Stargazer said:
Wouldn't the 9 degree rule on a Dish500 pointing towards 61.5 only apply to a Dish500 that has the skew set on it? What if the skew is set at 0? I am thinking that one lnbf would be focused on a certain part of the dish (not the center but to one side) so putting an lnbf on the other side would focus in on a different part of the dish. One would have to make an adapter to where each lnbf would focus in on the center of the dish. It is easier to just get a dual lnbf. They can be had for very cheap maybe even free if you find some old dishes lying around.
Dish500 skew has nothing to do with this - it's nothing more than tilt to compensate for the difference in elevation between the two azimuths.
The shape of the dish can be thought of as a mirror - although a bent one - which means it has a focal length. That is, the LNBF must be a specific distance from the surface in order to get the maximum gain, which is very important to get sufficient signal to operate. For any given focal length, you can only have one feedhorn "there", and that feedhorn will be "seeing" a bird at a specific angle bounced off the pan.
With a standard Dish500, pointing at 110/119, if you put another LNBF in between, it would point at 114.5 (and have a better gain factor than the other two spots). An LNBF outside of the standard two will have less gain. This BTW, is the problem with SuperDish - the outside LNBF (110 on a 121 SD, 119 on a 105 SD) doesn't have a good focus point.
Now, that's a lot to swallow without diagrams that I don't have, but maybe it's enough.
Back to the original question - can you mount two LNBFs on a Dish500 ad have both "see" the same bird? Yes, but it's not likely they'd have anywhere near enough signal to work. They'd have to be closer to or farther from the pan than "focused". I can visualize what I'm trying to explain - it's like a camera lens. This link
http://farside.ph.utexas.edu/teaching/302l/lectures/node114.html (which has nothing to do with DBS) has a decent set of diagrams that might help.