Left to Right:

1) Hubble Space Telescope 2.4m RC in space + WFPCII
2) Astrophysics 6" APO refractor on Earth (13000mm FL) + FLI ProLine 11002 (by Mike Sidonio)
3) ESO 2.2m RC on Earth + Wide Field Imager CCD
4) 20" Corrected Cassegrain from Earth + KAI11000 CCD (by Johannes Schedler)

Crops were taken from the original full frame higher resolution images here:

1) Hubble: http://us.st12.yimg.com/us.st.yimg.com/I/skyimage_2042_9611785

2) Mike Sidonio: http://www.pbase.com/strongmanmike2002/image/94204109/original

3) ESO 2.2m: http://www.eso.org/gallery/v/ESOPIA/Nebulae/phot-05a-09-fullres_001.jpg.html

4) Johannes Schedler: http://panther-observatory.com/