I am helping a friend install a Sony vw60 projector in his basement. He already has the ceiling finished and did not plan well for installing a mount. Therefore, no 2X4 was installed between the floor joists and the ceiling is drywalled. I cannot find a joist to lag the screws in so the projector is centered in the room (it seems it cannot be offset even the slightest because there is no horizontal lens shift). Is there something else I can get to span the joists to ensure a secure installation? Do you have any other reccomendations for installation? Thanks.

You could span a couple of joists with a piece of plywood and dress it up with some trim and paint to match the ceiling.

That's what I was thinking but it would ruin the nice finished ceiling. I was hoping for another solution if there is even on out there.

As BIGmouthinDC said - you can span 2 joists with any board. If the ceiling is white, you might choose MDF that is pre-finished with a white finish (plastic or paint). There is a small amount of horizontal shift in the projector, you need a screwdriver to change it, see the 60 manual. Another option is that Chief makes a "horizontal shift kit", I use this kit on my VW50 - it allows you to offset the projector horizontally by up to 3 inches.

Another option, and probably not the one you wanted to hear, is to cut out a section of the drywall between the joists. Then add some support and put the drywall back and re-finish. Because this area will be above the PJ, it should not be very noticeable even if you do not end up with a spectacular drywall finishing job. I have several blemished above my PJ where I have messed up the paint job, fortunately you can not see them unless you have a ladder. If the projector is going to hang down a fair amount from the ceiling (on a pole), then obviously the area will be more noticeable.