Saturn and a Faint Open Cluster

Well, Sky and Telescope thought the open cluster, NGC 2420, being 11th mag, was
too faint to bother with, but Saturn will pass in front of this cluster the next
two nights, in case anyone wanted to check on it. Unfortunately, tonight, it's
gonna rain in LA. sigh.
--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
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Dave -

These kinds of "lesser" events must happen all the time. Do you have
an online resource for determining this or just study the current sky
chart?

Mark


David Nakamoto wrote:
Well, Sky and Telescope thought the open cluster, NGC 2420, being
11th mag, was
too faint to bother with, but Saturn will pass in front of this
cluster the next
two nights, in case anyone wanted to check on it. Unfortunately,
tonight, it's
gonna rain in LA. sigh.
--
Sincerely,
--- Dave

----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington

----------------------------------------------------------------------

Saturn will pass in front of [ngc2420] the next
two nights, in case anyone wanted to check on it. Unfortunately,
tonight, it's
gonna rain in LA. sigh.

Don't sweat it. The fat Wolf Moon will be washing it out anyway.

'Hey, Wolf Moon
Come cast your spell on me
Beware the woods at night
Beware the Lunar light' - Type O Negative

On Tue, 25 Jan 2005 21:46:55 GMT, "David Nakamoto"
wrote:

Well, Sky and Telescope thought the open cluster, NGC 2420, being 11th mag, was
too faint to bother with, but Saturn will pass in front of this cluster the next
two nights, in case anyone wanted to check on it. Unfortunately, tonight, it's
gonna rain in LA. sigh.

Snow in Toronto.

I set up Starry Night Pro for my locale, and monitor various planets that
interest me, principally Jupiter and Saturn, and principally when they enter
into the evening sky, and just look. It doesn't take long.

And no, these don't happen that often. There are not many deep sky objects
along the ecliptic, and there are many chances because of the small size of most
deep sky objects, or their faintness.

Sky and Telescope's reasoning was that the cluster is too faint to see through
most amateur instruments. Forget the fact that open clusters usually are more
visible than their stated magnitudes would indicate, partially the difference
between the eye and photographic film, and partially because any object
resolvable into stars seems to be brighter than the estimates in my experience.
--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------

"Mark" wrote in message
ups.com...
Dave -

These kinds of "lesser" events must happen all the time. Do you have
an online resource for determining this or just study the current sky
chart?

Mark


David Nakamoto wrote:
Well, Sky and Telescope thought the open cluster, NGC 2420, being
11th mag, was
too faint to bother with, but Saturn will pass in front of this
cluster the next
two nights, in case anyone wanted to check on it. Unfortunately,
tonight, it's
gonna rain in LA. sigh.
--
Sincerely,
--- Dave

----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington

----------------------------------------------------------------------

David Nakamoto wrote:

Well, Sky and Telescope thought the open cluster, NGC 2420,
being 11th mag, was too faint to bother with, but Saturn will
pass in front of this cluster the next two nights

"Mark" responded:

These kinds of "lesser" events must happen all the time.

And David Nakamoto then said:

No, these don't happen that often...
Sky and Telescope's reasoning was that the cluster is too faint
to see through most amateur instruments. Forget the fact that
open clusters usually are more visible than their stated magnitudes
would indicate ...

As David Nakamoto says, it's pretty rare for a planet to pass directly
in front of a deep-sky object. I'm not sure whether S&T omitted it
because
the cluster is faint or whether it was an oversight.

I disagree with the assertion that open clusters are easier to see than
their magnitudes suggest; in fact, I would have said exactly the
opposite.
There's plenty of mag 6 and mag 7 open clusters that are barely
detectable,
let alone mag 11. Of course, it all depends on the degree of
concentration.
But highly concentrated open clusters are the rare exception.

In this case, however, Sky Catalog 2000.0 actually lists the cluster as
mag 8.3; it's the brightest star that's listed as 11th magnitude.
Looking
at the charts, however, it seems to me that that star isn't a true
cluster
member; I think all the true members are mag 12 and fainter. That would
agree with my observation through a 7-inch scope: "@60X cloudy patch,
roughly 6' circle, resolve about 9 stars with averted vision." Averted
vision usually gets me down somewhere into 13th magnitude with that
scope.

Now, it's one thing observing a cluster on its own under a dark sky;
under full Moon with a mag 0 planet in the middle is a whole 'nother
ball game. My guess is that this would be a challenging observation in
a 12-inch scope. But challenging doesn't mean impossible! I would be
very interested in reports or photographs from anybody who actually
did observe this event.
- Tony Flanders
(in my official capacity as S&T editor)

On 25 Jan 2005 13:58:53 -0800, "Mark" wrote:

These kinds of "lesser" events must happen all the time. Do you have
an online resource for determining this or just study the current sky
chart?

