Lacaille

Class 1: "Nebulosities not accompanied by stars"

Class 2: "Nebulosities due to clusters"

Class 3: "Stars accompanied by nebulosity"

IN 1755, 16 years before the first instalment of Messier's catalogue of nebulae and clusters was printed . . . a rather similar tabulation had appeared . . . This list of 42 southern nebulae was abstracted by Abbe Nicolas Louis de Lacaille (1713-62) from his catalogue of about 10,000 stars compiled during an expedition to the Cape of Good Hope in South Africa. (Gingerich, 1960)

Lacaille divided his 'nebulous stars' into three classes: Class 1: "Nebulosities not accompanied by stars", Class 2: "Nebulosities due to clusters" and Class 3: "Stars accompanied by nebulosity".

In his report to the French Academy of Sciences, Lacaille wrote: "The so-called nebulous stars offer to the eyes of the observers a spectacle so varied that their exact and detailed description can occupy astronomers for a long time and give rise to a great number of curious reflections on the part of philosophers. As singular as those nebulae are which can be seen from Europe, those which lie in the vicinity of the south pole concede to them nothing, either in number of appearance. I am sketching out this description and list to serve as a guide for those with the equipment and leisure to study them with larger telescopes. I would have greatly desired to present something more detailed and instructive in this article, but with ordinary refractors of 15 to 18 inches [in length] such as I had at the Cape of Good Hope, I had neither adequate nor convenient enough instruments for this kind of research. Those who do take the trouble to see what has occupied me during my foreign sojourn will see well enough that I did not have time to make that sort of observation."

"I have found a great number of the three types of nebulosities in the southern part of the sky, but I do not flatter myself to think that I have noticed them all, especially those of the first and third types, because they can only be perceived after twilight and in the absence of the moon. However, I do hope that the list is passably complete in regard to the most remarkable of the three types." (Quoted from Gingerich)

"Lacaille seems to have been the first person ever to observe systematically the whole sky"
-- D S Evans

Evans (1990) notes: "Considering that this list is based on the data from [the star catalogue], that is, almost always one shot of the passing sky in a very small telescope, certainly very inferior to modern binoculars, it is as good as might be expected. One can also reflect that Lacaille seems to have been the first person ever to observe systematically the whole sky, an honor which the present author once ascribed to Sir John Herschel, who used much the same technique with a telescope of some ten times larger diameter from a site some 6 miles south of Lacaille's. He, of course, did very much better and is the principal source of the southern data in the NGC."

LACAILLE ALSO STUDIED the Magellanic Clouds: "As a result of examining several times with a telescope . . . those parts of the Milky Way where the whiteness is most remarkable and comparing them with the two clouds common called the Magellanic Clouds, which the Dutch and Danes call the Cape Clouds, I saw that the white parts of the sky were similar in nature, or that the clouds are detached parts of the Milky Way, which itself is often made of separated bits. It is not certain that the whiteness of these parts is caused, according to received wisdom, by clusters of faint stars more closely packed than in other parts of the sky, whether of the Milky Way or of the Clouds, I never saw with the ... telescope anything but a whiteness of the sky and no more stars than elsewhere where the sky is dark. I think I may speculate that the nebulosities of the first kind are nothing more than bits of the Milky Way spread round the sky, and that those of the third kind are stars, which by accident are in front of luminous patches." (Quoted from Evans)

"One can add among the phenomena which strike the eye of anyone looking at the southern sky, a space of about 3 degrees in every direction which seems intensely black in the eastern part of the Southern Cross. This is caused by the contrast with the brightness of the Milky Way which surrounds this space on all sides."

Class 1 "Nebulosities not accompanied by stars"

1
2
3
4
5
6
7
8
9
10
11
12
14

NGC 104
NGC 2070
NGC 2477
NGC 4833
NGC 5139
NGC 5236
NGC 5281
NGC 6124
NGC 6121
NGC 6242
NGC 6637
NGC 6656
NGC 6809

gc
neb
oc
gc
gc
gal
oc
oc
gc
oc
gc
gc
gc

00h 24m
05h 38
07h 52
12h 59
13h 26
13h 37
13h 46
16h 25
16h 23
16h 55
18h 31
18h 36
19h 40

-72° 05
-69° 05
-38° 32
-70° 53
-47° 28
-29° 52
-62° 53
-40° 39
-26° 32
-39° 28
-32° 21
-23° 54
-30° 58

Class 2 "Nebulosities due to clusters"

3
4
5
7
9
10
12
13
14

NGC 2516
NGC 2546
IC 2391
NGC 3228
IC 2602
NGC 3532
NGC 4755
NGC 6231
NGC 6475

oc
oc
oc
oc
oc
oc
oc
oc
oc

07h 58m
08h 12
08h 40
10h 21
10h 43
11h 06
12h 53
16h 54
17h 53

-60° 51'
-37° 37
-53° 03
-51° 42
-64° 23
-58° 39
-60° 19
-41° 49
-34° 47

Class 3 "Nebulosities not accompanied by stars"

2
4
5,6
7
8
10
11
12
13

NGC 2547
IC 2488
NGC 3372
NGC 3766
NGC 5662
NGC 6025
NGC 6397
NGC 6405
NGC 6523

oc
oc
neb
oc
oc
oc
gc
oc
neb

08h 10m
09h 27
10h 45
11h 36
14h 35
16h 03
17h 40
17h 40
18h 04

-49° 15
-56° 58
-59° 52
-61° 35
-56° 32
-60° 26
-53° 40
-32° 12
-24° 19

References

Gingerich, O. (1960) "Abbe Lacaille's List of Clusters and Nebulae", Sky & Telescope 19(4, February), 207.

Evans, D. S. (1990) "Lacaille: Astronomer, Traveller", Pachart History of Astronomy Series, Volume 9., Pachart Publishing House, Tucson, AZ, USA. ISBN 0-88126-284-6.

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"Deepsky Observers Companion" (http://www.global.co.za/~auke) Copyright 1998 Auke Slotegraaf ([email protected]). All rights reserved. Uranometria 2000.0 copyright (c) 1987-1996 Willmann-Bell, Inc. Page last updated 1997 December 03. There are two types of people in this world, good and bad. The good sleep better, but the bad seem to enjoy the waking hours much more.