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Originally Posted by Rigel003
Hi Matt
>snip
Something that may be of interest - I've read that SCTs are corrected for spherical aberration only for a specific distance between the primary and secondary mirrors (from the early days when everyone had a 1 1/4" visual back and simple eyepiece). When you extend the optical train with large 2" diagonals, barlows etc. you have to move the primary further forward to focus and need to expect some slight amount of spherical aberration, under or over correction, not sure which.
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Hi Graeme
Thanks - that is very interesting information regarding SA, as I have just added a flip mirror unit to the JMI motofocus on the C9.25, which further extends the back plane to a total of approx 6 to 7 inches, or 15 to 18 cms, from the bare position.
Hmm, one night I must capture some star test avi's with the SCT in the OEM bare configuration, then add the JMI motofocus and finally add the Meade flip mirror and see what results I get.
Cheers
Dennis