I'm getting close to pulling the trigger on my first projector. Most likely an Optoma HD65. I am putting it in a basement with a low ceiling. My question is does the projector (most likely the Optoma HD65, but maybe this applies to all/most?) have to be dead center of the screen? Meaning centered perfectly for left and right and top and bottom of the screen. Do the projectors allow for some off centered adjustments?

Any advice is greatly appreciated. I just want to know where I can actually put the projector before I buy it.

That model does not have lens shift, which means you MUST be dead center on the screen (Lens to vertical centerline of screen). But even with the projectors that DO have shift, you still need to be as close to center as you can. The shift range is limited and you lose image quality. A number of people here and in other forums have wanted to put their projector way off to the side and that just won't work.

As far as the height of the projector, it will have to be mounted at or very near the top of the screen, upside down.

A good installation starts with mounting the projector according to the manufacturers specs, as detailed in the manual. You want to have as little correction as possible.

I'm getting close to pulling the trigger on my first projector. Most likely an Optoma HD65. I am putting it in a basement with a low ceiling. My question is does the projector (most likely the Optoma HD65, but maybe this applies to all/most?) have to be dead center of the screen? Meaning centered perfectly for left and right and top and bottom of the screen. Do the projectors allow for some off centered adjustments?

Any advice is greatly appreciated. I just want to know where I can actually put the projector before I buy it.

I don't know about the HD65 but even without lens shift, you can have the ability to keystone the image electronically, in both side and vertical orientations. This will remove some of the geometry error associated with being off center but how far depends on the projector. You'll have to check with Optima or wait for another person here to comment on that. Also, try posting in the HD65 thread, that'll get you a much more informed reply.

Either way, being centered will offer somewhat better image quality. Is the image degradation noticeable? I don't really think so, but some will say it is.

Also, you can table mount the projector, this is pretty common, especially for those using a retro-reflective screen. (ex: DaLite Hi Power)

Because of the optics involved with DLP style projectors like the HD65, they have very little to no lens shift. While it is possible to use keystone correction to straighten out the geometry of off center installations, be warned that this will have a negative effect on picture quality.

If projector placement is a problem, then I would recommend you consider a LCD projector like the Sanyo PLV-Z60 or similar models. LCD projectors by the nature of their optics have the capability of very large lens shifts. Because of this many don't even have keystone correction!