# On the assessment of the nature of open star clusters and the determination of their basic parameters with limited data

## TL;DR

This paper critically evaluates methods for determining open star cluster parameters, emphasizing the superiority of dedicated studies over automatic tools, especially with limited data, through detailed analysis of six specific clusters.

## Contribution

It demonstrates that dedicated, detailed analysis provides more accurate cluster parameters than automatic surveys, highlighting discrepancies and the importance of careful methodology.

## Key findings

- Dedicated studies yield more reliable cluster parameters.
- Automatic tools often produce contradictory results.
- Manual analysis improves understanding of poorly known clusters.

## Abstract

Our knowledge of stellar evolution and of the structure and chemical evolution of the Galactic disk largely builds on the study of open star clusters. Because of their crucial role in these relevant topics, large homogeneous catalogues of open cluster parameters are highly desirable. Although efforts have been made to develop automatic tools to analyse large numbers of clusters, the results obtained so far vary from study to study, and sometimes are very contradictory when compared to dedicated studies of individual clusters. In this work we highlight the common causes of these discrepancies for some open clusters, and show that at present dedicated studies yield a much better assessment of the nature of star clusters, even in the absence of ideal data-sets. We make use of deep, wide-field, multi-colour photometry to discuss the nature of six strategically selected open star clusters: Trumpler~22, Lynga~6, Hogg~19, Hogg~21, Pismis~10 and Pismis~14. We have precisely derived their basic parameters by means of a combination of star counts and photometric diagrams. Trumpler~22 and Lynga~6 are included in our study because they are widely known, and thus provided a check of our data and methodology. The remaining four clusters are very poorly known, and their available parameters have been obtained using automatic tools only. Our results are in some cases in severe disagreement with those from automatic surveys.