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This is a reasonably complicated discussion as there are so many factors that have to be taken into account.
Mike uses a 12" F/3.8 with a ICX-694 which gives a sampling around 0.82"/pixel. This just so happens to be almost identical to a 12" F/8 with a 16803/11002/6306 which all have 9 micron pixels (I think the 6303 does anyway). Technically its closer to a F/7.5 than F/8 but as a standard RC is F/8 lets roll with that.
Both scopes need correctors of various kinds, both can be built both optically and structurally good, both have the same aperture and image scale (or near enough). Both of these should perform very similar to one another but one has about twice the focal length of the other. Both of these should perform similar to a 12" f/3 with an QSI690 as the image scale remains the same as does the aperture.
In terms of cost effectiveness I would say.
12" Newt + ICX-694
12" RC + 9 micron pixel (choose your poison)
RH300 + ICX-814
The difference between all of these systems them comes down to the quality of the optics and mechanics. GSOs are generally optically pretty good but mechanically leave a bit to be desired. A reasonable newtonian isn't overly expensive and even some of the premium ones are still less than what a comparable RC would cost. Throw in a smaller (cheaper CCD) and CONSIDERABLY cheaper filters, a good newtonian is difficult to beat from a price/performance aspect.
Suavi does bring up an important point, smaller pixels are most definitely more stressing on any optical system.... but likely not in this case. One of the benefits of higher resolution imaging is that your seeing conditions do help mask a lot of problem. Peter Ward a while back made the comment that he thought he had his RC nicely collimated until he had a night of very good seeing which then showed that it was a smidgen off.
A good example of this is with some of the Celestron Edge 14" scopes, some of them have an on-axis performance of something like 20 microns but because they're a 14" f/10, that equates to 1.16" resolution which when using a 11002 sensor still equates of a FWHM of 2 pixels under average seeing. If a small refractor had 20 micron on-axis spot sizes you'd send it back.
The cheapest option would be to get a reasonable 10" F/5 with a RCC Coma Corrector (think I got that right). Teleskop Service make a 10" F/5 ONTC with carbon fibre tube and various mods that they can do pre-shipment.
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