looking ahead is a good plan... again, the 8" F/12.5 mak is perhaps a bit slow for imaging with..
I dont know what focal reducers are available to speed these optical systems up, however its well known that the meade/celestron 8" SCT's are great performers, and with the meade/celestron reducer fitted, they are both F/6.3, which is fast enough for photography purposes...
Alternatively from an SCT, a 10" newtonian reflector is also a good option. There are quite a few forum members imaging very successfully with EQ6 pro + 10" Newt + 80mm guide scope... A rig like that is a fairly safe bet for moderate-long focal length imaging. and at F/5, its also a rather fast system.. A lot cheaper than an 8" SCT too...
2nd hand, C8's and Meade 8" SCT's come up a fair bit, and are usually priced between $750 ~ $1000 depending on accessories, condition, age etc.. and at that price range they are a fantastic bit of gear...
A brand new 10" newtonian would probably be around $500 +/- a bit..
There are plenty of options, I dont know much about mak cassegrain's, but schmidtt casses and newtonians are always a sure fire system.. Many people use them, they have fantastic track records for producing results..
If you were looking for a maksutov, I would direct you towards the Intes Micro scopes, or, the Orion 190mm F/5.3 Maksutov Newtonan.
Theres countless options really..
You need to first decide what it is you want your long focus scope mostly for.. DSO imaging/planetary imaging, observing etc..
A 10" newtonian will excell for planetary imaging over an 8" SCT/MCT because it has the aperture advantage. Apeture is everything for planetary imaging.. for observing mounted on the gem, it could be a bit of a pain, as the eyepiece can be in some pretty crazy locations depending where the scope is pointed.. for DSO's the 10" has 2 upsides, its fast @ F/5, and it has aperture. 10" of light gathering area at F/5 makes it a very useful tool. Downsides are its big, moderately heavy, and on the upper weight limit of the mount when coupled with a guide scope, cameras/ cables etc etc.. Newts suffer from coma, however this is easily fixed with a ba'ader MPCC corrector.
An 8" SCT is very versatile for all aspects, for planetary imaging, it has enough aperture to capture good detail and feed your camera plenty of light, at F/10 it has a fairly long focal length for planetary this is good. For observing, it has enough aperture to show off good detail for a lot of dso's and plenty of focal length for viewing the planets. and, no matter where its pointed, the eyepiece is always in a fairly convenient location. For DSO imaging, you can image at F/10, this will require longer exposures, however you will have a very long focal lenght to capture the smaller objects in the sky, then, insert the 6.3 focal reducer, and you're back down to ~1200mm, a great focal length for imaging some of the more sizeable objects, and with a faster ratio of 6.3, you're exposures will be of a managable duration... The SCT design also has the downside of coma, unless you buy a new Meade ACF (advanced coma free) OTA (Pricey at the moment due to the AUD's value against the greenback) The reducer does handle this issue well though.
I dont know much about the Mak's, Nor do you see many people using them for imaging yet, however the Orion 7.5" mak newt does have a good set of specifications, however for planetary imaging/observing, 7" is starting to cut things a bit fine.. at F/5.3, for deep sky it would be nice, although a bit short to call it "long focal length" at 1000mm. Orion claim the mak newt does not suffer from this, however thats just marketing talk, and until I see results from the unit, I cant speak to this.
Theres MANY MANY decisions to make in the future... How did I choose? I first decided what I wanted to use the scopes primarily for, Then, I looked at images taken by many of my favorite astro photographers, and modeled my own rig based on theirs...
Best of luck with your decisions, And its good to hear you're sticking with the ED80 + ST80 as a starting setup.
You'll have plenty of fun, and learn heaps!
Cheers
Alex.
An 8" SCT will be very versatile, for obse