[sac-forum] Call for Observations
- From: "AJ Crayon" <acrayon@xxxxxxx>
- To: "SAC Forum" <sac-forum@xxxxxxxxxxxxx>
- Date: Thu, 5 Jul 2007 22:36:33 -0700
Unfortunately the clouds will play a big hand in our observing plans for this
month's session. They are, naturally, a sign of the upcoming monsoon season.
Regardless here is a copy of the objects for the next several months and they
include the constellations Serpens, Scorpius and Lyra.
The constellation Serpens is divided into two parts, separated by Ophiuchus.
For this session the western part will be studied and the east will be saved
for another time. First for this session is the extremely faint globular
cluster Palomar 5. To get there, it is 29' in PA 172 deg from 4 Serpentis. If
you don't have a 20" or larger telescope try using a hood and averted vision
while waiting for moments of good seeing. Don't forget that lightly tapping
the telescope will help bring out the brighter stars. It probably won't have
the characteristics of a globular, but a few faint stars, that come and go,
should be good enough. After this gem the incomparable M 5 awaits. There
shouldn't be a problem locating and observing. If it is visible in your
finder, please include that in your comments. After these two globular
clusters it is all galaxies and we begin with the barred spiral NGC5921. At
mag 10.8 can you discern the bar, even if it is an elongated, slightly brighter
middle? Next, slew on over to NGC5957. This 11.7 mag galaxy has an NGC
designation of cometary. Do you agree? The next hop is to NGC5962, an 11.3
mag late type spiral galaxy. Slewing north about 4 deg and a little to the
west is NGC5970; a mag 11.5 late type barred spiral galaxy. Be careful not to
let the 7th mag stars interfere with your observation. The last two galaxies
are close to the eastern edge of this part of the constellation. Start with
NGC6070, an 11.8 mag that is joined by some pretty faint galaxies; but about
all we will see is the elongation. NGC6118 is the last, at magnitude 11.7. It
is the more elongated of the last two and, perhaps, has the lowest surface
brightness. So don't expect much.
In order to stay a step or two ahead of the summer monsoon the next
constellation in the monthly sequence will be covered in this column. It isn't
clear what I'm getting myself into but I'd like for us to do an observing
sequence on the Table of Scorpius. This is a magnificent section of this
constellation that stands out to the naked eye, is an excellent binocular area,
yet to review with a telescope is a very rewarding experience. While there are
a number of open clusters there are some interesting dark nebulae involved that
will add some variety to the process. NGC6242, to the northern part of this
section of sky, will be the beginning. It is bright and large so should be
easily found. Next is Trumpler 24 about a degree in size and containing some
200 stars. Involved in its northern part is the bright nebula IC 4628, it to
has several stars involved that belong to the cluster. Just to the west is the
rather elongated dark nebula Barnard 48. The SAC database indicates a UHC
brings out the bright nebula. Try this and let us know your results. Next
slew your telescope west, to Collinder 316, which almost involves all of Tr.
24. This cluster is about 1.5 degrees in size, but is rather scattered about.
Just to the west is the cluster NGC6227 that is 18', large and rich. Back in
1985 it was non-existent and is with SIMBAD, yet NED gave coordinates as 16h
51m 33.54s and -41 13' 50.2" which looks to be a 5th magnitude star in a rich
Milky Way Field. Are there enough stars in an 18' area to qualify as an open
cluster? Before leaving this area slew south to NGC6231, a cluster we have
already done, but not as part of this kind of observing sequence. This is a
2nd magnitude cluster and should be visible to the naked eye. Can you see it?
Continue your slew south and take a quick look at zeta 1 and zeta 2 area as
there are some pretty bright stars there. Finally slew farther south to SL 17,
another dark nebula elongated in a somewhat northern position. The SL
references the dark nebula catalog of Sandqvist and Lindroos.
For October let's take on Lyra for the first time. We are all aware of the gem
there, but there's more to the Lyre than the Ring Nebula. So, before getting
there let's check what else there is to offer and start from the northern
region. First up, in the same 15' field of view will be the galaxies NGC6702
and NGC6703. The former will be the more difficult of the two, at mag 12.2 and
about half the size. For the next galaxy, slew to NGC6646. This one is about
2deg northwest from Vega. For a change, go to the yellow and blue double star
Struve 525. Reminds you of Albiero, doesn't it? Reason this was selected is
due to the proximity to next selection, but I wanted you to stop and smell, I
mean view, this one because it gets passed by on the way to the magnificent
Ring Nebula. Yes, just to make it clear M57 is next on the list. There has
been much discussion amongst amateurs and professionals about the visibility of
its central star. It is considered variable from 14th to 16th mag and,
regardless, you will need a clear transparent sky for any chance at seeing this
one. Let us know if you see it - a simple yes or no should do. Before ending
there are two more observations on the list. NGC6765 wonder of all wonders
this is another planetary nebula. Yes its magnitude is listed at near 13th,
but don't let this stop you as it should be, at least, stellar in an 8". The
NGC description in the SAC database lists it as elongated. Does this show up
in larger telescopes? After this you will understand why it is a little known
planetary. The final selection is the famous variable star RR Lyre. Its fame
comes from being called a standard candle that is its absolute magnitude has
been well determined. From knowledge of the absolute and visual magnitudes
they are able to determine its distance. Pretty neat!
Let's hope the weather pitches us a curve and clears up for this weekend. And
the monsoons start is delayed.
Clear skies to all,
aj
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