Hi Rob,
Well a couple of the other guys have already given you the previous history of Quantum Optics, being a breakaway from Questar in the late 1970's.
Unfortunately they only lasted 4 or 5 years, in production. The Quantum 8 was a scope they introduced towards the end of the company's life, as it approached death, with a view to boost flagging sales. Sadly, there were only about 8 of these produced and due to the company's pending demise, quality control on the Quantum 8's was bad and a couple of the Quantum 8's were lemons. The good news is that the Quantum 8 Jack Apfelbaum brought in to Australia (the one now for sale) is a good one. I looked through this at the South Pacific Star Party about 10 years ago.
However, that doesn't make it a purchaseable commodity for mine, unless you are looking at it as a collectors item or want the, "nostalgia" value.
We considered purchasing this telescope from Jack Apfelbaum to become part of our
3RF Australia scope arsenal for use at the
Ozsky Star Safari, prior to the current owner buying it. However, we decided against the purchase as most of our US visitors and clients are after larger aperture scopes, more suited to DSO viewing. Further, we decided that if we did wish to purchase a large Maksutov, one of the new Russian Maks would be a better option, being cheaper and a better telescope due to the newer coatings and coating technologies.
That Quantum 8 would have been manufactured in 1981 or 1982, making it about 32 years old. There have been monumental changes in coating technology over the past 32 years and those 32 year old coatings would have had to deteriorate to some degree, reducing light gathering ability, compared to a new scope of equal aperture.
I posted this comparison in another thread last week showing the light loss comparisons due to the compounding effect of multiple optical surfaces. and the deterioration in coatings over time.
If we assume the reflectivity of each mirror in the Intes has dropped from 87% when new, to 80% at 20 yrs old; and we assume transmission on the corrector has dropped from say 97% to 94% after 20 years, the overall drop in light transmission drops from 73.4% when new, to 60.1% at 20 yrs of age, or a decrease of 18.1%.
Lets assume the Skywatcher with its newer technologies has 90% reflectivity on both mirrors and a corrector plate transmission of 98%. This gives an overall light transmission for the scope of 79.4%. This is a 6% increase over the Intes when it was new and a massive increase over the Intes with its aged coatings.
With that Quantum being 32 years old, it would only get worse than the scenario for the 20 year old Intes in the above comparison.
The quality of the Russian Maksutovs from Intes and Intes Micro is excellent.
Here is a link to a test report on an Intes Micro M715 by Wolgang Rohr in Germany. This is a 7"/F15 Maksutov with a "system" strehl ratio of .985. It just doesn't get any better than this.
On the basis you can buy the Intes Micro M715 "deluxe" (7"/F15) for $4,225 and the Intes Micro M815 "deluxe" (8"/F15) for $6,175 you might want to seriously think about a Russian Mak. If you wish to use the scope for Deep Sky work and want a bit more versatility you might want to consider the F9 versions of these scopes (M709 and M809). Further if you didn't feel the need to buy the "deluxe" versions you save about another $1,000 per scope.
On the other hand if you want a scope that has some "collectability" to it then the Quantum 8 is a great scope, albeit with 32 year old coatings and coating technology.
Cheers,
John B