I wonder how Messier did it

[Gazabone]

I think I'm right in saying that Messier used 2 lenses placed apart (nothing connecting them) which is quite remarkable in itself.

What puzzles me though is that he found some of the dimmer objects in his catalogue at all (eg M97 and ok, strictly speaking it wasn't Messier himself that discovered it) yet didn't immediately distinguish that some of the other objects (eg open clusters like M6) were not comets.

It was certainly a feat for his time but it still puzzles me how he saw some of the objects at all yet still thought other objects looked like comets.

[swamp thing]

He had pristine skies with almost no LP back then.

One cannot stress how HUGE a difference it makes to have good dark skies. 

[Owmuchonomy]

Yes, I concur.  Pitch black skies I imagine.  Unbeatable.  Herschel managed it from his back garden in Bath.  Wouldn't be able to do that now.

[Martin Meredith]

I thought the same until I read that Messier suffered from significant light pollution from his observatory near the centre of Paris. Here's a quote from p52 of Atlas of the Messier Objects, by Stoyan et al, Cambridge University Press):

"We may simply be underestimating the light pollution of nocturnal Paris in the 18th century. In fact, at that time, Paris was the largest city in the world with a population of 800,000. There are contemporary descriptions of how chaotic the situation was in the large city. Smoke from oven-heated houses, numerous factories and open fires must have created air pollution considerably worse than today's, scattering and absorbing more starlight. In addition, all public streets and squares were floodlit by oil-burning lamps… hence Messier's night sky may have been much worse than we imagine".

This is a highly-recommended book, by the way, with about 40 pages of Messier history before the atlas section itself. There is some description of the telescopes Messier used too. From my reading, it seems he used 5 different scopes at various points (2 chromatic refractors, an achromat, a Gregorian reflector, and a Newtonian reflector).

Martin

[cotterless45]

I don't think they left the street lights on all night or bothered with security lights ,

Nick.

[ollypenrice]

"Floodlit" by oil burning lamps is not a very 'historical' expression. The online etymology dictionary dates the word's appearance at 1924.

The expression, 'Huddled round a roaring candle' comes to mind...' 

Smoke might have been another matter, I have no idea.

How bad would your sky and/or telescope have to be to mistake M45 for a comet?  I suspect Messier may have had an audience in mind for his catalogue but that's pure guesswork. I know nothing about him to speak of.

Olly

[pipnina]

"Floodlit" by oil burning lamps is not a very 'historical' expression. The online etymology dictionary dates the word's appearance at 1924.

The expression, 'Huddled round a roaring candle' comes to mind...' 

Smoke might have been another matter, I have no idea.

How bad would your sky and/or telescope have to be to mistake M45 for a comet?  I suspect Messier may have had an audience in mind for his catalogue but that's pure guesswork. I know nothing about him to speak of.

Olly

Was it not the case he created the catalogue of objects that weren't comets, but he thought were interesting anyway? Haven't studied the man but that's the impression I got.

I mean, the pleiades is an extremely easy naked-eye object. I can manage it from my back garden which is wrought with LP. Not the worst... But still bad.

[Martin Meredith]

Its an interesting and relevant question when trying to understand Messier's observations as to how much light/smoke pollution was an issue (along with understanding the limitations of his scopes).

Good old Wikipedia states:

Between 1745 and 1769, the old lanterns were gradually replaced by a new model called a réverbère which, mounted on a lamp post, gave off a much brighter light. By 1789 there were 5,694 new lanterns in service. A few years later the most popular revolutionary song, Ça ira! urged Parisians to hang aristocrats from the new lanterns.

(OK, the last bit is not strictly relevant ;-)

Messier observed from the Naval Observatory just south of the centre (Left Bank-ish) , whereas the 'proper' Royal Observatory was located quite a way south, further out that the modern Montparnasse district. One might speculate that this was to avoid the worst of the light and/or smoke?

O'Meara, in his book The Messier Objects, refers to the "poor location of his observatory" and notes that Lalande "could only lament that the precise and zealous Messier could not live under purer and less cloudy skies".

