15x50mm IS binoculars (2/23/06): easily visible as a faint, oval patch.
John Bevis discovered M1 = NGC 1952 = h357 around 1731 using a 3-inch (+/-) refractor of 24 ft focal length. He labeled it as a nebula in his Uranographia Britannica star atlas, which was completed in 1750, though not published in 1786. Charles Messier independently discovered M1 on 28 Aug 1758. While searching for comet Halley on its first predicted return, he found instead another comet, which turned out to have been discovered earlier. Then while tracking this comet he found M1, which Messier noted "contains no star; it is a whitish light, elongated like the flame of a taper." Bevis informed Messier of his earlier discovery in 1771. Messier?s rediscovery of M1 was the inspiration to begin the compilation of his catalog.
William Herschel made numerous observations with his various telescopes, though first observed it on 24 Mar 1783 with this 6.2-inch reflector. With his workhorse 18.7-inch he attempted to resolve the nebula into stars: "Very bright, of an irregular figure; full 5 minutes in longest direction. I suspect it to consist of stars."
Much of the following is gleaned from Wolfgang Steinicke's book on "Observing and Cataloguing Nebulae and Star Clusters". William Parsons (third Earl of Rosse) and friends Romney Robinson and James South observed M1 with his first (compound) 36-inch in early November 1840. A few weeks later Robinson wrote Rosse to examine other nebulae as "I am anxious to know whether they all have tails and claws". Parsons sketched M1 in 1844 (using his solid 36") with filaments or streamers extending out of the body and a long tail (see http://messier.seds.org/more/m001_rosse.html). His description reads: ".. a cluster; we perceive in this [36-inch telescope], however, a considerable change of appearance; it is no longer an oval resolvable [mottled] Nebula; we see resolvable filaments singularly disposed, springing principally from its southern extremity, and not, as is usual in clusters, irregularly in all directions. Probably greater power would bring out other filaments, and it would then assume the ordinary form of a cluster. It is stubbed with stars, mixed however with a nebulosity probably consisting of stars too minute to be recognized. It is an easy object, and I have shown it to many, and all have been at once struck with its remarkable aspect. Everything in the sketch can be seen under moderately favourable circumstances."
Romney Robinson, director of Armagh Observatory and a regular observer at Birr Castle, remarked "it is ragged, bifurcated at the top, and has streamers running out like claws in every direction." This description, along with the 1844 sketch, probably led the popular nickname "Crab Nebula".
William Lassell was certainly influenced by the sketch. He observed M1 in December 1852 with his 24" reflector and commented, "long filaments run out on all sides". Three weeks later, he noted "the outlying claws are only just circumscribed by the edge of the field of 6' in diameter." Father Angelo Secchi was also influenced; his sketch made around 1856 using a 9.5" refractor strikingly mimics the 1844 sketch with a long tail and external feelers! Secchi claimed the agreement in features demonstrated the strength of his telescope.
Interestingly, R.J. Mitchell resketched the Crab in 1855 with a much more traditional shape. Dreyer commented in The Observatory, Vol. 37, p. 399-402 (1914), "The only published drawing which is a complete failure, is that of M1, the "Crab Nebula", which has unfortunately been reproduced in many popular books. It was made with the 3-foot, and long "feelers" were never again seen with the 3-foot nor with the 6-foot." Still the nickname stuck. See More http://www.southastrodel.com NGC 1952 .htm for more historical observations.
Isaac Roberts first captured M1 photographically in 1892 with his 20-inch reflector.
In 1921 Carl Lampland suspected internal motion and based on plates with the the 40-inch reflector at Lowell, showed the nebula had changed shape. He also discovered the close double star at the center (5" separation).
Also in 1921 Lundmark mentioned (PASP, 33, 234) that the nova of 1054 was near NGC 1952 and in 1928 Edwin Hubble (http://adsabs.harvard.edu/full/1928ASPL....1...55H) stated the nebula "is expanding rapidly and at such a rate that it must have required about 900 years to reach its present dimensions. For, in the ancient accounts of celestial phenomena only one nova has been recorded in the region of the Crab Nebula. This account is found in the Chinese annals, the position fits as closely as it can read, and the year was 1054!" The Chinese text noted "Thereafter, a "guest star" appeared on 4 Jul
In 1937 Nicholas Mayall made a spectral analysis (PASP, 49, 101) and in 1939 (ASPL, Vol 3, 145) announced the Crab Nebula was a supernova remnant.
In 1951 Australian astronomer John Bolton showed that M1 was a strong radio source (brightest in Taurus) and was named Taurus A. In 1968 a pulsar (rapidly rotating neutron star) was discovered in M31 with a period of 33 milliseconds (southwestern of the two central mag 16.5 stars).
200/250mm - 8" (10/4/80): moderately bright, irregular shape, fairly large, indentation on the NW and SE ends.
300/350mm - 13.1" (1/18/85): large, bright, irregular potato shape, large indentation on following end. Easy in 16x80 finder.
400/500mm - 17.5" (2/8/86): very bright, unusual potato shape with an irregular surface brightness, 6'x4', broad concentration towards center. Very irregular elongated shape with extensions or "arms" towards the NW and SE, ragged edges at periphery. A large dark indentation or "bay" intrudes on the NE side of the SE extension, so this end is thinner and less prominent. A few faint stars are superimposed. Using an OIII filter, the overall structure is muted but a bright inner streak is visible in the SW quadrant (oriented ~E-W) and this streak is not noticeable without the filter.
900/1200mm - 48" (10/23/14): remarkable intricate filamentary structure at 488x using a DGM Optics OIII filter. I didn't try to take detailed notes, but the entire surface of M1, which filled over half the field, was resolved into an intertwined maze of thin, twisting filaments. This complex structure was more evident than the view I had a year ago at 287x.
48" (11/2/13): using 488x I immediately focused in on a close unequal mag double star (roughly mag 16/16.5) that was visible near the center but a bit offset from the geometric center towards the SE side of the nebula. The fainter southwest component (CM Tau) is the famous pulsar (rotating neutron star) at the heart of the Crab Nebula, which was discovered in 1968 and pulses 30 times/sec!
Although this observation was exciting (first definite view of the pulsar), the real jaw-dropping sight was at 287x using a DGM Optics OIII filter, which lit up the interior filaments! The two bright filaments that meander E-W through the nebula (dipping just south of the pulsar) were very prominent with slightly fainter side filaments extending south and north. Scanning with averted vision, numerous additional very faint, thin radial filaments extending outward were evident throughout the nebula. In addition, the periphery had a ragged or curdled appearance, particularly along the northern edge. The eypiece view approached the iconic HST image of the Crab Nebula !
Notes by Steve Gottlieb