Stephen Johnston

Stephen Johnston

@stephenaj.bsky.social

Curator Emeritus at Oxford's History of Science Museum, with interests in instruments and material culture. Current research focus on armillary spheres and astrolabes in medieval Europe. (Disclaimer: focus known to wander.)

459 followers175 following566 posts

Stephen Johnston
@stephenaj.bsky.social

It's part of Peter Heering and Roland Wittje's Objects of Understanding: Historical Perspectives on Material Artefacts and Practices in Science Education - the proceedings of a COVID-delayed conference. (When the rearranged meeting finally happened I couldn't go!) biblioscout.net/en/book/10.2...

biblioscout.netObjects of Understanding“Objects of Understanding” brings together studies of artifacts, collections, and practices in science education from the early 18th century to co...
Stephen Johnston
@stephenaj.bsky.social

Haha - how wrong I was!

Stephen Johnston@stephenaj.bsky.social

Setting aside my unspeakable jealousy of Belgian skies, it was actually pretty dramatic suddenly having slivers of sun reappear - a story that kept unfolding. But the sun's now disappeared into the haze towards the horizon and I don't think we'll see any more now...

Stephen Johnston reposted

DLR-next
@dlr-next.bsky.social

Weil es so kompliziert ist, hier nochmal eine unserer aufwendigen Visualisierungen, die (natürlich nur stark vereinfacht) den Unterschied zwischen einer partiellen und einer totalen Sonnenfinsternis zeigt.

View full thread
Stephen Johnston
@stephenaj.bsky.social

The marks are not adjacent - hopefully they can be spotted here on the back of the rete. Each is placed near a particular star pointer. Could they be associated with the stars ALFERAZ (Alpheratz) and WEGA (Vega)? But why hide them out of sight on the back? Questions, questions.... 4/4

Stephen Johnston
@stephenaj.bsky.social

A couple of marks on the back of the rete had already been recorded. But I wasn't expecting such a clearly defined character as this. It certainly seems purposive and even expressive. Is it a maker's personal mark? If not, what else might it be? 2/4

Stephen Johnston
@stephenaj.bsky.social

If everything goes according to plan, there will be an article in the December issue of the Bulletin of the Scientific Instrument Society. As you'll see, the qualified "newness" of the find isn't just because it's an old object. It was described 70 years ago when sold at a London auction. 1/2

David ALBERTO@astrolabe-science.fr

Just finished reading your blog post. Very exciting find! Eager to learn more about this object.

Stephen Johnston
@stephenaj.bsky.social

That's what I tracked down 6 months ago, just before heading out to Florida (bsky.app/profile/step...). And there have been further twists and turns since then - so that while the SIS article will be about the object, it will also focus on its meaning and use for display in 1950s and '60s Florida.

Stephen Johnston@stephenaj.bsky.social

Visiting to see a specific auction catalogue ahead of a #TopSecret mission later this month. So, for now, all I can say is: check out the switch for the reader lamp in the background - maybe it's actually older than this set of all the Sotheby's London sale catalogues from May 1957?!

Stephen Johnston
@stephenaj.bsky.social

For all those dropping everything to attend this seminar tomorrow, there's now a new, simplified link from @luiscamposribeiro.bsky.social: us02web.zoom.us/j/82936830101 See you there!

Barbara Bienias@bbienias.bsky.social

I hope you might be interested in my talk on Henry Coley and his astrological notebooks this Wed (1 July) at 6 pm Lisbon time. Zoom link/QR code is in the poster below. #earlymodernsky #astrology #almanacs #historyofscience #manuscripts #helenaavelarseminar

Stephen Johnston
@stephenaj.bsky.social

Another edition of the excellent Coffee with a Codex series - this time playing away from home with a new acquisition in upstate New York (www.rit.edu/carycollecti...). The live timing was perfect for a viewing party at GHA 2026 eida.hypotheses.org/seminars-2/2....

