I agree with Mike a TOA150B with flattener and reducer and Q extender is hard to beat in the refractor game. See Marcus Davies images on this site. He has shown consistently more detail in his images than I thought a 6 inch APO could show. Expensive though.
AP155EDF is the other one that is about the best there is. Especially with the AP reducer/flattener (155TCC). They come up occasionally usually for about US$9500 although there was one recently that went for a lot less. But it was quite a bit older and had the 2.7 inch focuser - you really want the 4 inch focuser. 2nd hand TOA150's when they do come up (not that often) usually go for around US$9000-9500. They used to be about $9000 new in the US now they are $11,400 at optcorp.com! I guess the Yen has appreciated against the US$ and there nust have been some price increases.
If I were shopping for a 6 inch APO my list would go like this:
AP155 with 4 inch greaseless focuser and feathertouch microfocuser and 155TCC reducer/flattener and 4 inch flattener.
TOA150B with flattener, super reducer and Q extender.
TEC160FL with flattener and new rings (ditch the TEC ones they damage the scope).
And thats it.
What mount are you looking at? For a scope that size the Paramount MX is probably the one to get.
Astromart ads often say CONUS only. If I want something I let them know that it is really no different than shipping to Texas. Also their market is depressed and they may not have US buyers so easily.
There is a TOA130 just listed for US$4800 for example (its only 2.7 inch focuser though and you need the 4 inch).
http://www.astromart.com/classifieds...fied_id=750060
The TOA150 was given a beefier focuser about 2 years ago and they name that the TOA150B. The original TOA150 would be fine for STL11 type cameras but heavier 16803 chipped cameras may test it hence the later model.
Speaking of APM/TMB there was a 175/F8 TMB for sale on Astromart about 5 weeks ago for US$8500 I think. That seemed like a huge bargain. Those scope don't seem to hold their value well. New that would be about $16,000 or more.
Yes with Strehl I am sure there are ways to massage the figures. TEC quote .99 in the green band (they primarily design for visual and green is the bulk of your eyesight). AP probably would be the most honest. I read in posts where Roland goes for .99.
Greg.