A small southern constellation, introduced by the French astronomer Nicolas Louis de Lacaille to commemorate the reticle in the eyepiece of his small telescope with which he measured star positions from the Cape of Good Hope in 1751–52. It consisted of a diamond shape formed by silk threads inserted into the eyepiece which helped him judge the position of stars as they passed through the field of view.
In the notes to his southern star catalogue published by the French Royal Academy of Sciences in 1756 Lacaille described it as “The little instrument used to construct this catalogue. It is constructed by the intersection of four lines drawn from each corner of a square to the middle of the two opposite sides.” The constellation’s brightest star, Alpha Reticuli, is of third magnitude, but is not named.
Lacaille’s Reticulum replaced a previous constellation in this area called Rhombus introduced in 1621 on a globe by the German astronomer Isaac Habrecht II (1589–1633). It later appeared in print in Habrecht’s Planiglobium Coeleste, et Terrestre published in 1628. Habrecht’s Rhombus, though, was considerably larger than Lacaille’s Reticulum and extended further south. It consisted of the present-day Alpha and Beta Reticuli plus Gamma and Nu Hydri, forming a quadrilateral in the space between Dorado and Hydrus.
Reticulum, shown on Bode’s Uranographia under the name Reticulus.
For Lacaille’s original depiction, see here.
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