Todd is correct in saying that this will require more than one exposure.


If you're using Photoshop's noise reduction, or some other noise reduction, you can clean up the photos that way.


I would suggest taking a few exposures (set your camera to Av, as high of an ISO that you can that will give you a fairly fast shutter speed --perhaps, 1 second at the longest), then for your first shot at 0 eV, take the shot. Do another one at -1 eV, and another at -2 eV. One at +1 eV would bring out the shadows more, but the exposure will be longer.


Time the shots when the beam is where you want it to be. Since you can hang around for a long time while the beam spins around, you have an opportunity to take lots of shots, so don't skimp.


Pick the best of the various eV images that match up. Blend the images together. You should be able to get a good blend this way.


If you try bracketing with 3 exposures, you'll miss two out of the three shots for a proper "beam" look, so I wouldn't recommend bracketing on a moving object ( in this case, the light). That's why you should wait for the beam to swing to the right spot, and take your "x eV" shots individually (I hope I'm explaining this clearly enough).


If I were you, as long as there is no wind, don't worry about mirror lockup. Go ahead and use it if you want to, but there will be some measure of overlap with the various images, and it may wipe out any benefit of mirror lockup (what I mean by that is that some blurriness may still occur with the blending).


Definitely use a tripod and a remote release cord.


You've got a great scene to photograph. I hope it works out for you.


Alan