I recently got a C90 (one of the rubber armored spotting scope versions from maybe the late '80s or early '90s) in pretty good condition. First light was a couple of nights ago; I was out walking the dog and saw that the neighbors' kids around the corner had a lemonade stand set up, so after enjoying some lemonade and chatting with the neighbors I grabbed the C90 on a photo tripod and shared a quick peek at Saturn and the full moon with the family and another neighbor family that was hanging out in the driveway.
I'm pretty happy with the C90 and am looking forward to using it as a quick look grab-and-go, but I'm not thrilled with the .965" to 1.25" diagonal that it came with. It's a 45° erect image one, and while I'm sure it'll do nicely for terrestrial use, I think I could do better for astronomical use. Part of the reason I chose Saturn and the moon and not, say, M13 as targets was because they were both low to the sky. (Jupiter was low to the sky as well, but hopelessly lost behind a tree.) I could probably be reasonably happy with a .965" to 1.25" mirror diagonal, but it would be nice to have the versatility of using other 1.25" accessories.
In my brief research on the subject, it sounds like there was something called the LAR (Large Accessory Ring), which isn't made any more and is hard to find. I can't find any pictures of what the LAR looked like, or a good description of how it worked, but there are a couple of more modern options that seem like they would be useful, both marketed as adapting Meade ETX threads (which supposedly the old C90s used as well) to standard SCT threads:
How similar are these to the LAR? Is there a particular reason I'd pick one over the other? Also, a quick test with a 1.25" barrel showed that it wouldn't fit through the bore back of the MCT, so that means that once I put a 1.25" visual back on one of those adapters, an accessory would potentially bottom out against something, as opposed to passing straight through on an SCT with a full 2" bore. Is that going to be problematic?
Are there other options besides a .965" to 1.25" diagonal, or one of the above adapters, that I haven't considered? Does anybody have a favorite .965" to 1.25" diagonal, if I decide to go that route?