reference time - a clock that could withstand ocean passages - was still 200 years away.

But local time itself is unattainable with the astrolabe pictured in the passport, because the designers have cut off the suspension ring and throne that attaches it to the mater.  The ring is crucial for sightings of the Sun or a star, because the astrolabe has to hang vertically.  Without it, the astrolabe is no longer an observational instrument.

That may seem like nitpicking, but it tells us something about the way astrolabes are (and were) seen.  They have always had symbolic value, representing astronomical knowledge as well as artistry and the owner's wealth and status.  Today in many museums they are presented as art objects, out of context and, often, supported from below rather then suspended by the ring (admittedly for sound preservation purposes).  They now seem to symbolise ancient, arcane knowledge, and this symbolic value trumps accuracy, much like the "save" icon in most computer programs is a 3.5" floppy disk, though you're unlikely to be storing your work on those any more.

Of course I don't mind that - I'm happy people find astrolabes evocative and attractive.  And, as I say, they've always had symbolic value.  But once in a while it's worth reminding ourselves of the specific contexts where, for a thousand years, they were also complex scientific objects with practical purposes.

Update, 25/08/2015: I wrote to the New Zealand Passport Office to see if I could find out more, and received a very friendly response.  The officer wrote: "I have spoken directly with some of those involved in the design process of the latest version of the New Zealand passport, which was produced in 2009 and the astrolabe design appears because it is a symbol for travel and a relatively complex shape. [...]
The specific astrolabe was not chosen for any particular reason except that it fit with the overall theme.  I was unable to ascertain whether the astrolabe featured in the book is the specific 16th century Italian you have identified but your analysis would suggest that it is the case.  Unfortunately I am not able to be more specific than that.  
Thank you very much for writing to us and I have noted with pleasure your compliment for our 'beautiful' passport."

String Theory - Medieval-style

Apologies for the long hiatus!  I've been busy with lots of things, among them the birth of my first child.  I'll post his horoscope here soon!  But first, here's a few thoughts I've been mulling over for a while...

My research centres on scientific instruments.  I study descriptions and images of them, attempt to follow the instructions to make and use them, examine the instruments themselves, and sometimes review or help curate exhibitions of them.  With all this, I spend a lot of time thinking about materials.

When we think about astrolabes, we tend to think of the shiny brass objects that are most common in museums.  Lots of attention has been paid to the kinds of metals that were used, and how they were shaped.  (Recent increases in the affordability of analytical technology means that this area is ripe for new discoveries - and I hope to blog soon about some research I've been involved in.)

But there are other materials too.  You don't have to think about this subject for very long to realise that the ornate astronomical instruments now on display in museums were probably not the same ones used for practical navigation at sea: sailors would have taken advantage of simpler designs and cheaper materials, principally wood.  Nor were they the same ones used for study in the new universities: teaching and learning took place with instruments made of parchment or paper.

Equatorium of Jupiter, from Peter Apian's
Astronomicum Caesareum (1540)

But one material is rarely mentioned in the scholarly literature: string.  This is despite the fact that it appears in many descriptions of instruments, and a good number of the surviving examples too.  The image on the right shows the equatorium for Jupiter, from Peter Apian's Astronomicum Caesareum (1540).  This sumptuous work, dedicated to Emperor Charles V, is hardly an ordinary equatorium treatise, but in its use of string it is entirely typical.

Before being incorporated into astronomical compendia like this, threads had been used for centuries in practical surveying instruments such as quadrants.  The easiest way to measure an angle, such as the height of a building, was via a plumb-bob (a lead weight hanging on a string) that could move over a circumference marked on a brass or wood quarter-circle (see the image below).

It's a small step from that to the use of threads as pointers, to read angles on scales on the circumference of more theoretical instruments.  It's easy to see why this step was taken: they were flexible, easy to attach, use and replace; they were narrow and thus relatively precise.  And crucially, of course, they were cheap.

Detail from British Library MS Burney 275, f.390v (early 14th century). The
bear and goat on the right are using a surveying quadrant with plumb-bob.

 How cheap? Of course that depended on what the threads were made of.  Sadly most instrument treatises are silent on the subject of what kind of string to use, where to find it and how to cut it.  So we have to assume that instrument makers used the cheapest thing they could find, or whatever was to hand.  This probably meant threads made of hemp or flax.


Unusually, though, the Equatorie of the Planetis (the manuscript that's the focus of my research) does talk about materials.  (One of the reasons I find it so fascinating is that it goes into many of the practical details that are absent from most medieval scientific treatises.)  It says:

Note that every centre [of each planet's equant circle] must be also small as a needle, and in every equant must be a silk thread.

