IC 2118, aka the Witch Head Nebula, is a large reflection nebula in Eridanus. Rigel (Beta Orionis) illuminates interstellar dust — the reflected light is biased towards the blue not only because Rigel’s light is bluish, but because blue wavelengths are reflected more efficiently than red/green wavelengths.  

Technical details:

Imaged by SSRO at New Mexico Skies in 2007 using a 4″ FSQ 106N @ f/5 with an SBIG STL11K on a Paramount ME. Image scale 3.5″/pixel. This is a 3 panel mosaic with about 15 hours of data. Calibration in CCDsoft, alignment in Registar, integration in Sigma Combine, and the rest in Photoshop. Chosen for the 2010 UNESCO World Science Day poster.