I have no idea what the LP and smoke was really like, but I think we need to consider the possibility that things were some way from ideal (quite apart from his instruments) in interpreting Messier's observations.

Martin

[goodricke1]

I suspect Messier may have had an audience in mind for his catalogue

Yes indeed - Lacaille brought out a catalogue with 42 objects in 1755 and it looks like Messier wanted to eclipse that total with a few unlikely 'comets'...

http://messier.seds.org/m-q&a.html#why_M42-45

[chiltonstar]

Coming back to the title of the thread, I think we have to assume as well that Messier was a rather good observer!

Chris

[Mr Spock]

He may well have seen some of the fainter objects. The question should then be, why didn't he see the many other objects which were brighter?

[MAN or ASTROMAN]

Was it not the case he created the catalogue of objects that weren't comets, but he thought were interesting anyway? Haven't studied the man but that's the impression I got.

 

I mean, the pleiades is an extremely easy naked-eye object. I can manage it from my back garden which is wrought with LP. Not the worst... But still bad.

Didn't he just 'Shoehorn' in well known objects like M42 and the Pleiades just to up the numbers,so he could have more objects in the first edition of his catalogue than a rival Astronomer's (who's name escapes me just now)?

[Gazabone]

Many thanks for all the replies to this thread, it's made very interesting reading indeed and opened up ideas that hadn't occurred me before, particularly the state of the skies he had (were they pristine or polluted with either light and/or smoke), whether he wanted to outdo other cataloguers and why didn't he catalogue some objects that were brighter than some he did catalogue.

A bit more research for me to get stuck into methinks.

Thank you all.

[laudropb]

I think he was a very dedicated and skilful observer. That must have helped some.

[mikeDnight]

Didn't he just 'Shoehorn' in well known objects like M42 and the Pleiades just to up the numbers,so he could have more objects in the first edition of his catalogue than a rival Astronomer's (who's name escapes me just now)?

For a certainty Messier did not believe the Pleiades cluster to be a comet, so why did he include it in his list of comet impersonators? For me that's an easy question to answer, as I sincerely believe he saw the nebulosity around at least one of the stars. The nebulosity was allegedly discovered by Wilhelm Tempel, who observed it around the pleiad Merope while using a 4" refractor in Italy in 1859. Some claim to have seen the nebulosity with the naked eye and the Pleiades are even recorded in a poem by Tennyson as being tangled in a silver braid.

The ñebulosity is an easy target in a 4" refractor and as one of Messiers telescopes was a 7" Gregorian Cassegrain - of questionable quality I might add, - he at least stood a pretty decent chance of detecting the haze around Merope, which actually does look like a comet passing in front of a star. So, in my mind it was Charlie Messier who was the true discoverer of the nebulosity and certainly not Tempel. If so, the designation M45 should really refere to the nebula alone and not the cluster.

Mike

[Piero]

It was certainly a feat for his time but it still puzzles me how he saw some of the objects at all yet still thought other objects looked like comets.

It is certainly surprising. But what actually surprises me is that he found those objects simply scanning the sky, with little field of view, and without any atlas. I mean he did not even know that a large portion of targets could have been found with his telescope pointed towards the Milky Way. He might have suspected this, but this is not obvious as he did not even know what the Milky Way was! 

Another thing is "seeing" and "spotting". It is feasible to spot a large part of the Messier Catalogue under moderately light polluted skies, although recognising what that faint light is is another story. There is where aperture is needed. Spotting a 9-10mag galaxy with a 60mm is possibly like spotting a 13-14mag galaxy with a 200-250mm. In both the cases, these targets are at the limit of one's telescope, and you need your best acuity to catch them. Very rewarding though! 

A shame that he was so interested in comets and therefore ended up being disappointed for spotting those grey smudges in the skies! What a waste of time he might have thought!

I would really like to know what he would have thought if he actually had known what he was observing in Paris!

The first man on Earth looking at grey smudges (aka galaxies, nebulae, small open clusters, globular clusters, planetary nebulae, etc)! It doesn't happen every day!