These are the biggest nebulae in the SAC catalogue. The size is given in arc-minutes.
OBJECT SIZE_MAX
Sh2-312 720 m, part of Gum nebula?
Sh2-276 600 m, Barnard's Loop
Gum 12 264 m, Gum nebula
NGC 6960 210 m, Veil nebula
Sh2-240 200 m, Simeis 147
IC 353 180 m
IC 360 180 m
IC 2118 180 m
RCW 59 180 m
NGC 1499 160 m
Sh2- 1 150 m
Ced 122 144 m
NGC 3372 120 m
NGC 6334 120 m
Sh2- 91 120 m
NGC 7000 120 m
M 45 100 m
M 42 90 m
IC 434 90 m
IC 4628 90 m
NGC 6533 90 m
IC 1396 89 m
vdB 107 85 m
Sh2-205 80 m
NGC 2238 80 m
NGC 2237 80 m
NGC 2246 80 m
NGC 6727 80 m
IC 2948 75 m
For more information on Sh2 objects see
http://galaxymap.org/cgi-bin/sharpless.py?s=1
For more information on RCW objects see
http://galaxymap.org/cgi-bin/rcw.py?s=1