We present the X-ray catalog and basic results from our Chandra Large Area Synoptic X-ray Survey ( CLASXS ) of the Lockman Hole-Northwest field .
Our 9 ACIS-I fields cover a contiguous solid angle of \sim 0.4 deg ^ { 2 } and reach fluxes of 5 \times 10 ^ { -16 } { \thinspace ergs } { \thinspace cm } ^ { -2 } { \thinspace s } ^ { -1 } ( 0.4 - 2 keV ) and 3 \times 10 ^ { -15 } { \thinspace ergs } { \thinspace cm } ^ { -2 } { \thinspace s } ^ { -1 } ( 2 - 8 keV ) .
Our survey bridges the gap between ultradeep pencil-beam surveys , such as the Chandra Deep Fields ( CDFs ) , and shallower , large area surveys , allowing a better probe of the X-ray sources that contribute most of the 2–10 keV cosmic X-ray background ( CXB ) .
We find a total of 525 X-ray point sources and 4 extended sources .
At \sim 10 ^ { -14 } { \thinspace ergs } { \thinspace cm } ^ { -2 } { \thinspace s } ^ { -1 } ( 2 - 8 keV ) , our number counts are significantly higher than those of several non-contiguous , large area surveys .
Such a large difference is an indication of clustering in the X-ray sources .
On the other hand , the integrated flux from the CLASXS field , combined with ASCA and Chandra ultradeep surveys , is consistent with results from other large area surveys , within the variance of the CXB .

We see spectral evolution in the hardening of the sources at fluxes below 10 ^ { -14 } { \thinspace ergs } { \thinspace cm } ^ { -2 } { \thinspace s } ^ { -1 } , which agrees with previous observations from Chandra and XMM-Newton .
About 1/3 of the sources in the CLASXS field have multiple observations , allowing variability tests .
Above 4 \times 10 ^ { -14 } { \thinspace ergs } { \thinspace cm } ^ { -2 } { \thinspace s } ^ { -1 } ( 0.4 - 8 keV ) , \sim 60 \% of the sources are variable .
We also investigated the spectral variability of the variable sources .
While most show spectral softening with increasing flux , or no significant spectral change , there are a few sources that show a different trend .

Four extended sources in CLASXS is consistent with the previously measured LogN-LogS of galaxy clusters .
Using X-ray spectra and optical colors , we argue that 3 of the 4 extended sources are galaxy clusters or galaxy groups .
We report the discovery of a gravitational lensing arc associated with one of these sources .
Using red sequence and brightest cluster galaxy methods , we find that the redshifts of the extended sources are in the range z \sim 0.5 - 1 .
The inferred masses within the Einstein radii are consistent with the mass profiles of local groups scaled to the same virial radii .