The Lacaille Constellations

In the middle of the 18th century a French astronomer by the name of Nicolas-Louis de Lacaille made a famous voyage to the Cape of Good Hope.  His story is quite remarkable and I hope to explore it in a later blog post.  Lecaille cataloged nearly 10,000 southern stars during his two year expedition to the Cape.  He introduced 14 new constellations which, as of 1928, have been officially recognized by the International Astronomical Union.  There are a total of 88 constellations in the sky.  Lacaille's contribution accounts for more than 15% of the total.

Nicolas-Louis de Lacaille¹

Lecaille, ever an enlightenment scientist, named his constellations after objects found within a lab.  One, Mons Mensa, was named after a landmark in South Africa -- Table Mountain.  He also split the large Argo Navis into three separate constellations: Vela, Puppis and Carina.

I live in Calgary and am unable to see a lot of the southern constellations from my home.  The lowest declination on the celestial sphere visible from Calgary is about -39°S.  This leaves 39°S - 90°S permanently below the southern horizon.

Lecaille's dedication to exactitude and completeness has inspired me to write some words about each of 'his' constellations.  We are able to see some of them from Calgary.  The list below shows the names of the constellations and their declination range.

Constellation	~Declination Range (°S)	Representation
Antlia	24.5 - 40.5	Air Pump
Caelum	27 - 48.5	Chisel
Circinus	55.5 - 70.5	Compass
Fornax	24 - 39.5	Brazier
Horologium	40 - 66	Pendulum Clock
Mensa	70 - 85	Table Mountain
Microscopium	27.5 - 45	Microscope
Norma	42.5 - 60.5	Carpenter's Square
Octans	74.5 - 90	Octant
Pictor	43 - 64	Easel
Pyxis	17.5 - 37	Compass Box
Reticulum	53 - 67	Reticle
Sculptor	25 - 39	Sculptor
Telescopium	45 - 57	Telescope

Six of the constellations are either fully or partially visible from Calgary.  According to my night sky software, Horologium's borders barely creep across the southern horizon.  However, to have a good shot at seeing any of this constellation's stars you would have to be in deep Southern Alberta.  In fact, I might hold a competition for anyone observing and logging a star in Horologium from Alberta.

Currently at this time of year (End of October), Sculptor, Microscopium and Fornax are in the evening sky.  We will go through each of these constellations in the coming weeks.  I will start with the ones visible from Calgary so you can attempt to view them in the southern sky with your naked eye!


¹  (Image Credit: Mille Le Jeuneux - Stoyan R. et al. Atlas of the Messier Objects: Highlights of the Deep Sky. -- Cambridge: Cambridge University Press)