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Further thoughts
Hi Tony,
I have added an uncropped picture taken with my 150mm Esprit, you should be expecting the same results with the 120. On mine the distance from the CCD chip to the face on the corrector "past the thread" is 96mm. In the past when I have been checking the back focus distance I have assembled the whole lot and then removed the corrector and used vernier calipers to physically measure the depth to the CCD (I usually place a small piece of kimwipe over the CCD chip so I don't scratch it). I do this every time now, because I once got caught out where I failed to take into account the T Ring on the Canon (extra 10mm), if you measure the depth this way then it has to be correct. If the measured back focus distance is correct, then it can only be one of three things.
1. The CCD chip is tilted.
2. The corrector is faulty.
3. You Telescope is misaligned (not very likely, but still in the mix)
See if your supplier will lend you a new corrector so that you can rule that out of the equation.
Just my thoughts on the subject.
Cheers
Peter
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