StefferKluge posted:

I'm wondering where in the optical train would be the best spot
to put them, to keep their imperfections from deteriorating
sharpness and contrast as far as possible.

I've got filter threads:

- on the diagonal (facing the OTA),
- on the back of the 2" - 1.25" adapter,
- on the Barlow,
- and obviously on the eyepieces.

The best place is on the eyepiece. This way, the edge of the filter will not
vignette the field any more than is absolutely necessary. Placing it farther
forward may or may not intrude on the incoming light cone. The second best
place is on the 2" to 1.25" adapter if you have 2 inch filters and want to use
them on 1.25" eyepieces. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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