  The Hungarian-made Automated Telescope network (HATnet) is an ongoing project
to detect transiting extra-solar planets using small aperture (11 cm diameter),
robotic telescopes. In this paper we present the results from using image
subtraction photometry to reduce a crowded stellar field observed with one of
the HATnet telescopes (HAT-5). This field was chosen to overlap with the
planned Kepler mission. We obtained I-band light curves for 98,000 objects in a
8.3x8.3 square degree field of view, near the Galactic plane in the
constellations Cygnus and Lyra. These observations include 788 5-minute
exposures over 30 days. For the brightest stars (I~8.0) we achieved a precision
of 3.5 millimagnitudes, falling to 0.1 magnitudes at the faint end (I~14). From
these light curves we identify 1617 variable stars, of which 1439 are newly
discovered. The fact that nearly 90% of the variables were previously
undetected further demonstrates the vast number of variables yet to be
discovered even among fairly bright stars in our Galaxy. We also discuss some
of the most interesting cases. These include: V1171 Cyg, a triple system with
the inner two stars in P=1.462 day period eclipsing orbit and the outer star a
P=4.86 day Cepheid; HD227269, an eccentric eclipsing system with a P=4.86 day
period that also shows P=2.907 day pulsations; WW Cyg, a well studied eclipsing
binary; V482 Cyg, an RCB star; and V546 Cyg, a PV Tel Variable. We also detect
a number of small amplitude variables, in some cases with full amplitude as low
as 10 mmag.
