Three Big Globs
by Ramesh Pooran
The evening skies of early summer are graced by, among other things,
three
splendid globular clusters, two of which bear single digit Messier numbers.
The third, Messier 13 in Hercules, is often used as a showpiece object. And
rightly so. This cluster is remarkably easy to find and looks good in almost
any telescope. Small scopes show a dusting of stars around a lambent cotton
puff. A five inch refractor will show myriad points of light which sharply
increase in density near the centre. A large reflector will allow you to
peer deep into the globular's heart through a multi-layer coating of stars.
The other two globulars, Messier 3 in Canes Venatici and Messier 5 in
Serpens (Caput) are easily comparable and not as out-of-the way as you might
think. The starting point for finding all three globulars is Arcturus, the
lucida of Bootes. M13, of course, is easy. Imagine a line from Arcturus to
Vega. M13 is located where that line intersects the western edge of the
keystone of Hercules. Use binoculars to sweep the area, then line up your
scope with a Telrad or other similar device and voila!
Messier 3 is located along an imaginary line from Arcturus to Cor Caroli,
the brightest star in Canes Venatici. (This little constellation is located
just below the handle of the Big Dipper.) M3 is about one-third of the way
between Arcturus and Cor Caroli. Again, sweep the area with binoculars to
zero in on this glob.
Messier 5 resides in a area devoid of conspicuous stars, but the line from
Cor Caroli to Arcturus points almost directly to it. If this imaginary line
is extended so that Arcturus is at its midpoint, then M5 will be found
dangling on the other end.
No matter what scope you have each of these globulars will repay your
efforts to find them. My favourite is M13 (hey, I'm normal!), but M5 comes a
very close second and M3 is not far behind. Take a look, you won't regret
it.
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