Schoenberg Institute for Manuscript Studies@sims-mss.bsky.social

If you missed our visit with Rochester Institute of Technology's Cary Collection 15th century Italian copy of Johannes de Sacrobosco's De Sphera Mundi (bound with two other texts) you can watch it now! It has some unusual diagrams that are worth seeing. youtu.be/FSyZjp5Fm4g

youtu.beCoffee with a Codex: Astronomy Manuscript in Rochester, NYYouTube video by SchoenbergInstitute
Stephen Johnston
@stephenaj.bsky.social

Stay to the end and you can hear yours truly almost falling off my chair at the extraordinary armillary sphere images in this C15 Italian Sacrobosco MS - which, thanks to Cary Collection staff, now has a significant role in my chapter for the EIDA project's collective volume (eida.hypotheses.org)

eida.hypotheses.orgHomeEIDA is an ANR PRC project (ANR-22-CE38-0014) that was awarded during the 2022 session. The project aims at developing a new critique of astronomical diagrams of the 8th-18th centuries found in Chines...
Stephen Johnston
@stephenaj.bsky.social

Being back in Paris meant another chance to visit the Réserves of the @museeartsetmetiers.bsky.social in St Denis. This time I was able to take a microscope to document this astrolabe - thought to be (at least partly) from the workshop of Regiomontanus.

Stephen Johnston@stephenaj.bsky.social

This was a first reconnaissance visit. The exceptional instruments will need further study. Among them an astrolabe from the workshop of Regiomontanus, whose replacement horse was wedged in so tightly that we could not open it. 17/25

Stephen Johnston
@stephenaj.bsky.social

And who knew? A handcrafted 15th-century emoji from the retaining tab of one of the latitude plates! (Those punched zeros and single scratch mark are actually meaningful in the context of this astrolabe - it just so happens that they speak to C21 visual culture rather more cutely....)

Stephen Johnston
@stephenaj.bsky.social

On Monday I get to present with some of the small but incredible collection of @labnf.bsky.social. It's extremely cool to begin a hands-on session by saying "This 11th-century celestial globe is one of the two oldest surviving Islamicate examples in the world." gallica.bnf.fr/ark:/12148/b...

Stephen Johnston@stephenaj.bsky.social

Looking forward to welcoming the new cohort of international students in Paris on Monday. And also very conscious of all the hard work behind the scenes to run this marvellous approach to the astral sciences again, this time with a new focus. Hats off to the core team for their organising efforts!

Stephen Johnston
@stephenaj.bsky.social

Looking forward to welcoming the new cohort of international students in Paris on Monday. And also very conscious of all the hard work behind the scenes to run this marvellous approach to the astral sciences again, this time with a new focus. Hats off to the core team for their organising efforts!

COSMOPOET@cosmopoet.bsky.social

Starting on Monday we will be teaching the history of the astral sciences on a global scale with the historical sources themselves: manuscripts, prints, globes, astrolabes - thanks to @labnf.bsky.social and @obs-paris-psl.bsky.social for hosting us!! ✨✨ eida.hypotheses.org/seminars-2/2... #histsci

eida.hypotheses.org2026-Training week: Global history of astronomy week on primary sources A focus on cosmology, physics and astrologyorg.: Eleonora Andriani, Christian Förstel, Victor Gysembergh, Catherine Hofmann, Matthieu Husson, Anuj Misra, Han Qi, Stephen Johnston, Agathe Keller, Romain Lefebvre, Guillaume Loizelet, Divna Manol...
Stephen Johnston
@stephenaj.bsky.social

On this day in 1583.... (makes a great change from following the news in 2026)

Neil Younger@neilayounger.bsky.social

In London, Bartholomew Newsam, clock-keeper to the queen, receives a payment of 32s 8d for 'mending of clocks during the past year.' This clock, belonging to the British Museum, is an example of his work. 5/

Stephen Johnston
@stephenaj.bsky.social

Astrolabes, astrological rolls and maps, among other goodies, all available online next Monday and Tuesday

