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Wayne/ Bojan,
The design of the reducer is supposed to be 1. a reduction in effective focal length while 2. providing a flatter field.
My checking of reducers has always (excuse the pun!) focused on the on-axis image - I use my SCT for spectroscopy only.
Baader issued a chart for checking reducer spacing, not for the reduction factor but the suppressing of aberrations.
This infers that if you're seeing what looks like coma at the edges, the the reducer spacing is too close.......
Last edited by Merlin66; 14-07-2020 at 08:42 AM.
Reason: Correction
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