I agree H, The Not too long, not too short perspective gives a very different look. You see a lot of images from the 50mm / 90mm / 135mm lens ranges Then a lot of images from telescopes ranging from 480mm to 650mm
This is that very sweet middle ground... Big enough front aperture at 112mm to suck down a lot of light and resolve reasonable detail, fast enough to go really really deep with short exposures and just the right focal length to really show off extended areas of nebulosity like lambda cent. Eta Car, Rosette/Cone make a nice two panel mosaic with this length... M45 becomes a floating blue island... All the favorites take on a new face with such a wide view...
My 450D is about to recieve a cold finger too to slam it down to -5°C to make the most of it...
I'd say 20 minute Ha exposures at f/2.8 ought to go deep enough!
As a note - all the above images are series of 1 minute sub-exposures as the system sucks the light pollution in if I go over 1min per sub.. I can detect mag 13 galaxies in a 1min sub and with 20x1min stacked you can make out mag 14....
Here is a test from the new flats/flat darks.