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 67-square-degree field of view centered at ( \alpha, \delta ) = ( 19 ^ { h } 44 ^ { m } 00 \fs 0 , +37 \arcdeg 32 \arcmin 00 \farcs 0 ) ( J2000.0 ) , 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 \sim 8.0 ) we achieved a precision of 3.5 millimagnitudes , falling to 0.1 magnitudes at the faint end ( I \sim 
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 .
This includes : V1171 Cyg , a triple system with the inner two stars in a 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 .