What if Messier had been an Aussie?

[NereidT]

I'm new here, so I'm not sure if this the best place for this thread ...

By the title, I mean, what ~100 objects would he have chosen, had he lived in Australia?

Assume he lived not too far north (so the south celestial pole would have been well up in the sky), and at a site with at least a decent number of clear moonless nights a year, spread throughout the year (so he could have observed the full celestial sphere, well, over a period of several years). Also assume he had a telescope comparable to the one(s) he actually used, in France.

I'm particularly interested in what we - today - call galaxies he'd have included among his list of a hundred or so objects (like the joke 'why did the dinosaur cross the road? because chickens hadn't been invented then.' "Galaxies" weren't 'invented' until well after Messier had died).

Of course, many 'Aussie Messier' objects would be the same as the real Messier objects; there's a good chunk of the sky that can be clearly seen from both Sydney and Paris (for example)! So I'm not interested in those, except - perhaps - the southern Dec ones that he 'should' have seen, but didn't, because they never rose high enough in his sky to observe clearly (but did clear his southern horizon).

I know about the Caldwell objects; they're a good place to start trying to answer my question, but - for various reasons - by no means the full answer itself! :P

If you're interested, I can give you a link to a discussion I started on a different forum, on this topic (PM me, please).

[clive milne]

I think it would be a fair assumption that the list would have extended way past 100 objects.

[NereidT]

I'm not so sure of that.

Leave out the Messier objects which don't seem to be deep sky objects at all (e.g. M73), the question becomes one of trying to decide which supernova remnants (like M1), planetary nebulae (like M57), star-forming nebulae (like M16), globular clusters (like M13), open clusters (like M44), and external galaxies (like M33) south of Dec -35°* are obvious enough in a telescope like Messier's.

Once you've got that, and once you've decided where (latitude) you want your Aussie Messier to have lived, it's a relatively straight-forward exercise to just add things up. Mind you, deciding on which open clusters to add may not be so easy ...

* or -30°, given that objects which did not rise high in Messier's sky would have been harder to detect; e.g. M83 is there, but it was a toughie for him, despite the fact that it's actually a very bright galaxy

[Calibos]

One also has to think in the following terms. What do I keep mistaking for comets to add to my list of non comet fuzzy patches in the sky. ie. Remember, Messiers list wasn't about being the best DSO's visible to him, it was the list of things that should be ignored when looking for comets. Though the Best DSO and Messier list do overlap by quite a bit for obvious reasons.

[clive milne]

He obviously started off with that intent, but I'm guessing M45 might represent the point where he started cataloguing DSO's as an activity worth the effort in itself.

Obviously M45 would not have been so far down the list by virtue of its relative obscurity, and there is little chance that its inclusion is consistent with the purpose of the prior entries. There is no way it could be confused as a comet.