Quote:
Originally posted by Vermin
Even the Televue EPs that are parafocal require some fine adjustment.
I've noticed the filter refocus requirement too (on a polarizing moon filter), it does not change the height of the EP so it must mean the glass refracts the light in some way (supposed to be optically flat).
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The glass is optically flat but the incoming rays aren't perpendicular to it. If my thinking isn't faulty, the focal point would be slightly further.
Your filters must be different to mine. Mine do change the height of the EP.