Throughout the Net
By Steve Coe
NGC 6121 is also known as M-4. It is
one of the most beautiful objects in the sky and one of my favorites
for many years. This huge globular cluster is visually at least 15
arc minutes in size using my 13" f/5.6 at 100X. It's magnitude is
given as 7.4 in Burnham's, and at a dark site in the Arizona desert,
I can just see a dim glow about one degree west of Antares. Raising
the power to 200X brings out lots of beautiful chains of stars which
curve out from a bright central bar. This bar can even be seen in
the finderscope as an elongated brightening in the middle of this
magnificent cluster of stars.
Antares is a rather difficult double star. If all you saw in the
statistics was the fact that the separation was 3 arc seconds and
the companion was 6.5 magnitude you might not think this double star
would be tough to split. However, seeing a close companion to a
first magnitude star is no easy task. This star seems to show off
its dual nature better during twilight. I believe the brighter
background doesn't let the bright star dazzle your eye. Seeing is better during twilight. Trying to use my old 17.5" Dobsonian at
full aperture was too much, so I stopped it down to 10" and got a
fine view and clean split on several occasions over the years,
usually at about 200X. My 13" has no trouble showing dark sky
between these stars on a steady night at 220X. Now, as to the color
of the companion; much has been written, some by me. I have always
seen the companion to Antares as light green. This could be a
contrast effect, since Antares is so obviously orange.
NGC 6144 is a very nice compact globular cluster, near Antares. I see it as pretty bright, large,
compressed and somewhat brighter in the middle at 135X. The surface
of this cluster is very mottled with stars just at the edge of
resolution at 200X and I can resolve 12 stars on a good night. This
cluster is at the edge of a very dark nebula, it is as if the stars
from one area were gathered up and lumped together.
NGC 6334, I see as faint, large, and irregular in shape at 100X.
This emission nebula is large, but seems to be several glowing
shapes the size of the 30' field in a 20mm Erfle eyepiece. The
nebulosity has 15 stars involved. Using the UHC filter brings up
the contrast of this object. There are four bright areas of the
nebula, with the entire field aglow with dim nebulosity.
NGC 6337 is a pretty faint, large, annular planetary nebula that
demands high power to see fine detail. At 320X there are two stars
involved, the stars straddle a dark area in the center of the
object. The UHC filter helps a little. This nice planetary does not
seem to get observed often.
NGC 6405 is M-6. I see it as very bright, very large, pretty rich,
and somewhat compressed at 60X. This cluster is easily naked eye
and several of the brighter members can be seen in 10X50 binoculars.
The shape has observers seeing a butterfly outline in this cluster
and I agree with that evaluation. There are even two delicate
curved chains of stars that form "antennae". BM SCO is a variable
star on the east side, it is a nice orange color. This beautiful
open cluster has always been a favorite object on a warm summer
NGC 6451 appears as a bright, pretty large, pretty rich, compressed
open cluster at 165X in my 17.5" f/4.5 with a 12.4mm Erfle eyepiece.
It is bright enough that it can be seen in the 8X50 finder. It
includes a close triple star which appears nebulous at low powers
and is resolved at 320X. I estimated 50 members in the cluster and
it includes a dark lane almost down the middle of the cluster.
NGC 6475 is M-7. It's very bright, very, very large, not
compressed, with many faint members at 60X. This huge cluster is
easily naked eye, even on poor nights. I can resolve 8 to 10 of the
brightest members in 10X50 binoculars. It is at its best in an RFT.
Using a 4.25" f/4 at 16X there is enough room around the cluster to
frame it in the Milky Way and there are 40 stars resolved with this
modest scope. Most large telescopes have a field of view too narrow
to provide a pleasing view of this cluster. See if you agree