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Science Forum Index » Astro - Amateur Forum » M67/NGC 2682 under very good seeing!
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| Anthony Ayiomamitis |
 Posted: Fri Feb 23, 2007 3:40 pm |
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Dear group,
What does one get when imaging an open star cluster with really good
seeing (FWHM=1.52")? Here is an example:
http://www.perseus.gr/Astro-DSO-NGC-2682.htm
There is a slight problem with the green channel and a very slight
gradient which I must resolve.
I hope you like it.
Anthony.
PS. With the weather currently very unpredictable, I must resort to the
imaging of "quick" targets. |
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| Brian Tung |
| Posted: Fri Feb 23, 2007 3:40 pm |
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Ben wrote:
Quote: AFAIC those chains are not spurious artifacts. I've been
looking for years at M38, M41, NGC 7789 and many others. I just
can't see the chains as random. Too much recursion.
I'm not sure whether the chains are *all* random, but many of them
surely are. There's too many stars for all the patterns to be physical.
The human brain is very good at seeing patterns, whether they are there
or not, physically. I floated the idea of a program to plot out simple
random open clusters (following the same density gradients and star
distributions, but with a known pseudo-random number generator), and
have the viewer decide whether a pattern can be seen in them or not.
They weren't interested, but I do think that it would be a provocative
exercise, to see whether patterns appear in nature more often than you'd
expect from pure chance.
Quote: What I think may cause them is the ejection of a massive star
from the cluster by a "hard binary". When the star leaves the
cluster it drags a few others with it. You see it in some Globulars
also.
I suspect that gravitational interaction isn't sufficient between two
otherwise unrelated stars in an open cluster for this mechanism to work,
but I haven't thought about it that much.
--
Brian Tung <brian@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html |
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| Brian Tung |
| Posted: Fri Feb 23, 2007 3:40 pm |
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| Michael McCulloch |
| Posted: Fri Feb 23, 2007 4:04 pm |
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On Fri, 23 Feb 2007 21:40:50 +0200, Anthony Ayiomamitis
<anthony@perseus.no2spam.gr> wrote:
Beautiful! I'd like to see more pics of open clusters like that. I get
tired of the same ol' nebulae.
Does anyone else find the star chains you can find in open clusters
interesting? Are they simply random alignments, or is there some
underlying physical/formation process that causes them to form chains?
I've observed and photographed some very obvious and *long* chains of
bright stars in M24 for example that would seem to be unlikely by pure
chance alignment.
---
Michael McCulloch |
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| Ben |
| Posted: Fri Feb 23, 2007 4:51 pm |
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On Feb 23, 1:40 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr>
wrote:
Quote: Dear group,
What does one get when imaging an open star cluster with really good
seeing (FWHM=1.52")? Here is an example:
http://www.perseus.gr/Astro-DSO-NGC-2682.htm
There is a slight problem with the green channel and a very slight
gradient which I must resolve.
I hope you like it.
Anthony.
PS. With the weather currently very unpredictable, I must resort to the
imaging of "quick" targets.
Anthony,
Like it? I love it. It's one of my favorite springtime
heralds.
AFAIC those chains are not spurious artifacts. I've been
looking for years at M38, M41, NGC 7789 and many others. I just
can't see the chains as random. Too much recursion.
What I think may cause them is the ejection of a massive star
from the cluster by a "hard binary". When the star leaves the
cluster it drags a few others with it. You see it in some Globulars
also.
Carry on Anthony,
Ben T
90.126 n 35.539 |
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| Pete Lawrence |
| Posted: Fri Feb 23, 2007 5:56 pm |
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On Fri, 23 Feb 2007 21:40:50 +0200, Anthony Ayiomamitis
<anthony@perseus.no2spam.gr> wrote:
Quote: Dear group,
What does one get when imaging an open star cluster with really good
seeing (FWHM=1.52")? Here is an example:
http://www.perseus.gr/Astro-DSO-NGC-2682.htm
There is a slight problem with the green channel and a very slight
gradient which I must resolve.
I hope you like it.
Anthony.
PS. With the weather currently very unpredictable, I must resort to the
imaging of "quick" targets.
That's a great shot of M67. An old cluster that deserves a bit of
respect, and that you've given it!
