drollere wrote:actually, messier wrote in 1784 that M88 was a "nebula without star", not "a spiral nebula without stars". the spiral form of galaxies wasn't resolved until William Herschel and Lord Rosse (William Parsons) observed galaxies with their 50" or 72" alt-az reflecting telescopes in the 19th century. messier apparently preferred a 6" refractor that supposedly only delivered the optics of a modern 3.5".
Sketch of M51 by Lord Rosse (William Parsons) in 1845
The spiral form of
non-face on galaxies like M88 wasn't resolved until long-duration photographic exposures:
http://en.wikipedia.org/wiki/Andromeda_Galaxy wrote:
<<At an apparent magnitude of 3.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects. The first photographs of M31 were taken in 1887 by Isaac Roberts from his private observatory in Sussex, England.
The long-duration exposure allowed the spiral structure of the galaxy to be seen for the first time. However, at the time this object was commonly believed to be a nebula within our galaxy, and Roberts mistakenly believed that M31 and similar spiral nebulae were actually solar systems being formed, with the satellites nascent planets.>>
[b]Messier[/b] wrote:
M31: (August 3, 1764) `The beautiful nebula of the belt of Andromeda, shaped like a spindle; M. Messier has investigated it with different instruments, & he didn't recognise a star: it resembles two cones or pyramides of light, opposed at their bases, the axes of which are in direction NW-SE; the two points of light or the apices are about 40 arc minutes apart; the common base of the pyramids is about 15'. This nebula was discovered by Simon Marius, & consequently observed by different astronomers. M. le Gentil has given a drawing in the Memoirs of the Academy for 1759, page 453. It is reported on the English Atlas.' (diam. 40')
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(Flammarion reports that Messier added a note in his personal copy of the catalog by hand: `I have employed different instruments, especially an excellent Gregorian telescope of 30 feet FL, the large mirror 6 inches in diameter, magnification 104x. The center of this nebula appears fairly clear in this instrument without any stars appearing. The light gradually diminishes until it becomes extinguished. The former measurements were made with a Newtonian telescope of 4.5 feet FL, provided with a silk thread micrometer. Diameter 40'. August 3, 1764.')
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Messier was the first to resolve globular cluster stars:
http://en.wikipedia.org/wiki/Globular_cluster wrote:
<<The first globular cluster discovered was M22 in 1665 by Abraham Ihle, a German amateur astronomer. However, given the small aperture of early telescopes,
individual stars within a globular cluster were not resolved until Charles Messier observed M4.
- M4: Messier (May 8, 1764) `Cluster of very small [faint] stars; with an inferior telescope, it appears more like a nebula; this cluster is situated near Antares & on its parallel.'
William Herschel began a survey program in 1782 using larger telescopes and was able to resolve the stars in all 33 of the known globular clusters. In addition he found 37 additional clusters. In Herschel's 1789 catalog of deep sky objects, his second such, he became the first to use the name globular cluster as their description.>>