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Reducer spacings v's effective focal ratio
I've prepared a spreadsheet which may be of interest. It calculates the final effective focal length and f ratio for various reducer fl's and spacings.
It also takes into account the changes in EFL due to the primary mirror shift in an SCT (based on Chris Lords original data, but updated)
You need to measure the final image plate scale (CCDInspector) to verify the optical train and actual spacings.
Ken
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