September is such a wonderful month to get outside and do
some observing. In July and August,
observing the summer constellations means having to begin very late in the
evening, something impossible for those who work next morning. In July it isn't truly dark until
after 11 pm. Along comes autumn equinox
with a nice surprise: most of those summer constellations are still available,
and darkness comes early enough now to allow at least an hour or two of
observing even during a work week. For
a time in September, the stars actually appear not to advance at all from one
night to the next, due to the earlier sunsets and darkness. So if you have had a tough time getting your
observing act together during the summer, you can still see the wonders of
Lyra, Cygnus, Aquila, and even Sagittarius over the next several weeks.
This time I
would like to talk about a pair of objects in Lyra. They are challenging ones that require larger apertures to
appreciate. Both objects, a planetary
nebula and an open cluster, look splendid in my 12" reflector, and in our club’s 14” telescope. Hopefully, I can entice you outside some night soon for a look.
Lyra has the
most famous planetary nebula in the heavens.
M 57, the Ring Nebula, is one of the most looked at objects in the
sky. It looks beautiful in a 3” scope,
and anything bigger is a bonus. On a
spectacularly clear night last October, I was able to glimpse the central star
with a 12” scope. There is even a very
faint IC galaxy very close by that also makes for a challenging search. However, I wish to talk about another
planetary nebula in Lyra, NGC 6765. It cannot be found with a 3” scope; not even
with a 6”. It is 40” in size and close
to 13th magnitude. It’s
central star is beyond reach of the 14” scope, at mag. 16.
Located
slightly north of globular cluster M 56, and preceding it by 6’ of R.A., this
object surprises even veteran observers, who are often intrigued to learn of
its existence. While it can be located
in an 8” scope on a very fine night, a bigger aperture is required to fully
appreciate its size and shape. It
is certainly no Ring Nebula, as it offers an overhead planetary nebula much more
tricky to observe in detail, though worthwhile for patient observers. It lies close enough to M 56 that making a
stopover here is not difficult. I
observed it over several nights in the 12” scope, trying to figure out exactly
what it was I was seeing. When tackling
new objects at the eyepiece, I avoid looking up photos until my sketch and
description is complete. Then I go to
Google Images for a peek.
In the eyepiece I saw a
large, faint object at 100x, nearly half the size of M 57. It is in a very rich star field, and it
bears magnification well, whereas at 200x it becomes oval. At first I thought I was seeing a star in
it, but on further viewing it seemed like a bright clump of nebulosity. My ultra-block filter worked very well here,
making the object brighter and larger.
Eventually I was able to discern two parts to the nebula. At first it was merely rectangular in shape,
but as I viewed it longer it began to resemble a snowman, with a small,
roundish head situated atop a larger, roundish body. Is there a “snowman nebula” out there already? If not, I nominate pn 6765!
7.5 degrees
north of M 56, and 4’ following is the unusual and eye-popping open cluster NGC 6791.
This one requires a big aperture to resolve the multitude of stars, the
brightest of which is mag. 15. Observed
back in the old days with the 8”, it was seen as a milky haze, quite large and
not that difficult to locate. With a
diameter of 10’ and a visual mag. of around 9.5, it is impressive even when not
resolving. However, it does begin to
resolve in the 12” at higher powers (187x begins to show stars; at 250x things
start to become overwhelming). For
those who love to view oc 7789 in Cassiopeia (which resolves well in a 6”
scope), 6791 is another step or two beyond.
I have viewed it in the club’s 14”, but I would really like to see this
in a 16” scope or higher. Stars, stars,
stars!
With all the
wonderful globular clusters out there, it is not surprising that M 56 gets
overlooked sometimes by summer skywatchers.
When seen directly overhead, M 56 is a real treasure. Once again, the larger the aperture the more
you will see. Since this spectacular
globular cluster is used this month as our nearest guide object, it would be a
shame not to include it in our explorations.
It makes a wonderful third object, beginning with the faint planetary,
following up with the challenging-to-resolve open cluster, and finishing with M
56. And if you haven’t seen M 57 in a
while, view it after viewing 6765 to appreciate the differences. Enjoy the night skies!
Mapman Mike
Mapman Mike
