Andrew Cooper
Nov 17, 2009    Hale Pohaku, HI (map)
46cm f/4.5 Newtonian, Deep Violet @ 95x
Seeing: 7 Transparency: 7 Moon: 0%

Large! bright, arranged in clumps and chains through the field, homogeneous, size is >45', fills the entire field with stars

Andrew Cooper
Mar 17, 2004    Sycamore House, Tucson, AZ (map)
28cm f/10 SCT

Big! Bright! rich open cluster of ~100 stars in a 25'+ area, RFT object, fills the low power 11" eyepiece field

Andrew Cooper
Feb 5, 1998    Sycamore House, Tucson, AZ (map)
20cm f/10 SCT

Cluster of 70+ stars covering over 0.5 degree

Rev. T.W. Webb
May 19, 1885    Hardwick, Herefordshire, England (map)

Group of pretty uniform 9 mg. stars, with a profusion of lesser ones.

― Celestial Objects for Common Telescopes, T. W. Webb, 1917

Captain William Henry Smyth
Apr 16, 1834    No. 6 The Crescent, Bedford, England (map)
150mm f/17.6 refractor by Tully 1827

A neat but minute, double star, in a tolerably compressed cluster on the Unicorn's flank, and lying 14° south-east of Procyon. A 9½, and B 10, both white. This object is in the midst of a splendid group, in a rich splashy region of stragglers, which fills the field of view, and has several small pairs, chiefly of the 9th magnitude. It was discovered by Miss Herschel in 1783, and was classed by ♅. in February, 1786.

― A Cycle of Celestial Objects Vol II, The Bedford Catalogue, William Henry Smyth, 1844

John Herschel
Feb 19, 1830    

A superb cluster which fills the whole field; stars of 9th and 10th to the 13th magnitude - and none below, but the whole ground of the sky on which it stands is singularly dotted over with infinitely minute points. Place that of a bright star, the southern of two which point into the concavity of an arc.

Charles Messier
Feb 19, 1771    

Cluster of very small stars, without nebulosity; this cluster is at a short distance from the three stars that form the beginning of the Unicorn's tail.

― Connaissance des Temps, 1781

Object Note

Open cluster Messier 48 (M48, NGC 2548) is a conspicuous open cluster in the head of the extended constellation Hydra, almost on its border to Monoceros.

This open cluster was discovered by Charles Messier and cataloged by him on February 19, 1771. However, as he did an error in data reduction, he gave a wrong position in his catalog so that the object was missing until Oswald Thomas identified it in 1934, and independently T.F. Morris in 1959. The identification of M48 by Oswald Thomas was confused by some historians, who have claimed erroneously instead that he had identified M47. As M48 was lost, two independent rediscoveries occurred: First, Johann Elert Bode apparently found it in or before 1782, and second, Caroline Herschel independently rediscovered it on March 8, 1783, and added it to her small list as No. 5. This latter discovery was published by Caroline's famous brother, William Herschel, who included it in his catalog as H VI.22 on February 1, 1786.

M48 is a quite conspicuous object and should be a naked-eye object under good conditions. The smallest binocular, or telescopes, show a large group of about 50 stars brighter than mag 13, the total number being at least 80. The more concentrated core extends over about 30 arc minutes, while the outskirts reach out to about 54', corresponding to a linear diameter of 23 light years at its distance of 1,500 light years (given so by Mallas/Kreimer and Kenneth Glyn Jones, while the Sky Catalog 2000 has 2,000 light years). M48 was classified as of Trumpler type I,2,m (Sky Catalog 2000), I,2,r (Glyn Jones) or I,3,r (Götz).

― SEDS Messier Notes

Drawings, descriptions, and CCD photos are copyright Andrew Cooper unless otherwise noted, no usage without permission.

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