Observations of the Satellites of Mars in Astronomische Nachrichten 91 Columns 11-14, 1877 (Hall) With Letters to the Editor: The Satellites of Mars (paper in original wraps) Nature 16 No. 414, p. 475, 4 October 1877 (Madan) WITH Names of the Satellites of Mars in Astronomische Nachrichten 92 Columns 47-48, March 14, 1878 (Hall)

1st Edition. FIRST EDITION OF ASAPH HALL'S DISCOVERY OF THE MOONS OF MARS. Three papers are included in this listing; the 2nd and 3rd are first editions as well. The first and most important is Hall's 1877 discovery of two moons orbiting Mars. The second, by Madan, proposes names for the moons and the third, by Hall, sanctions Madan's names.

Hall was an American astronomer and mathematician, a "highly experienced and motivated satellite observer... in charge of the Alvan Clark 26 inch Great Refractor" (Pascu, History of Telescopic Observations, 2013). His "discovery of the satellites owed as much to his knowledge and insight as to his imagination and willingness to doubt conventional wisdom" (Sheehan, The Planet Mars, 63).

In the first paper offered, ‘Observations and Orbits of the Satellites of Mars' -- the work that made him famous -- Hall details his discovery of the two moons orbiting Mars, including the history of his discovery as well as his search technique, timing, and the mathematics involved. While observing Saturn, Hall wrote: "In December, 1876, while observing the satellites of Saturn, I noticed a white spot on the ball of the planet, and the observations of this spot gave me the means of determining the time of the rotation of Saturn, or the length of Saturn's day, with considerable accuracy. This was a simple matter, but the resulting time of rotation was nearly a quarter of an hour different from what is generally given...and this discordance, since the error was multiplied by the number of rotations and the ephemeris soon became utterly wrong. This set before me in a clearer light than ever before the careless manner in which books are made, showed the necessity of consulting original papers, and made me ready to doubt [another scientific] assertion...[that] ‘Mars has no moon'" (Sheehan).

Described fully for the first time in the August 1877 paper offered, "Hall turned the giant refractor to Mars with the express goal of finding a moon or two... he new large refractor, the very favorable opposition of Mars, [and Hall's] decision to search for a satellite of Mars, his decision to search in the halo of the planet and finally, his search technique" were all decisions integral to his discovery (ibid). Hall's "unique search technique was to place Mars on the rotation axis of his micrometer, move the eyepiece along its slide so that Mars was just out of the field of view, and then rotating the micrometer head. This scheme produced a search area in the shape of an annulus a few arcmin wide around Mars but absent the "dazzling" light of the planet (Hall, 1878).

"With this technique the moons were discovered quickly when they first became visible (from behind/in front of Mars. Once the light from the planet was blocked, it was not difficult to detect them by eye" (Pascu). The paper offered here is Hall's first detailed publication of his observations. A very brief note announcing his discovery appeared earlier in the same year in The Observatory.

In the 2nd work: Two months following the publication of Hall's discovery, H. G. Madan proposed a name for the moons, each based on the Illiad: Phobos (Flight) and the other Deimos (Fear). Hall is often thought to have named the moons himself; he did not.

In the 3rd work offered, "Names of the Satellites of Mars," Hall officially names the two moons of Mars "Deimus" and "Phobos," explaining the rationale and fully attributing the names to Madan's suggestion. CONDITION & DETAILS: 2 complete Astronomische Nachrichtenare volumes in identical contemporary bindings; large pieces of tape on the spines, but no other library markings; red gilt-lettered labels at the spines. Minor edge scuffing; tightly bound. 4to. 91: [vii], 398, [1]. 92: [4], 398, [1]. The Nature issue is complete in its original wraps; rebacked at the spine. The issue is in a custom burgundy and black clamshell pamphlet case, gilt-tooled and lettered at the spine. 4to. [8]. Very good condition.