Mark
This is exactly what I have done, and for the same reason. I have a Megrez90 and a DMK21.
To answer your question - yes, it is sensitive enough to pick up guide stars.
I got the 2inch Lumicon from MyAstroShop -
http://www.myastroshop.com.au/produc...asp?id=MAS-115.
I haven't had it that long, but from what I have tied so far, it is working great.
Darrell