I have an event coming up where it will be necessary to stack 2 barco projectors to achieve desired brightness. However the lens will be the 0.73 TLD. Is it going to be possible or very difficult to align these units with such a short throw?
Most Barcos support lensshift with that lens model so you should be able to converge them although those aren't exactly the easiest lenses to do it with.
Short throw and stacked projectors is usually not a great conbination. Does Barcoaddress how much vertical lensshift is available with those lenses on the projectors you'll be using? Is that a sufficient distance to compensate for the offset from stacking?
You should double check this with the barcolens calculator but my recollection is that with the stacking frames the permissible lensshift with those lenses is sufficient to compensate.
With short throw lenses, you have less lens offset than you do with standard lenses, so it might be possible (you didn't mention which model Barco) but difficult. In addition, with the short throwlens, you want to minimize any keystoning as that will cause portions of your image to be out of focus.
What's your source? If you're able to output from a computer that can do mapping and multiple outputs, you could cornerpin the projectors (i.e. MadMapper). This makes stacking projectors infinitely easier.