The star atlas Will Tirion Sky Atlas 2000 00 Sky Publishing Corp 1981 ISBN 0 933346 33 6 has the great orion nebula between about 5h 33 m to 5h 37 m 5 0 to 6 5 That s roughly 65 RA by 60 Dec If you include the northern cloud 1977 the Dec goes from 4 35 to 6 5 That would give roughly 60 RA by 85 Dec For just NGC1976 M42 I get 5h33 5 m to 5h36 3 m 5 12 to 5 50 for roughly 42 by 38 round to 45 by 40 On the other hand Roger W Sinnott and Michael A C Perryman 1997 Millenium Star Atlas Vol 1 chart 278 ISBN 0 933346 82 4 has the nebulae NGC 1977 1982 1976 and 1980 between about 5h 34 m to 5h 37 m RA 4 50 to 5 55 That s roughly 45 RA by 65 Just NGC 1977 is the same in RA but Dec 5 15 to 5 40 for 45 RA by 35 Dec Personally I d go with Tirion as it s more inclusive If somebody has access to Hirshfeld and Sinnott 1985 Sky Catalogue 2000 0 Vol 2 That might be a better reference Or maybe there s something in Burnham s Celestial Handbook that will serve Anyway it looks like the listed dimensions are for the entire cloud rather than just the emission nebula NGC 1976