Insights into the properties of the Local (Orion) spiral arm. NGC 2302:
  First results and description of the program
  The spiral structure of the Milky Way is highly uncertain and is the subject
of much discussion nowadays. We present the first result from a program that
determines the properties of the Local spiral arm (LOA), together with a full
description of the program. In this context we have made a comprehensive study
of the young LOA open cluster NGC 2302, which includes a UBVRI photometric
analysis and determination of its kinematic properties - proper motion and
radial velocity - and of its orbital parameters. We determined the mean PM of
NGC 2302 relative to the local field of disk stars, and, through a comparison
with the UCAC4 catalog, we transformed this relative PM into an absolute one.
Using medium-resolution spectroscopy of 26 stars in the field of NGC 2302, we
derived its mean RV. Isochrone fits to the photometric diagrams allowed us to
determine the fundamental parameters of NGC 2302, including reddening,
distance, and age. The kinematic data and derived distance allowed us to
determine the space motion of NGC 2302. This was done by adopting a
time-independent, axisymmetric, and fully analytic gravitational potential for
the MW. We obtained an absolute PM for NGC 2302 of ($\mu_{\alpha}
\cos\delta,\mu_{\delta}) = (-2.09,-2.11)$ mas/yr, with standard errors of 0.410
and 0.400 mas/yr. The mean RV of NGC 2302 turned out to be 31.2 km/sec with a
standard error of 0.7 km/sec. Isochrone fits displaced for this reddening and
for a distance modulus of (m-M)o = 10.69 indicate an age of log(t) = 7.90-8.00
with a slight tendency toward the younger age. Inspection of the shape of the
orbit of NGC 2302 and the resulting orbital parameters indicate that it is a
typical population I object.
