Hi Gray,
Mr Rhor has done a lot of thorough optical testing of many scopes that is an eye opener:
http://translate.google.com/translat...history_state0=
To get one that performs through that tough testing has to be very special.
Having had several high quality APOs I think there are 3 main aspects to consider.
One is quality of optics - obviously.
One is quality and practicality of the mechanicals - millions of internet posts about the focusers, reflections etc etc.
One is about your intended use - weight, portability, imaging versus visual etc.
Imaging seems to be more demanding of a scope than visual. CCD cameras detect a wider range than our sight. Flex is not an issue with visual it is with imaging. Weight also is less important for visual except for portability whilst it can be very important for imaging and mounts.
Looking over some of Mr Rohrs tests you will find only really about 3 or 4 makers that make top end optics.
Tak, AP, TEC, APM/TMB. Tak, AP and TEC run around .98-.99 strehl. TEC may be lower strehl in the red channel (.88) and high in the blue (.98) and green(.99).
Tak TOA and AP would be good in all 3, some colours better than others but very high. APM/TMB are sold between -.95 to about .97 and sometimes higher. They are air spaced triplets from LZOS in Russia who make their own exotic OK4 glass which is similar to FPL53.
Its worth looking over the site and checking out the tests. They are often in German but mostly graphics. They are not explained and I guess you look at several and you can tell a good one when you see it. Start with TOA to see an excellent one so you can tell what is not excellent.
AP130GT sell rountinely fairly new for US$7500 on Astromart. Roland must have made quite a few of these last year and is about to make a bunch more so these are the most accessible Astrophysics scope.
Tak TOA are usually fairly available as well.
As far as optical tests go the best seemed to be TOA and AP. TEC is up there as well. The usual complaint about TOA is they are very heavy for their size. The usual complaint about AP is they are not available. I don't read any complaints about TEC. Nor APM/TMB for that matter.
Perhaps also a question mark over the focusers' heavy weight load performance (Tak had to bring out a TOA150B to handle this).
AP has a stainless steel drawtube rather than Aluminium that everyone else seems to use. Grab a 3mm thick aluminium tube sometime - you can make it flex by hand with a bit of force. That or something similar is what most use. AP uses stainless steel. It must be 4x stronger at least.
My experience is AP has the best mechanicals, the best or equal to the best optics (you'd have to be confident with Tak there and also TEC).
AP130GT may be a good match for your needs. Not sure if it comes with a 4 inch focuser which is ideal long term for imaging. 2.7 inch limits you to DSLR sized chips.
My choice would be an AP130, TEC140, Tak TOA130.
It depends on what size camera you are using and types of objects you want to image. None will be great for galaxy imaging except for the larger brighter galaxies and will be ideal for widerfield objects like nebula and globs, larger galaxies, things like Horsehead, Rosette, Eta C, Omega Cent, M42, Pleiades etc.
Greg.