The Caldwell Objects

"nebulous clusters" (Class II); and "stars accompanied
by nebulosity" (Class III). Of his work
Lacaille wrote: "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."
Lacaille's list of nebulae first appeared in
1755, in the Memoires of the French Royal
Academy of Sciences (16 years before Charles
Messier published his first list of 45 objects in the
same journal) and was published posthumously
as a catalog in 1763. NGC 2477 is the third object
in Lacaille's Class I and hence is denoted Lac 1-3.
This means he did not fully resolve the cluster
with his modest telescopes. He simply described
NGC 2477 as a "[g]reat nebula 15[']x 20' in
diameter."
In the February 1960 issue of Sky & Telescope,
Harvard University historian Owen Gingerich
related the following report that Lacaille gave to
the French Royal Academy:
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 or 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.
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Lacaille's work did not go unnoticed.
Magnanimous Messier credited Lacaille for his
discoveries in his now-famous 1771 catalog
(which wasn't published until 1774).
James Dunlop also observed NGC 2477 from
Parramatta and included it as No. 535 in his 1827
catalog, describing it as a "pretty large faint
nebula, easily resolvable into small stars, or
rather a cluster of very small stars, with a small
faint nebula near the north preceding
[northwestern] side, which is rather difficult to
resolve into exceedingly small stars."
Observers at tropical or southern latitudes
will find NGC 2477 in a naked-eye Cygnus- or
Grus-like asterism, with Canopus (Alpha
Carinae) serving as the bird's nose and Zeta
Puppis the tail; Tau (τ) and Sigma (σ) Puppis are
the two brightest stars in the bird's long, crooked
neck. Pi (π) Puppis, which is part of the nakedeye
open cluster Collinder 135, marks the
northern wingtip, while beautiful Gamma
The Caldwell Objects 285