Steffen Kluge wrote in message ...
According to Chuck Taylor :
Should filters be kept away from the focal plane? Kept close to
the focal plane?

If they are on the focal plane, you will see every bit of dust on them.
However, with most eyepieces, the focal plane is in a ways from the filter
threads.

In other words, it's good to screw them into the diagonal, so
dust and imperfections won't show? Why are most people putting
their filters on the eyepieces, I wonder?

Probably for conveniece since it's more of a hassle to remove a diagonal
just to change filters.

One solution would be a filter wheel or slider (either holding 4-6 filters)
and keeping one slot open (i.e., no filter) for a clear view.