--
Pete Lawrence
http://www.digitalsky.org.uk
Last updated June 2006 |
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| Anthony Ayiomamitis |
| Posted: Fri Feb 23, 2007 6:05 pm |
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Ben wrote:
Quote: Anthony,
Like it? I love it. It's one of my favorite springtime
heralds.
AFAIC those chains are not spurious artifacts. I've been
looking for years at M38, M41, NGC 7789 and many others. I just
can't see the chains as random. Too much recursion.
Ben,
Here is my M38 which you mention above and which was imaged a few months
ago:
http://www.perseus.gr/Astro-DSO-NGC-1912.htm
I would like to revisit this cluster later this year since the
transparency was a slight problem with this particular effort.
As far as the other two clusters you mention, M41 will be nailed shortly
(please be patient) since it is a seasonal target and I must get it now
before its too late whereas NGC 7789 (an existing outstanding item for
me) will have to wait a few months for Cassiopeia to become a seasonal
constellation once again (yes, it is circumpolar but hugs the horizon
right now).
Quote: What I think may cause them is the ejection of a massive star
from the cluster by a "hard binary". When the star leaves the
cluster it drags a few others with it. You see it in some Globulars
also.
Interesting. As for globulars, we are slowly getting into their season
and I will be pursuing them aggressively very shortly. Here is a TEST
photo of M15 from a few months ago which I think was based on only three
3-min subs (luminance only):
http://www.perseus.gr/Astro-DSO-NGC-7078.htm (please ignore the imaging
details to the right).
Thanks .... and rest assured I will.
Anthony.
Quote: Ben T
90.126 n 35.539
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| Chris L Peterson |
| Posted: Fri Feb 23, 2007 8:30 pm |
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On Fri, 23 Feb 2007 16:19:44 -0800 (PST), brian@isi.edu (Brian Tung)
wrote:
Quote: I suspect that gravitational interaction isn't sufficient between two
otherwise unrelated stars in an open cluster for this mechanism to work,
but I haven't thought about it that much.
And I suspect that even if several stars were close enough for such an
interaction, the result would be stars flung in all directions, not
dragged into a line.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com |
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| atasselli@hotmail.com |
| Posted: Fri Feb 23, 2007 9:04 pm |
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On 23 Feb, 19:40, Anthony Ayiomamitis <anth...@perseus.no2spam.gr>
wrote:
Quote: Dear group,
What does one get when imaging an open star cluster with really good
seeing (FWHM=1.52")? Here is an example:
I assume the same as when you have 3"?
Andrea T. |
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| Ben |
| Posted: Fri Feb 23, 2007 11:16 pm |
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On Feb 23, 6:50 pm, b...@isi.edu (Brian Tung) wrote:
Quote: Chris L Peterson wrote:
And I suspect that even if several stars were close enough for such an
interaction, the result would be stars flung in all directions, not
dragged into a line.
If we add our suspicions together, does that add up to an accusation?
Anthony, Brian, Chris, et al.
If I am to be accused of speculating I must confess right now.
This speculation is based on a couple of items I should mention
in my own defense:
(1) In the Oct, 1998 issue of S@T George Djorgovsky wrote a sterling
article titled "The Dynamic Lives of Globular Clusters". In it he
attributed the core collapse and rebound in these giants to the
playoff between potential and kinetic energies instigated by
"hard binaries" whose binding energies can equal that of the rest
of the cluster. (Say half a million stars) Any passerby to such
an object is going to eject something from the cluster whether it
be itself or one of the original partners. I don't think it's a
"line" as
much as it is a *scatter* which is interpreted in linear form as
Brian suggests. (The brain will "connect the dots".)
Look at M22 through a moderate aperture, that "globe within
a globe". (Burnham) There are plenty of stars between those inner
and outer globes but being low mass they tend to fall below 15th
magnitude. It seems to be the high-mass stars the are ejected
first. This is evidenced in all globulars when you compare your
visual observations with the photographs - brighter stars along the
borders.
(2) All clusters are unravelling and it seems the lineations are
more characteristic of *older* clusters than the younger. (Compare
M38 with M37.)
Now look at me - I've gone into a rant here......
Isn't Anthony's M15 lovely?
