Brandon you continue to amaze me with your pictures! Next time i'm in syracuse i would really like to check out your system! Maybe you could give me some photography pointers. Im buying myself a T1i after christmas.
The graininess is just due to noise on long exposures on digital cameras. I know on mine it has an option for long exposures. What it does is take the exposure twice and tries to do some noise rejection from the two images. Otherwise you will have to do some post noise processing.
Are you shooting digital or film? Either way grain, whether actual grain (film) or noise (digital) is not a function of aperture (f-stop) but rather ISO and choice of film stock, if shooting film. The higher f-stop allows you to achieve sharper focus, both real and perceived.
If thats your first go at night photos your def well on your way.
You can shoot 2 or 3 dif exposures & combine them in photoshop or even use HDR (high dynamic range) software like photomatrix.
this was one shot earlier in evening for sky then two a little later one lighter for darker areas & one darker exposure to keep lights from burning out, then put them together in photoshop. Obviously good tripod needed.