Baton Rouge Astronomical Society Monthly Observing Information page:
http://www.bro.lsu.edu/bras/observing.html

I have a picture of what it will look like there. It's under
the "Monthly Sky Charts" section. My The Sky version 5, level IV gives
a mag of about 8 for this cluster. My cutoff point for the charts is
12th mag, so I thought this would be well viewable. Didn't even
consider the Moon, which someone else said might wash it out.


Frederick J. Barnett http://www.eatel.net/~fred/
The Baton Rouge Astronomical Society http://www.bro.lsu.edu/bras/
The BREC, LSU, BRAS Highland Road Park Observatory http://www.bro.lsu.edu/hrpo/
"Someone's got to take the responsibility if the job's going to get done!! Do you think that's easy?!" Gregory Peck - The Guns Of Navarone

Nice glamour shot of 2420 (Saturn not included):
http://www.noao.edu/outreach/press/p...n2420b_med.jpg

David Nakamoto wrote:
Well, Sky and Telescope thought the open cluster, NGC 2420, being 11th mag, was
too faint to bother with, but Saturn will pass in front of this cluster the next
two nights, in case anyone wanted to check on it. Unfortunately, tonight, it's
gonna rain in LA. sigh.


Well, NGC 2440 is a small open cluster (10 arc minute diameter) with a
total integrated magnitude of about 8.3. Its brightest star is around
magnitude 9.4, with most of the rest of its nearly 100 members between
10th and 14th magnitude. I watched Saturn in the southern edge of the
cluster last night (1/26/05 at 0700 UT). I could see a few of the
brighter stars in the cluster in my 4 inch refractor but I didn't break
out the NexStar 9.25SCT due to some high cirrus and the bright moon.
Had the moon not been out, it would have been an interesting sight.
Clear skies to you.

wrote in message
ups.com...
David Nakamoto wrote:

Well, Sky and Telescope thought the open cluster, NGC 2420,
being 11th mag, was too faint to bother with, but Saturn will
pass in front of this cluster the next two nights

"Mark" responded:

These kinds of "lesser" events must happen all the time.

And David Nakamoto then said:

No, these don't happen that often...
Sky and Telescope's reasoning was that the cluster is too faint
to see through most amateur instruments. Forget the fact that
open clusters usually are more visible than their stated magnitudes
would indicate ...

As David Nakamoto says, it's pretty rare for a planet to pass directly
in front of a deep-sky object. I'm not sure whether S&T omitted it
because
the cluster is faint or whether it was an oversight.

No, I can personally attest that it was not an oversight, because I sent off a
message to the editors many months ago so they could have a chance to alert
everyone, but they wrote back to me that they felt the cluster was too faint to
be seen in most amateur instruments, and that Saturn's brightness might
overwhelm it. Forget that the cluster is twenty arc-minutes wide and Saturn is
forty arc-seconds wide or 30 times smaller. However, at eleventh mag, it might
have been a stretch to see, but my experience is that star clusters in general,
and opens in particular, are a little easier to see than their published
magnitudes.



I disagree with the assertion that open clusters are easier to see than
their magnitudes suggest; in fact, I would have said exactly the
opposite.
There's plenty of mag 6 and mag 7 open clusters that are barely
detectable,
let alone mag 11. Of course, it all depends on the degree of
concentration.
But highly concentrated open clusters are the rare exception.

I bow to your experience, since I've not observed many opens, but this one,
according to the digitized sky survey, seems fairly condensed, so I thought it
might seem like a diffuse globular rather than an open, sort of like M11 but a
lot fainter.



In this case, however, Sky Catalog 2000.0 actually lists the cluster as
mag 8.3; it's the brightest star that's listed as 11th magnitude.
Looking
at the charts, however, it seems to me that that star isn't a true
cluster
member; I think all the true members are mag 12 and fainter. That would
agree with my observation through a 7-inch scope: "@60X cloudy patch,
roughly 6' circle, resolve about 9 stars with averted vision." Averted
vision usually gets me down somewhere into 13th magnitude with that
scope.

Now, it's one thing observing a cluster on its own under a dark sky;
under full Moon with a mag 0 planet in the middle is a whole 'nother
ball game. My guess is that this would be a challenging observation in
a 12-inch scope. But challenging doesn't mean impossible! I would be
very interested in reports or photographs from anybody who actually
did observe this event.

I actually was thinking of it as an imaging event, but nothing would prevent
anyone from trying a visual observation . . . except if you've got overcast
skies and rain. NUTS !


- Tony Flanders
(in my official capacity as S&T editor)

Uh oh ! I'm talking to one of the Big Boys! I'm a dead man. ^_^
--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------