Some wonder why Messier added the Pleiades to his list, as that list was obstensibly a collection of objects which could
fool him into thinking (for a short time, anyway) that he'd discovered a comet. However, Charles Messier must have known that the Pleiades have been known since antiquity. This "tiny dipper" of stars lies to the upper right of Orion.
One point of contention has always been how many individual Pleiads a person can see. Although the cluster is nicknamed the Seven Sisters, many can only see five or six easily. However, if one's eyes are quite sharp and one's sky is quite dark a double-digit enumeration is possible.
Below are selected times during which the Seven Sisters reach their highest Baton Rouge altitude of eighty-four degrees...
14 September = 5:18am
18 September = 5:02am
22 September = 4:46am
26 September = 4:31am
30 September = 4:15am
4 October = 3:59am
8 October = 3:43am
12 October = 3:28am
16 October = 3:12am
20 October = 2:56am
24 October = 2:40am
28 October = 2:25am
1 November = 2:09am
5 November = 1:53am
9 November = 1:38am
Times above are Daylight. Times below are Standard.13 November = 12:22am
17 November = 12:06am
21 November = 11:46pm
25 November = 11:31pm
29 November = 11:15pm
3 December = 10:59pm
7 December = 10:44pm
11 December = 10:28pm
15 December = 10:12pm
19 December = 9:56pm
23 December = 9:41pm
27 December = 9:25pm
31 December = 9:09pm
4 January = 8:53pm
8 January = 8:38pm
12 January = 8:22pm
16 January = 8:06pm
20 January = 7:51pm
24 January = 7:35pm
28 January = 7:19pm
More information:
Celestial Handbook by Robert Burnham, pp. 1862-1886.
http://stars.astro.illinois.edu/sow/pleiades-p.htmlYear-Round Messier Marathon by Harvard Pennington, pp. 96-97.
http://www.daviddarling.info/encyclopedia/P/Pleiades.htmlCosmos by Carl Sagan, pp. 226 and 231 (original trade paperback).
Messier Objects by Stephen James O'Meara, pp. 144-147.
Turn Left at Orion by Guy Consolmagno and Dan Davis, pp. 40-41.