How many objects would there be in the Messier Catalogue if Messier had observed from both the northern and southern hemisphere instead of just observing from Paris? How many Messier objects would there be if he had seen every deep-sky object that it was possible to see using his telescopes? I used Steinicke’s NGC and IC catalogues to try and estimate an answer. However Steinicke’s catalogue does not of course include non-NGC and non-IC objects so my count is a conservative estimate. First I found the faintest Messier objects according to Steinicke’s catalogue. These were: 1. The faintest open cluster (OC) is M26 which is magnitude 8.0. 2. The faintest globular cluster (GC) is M72 which is magnitude 9.2. 3. The faintest planetary nebula (PN) is M76 which is magnitude 10.1 and 4. The faintest galaxies (Gal) are M91 and M98 which are both magnitude 10.1. 5. Most nebulae (Neb) have no magnitudes but the faintest five in Messier’s catalogue are M1, M16, M20, M43 and M78. Then I used the above magnitude limits to come up with A Complete Messier Catalogue. It is not the final Complete Messier Catalogue, just one attempt. Some of the included nebula may be too faint for Messier to see. My list contains a large number of open clusters and I was tempted to use the second faintest OC (magnitude 7.4) as my OC magnitude limit, but decided to use magnitude 8.0. The columns are: Cat Num, catalogue number Type and sub-type CON, constellation. Vmag SB, visual magnitude and surface brightness. Length and Width RA 2k min sec, Right Ascension 2000 declin m s, declination 2000. 10pm, southern season at 10pm. (11pm DST) This method gave 176 OC, 146 Gal, 81 GC, 29 Neb and 25 PN in A Complete Messier Catalogue. That is a total of 457 clusters, nebulae and galaxies and 111 of these are summer objects. The tab-delimited file below can be copied to MS Excel then filtered and sorted. The user can then delete objects that are too far north (or south) to see. Reference
http://www.ngcic.org/steinicke/2006/explan.htm
