This text is taken from Brian Peterson's excellent site:
Canon XSi, modded, Total RGB 46 min. = 23x2 min, ISO 1600
Baader MPCC, Bresser PN 8" OTA at F4, EQ6 mount, guided w/PHD and EQMOD
M 45, better known as the Pleiades, is an open cluster which is easily visible with the unaided eye. It is sometimes called "The Seven Sisters," and with a dark sky and good eyesight you can probably see 6 or 7 of the brightest stars in the cluster (actually, there are reports from centuries past of particularly well-sighted observers seeing up to 14 members of the cluster without a telescope).
The blue reflection nebula throughout the cluster is caused by the light from these bright stars reflecing off a cloud of gas and dust which the cluster happens to be passing through at this time -- it is not the leftovers of the cloud out of which this cluster formed. M 45 is 380 light years from the earth.