I switched from piggyback to tandem arrangements for all of my imaging and guide scope combinations hoping that doing so might reduce or eliminate what I believe to be differential flexure in some of my images.
For my tandem arrangement I have a DOVELM162 attached to the Declination top plate on my 1100GTO mount as the base dovetail slide. Then I have a SBD13SS attached to the DOVELM162 base, with another DOVELM162 to which the imaging scope is attached, and a DOVEDV10 for the guide scope. The sketch below shows the arrangement with the dimensions that balance the arrangement for my 180 EDT setup.
Although I did not see any significant reduction in the differential flexure, I did find that the tandem arrangement makes it possible to more precisely balance the scopes. Roland has some good instructions on the A-P web site for balancing a tandem setup. The most important step being to do some or all of this procedure indoors during the daytime so that you can see what you are doing.