COSMOPOET@cosmopoet.bsky.social

📣The collaboration between @obs-paris-psl.bsky.social and @csmc-hamburg.bsky.social continues with the second workshop dedicated to the spatio-temporal profile of multigraphic written artefacts: 18–19 May 2026, Paris, at Observatoire de Paris and online. 🤩

Stephen Johnston reposted

COSMOPOET
@cosmopoet.bsky.social

This week dedicated to #diagrams is now over, but the work continues towards the publication of our results and the next phase in the life of the #EIDA community. Huge thanks to @obs-paris-psl.bsky.social for hosting us and for sharing it's beautiful secrets with us! #msca #histsci

Stephen Johnston
@stephenaj.bsky.social

Is that first one the dials of Gonville and Caius College? Or am I overanticipating my own visit there on Tuesday?

COSMOPOET@cosmopoet.bsky.social

This week Cosmopoet is in sunny 🌞 (no joke!) Cambridge and there are clocks all around: some eat time, while others are on a diet ☺️

Stephen Johnston
@stephenaj.bsky.social

Astrology and the writing of history, addressed in a chunky 512 pages, and with an intriguing cover image too (a celestial planisphere from some sort of architectural setting? Will have to get the book to find out....)

This post is unavailable.
Stephen Johnston
@stephenaj.bsky.social

... and diagrams that were assembled and bound separately from a written text that they must have accompanied. But did Rossetti publish such an astronomical work? Not sure. (But his fortification book has images that remind me of fractals and the en.wikipedia.org/wiki/Mandelb... !)

Divna Manolova@dulila.bsky.social

Thinking of diagrams: www.youtube.com/watch?v=KeLU...

youtube.comPenn Library's LJS 175 - Figure de sistemi del mondo d'Aristotile, Copernico... (Video Orientation)YouTube video by SchoenbergInstitute
Stephen Johnston
@stephenaj.bsky.social

Visiting to see a specific auction catalogue ahead of a #TopSecret mission later this month. So, for now, all I can say is: check out the switch for the reader lamp in the background - maybe it's actually older than this set of all the Sotheby's London sale catalogues from May 1957?!

Stephen Johnston
@stephenaj.bsky.social

Can't resist adding: turns out that the NAL also has a separate copy of the sale catalogue, which is bound with the list of prices and buyers that was printed after the sale. Yes, you even got to see who bought things back in those days! (Though you had to pay for the privilege by subscribing....)

Stephen Johnston
@stephenaj.bsky.social

I loved the image at first sight but couldn't immediately fathom how it was created. Now there is a wonderfully clear thread to explain the kit and process, with the bonus of a hi-res zoomable version at the end. Hmm, could I print out a large version to go on the wall? (Or a backlit transparency?!)

Cees Bassa@cbassa.bsky.social

Since posting this 2025 year-long keogram, there have been quite a few questions asking how it was created and what is visible. In this thread I'll try to explain how it all works.

Stephen Johnston reposted

Cees Bassa
@cbassa.bsky.social

Happy new year! My all sky camera imaged the sky every 15 seconds and this picture shows what happened in the sky in 2025. It shows the length of the night and day with the hourglass shape, the monthly lunar cycle with the diagonal bands, the elevation of the Sun at local noon, and lots of clouds.

Stephen Johnston
@stephenaj.bsky.social

As the other external committee member with @eleonoraandriani.bsky.social I'm also hugely looking forward to the results of this doctoral project over the next few years - it will be genuinely fascinating to see the Escorial manuscript deeply investigated and fully unveiled.

Eleonora Andriani @eleonoraandriani.bsky.social

Honoured to be part of the doctoral committee for this project at Hasselt University. Read more here: www.uhasselt.be/nl/over-uhas... #historyofastronomy #historyofscience

Stephen Johnston
@stephenaj.bsky.social

Strictly local #Oxford interest, but can't help blurting out #Bodleian news. After at least 40 years of using the central library, and restricted to reading onsite, I've just collected a couple of books which I am about to walk out the door with. A loan, but feels like I'll be apprehended for theft!