The number one mistake MN190 owners make is moving the secondary. The MN190 secondary is positioned at the factory and should never be moved fore or aft of its position on the corrector plate. In other words offset is fixed. There are many threads on the Cloudy Nights forum on this topic.
The correct way to install a Moonlite focuser, which requires the special MN190 adaptor, is to centre the focuser tube over the secondary in its original position. The adaptor is required to allow the Moonlite to be moved far enough forward on the tube to sit directly over the secondary ( which should sit in the factory set position.).
Did you buy this scope new, or second hand? Because , there are MN190s which are sold which have already been buggered up by a previous owner, and for that reason they should not be purchased from unknown sources who do not under stand the optical setup.
In my experience, and as the designer of the Moonlite MN190 Adaptor, when the Moonlite is centred correctly over the secondary, it is pretty much correct and usually only requires basic primary adjustment to get the collimation spot on. A laser in the focuser tube should be all you need to maintain perfect collimation, and they tend to stay in collimation.
Last edited by glend; 29-09-2021 at 12:57 AM.
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