The Collinder List
If you own a good star atlas and look carefully at the objects represented on each star map, you’ll see hundreds of objects from the Messier catalog (M) and New General Catalog (NGC). But sometimes, you may come across objects with the obscure designations like Cr142 or Cr399 or Cr285. These “Cr” objects are open star clusters from the little-known Collinder catalog, a list of almost 500 open star clusters spread all over the northern and southern sky.
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The Collinder list was developed by Per Collinder, a Swedish graduate student in astronomy whose 1931 doctoral work involved the study of the structure and distribution of open star clusters in the Milky Way. An early version of his list appeared in his Ph.D. thesis, and eventually worked its way into mid-20th-century star maps like those in Norton’s Star Atlas.
Hundreds of these Collinder clusters are worth a look through binoculars or a telescope. You’ve likely seen quite a few of them without knowing it, including…
* The Double Cluster in Perseus (Cr24 and Cr25)
* The “Coathanger Cluster” (pictured above), also called Brocchi’s cluster (Cr399)
* The Ursa Major Moving Group (Cr285), which includes most of the stars of the Big Dipper
* The Hyades (Cr50) in Taurus
* The Beehive or Praesepe (Cr189), also known as M44.
* Orion’s Belt (Cr70)
Most of the objects in Collinder’s list are true star clusters. Though some, like the Coathanger, are simply asterisms, chance alignments of unrelated stars. And a few like Collinder 409 (a.k.a M71) are loosely-packed globular clusters. It wasn’t Collinder’s intent to map new star clusters, so the majority of the Collinder clusters also appear in the New General Catalog or Messier catalog.
We’ll point you towards some of the most appealing Collinder objects over the coming months, starting with a few pretty sights in the southern region of the constellation Canis Major, the Big Dog. And if you’re looking for things to see, check out some of these “Cr” objects for yourself with the help of a good star atlas. They make for good stargazing for those who tire of the same old Messier objects.
