Image of HEAO-2 during flight preparation checks courtesy of TRW.
The Cygnus Loop image is a color version of Fig. 1 of a paper by W.H. Ku et
al. in 1984, Astrophysical Journal, Vol. 278, p. 615-618 who give a
detailed discussion of the interpretation (as well as a scale and
The supernova remnant is about 2.5 degrees across. In this image, North is up and East is to the right. Most other images of this remnant are flipped horizontally, so East is
on the left.