Dear Group,

The oldest (or second oldest) open star cluster in our galaxy is
Berkeley 17 in Auriga with an estimated age of 10.06 billion years.

Dear Group,

The oldest (or second oldest) open star cluster in our galaxy is
Berkeley 17 in Auriga with an estimated age of 10.06 billion years.
Lying at a distance of 8,800 light-years away, the cluster is quite dim
with a magnitude of only 14.0.

NGC 6791 in Lyra has produced conflicting age estimates including a
figure of 10.20 billion years. As a result, there is some ambiguity as
to whether NGC 6791 or Berkeley 17 is the oldest cluster.

Further details and a photo based on two hours total exposure is
available athttp://www.perseus.gr/Astro-DSO-Cluster-Berkeley-17.htm.
Clicking on the image will yield an image with better image scale for
viewing.

In checking for other photos of Berkeley 17, I could only find one
example taken using film emulsion. If anyone is aware of other sample
images, I would be most interested.

Clear skies!

Anthony.

Your header declares that the brightest stars are only
16th magnitude. I think that is shortchanging this old fellow
a bit and that figure ought to be revised upward to about
13th. Anyway I don't have any trouble seeing about 15 - 20
members with my 10 in.

Great Work!

Ben, 90.126 n 35.539

On Mar 14, 7:38 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr
wrote:

Dear Group,

The oldest (or second oldest) open star cluster in our galaxy is
Berkeley 17 in Auriga with an estimated age of 10.06 billion years.


Anthony,

An exquisite image to say the least with round sharp points
all across the field. Isn't it a real challenge to separate the
true cluster members from the background star points?

Your header declares that the brightest stars are only
16th magnitude. I think that is shortchanging this old fellow
a bit and that figure ought to be revised upward to about
13th.

Anyway I don't have any trouble seeing about 15 - 20
members with my 10 in.

Great Work!

Ben, 90.126 n 35.539

Your header declares that the brightest stars are only
16th magnitude. I think that is shortchanging this old fellow
a bit and that figure ought to be revised upward to about
13th. Anyway I don't have any trouble seeing about 15 - 20
members with my 10 in.

Great Work!

Ben, 90.126 n 35.539


Oops!

I just checked Uranometria's DSFG and they are in total
agreement with you. This means I must have been looking at
something else.

Still a great image even if it is as difficult as 6791.

Regards,
Ben

Not that I doubt you but can I please trouble you for a reference so
that I can get a precise estimate and which I can also use in the future
for forthcoming Berkeley clusters?

An exquisite image to say the least with round sharp points
all across the field. Isn't it a real challenge to separate the
true cluster members from the background star points?

The cluster and its minute member stars are much better visible with the
larger image (when you click on the initial itself).

Dear Group,

The oldest (or second oldest) open star cluster in our galaxy is Berkeley
17 in Auriga with an estimated age of 10.06 billion years. Lying at a
distance of 8,800 light-years away, the cluster is quite dim with a
magnitude of only 14.0.

NGC 6791 in Lyra has produced conflicting age estimates including a figure
of 10.20 billion years. As a result, there is some ambiguity as to whether
NGC 6791 or Berkeley 17 is the oldest cluster.

Further details and a photo based on two hours total exposure is available
at http://www.perseus.gr/Astro-DSO-Cluster-Berkeley-17.htm . Clicking on
the image will yield an image with better image scale for viewing.

In checking for other photos of Berkeley 17, I could only find one example
taken using film emulsion. If anyone is aware of other sample images, I
would be most interested.

Clear skies!

Anthony.

Dear Group,

The oldest (or second oldest) open star cluster in our galaxy is
Berkeley 17 in Auriga with an estimated age of 10.06 billion years.
Lying at a distance of 8,800 light-years away, the cluster is quite dim
with a magnitude of only 14.0.

NGC 6791 in Lyra has produced conflicting age estimates including a
figure of 10.20 billion years. As a result, there is some ambiguity as
to whether NGC 6791 or Berkeley 17 is the oldest cluster.

Further details and a photo based on two hours total exposure is
available at http://www.perseus.gr/Astro-DSO-Cluster-Berkeley-17.htm .
Clicking on the image will yield an image with better image scale for
viewing.

In checking for other photos of Berkeley 17, I could only find one
example taken using film emulsion. If anyone is aware of other sample
images, I would be most interested.

Clear skies!

Anthony.

Hi, Antony and Ben

Ben wrote:
An exquisite image to say the least with round sharp points
all across the field. Isn't it a real challenge to separate the
true cluster members from the background star points?
Antony wrote:
The cluster and its minute member stars are much better visible with the
larger image (when you click on the initial itself).

I am happy to see that interesting objects such as open and globular
cluster turn out, of some interest.
However I must remember to Antony and Ben, that the only scientific
procedure to select the true cluster members from field stars, is the
knowledge of cluster reddening. Through reddening values we can
obtain Vo = visual magnituides without reddening effects. Subsequently
it will be possible - applying an empirical zams relation, like that
of Schmidt-Kaler - to obtain the absolute magnitudes and the medium
cluster distance modulus. An alternatively procedure, without any
calculations, can be represented by the construction of a Color-
Magnitude diagram that allows us to separate, graphically, cluster
star members lying on zero age main sequence, from field stars. This
second way, unfortunately, require science images through Johnson
filters for instance.

Regards, Valter.

On Mar 15, 5:21 am, "Valter Arnò" <s...@progind.it> wrote:



Hi, Antony and Ben

Ben wrote:
An exquisite image to say the least with round sharp points
all across the field. Isn't it a real challenge to separate the
true cluster members from the background star points?
Antony wrote:
The cluster and its minute member stars are much better visible with the
larger image (when you click on the initial itself).

I am happy to see that interesting objects such as open and globular
cluster turn out, of some interest.
However I must remember to Antony and Ben, that the only scientific
procedure to select the true cluster members from field stars, is the
knowledge of cluster reddening. Through reddening values we can
obtain Vo = visual magnituides without reddening effects. Subsequently
it will be possible - applying an empirical zams relation, like that
of Schmidt-Kaler - to obtain the absolute magnitudes and the medium
cluster distance modulus. An alternatively procedure, without any
calculations, can be represented by the construction of a Color-
Magnitude diagram that allows us to separate, graphically, cluster
star members lying on zero age main sequence, from field stars. This
second way, unfortunately, require science images through Johnson
filters for instance.

Regards, Valter.

Valter,

Yes, this cluster is obvoiusly dominated by reddened
solar - mass stars or it wouldn't have lasted this long. Also
the prevalence of these masses may have contributed to
the cluster's stability.
I'm not familiar with the Schmidt - Kaler method. Could you
link us to something that would explain?
Your website is interesting but my computer is so slow
it takes forever to load it.

Regards,

Ben

Which is a little disconcerting because it should have appeared
as a proper little smudge like Tombaugh 5. But it didn't.
That means I was seeing something else and Be 17 is going
to be another tough object and I may not be able to see it at all.

"Ben" <> wrote
..

First point: Anthony has a great picture here!!

It looks to me like the brighter stars in the image are evenly spread over
the field, while the cluster is made up of only dimmer stars. It would
probably be a very difficult visual target.

George N