A lot of people use a QHY 5 as an autoguider. I believe it is the same chip as the popular Starlight Express Lodestar.
As far as using a filter I would not do that. Narrowband filters are designed to block out all light except that narrow band of light. So you may find it very difficult to find a guide star. But try it out, perhaps its not such a narrow O111 filter.
Greg.
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