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Tony Ashmore


This section reviews 'Biographical Index of British Sundial Makers from the Seventh Century to 1920 (2nd Edition)' by Jill Wilson, praising its enhancements, new names, and comprehensive scope beyond simple indexing. It also reviews 'The Astrolabe' by James E. Morrison, highlighting it as a much-needed, comprehensive guide to astrolabe design, function, and construction.
Dials: Astrolabe, Book Reviews, Historical Dials

This fourth part of a series describes universal astrolabes, focusing on the Saphea, Rojas, and De la Hire projections. These instruments, developed from the 11th to 17th centuries, could be used at all latitudes, offering flexibility for astronomical and timekeeping purposes, despite the increasing complexity of their design.
Dials: Astrolabe, Historical Dials, How Sundials Work, Mathematics of Dialling

This part of the Astrolabes series covers instruments related to, but distinct from, planispheric astrolabes. It discusses the rare spherical and linear astrolabes, monumental and domestic astrolabe clocks, mariner's astrolabes (not true astrolabes), and various types of quadrants, including horary and astrolabe quadrants, detailing their history and use.
Dials: Astrolabe, Dialling Tools, Historical Dials, How Sundials Work

This section contains correspondence from readers. Chris Lusby Taylor discusses the use of Hooke’s joint for delineating declining and reclining dials, while Allan Mills replies regarding an error in a previous paper. Tony Ashmore suggests an interpretation for the 'Egyptian Face' design on a sundial pillar at Lord Tennyson's home, attributing it to Ptolemy.
Dials: Unusual, How Sundials Work, Mathematics of Dialling

This is the first part of a series introducing astrolabes, describing them as two-dimensional analogue computers for solving spherical trigonometric problems and finding time. It covers their history from Greek origins through Arab development to European decline, and explains the principles of their design including the rete and engraved plates for different latitudes.
Dials: Astrolabe, Historical Dials, How Sundials Work, Mathematics of Dialling

This second part details the characteristics and scales of European astrolabes. It covers the use of Latin script and numerals, simple throne designs (with some Flemish exceptions), and variable rete strapwork. The article also explains the zodiac/calendar scales, shadow squares for surveying, and three methods for determining unequal (planetary) hours found on these instruments.
Dials: Astrolabe, Historical Dials, How Sundials Work

This article, part three of a series, delves into Arabic astrolabes, noting their historical significance in Islamic cultures from before the tenth to the nineteenth century. It describes their general characteristics, such as the use of Arabic scripts, the absence of equal hour scales, and the prominence of astrological scales. It also details specific features like thrones, retes, plates, and scales on the back, including shadow squares and sine/cosine grids.
Dials: Astrolabe, Mathematics of Dialling, Historical Dials