On 16 Mar, 09:13, "Ben" wrote:
On Mar 15, 5:21 am, "Valter Arnò" 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


Hi, Ben

You can find more on open clusters studies, complete techniques and
methodology through the following link: http://prints.iiap.res.in/bitstream/...nnapurni.S.pdf

Regards, Valter