I have performed some Focusing tests with the Paracorr and my 200mm / F6 Newtonian, which I think will be of interest to anyone using or purchasing a Paracorr.
The Televue recommended spacing between the Paracorr and the imaging chip is 55+/-4mm; however I have found that a tolerance of +/-4mm does not appear to ensure that good focus is achieved.
Here are the test shots that I have taken (refer to the text underneath for the test descriptions):
http://upload.pbase.com/david_fitz_h...11410/original
Note that the optimal focus distance between the CCD chip and Paracorr will also most likely vary with the focal ratio and aperture.