SmartDraw includes thousands of professional-looking diagrams like this that you can easily edit and make your own.
Text in this example:
Constellations of Northern Hemisphere Spring
Leo (the Lion) LEGEND -1 (Magnitude) 0 1 2 3 4 Variable star Open Cluster Globular cluster Galaxy Planetary nebula Diffuse nebula a Regulus Denebola b g Algieba d Zosma e m k l z h o r s i q M 66 M 65 M 105 M 96 M 95