Project Goals

The main goal of this project is: to approach, advance amateurs, towards photometric studies of galactic clusters.

To introduce this research field we have preferred open clusters. The reasons for this choice, is evidently due to the presence of more or less dense crowded fields in globular clusters, rather than in open clusters.

Therefore what we will learn using open clusters it will be applicable also to anular regions in globular clusters distinguishing, of course, between the peculiarities of the two stellar populations.

A photometric study of an open cluster, leads us to obtain following results:

  1. †††† Obtain: medium and individual colour excess E(B-V).
  2. †††† Obtain: individuals intrinsic colours of various members.
  3. †††† Find a value for: R = Av/E(B-V) within and around the cluster area.
  4. †††† Construct both: apparent and true, two colour and colour-magnitude diagrams.
  5. †††† Obtain: both apparent and true distance modulus.
  6. †††† Obtain: luminosity function.
  7. †††† Obtain: PDMF and IMF.
  8. †††† Obtain: cluster age.
  9. †††† Obtain: (Fe/H) ratio.
  10. †††† Obtain both: theoretical Hr diagram Log(Teff), Log(L/Ls) and Log(Teff), Mbol.
  11. †††† Study: evolutionary sequences on theoretical diagram.
  12. †††† Study: objects found inside instability strips.
  13. †††† Calibrate: absolute magnitudes for Ia, Iab and Ib luminosity classes objects eventually members.

These studies are important because they help us to understand clusters evolutionary state, through the analysis of the position of their members on the HR theoretical diagrams.

Particularly important are those clusters containing, as members, Cepheids or† A,F,G - SLGs ( Super Luminous Giant Stars ) belonging to Ia, Iab or Ib luminosity classes.

For such particular objects the determination of their intrinsic brightness, through cluster photometric study, can produce a serious contribution to the cosmic distance scale (eg. standard candles).

© 2006 - Valter Arnò.