I know some of what I'm going to say has already been said in several places on this forum, but for the purpose of my discussion, I will summarize some things.
The William Optics binoviewer, coupled with the 1.6 OCA that is supplied with the binoviewer, will not allow the SW 100 ED to come to focus.
One answer is to buy a Barlow that allows you to remove the 2x "cell" from the Barlow and attach that to the WO binoviewer. That works. I know because I tried it but it creates a lot of extra magnification...maybe 3.5-4X, I've been led to believe. I'm not happy with this solution because I don't like the significant increase in magnification.
Another answer is to buy a 1.25" diagonal and screw the 1.6 OCA into the front of the diagonal, closest to the objective lens. This, I'm told, will yield more than 1.6x power; maybe around 2.1x. Again, more power than some of us would like.
Now, let's look at Siebert Optics solutions:
They have an OCA that will increase the power only 1.25x, however, in order to use it, you will need a 1.25" diagonal. The OCA is $199.00 plus the cost of a 1.25" diagonal, if you don't already have one.
Siebert also has a "low profile" modified diagonal with a corrector that apparently will add NO extra magnification and attaches directly to the WO binoviewer and it will fit the 2" focuser on the SW 100 scope. This solution is $199.00 and obviously, you won't need to buy a 1.25" diagonal.
I kind of like the 2nd solution from Sieberts but wonder if anyone has tried it and can guarantee me that the SW100 ED will focus properly.
While I like the 2nd Siebert's solution, I'm not sure I want to do all my binoviewing through a 1.25" diagonal.....won't something be lost? I'm assuming that what would be lost are the benefits 2" diagonals bring to the table, right?
Thanks for any help you can provide,