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Thanks for the compliments, guys.
John: Yes, I neglected the instructions to do Classical offset, which makes the optical and mechanical axes coincident. For visual use it isn't critical, and, at f/5 (my chosen f/ratio), the offset is too small to have a dramatic effect on DSC accuracy (especially with the Argo Navis), but at shorter f/ratios you are correct that perhaps making the two axes coincident would be of more value.
I have found that the tilt of the optical axis away from the mechanical axis is, more or less, equal to the offset required in Classical offset, so I might add a caveat that if the offset is less than or equal to 1/8", the likelihood is that the New Model collimation is unlikely to affect your DSC accuracy.
But if offset calculations indicate a greater offset is required, it might be worthwhile to build in the Classical offset movement of having the secondary positioned slightly away from the focuser by the calculated amount (there are on-line calculators for offset).
The beauty of the New Model is that offset is automatically built in when collimating, whether the focuser is "square" to the tube or not. As such, it is easier for the user. But I agree that there are circumstances where perfect coincidence of optical and mechanical axes would be called for.
Perhaps I will incorporate those instructions in version 4.
Don Pensack
Los Angeles.
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