That big ass star is Alnitak , designation ζ Orionis or
Zeta Orionis, abbreviated Zeta Ori, ζ Ori) or 50 Orionis (abbreviated 50 Ori), is a triple star system in Orion. It is one of the three main stars of Orions Beltit is a hot blue supergiant with an absolute magnitude of -6.0 and is the brightest class O star in the night sky with a visual magnitude of +2.0.
It has two bluish 4th magnitude companions, one finely resolved and one only detected interferometrically and spectroscopically, producing a combined magnitude for the trio of +1.77., and everyone who images the Horse head has issues with that star. 