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SCT's rule the planetary imaging game. Have a look at Paul Haese, Damien Peach. Anothony Wesley made his own planetary scope which as I recall is a Newt based scope.
A key point is being able to cool the optics. SCTs have lots of thermal tube currents that prevent you getting that extra bit.
My CDK17 has a fan and temperature control. I know from experience if the mirror temp is more than about 1C different from ambient you will not be at maximum sharpness the scope is capable of.
As far as TEC180 versus TEC140. I have a TEC180FL and an AP140.
For deep sky imaging the difference is AP140 is a wider field scope and TEC180 will show more detail. Otherwise the images of the same object look very very similar.
As far as viewing goes, I have read on the TEC Yahoo Group, 140 to 160 is a bigger jump in visual than 160 to 180.
I think that is for 2 reasons. 1, the percentage increase in surface area is greater in 140 to 160 over 160 to 180. 2ndly, 6 inch APO is kind of a sweet spot for APO refractors.
I love my TEC180 though. Although if I were wanting to do planetary I think I would use my CDK17 or get a 14 inch SCT and fit a cooling solution to it. Also unless Yuri has glass left for 180's I am not sure he is making anymore of these for now until glass supply returns to normal. I don't have current data but last was he had enough glass to do several more TEC180's and once they were made that was it for now until he can get more glass. I read the other day someone commenting he was no longer making them. You'd have to contact Yuri to get the latest update. These APO makers have a hell of a time getting the glass and then when they get it, getting glass good enough to make these lenses. TEC was hitting a 30% rejection rate of glass. This glass is not returnable and is very expensive. So its the glass manufacturers that make their business hell and push them in a certain direction like 140mm or smaller.
Then get a u-beaut planetary cam. There's lots of choice with planetary cameras these days
Greg.
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