Why silk? Was silk finer than other threads, and thus more precise? Was silk in this context meant metaphorically, and the writer really just wanted some very soft and flexible thread? Was it included to give a sense of luxury or importance to the astronomical work, as if only the finest materials were suitable for the tasks undertaken? Or is the whole thing a flight of fancy, in which the writer was indulging his imagination in describing an instrument that he had no intention of making?

I'm not sure, but I'd like to think there is a practical reason.  After all, the Equatorie of the Planetis design also includes a revolving metal pointer, which was the standard device used on astrolabes.  A metal pointer was needed on the brass epicycle because the radius of each of the planets needed to be marked at the appropriate point along its length.  But on the face of the equatorium, with an equant centre for each planet, something more manageable was required.  So we can see the designer of the equatorium choosing appropriate techniques and materials at each stage, with the clear goal of producing a user-friendly, effective planetary computer.

And what difference would a material other than silk, say flax, hemp or polypropylene, make?  I don't know, but I'm starting to think another reconstruction experiment is required!

Ships, Clocks & Stars

I recently visited, and very much enjoyed, the exhibition at the National Maritime Museum about the quest for longitude.  It's on until 4th January, and I highly recommend it.  I liked it so much I wrote a review of it for the Science Museum journal!

Touching, But What's the Point?

by Jenny Bulstrode

Astrolabes and Stuff is proud to present its first ever guest post!  For this we must thank Jenny Bulstrode, a student in the Department of History and Philosophy of Science at Cambridge.

Quadrants, sextants, octants, none of them really meant much to me until last year. They’re all descendants of astrolabes. They’re all based around a circle with a scale marked on it. They’re all just fans of metal with bits on. The only way I could see the Navy using one was as an elaborate bottle opener.

No, I'm still not sure what it is

If anyone asks all you generally need to know is this versatile bit of kit was a tool for measuring the angle between two distant objects. This made it handy for everything from telling the time to surveying.  Last year I found out a bit on how they were used but rather more on how one particular eighteenth century instrument maker, John Bird, made them, and why we should care. It’s these last two points I want to share with you.

‘Now use your hands to warm the metal.. except you Bob,
your hands are too clammy’ (not Bird’s original words)

Metal expands when heated. Enough to get the lid off that gherkin jar by running it under the hot tap, more than enough to mess up the precision process of marking a scale on a circle. John Bird used the warmth of his hands to standardise the expansion of his tools and the circle he was working on. As if that doesn’t seem odd enough, he then wrote about it, in his instruction manual.

Temperature control was so important Bird wouldn't allow a fire to warm the room. Even candles were forbidden because they gave out too much heat. (Actually my mum has a similar policy for controlling utility bills). With little light to work by Bird detected points and traced guideline scratches using his fingertips. Magnifying lenses were widely used by eighteenth century instrument makers, including Bird, but what he really had faith in was his sensitive touch.   

Almost as though fingertips were designed
to move tiny puncture marks in metal…

Finally, when checking back revealed a point slightly out of position, Bird would ‘coax’ it into place. Extraordinary as it sounds, through fingertip pressure on the brass, he would shuffle the point along. His fingertips worked to control, detect, and even correct the scale marking process.

All very touching (see what I did there?) but what’s the point? Three things stand out to me. Firstly, John Bird was one of the last circle dividers working exclusively by hand. Towards the end of his life new, automated machines started taking up the job. That’s the old story of mass-production taking over, right? Except for nearly a century after his death these ‘automated’ machines used handmade circles, including Bird’s, to cut copies from. The action of the machine had to be guided, by hand. In fact even when the machines made errors, which they did, often, the points were still ‘coaxed’ into place. Bird might’ve died but his hands were still very active...

Not a bomb, just a highly controlled loaf

Secondly, handmade does not just mean surprisingly expensive bread. Of course it means those elements of delicacy, care, and exclusivity we associate with a walnut and fig pavé but it can also mean industrial quality control. When Bird used his hands to control the expansion of the metal he was setting an industrial standard. Granted it was one based on his body temperature but the principle for control was the same.

Finally, and above all: Bird achieved an unprecedented level of precision in his instruments. In fact, he divided circles so precisely he was commissioned to make the Mural Arc at Greenwich. This Arc set the standard for British Mean Time. I think if there is a point to be taken from all this it is that a huge idea like ‘Time’ can be traced back, defined even, to something as human as the pressure of a man’s fingertip.

While instrument makers were busy constructing time with their hands,
Time the avatar went to all the good parties