Ben T
90.126 n 35.539 |
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| Anthony Ayiomamitis |
| Posted: Sat Feb 24, 2007 9:56 am |
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atasselli@hotmail.com wrote:
Quote: On 23 Feb, 19:40, Anthony Ayiomamitis <anth...@perseus.no2spam.gr
wrote:
Dear group,
What does one get when imaging an open star cluster with really good
seeing (FWHM=1.52")? Here is an example:
Hi Andrea,
Quote:
I assume the same as when you have 3"?
I wish this to be the case but unfortunately it isn't. Here is a very
poor result where seeing was around 3.0" from what I recall:
http://www.perseus.gr/Astro-DSO-NGC-7654.htm
Anthony.
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| Anthony Ayiomamitis |
| Posted: Sat Feb 24, 2007 10:00 am |
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Ben wrote:
Quote: On Feb 23, 6:50 pm, b...@isi.edu (Brian Tung) wrote:
Chris L Peterson wrote:
And I suspect that even if several stars were close enough for such an
interaction, the result would be stars flung in all directions, not
dragged into a line.
If we add our suspicions together, does that add up to an accusation?
Anthony, Brian, Chris, et al.
If I am to be accused of speculating I must confess right now.
This speculation is based on a couple of items I should mention
in my own defense:
(1) In the Oct, 1998 issue of S@T George Djorgovsky wrote a sterling
article titled "The Dynamic Lives of Globular Clusters". In it he
Thanks for the reference and which I will dig out.
I did some research a few weeks ago and found references to the
existence of approximately 1500 open clusters in our galaxy. I will try
and get a complete listing (at least for the northern hemisphere) and
start pursuing them (especially when the weather is bad and only small
windows of opportunity exist for imaging).
Anthony. |
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| Anthony Ayiomamitis |
| Posted: Sat Feb 24, 2007 10:02 am |
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Pete Lawrence wrote:
Quote: On Fri, 23 Feb 2007 21:40:50 +0200, Anthony Ayiomamitis
anthony@perseus.no2spam.gr> wrote:
Dear group,
What does one get when imaging an open star cluster with really good
seeing (FWHM=1.52")? Here is an example:
http://www.perseus.gr/Astro-DSO-NGC-2682.htm
There is a slight problem with the green channel and a very slight
gradient which I must resolve.
I hope you like it.
Anthony.
PS. With the weather currently very unpredictable, I must resort to the
imaging of "quick" targets.
That's a great shot of M67. An old cluster that deserves a bit of
respect, and that you've given it!
Thanks Pete! If it wasn't for M44 (also in Cancer), I suspect this
cluster would have been a little more popular than what it probably is
right now.
Anthony. |
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| atasselli@hotmail.com |
| Posted: Sat Feb 24, 2007 12:50 pm |
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On 24 Feb, 13:56, Anthony Ayiomamitis <anth...@perseus.no2spam.gr>
wrote:
Quote: atasse...@hotmail.com wrote:
On 23 Feb, 19:40, Anthony Ayiomamitis <anth...@perseus.no2spam.gr
wrote:
Dear group,
What does one get when imaging an open star cluster with really good
seeing (FWHM=1.52")? Here is an example:
Hi Andrea,
Hi,
What is worng with the NGC7654 pic? I can find hardly a difference
(well the field isn't exactly flat but neither the other was and maybe
just a bit of color cast) and if anything I'd rather have this then
the other. Apparently there is very little difference whether the
seeing was 1.5" or 3". BTW, at your image scale the average fwhm would
have been 1.3 pixels yet the final image show far larger star
diameters. One is left wondering what is all the fuss about excellent
seeing if the end results is about the same.
Andrea T. |
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| Chris L Peterson |
| Posted: Sat Feb 24, 2007 12:55 pm |
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On 24 Feb 2007 08:50:06 -0800, "atasselli@hotmail.com"
<atasselli@hotmail.com> wrote:
Quote: BTW, at your image scale the average fwhm would
have been 1.3 pixels yet the final image show far larger star
diameters.
There's no simple relationship between FWHM and apparent star diameters
(except comparatively, between two images made with the same equipment).
Any well exposed image of a rich star field will show star diameters
ranging from one pixel to many, regardless of the FWHM.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com |
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