The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been used for the past 25 years as a reference source in TeV astronomy , for calibration and verification of new TeV instruments .
The High Altitude Water Cherenkov Observatory ( HAWC ) , completed in early 2015 , has been used to observe the Crab Nebula at high significance across nearly the full spectrum of energies to which HAWC is sensitive .
HAWC is unique for its wide field-of-view , nearly 2 sr at any instant , and its high-energy reach , up to 100 TeV .
HAWC ’ s sensitivity improves with the gamma-ray energy .
Above \sim 1 TeV the sensitivity is driven by the best background rejection and angular resolution ever achieved for a wide-field ground array .

We present a time-integrated analysis of the Crab using 507 live days of HAWC data from 2014 November to 2016 June .
The spectrum of the Crab is fit to a function of the form \phi ( E ) = \phi _ { 0 } ( E / E _ { 0 } ) ^ { - \alpha - \beta \cdot { ln } ( E / E _ { 0 } ) } .
The data is well-fit with values of \alpha = 2.63 \pm 0.03 , \beta = 0.15 \pm 0.03 , and log _ { 10 } ( \phi _ { 0 } ~ { } { cm ^ { 2 } } ~ { } { s } ~ { } { TeV } ) = -12.60 \pm 0.02 when E _ { 0 } is fixed at 7 TeV and the fit applies between 1 and 37 TeV .
Study of the systematic errors in this HAWC measurement is discussed and estimated to be \pm 50 % in the photon flux between 1 and 37 TeV .

Confirmation of the Crab flux serves to establish the HAWC instrument ’ s sensitivity for surveys of the sky .
The HAWC survey will exceed sensitivity of current-generation observatories and open a new view of 2/3 of the sky above 10 TeV .