We combined the above photometric data with kinematical data for proper motions and radial velocities.
Platais et al. (2003) presented a technique to obtain precise proper motions of stars in the region of NGC 188, using old photographic plates with assorted large aperture reflectors, in combination with recent CCD Mosaic Imager frames.
They used their proper motions to determine astrometric membership
probabilities down to V = 21 in the 0.75 deg 2 area around NGC 188.
For our study, we consider stars with membership probabilities higher than 50% from the catalogue given by Platais et al. (2003) , which gives us 562 member stars.
Geller et al. (2008) presented the results of ongoing radial velocity (RV) survey for NGC 188 by WIYN. 1
The data set observed by 3.5-m WIYN telescope on Kitt Peak in Arizona spans a time baseline of 11 years, a magnitude range of 12 ≤V ≤16.5 (1.18 −0.94 M ) and covers an area of one degree diameter on the sky.
For the kinematical studies, the values of radial velocity for NGC 188 stars have been taken from Geller et al. (2008) .