Image Details
Caption: Figure 1.
(a) The 18,180 objects within a radius of 30﹩^{\prime} ﹩ of the cluster center, at R.A. = 273﹩\mathop{.}\limits^{\unicode{x000b0}}﹩412000, decl. = –31﹩\mathop{.}\limits^{\unicode{x000b0}}﹩826444 with BDBS i-band measurements between 10.4 and 19.8 mag., overlaid on a variable extinction map (I. T. Simion et al. 2017; J. A. Kader et al. 2023) in the BDBS i band. (b) Gaia DR3 sources were queried from gaiadr3.gaia_source around the SIMBAD center of NGC 6569 and filtered to have measured proper motions, G < 19, and RUWE < 1.4. Three subsets are shown: (i) an inner ﹩{5}^{{\prime} \rm{}\,\rm{}\,}﹩ circle around the cluster center (“cluster”; blue points), (ii) a ﹩1{5}^{{\prime} \rm{}\,\rm{}\,}﹩–﹩6{0}^{{\prime} \rm{}\,\rm{}\,}﹩ annulus (“bulge/field”; gray density histogram, randomly subsampled to 1.2 × 105 rows via random_index for speed), and (iii) a ﹩{2}^{{\prime} \rm{}\,\rm{}\,}﹩ core used only to estimate the cluster’s mean motion. The green star marks the median cluster proper motion from the ﹩{2}^{{\prime} \rm{}\,\rm{}\,}﹩ core. Tiny black dots show proper motions from our BDBS catalog overplotted on the same axes. Axes are ﹩{\mu }_{\alpha * }\equiv d\alpha /dt\cos \delta ﹩ versus μδ, in mas yr−1. No parallax or CMD cleaning is applied here, so the ﹩{5}^{{\prime} \rm{}\,\rm{}\,}﹩ (blue) selection includes some field contaminants.
© 2026. The Author(s). Published by the American Astronomical Society.