May 23, 1764. 5.
15h 06m 36s (226d 39' 04") +2d 57' 16"
Beautiful Nebula discovered between the Balance [Libra] & the Serpent
[Serpens], near the star in the Serpent, of 6th magnitude, which is the 5th
according to the Catalog of Flamsteed [5 Ser]: it doesn't contain
any star; it is round, & one sees it very well, in a fine [clear dark]
sky, with an ordinary refractor of 1-foot [FL]. M. Messier has reported it
in the chart of the comet of 1763.
Mem. Acad for the year 1774, page 40. Reviewed on Sep. 5, 1780,
January 30 & March 22, 1781.
(Diam. 3')
[Mem. Acad. for 1771, p. 437 (first Messier catalog)]
The night of May 23 to 24, 1764, I have discovered a beautiful nebula in the
constellation of Serpens, near the star of sixth magnitude; the fifth
according to the catalog of Flamsteed. That nebula doesn't contain any star;
it is round, & could have a diameter of 3 arc minutes; one can see it
very well, under a good sky, with an ordinary [non-achromatic] refractor of
one foot [FL]. I have observed that nebula in the Meridian, & I have
compared it to the star Alpha Serpentis. Its position was right ascansion
226d 39' 4", & its declination 2d 57' 16" north. On March 11, 1769, at
about four o'clock in the morning, I have reviewed that nebula with a good
Gregorian telescope of 30 pouces, which magnified 104 times, & I have
ensured that it doesn't contain any star.
[p. 454]
1764.May.23. RA: 226.39. 4, Dec: 2.57.16.B, Diam: 0. 3.
Beautiful nebula without stars, between the Serpent ∓ the Ballance near
the star of 6th magnitude, the fifth of the Serpent, according to Flamsteed.
[PT 1800 p. 73 & 75-76,reprinted in
Scientific Papers, Vol. 2, p. 44 & 46]
March 4, 1783. With the 7-feet reflector, I viewed the nebula near the 5th
Serpentis, discovered by Mr. Messier, in 1764 [M 5 = NGC 5904].
"It has several stars in it; they are however too small that I can but just
perceive some, and suspect others."
May 31, 1783. The same nebula with a 10-feet reflactor; penetrating power
1/2 * sqrt(43*(89^ 2-16^ 2)) = 28.67.
"With a magnifying power of 250, it is all resolved into stars: they are very
close, and the appearance is beautiful. With 600, perfectly resolved. There
is a considerable star not far from the middle; another not far from one
side, but out of the cluster; another pretty bright one; a great number of
small ones."
Here we have a case where the penetrating power of 20 fell short, when 29
resolved the nebula completely. This object requires also great magnifying
power to shew the stars of it well; but that power had before been tried, in
the 7-feet, as far as 460, without success, and could only give an indication
of its being composed of stars; whereas the lower magnifying power of 250,
with a greater penetrating power, in the 10-feet instrument, resolved the
whole nebula into stars.
Feb. 24, 1786. I viewed the nebula near Flamsteed's 5 Serpentis, which has
been mentioned before [M 5] with my 20-feet reflector; magnifying power 157.
"The most beautiful extremely compressed cluster of small stars; the greatest
part of them gathered together into a brilliant nucleus, evidently consisting
of stars, surrounded with many detached gathering stars of the same size and
colour. R.A. 15h 7' 12"; P.D. 87d 8'."
May 27, 1791. I viewed the same object with my 40-feet telescope; penetrating
power sqrt(64*480|^2)/2 = 191.69; magnifying power 370.
"A beautiful cluster of stars. I counted about 200 of them. The middle of it
is so compressed that it is impossible to distinguish the stars."
[PT 1814, p. 275, reprinted in Scinetific Papers, Vol. 2, p. 535]
May 27, 1791. 40 feet telescope, power 370. "The 5th of the Connoiss.
[M 5 = NGC 5904] is a beautiful cluster of stars; I counted 200 of them; but
the middle of it is so compressed that it is impossible to distinguish the
stars." (*)
(*) A 40 feet telescope should only be used for examining objects that other
instruments will not reach. To look through one larger than required is loss
of time, which, in a fine night, an astronomer has not to spare; but it ought
to be known that the opportunities of using the 40 feet reflector are
rendered very scarce by two material circumstances. The first is the
changable temperature of the atmosphere, by which the mirror is often covered
with condensation of vapour upon its surface, which renders it useless for
many hours; and in cold weather by freezing upon it for the whole night, and
even for weeks together; for the ice cannot be safely taken off till a
general thaw removes it. The next is that, with all imaginable care, the
polish of a mirror exposed like that of the 40 feet telescope, though well
covered up, will only preserve its required lustre and delicacy about two
years. The three observations I have given must consequently be looked upon
as having been made by three different mirrors; but if we will have superior
views of the heavens, we must submit to circumstances that cannot easily be
altered.
[PT 1818, p. 437, reprinted in Scientific Papers, Vol. 2, p. 596]
The 5th of the Connoissance. [M 5 = NGC 5904]
"1813, 7 feet finder. It is near a star of equal brightness; the star is
clear but the object is hazy."
"1783, 7 feet telescope. It consists of stars; they are however so small that
I can but just perceive some, and suspect others.
1810, the globular figure is visible."
"1783, 10 feet telescope. With 600, all resolved into stars."
"1785, 1786, 20 feet telescope. A very compressed cluster of stars, 7 or 8
minutes in diameter; the greatest compression about 2 or 2 1/2 minutes."
"1792, 40 feet telescope. With 370 I counted about 200 stars; the middle is
so compressed, that it is impossible to distinguish the stars."
The profundity of this cluster, by the observation of the 7 feet telescope,
is of the 243d order.