Re: Cherokee #6: Pronto & Aquila/Serpens

Cherokee wrote:

> M26
>
> I used my SA2k to locate this fain object. I followed a chain of 4
> stars downwards from M11 and this led me directly to M26. M26 itself
> is a very dim, compact hazy spot.

I'm curious what magnification you were using. M26 is the faintest
open cluster in Messier's list, but even so, you should be able to
resolve some individual stars. My notes for the Ranger say that even
in the suburbs, I could see one star easily with direct vision at
60X, and 3 or 4 with averted vision.

I don't know why I never thought of this before, but when I was
looking at M26 last weekend, I realized that it is trivial to
locate in a reasonably dark sky, as it forms an almost perfect
isoceles right triangle with two naked-eye stars: Delta and
Epsilon Scuti. No need to hop down from M11.

> Serpens
>
> My Nightwatch outlines Serpens as 2 stars and a straight line. How
> does this constitute a constellation??

As Anthony Ayiomamitis says, this constellation was brutalized by
the International Astronomical Union when they "regularized" the
constellations in the 1920's. As a side-effect of redefining
constellations as regions of the sky rather than collections
of stars, they ended up decreeing that no star could belong to
two constellations at the same time. The critical stars in
Serpens happen to be also the "waist" of Ophiuchus, so Serpens
ended up split into two pieces. Serpens Caput, the head, is still
a pretty interesting shape, but Serpens Cauda, the tail, is just
a line of medium-bright stars. See the Ophiuchus/Serpens chart
on page 128 of the Audubon Guide for details.

No other constellation suffered as much, but Pegasus lost a
critical star that it used to share with Andromeda, and Auriga
lost a critical star that it used to share with Taurus.

Now that you own a good detailed atlas, you should take a step
backward and get a good all-sky chart, or set of charts. Here
are a couple of suggestions:

* Buy a planisphere. Immensely useful, and cheap. But limited
detail, and seriously distorts the southerly constellations.

* Orion's Deep Map 600 -- much more detailed than the above,
but even worse distortion, and useless as a guide to what's
up at any time and season. For many DSO's, will obviate the
need to refer to Sky Atlas 2000.0.

* Get a series of monthly charts -- minimal possible distortion
for an all-sky view. I happen to think that the company I work
for (Sky Publishing) puts out the best in the business -- and
thought so before I started working here, too! Skywatch, our
annual magazine, has a full set for the entire year.

> IC4756
>
> A huge sprawling cluster of stars. Overflowed my eyepiece view. Very
> impressive and well worth finding.

Yes, this is one of the finest and most under-appreciated clusters in
the sky -- perhaps because it has an IC number rather than an NGC or
Messier designation. And it's a perfect match for binoculars or a
small telescope. IC 4665 is pretty nice too, although no match
for IC 4756 (to my taste).

- Tony Flanders

.

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