Can anyone supply me with details of changes made by Meade to the optical specification in moving from the LX200 GPS series to the current LX200 ACF series telescopes, in particular, the 12" size?
Replies will be appreciated if posted within the next 10 hours.

No change in optical specs. They just lost a lawsuit and are no longer allowed to call it an "Advanced Ritchey-Chretien"!

See Meade to change model names per lawsuit settlement thread farther down this page.

Welcome aboard!

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

Thanks Kaptain K for your reply.
In my opening post, I should have stated:
'Can anyone supply me with details of changes made by Meade to the optical specification in moving from the LX200 GPS series to the ARC LX200 series telescopes, in particular, the 12" size?'
Any further advice?

They did make a change going from the LX200 to the RCX400 and LX200R models. The change reduces coma making for a wider field for astrophoto work. It also reduces the curvature of the field but not to flat. Still it makes it possible to use a full 35mm size frame with only a minor increase in star size at the corners (how minor depends on your seeing). But they went and called it a RC design. That got the RC boys all in a dither as well as some amateurs. It does perform much like a poor mans RC but uses a parabolic secondary, not hyperbolic and, of course, a fog prone corrector plate. With that added element there is some chromatic problems (especially in the blue) that, while less than in the standard SCT (Meade or Celestron) version is not present at all in the true RC. It does cause some blue fringing on very high contrast edges but less than seen in the GPS. It's an improvement but certainly not an RC. The change in name to ACF better describes the system.

The main change was in going to the parabolic rather than spherical secondary from what I've been told. Right now they are out of production while it is moved to Mexico. OTA's won't be available for some time it appears, just complete scopes. The old RCX400 is being redesigned. I've not heard what they are redesigning. So it will be some time before that version returns to the market. The 14" models of either is being discontinued completely. For a full 35mm frame taken with a 14" LX200R (now LX200ACF) see:
http://www.spacebanter.com/attachmen...tid=1657&stc=1

I suspect there's little difference with the 12. A friend who has both a 10" GPS and 10" LX200R does get obviously better images with his new R though he's having problems with it holding collimation. It's currently back to the factory for repair. A problem I haven't seen with mine though I do have to recollimate going from warm to cold weather and then back again. The shot above was taken last spring before I readjusted for summer and you'll see more distortion on the right than the left because of this. It's an easy quick fix, I just hadn't made it yet and should have.

As with any SCT keeping the corrector fog free takes both a good dew shield and dew heater if you don't live in the desert.

See the link below for the RC take on the RCX design. The R differs mostly in that the RCX is faster and uses moving secondary focus like a true RC while the R is slower and uses moving objective mirror focus though I lock the mirror and use a 3" Crayford focuser controlled by a RoboFocus controller as temperature compensation is needed with the aluminum tube with my rapidly changing night temperatures.

http://www.star-instruments.com/images/MeadeRCX.pdf

I should add that used visually I see little difference between the two. Considering the smaller secondary in a standard SCT I suspect the standard model might be very slightly better for planetary work if all else is equal. Though only a very picky user is likely to see the difference (or imagine it).

Rick