Stephen Johnston
@StephenHSM
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Curator Emeritus at Oxford's History of Science Museum; historian of science, technology and mathematics, particularly instruments and material culture.
Oxford, UK
Joined May 2011
Event for the @OCISOxford and @HSMOxford exhibition "Lines of Faith: Astronomy and the Art of the Astrolabe in the Islamic World": Joumana Medlej @joumajnouna leads a study day on Abjad numerals - Saturday 17 May. Full details at
eventbrite.co.uk
A hands-on afternoon led by renowned artist-scholar Joumana Medlej. Explore, learn and practise the Arabic Abjad numeral system.
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We are pleased to host an Open House for University of Oxford Freshers (undergraduate-level and graduate-level students) on Saturday, 30th November. To attend, please register by noon on Friday 29th November. Registration link: https://t.co/VZAtLmhlBk
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No time right now to look systematically, but perhaps double latitude plates with Regiomontanus (fixed equatorial) houses were more common than anyone could reasonably suppose? Here's another Indo-Persian example from @HSMOxford: https://t.co/8Zcs4kXOAS
#astrolabe #astrology
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The giveaway that these are Regiomontanus houses comes from the fact that the two sets of arcs all intersect on the equator - even though one is upside down compared to the other!
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New uses for @SchemeOfHeaven's online astrolabe: recreating an astrolabe plate from @HSMOxford: https://t.co/81DlQUxZ2w. The original might look more aesthetic than functional but its combination of "Regiomontanus" houses for 24° and 30° is revealed by my DIY photo editing.
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Banner became intolerable after an hour, so now it's from Jordan's edition of Stoeffler on the astrolabe - but focusing on the same spot
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@WhippleMuseum Little bit monochromatic, so catch the banner now, since I doubt it will stay long. (Especially if I'm issued with a cease and desist for publishing so commercially desirable a pair of images without permission.)
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New profile pic and banner image after an inspiring morning @WhippleMuseum with Josh Nall and a (reworked) medieval astrolabe - as well as a digital microscope.
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And I guess in the spirit of before and after we need to see the volvelle where it is now. The moral for today? Apparently some historians of science don't just write history, they change it – well, they certainly alter the historical record.....
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@DrKarrSchmidt He evidently discovered a misplaced volvelle #MovableMayhem at p. 231 and arranged for it to be moved to the right place elsewhere in the volume. The transfer was unambiguously documented by keeping a photocopy (photostat?) of the offending assemblage.
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Nice surprise the other day at the Whipple Library @hpslib to find myself in 50 year old footsteps. Opened up a box with a 1588 ed of Giovanni Paolo Gallucci, Theatrum mundi - to find Owen Gingerich had already been here.
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New #astrolabe feature: A "presentation mode" button (small gray triangle, upper-right). This lets you access the toggle switches at the bottom of the page without having to scroll away from the astrolabe. Thank you @StephenHSM for the suggestion! https://t.co/cnMkhgQKVL
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@SchemeOfHeaven Not that I only follow you for https://t.co/vBOfyGGkoQ and utterly identify you with it! (6/5)
alexboxer.com
Interactive astrolabe
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And (I’ve started so I’ll finish) what about a switch for the unequal hour lines? Would be great to demonstrate them in their traditional place on the plate – and handy as a prompt to introduce planetary hours. 🙏🙏🙏🙏 Pretty please? (5/5)
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So could there be two switches: one to turn on the sun and another for all the rest of the classical planets? That would make for a satisfying modern version of the historical instrument, while still enabling the cool equatorium extension. (4/5)
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Currently there is a single on/off switch for all 7 classical planets. When it’s on it creates a combined astrolabe-equatorium. But it would be great to also have the possibility of showing the classic astrolabe with only sun and stars. (3/5)
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Two things would be invaluable for an astrolabe demonstration I’m doing at an online workshop “When the Stars Tell Time” in early July. (2/5)
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Returning to my online #astrolabe after several years to add Regiomontanus and Alchabitius cusps. Have to remind myself how these are defined. I take Regiomontanus' Tabulæ Directionum, Prob. 14 as my guide. Should have results soon. @StephenHSM @Seb_Falk
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How to study astrolabes? A computerized checklist to try and track down all known examples - 1973 style. Amazing achievement, and what an interface! (by Sharon Gibbs, Janice Henderson, Derek de Solla Price)
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