Of the three choices you give, I'd go with the Eon or Megrez 90. There is a Megrez 90 for sale right now in the classified section for a good price.
The Eon looks like they have upgraded the focuser from the stock ED80 to be on par with the Megrez. Even though it is smaller aperture, the lower f/ratio means that you will get about the same illumination on nebula, etc; they will just be 80% of the size in the Eon.
I've mounted an ED80 on top of an LX200 before, and I know that it is really pushing it for the fork mount, but it can be done. You need good balancing to do it without over-driving the motors, and should reduce the maximum slew speed to be safe. Weight wise, the lightest is the Meade, followed by the Eon, followed by the Megrez. There is only a half kilo spread between them, but it might make or break it for you.
On the plus side, refractors have good resale value, so even if it does not work out for you, you likely will not be out much.
To give you an idea of scale and what you will need for counterweights, I have attached some old shots of the 10" LX200 with an ED80 on top.
I went through exactly this decision a year or so ago.
Another to include in your list is the Taskahashi Sky90. That can be purchased second hand for the same price as a Megrez 90 APO new - I saw one come up for sale the day after I purchased my Megrez 90APO .
I purchased the Megrez 90 APO over the others because it had the most consistent good reviews as compared to the Meade which had good and bad, and Orion which had good and bad.
My Megrez 90 APO has turned out to be very good. It's not perfect, I do need a field flatenner for DSLR shots through it, but it's a lot lot better than my old Megrez 80 SD. The colour correction on the Megrez 90 APO is great. The field of the Megrez 90 APO is much flatter than what I have seen of the Orions.
What I don't like about the Megrez 90 APO .... that I still need a flatenner (Sky90 wouldn't), and the focuser design of the new scopes is rack & pinnion dual speed. Accurate to focus but not as pleasant to use as the crayfords.
There are a few different versions of the Megrez 90 APO from different times. If you buy a second hand one it won't necessarily be the same as the new ones, so make sure you're aware of what you're buying.
The case that came with my Megrez 90 APO is built like a tank, almost too much so (could be more compact).
What I don't like about the Megrez 90 APO .... that I still need a flatenner (Sky90 wouldn't)
Field Curvature in a refractor is pretty much a function of it's focal length, so both the Sky90 and the Megrez90 would have similar amounts of field curvature, the Sky90 probably a little more since it is a faster scope. The Tak petzvels (FSQ scopes) don't need flatteners.
Field Curvature in a refractor is pretty much a function of it's focal length, so both the Sky90 and the Megrez90 would have similar amounts of field curvature, the Sky90 probably a little more since it is a faster scope. The Tak petzvels (FSQ scopes) don't need flatteners.
The comparison shots I saw at the time I was looking certainly showed the Sky90 without flattener was flat, and the Megrez 90 with flattener which came out to very nearly the same focal length as the Sky90 were flat. But Megrez 90 on it's own was more curved.
Are you certain you didn't see the Tak images taken with the dedicated F4.5 reducer/flattener that takahashi has available for the scope? Most astro images I see on the web are at F/4.5 with the Sky90.
Are you certain you didn't see the Tak images taken with the dedicated F4.5 reducer/flattener that takahashi has available for the scope? Most astro images I see on the web are at F/4.5 with the Sky90.
Nup, wouldn't have a clue
I'd suggest Peter considers the Sky90 in his decision, and if interested in it compares shots himself.
The Tak with the flattener will give you a 45mm image circle @ F/4.5
The Megrez 90 with WO FFIV flattener will actually extend the focal length out beyond the native F/6.9 of the scope into the F/7.? I'm not sure about the other 3 field flatteners WO sell (the IV flattener is the one listed as an accessory for this scope on the WO website though). The tak flattener is also a dedicated flattener designed specifically for this scope, and it is tiny compared to the WO IV flattener which is HUGE
Lol, the Flattener 4 is so big because the smooth part above the grip area is basically an extension tube to get the proper chip to lens distance. The second element moves back and forth on a helical arrangement to set the focal length.
WO also now have the Flat 88, which is designed for the Megrez 88 but I would also be curious to test it on other scopes as well.
