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Since today is 29th February, a leap-year-themed post is in order.  This one answers the question you’ve all been asking: how are leap years represented on astrolabes? First, a word about the Julian calendar.  Most astrolabes were made before the Gregorian calendar reform (1582), and that made life a bit simpler for instrument-makers.  In the Julian calendar, leap years happen every four years, without exception.  On the other hand, the Gregorian calendar got rid of 3 leap da

I submitted my PhD thesis last week (and now have a little more time to post on this blog).  In large part it’s a study of this fascinating instrument. If you've read this blog before, you'll know I've studied a 1950s replica of this equatorium, made my own replica - and then made it again in a smaller form and (slightly) more authentic materials. But until now, I’d never made an edible equatorium. I made the face out of chocolate shortbread (an adaptation of Jamie Oliver’s r

I’ve written a blog post entitled “How to cast a medieval horoscope” before.  But I didn’t tell the whole story. Regular readers of this blog (are there any?) will know that the main focus of my research is equatoria – devices designed to compute the positions of the Sun, Moon and planets.  I’ve made and used two of them – three if you count the fully functional virtual model which I helped create (though I can’t claim much of the credit – that goes to the amazing Ben Blundel

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 l

I wrote this post for the Peterhouse Perne and Ward Libraries blog.  It is cross-posted from there with their kind permission. 28 May saw the launch at the Whipple Museum of the online Peterhouse Manuscripts Collection, housed in the Cambridge Digital Library. The collection aims to present highlights from the College’s collection of 276 medieval manuscripts, and will be developed as time and funding allow. High-quality images are presented alongside searchable transcript

Regular readers of this blog (if there are any, I should apologise to them for my long silence) will be familiar with the story of King Arthur’s Table.  You won’t need me to remind you how I was lucky enough to discover this forgotten object in the stores of the Whipple Museum of the History of Science, and then spent much of 2013 investigating its biography. You’ll already know, I’m sure, that the story takes in Sir Lawrence Bragg, the Cavendish Laboratory and its workshops.

I was pleased to be able to speak at (and help organise) the Connecting with Collections Symposium a few weeks ago.  That event showcased some of the work that was done as part of the AHRC-funded Connecting with Collections internship scheme. The day went pretty well, I think.  For those that weren’t able to make it, I have put a recording of my presentation together with the slides I used, to create a lovely video which summarises the research I did during my internship.  I

I wrote this post for the blog of the 24th International Congress of History of Science, Technology and Medicine (iCHSTM), which takes place in Manchester on 21-28 July 2013.  Loyal readers of this blog won’t find much new here, but it’s a fair summary of my research so far. I have modified my views slightly since writing this, mainly about how sophisticated an astronomer the equatorium’s creator was, and how sure we can be about Schöner’s purposes.  I’m looking forward to di

I’m flying to Chicago on Wednesday.  There’ll be an unusual object in my luggage (is it wise to put that kind of statement online?).  Yes, you guessed it: it’s another equatorium. Loyal readers will remember my early series of posts (here, here and here) in which I described how I made, and learned to use, a medieval equatorium.  Although I am no great artist, I managed to create a passable replica of the instrument described in the manuscript I'm studying.  In the process

This post is cross-posted from the Connecting with Collections blog. I recently read a fascinating article about the early years of the discipline of history of science in Cambridge.  It was helpful to me in lots of ways but one idea the author, Anna-K Mayer, had was to examine various photographs of the key figures in that story – famous historians and scientists like Herbert Butterfield and Joseph Needham.  These men were public figures, and they took care over how they

This post is cross-posted from the Connecting with Collections blog. At the start of this project I was only hoping to find some documentation linked to the equatorium that Derek Price built – so I was amazed when I found the equatorium itself.  It’s now on display in the Whipple Museum for the History of Science (open Monday-Friday, 12.30-4.30; admission free). But I still haven’t found much of the documentation I was searching for in the first place.  I imagined I’d be ab

This post is cross-posted from the Connecting with Collections blog. Last Friday was a proud day, as the object I re-discovered and am now researching went on display at the Whipple Museum of the History of Science.  Here it is in its new home: The smaller model is the one I built (see my earlier posts for the full story).  We’re displaying both models as an example of research in the Museum, and the work of the Connecting with Collections project.  The glass panel will soo

This is a question I’ve been asked several times, and it’s a reasonable one given that this blog is called “Astrolabes and Stuff”, yet I’ve mainly been posting about equatoria.  So I’m going to answer it in this post. First, it’s important to stress the one thing astrolabes and equatoria have in common.  They are both tools, calculating devices.  As such, they simplify (and approximate) tasks that could have been done by geometrical calculation – but the astrolabe and equator

We all miss the Sun at this time of year, don’t we?  (Unless you’re reading this from Australia, I suppose.)  Luckily for you, this blog post will help you find it! In previous posts we’ve learned how to make and calibrate a planetary equatorium, and how to use it to find the longitude of the planets and Moon.  In my last equatorium post I mentioned latitude for the first time: unlike the planets, the Moon’s latitude matters because medieval astronomers were rather keen to be

Who's read Prisoners of the Sun?  In this enthralling Tintin story our hero is captured by a group of Inca who have survived in secret.  He and Captain Haddock are sentenced to be burned alive; their pyre is to be set alight by the rays of the sun.  Tintin is allowed to choose his time of death and cleverly picks the execution to coincide with a solar eclipse.  The amazed tribesmen believe he can command the sun god and immediately set him free. This trick is not entirely

*well, on a disc of MDF, anyway. Want to know how to find the moon?  Of course you do! So far on this blog I have constructed and calibrated a medieval planetary equatorium, and shown you how to use it to find the longitudes of the planets (most recently Mercury).  Now it’s the turn of the Moon. This will be a two-part post, because – unlike for the planets – our equatorium will not only tell us the longitude of the Moon, but also its latitude. Celestial longitude is measured

This week I’m back with my equatorium, trying to pin down precisely how well it models Ptolemy’s planetary theories (and, in turn, finding out the strengths and weaknesses of those theories in predicting the locations of the planets in the night sky).  Today it’s the turn of the Winged Messenger, Mercury. In my last “medieval craftsmanship” post I described the procedure for using the Equatorie of the Planetis to find the longitude of most planets.  I mentioned that the proce

[Drumroll] Ladies and gentlemen, I shall now demonstrate the use of a medieval planetary equatorium! In the first two posts in this series (here and here) I described how I made the physical structure of an equatorium according to the instructions in a fourteenth-century manuscript, and explained how I marked out the equatorium so that it could be used to find the location of the sun, the moon and the planets. (Technical point: skip this paragraph if you’re not interested.) 

In my first post I described how I began making an equatorium according to the instructions in the fourteenth-century manuscript I’m researching.  Since writing that post, I discovered a full-size replica made in the 1950s (you can read about that here).  Needless to say, that replica is far more attractive and probably more accurate than anything I can make at home with my saw and pencil, but I never said beauty or accuracy were priorities of mine.  So I went ahead with my o

I’ve just started a research project focusing on a medieval manuscript, The Equatorie of the Planetis.  This manuscript describes the construction and use of a curious astronomical instrument, and my previous post was about the first stages in my attempt to reconstruct that instrument, in order to better understand the manuscript. I’m still working on that, and will write all about the fun I had trying to divide a three-foot circle into 360 equal degrees very soon.  Before th