by application of Eqn. (1) over the entire CMD region shown in Figure 2. Here we assume that the field stars outside the tidal radius are uniformly distributed throughout the annulus area.

$$s/n(i,j) = \frac{n_{c}(i,j) - gn_{f}(i,j)}{\sqrt{n_{c}(i,j) + g^{2}n_{f}(i,j)}}.
\label{eq1}$$

In the above, $n_{c}$ and $n_{f}$ refer to the number of stars in each sub-grid with color index $i$ and magnitude index $j$, counted within the cluster region and field region, respectively. The parameter $g$ represents the ratio of the cluster area to the field area.

The following procedures are followed in order to find the optimal range of colors and magnitudes that correspond to the likely members of each cluster. First, we sort the elements of $s/n(i,j)$ in descending order, so that we obtain a one-dimensional array of $s/n(i,j)$ with index $l$; the array element with the highest $s/n(i,j)$ corresponds to $l=1$. The next step is to obtain star counts in gradually larger regions of the CMDs. The accumulated area is represented as $a_{k} = ka_{l}$, where $a_{l} = 0.01$ mag$^{2}$, which is the same for all sub-grids, and is the area of a single sub-grid in the CMD array, and the $k$ is the number of sub-grids to 