Halley’s Zodiacus Stellatus

By HALLEY, Edmond; John SENEX, 1763 

Zodiacus Stellatus Fixas omnes Hactenus cognitas ad quas lunae appulsus ullibi terrarum telescopio observari potrunt complexus.

  • Author: HALLEY, Edmond; John SENEX
  • Publication place: London
  • Publisher: Printed for John Bowles, Robert Sayer, and Carrington Bowles
  • Publication date: c1768
  • Physical description: Large folio (670 by 420 mm), engraved charts on two sheets, quarter buckram, red marbled paper wrappers, a few nicks and tears.
  • Dimensions: (each plate) 550 by 670mm (21.75 by 26.5 inches).
  • Inventory reference: 20188


Senex’s Zodiacus Stellatus’ was first published in 1718. A catalogue issued in that year records Just Finish’d. 1. A New and Exact Map of the Zodiack on two Imperial Sheets, wherein the Stars are laid down from the best and latest Observations, together with an Explanation of its Uses both in Astronomy, and for Determining the Longitude at Sea”, but the first appearance can be narrowed down from two advertisements placed in the Post Boy’ (issue 4477) for 5th-8th April, 1718, and repeated in the subsequent issue:

This Day is publish’d, [printer’s symbols] Zodiacus Stellatus fixas omnes hactenus cognitas, ad quas Lunæ appulsus ullibi terrarum Telescopio observari poterunt, complexus. Or, An exact Description of all the fix’d Stars, to which the Moon or Planets can at any time apply, carefully laid down on two large sheets, from the British Catalogue of Stars lately publish’d; being of use to all Lovers of Astronomy, and particularly to such as may be desirous to put in Practice the Art of finding the Longitude by Help of the Moon.“

These two announcements contain valuable information about the sources and making of the star chart not found on the chart itself, which explain the importance of the delineation.

The Zodiacus Stellatus’ has a chequered past. John Flamsteed, the Astronomer Royal, was a perfectionist; as such, he was determined that his material should not be published until he was satisfied with its accuracy, a day which never quite arrived. However, in 1712, under pressure from Isaac Newton and Edmond Halley (among others), he provided the Royal Society with a manuscript copy of his catalogue of stars and an explanatory text, giving them permission to edit the text (but not the catalogue) for publication. Instead, Halley published the Catalogue of Stars without Flamsteed’s permission. An enraged Flamsteed responded by buying every copy of the book he could find (about three hundred out of the four hundred printed) and destroying them all. Subsequently, Halley took the raw data from the catalogue and constructed a star chart, the Zodiacus Stellatus’, from Flamsteed’s observations, which was published under Senex’s name. In a letter from one of Flamsteed’s assistants to another from 1720, Joseph Crosthwaite commented:

”… Senex is so much a tool of Dr. Halley’s, and affronted Mr. Flamsteed so much in his lifetime by engraving the Zodiacus Stellatus’, and putting his own name to it, in order to screen Dr. Halley from the law, that I am afraid he is not to be trusted.” (quoted by Warner, The Sky Explored’, p.242).

As Crosthwaite noted, the map was issued without credit either to Flamsteed or Halley, but Senex’s catalogue description makes the link clear. The Zodiacus Stellatus’ depicts the zodiac constellations in three long strips arranged vertically over two pages [i.e. sheets]… Each sheet was centred 8 degrees above and below the ecliptic using a cylindrical projection with geocentric orientation” [Kanas, Star Charts’, p.206]. It was the second European printed zodiac chart but its basis on Flamsteed’s authoritative observations made it far superior to its predecessor, and it remained in wide usage for many decades to come. 

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