[rogerg (Roger)]

I don't really have a good scope for the Moon. It's been bugging me a bit, and I'm wondering how cheaply I can get something which would give reasonable results.

Using my 6D I currently have:
My Megrez 90 has Fl ~620mm resulting in ~890 pixel diameter
My Megrez 90 with 2x doubler results in ~ 1764 pixel diameter

Options I see:
My Megrez 90 with 2x doubler + 1.4x extender results in ~ 2470 pixel diameter
My Megrez 90 with 2x doubler + 2x doubler results in ~ 3528 pixel diameter which only just fits in the frame.

I own a 2x but would have to buy the quite expensive 1.4x.

I wonder what the result would be like with all these doublers? People use 5x powermates and stack doublers for planetary work, I wonder what the loss of quality would be like?

Other options I see is a new cheap-ish longer focal length refractor:
Skywatcher 100ED with 2x doubler results in ~2561 pixel diameter

Refractors rarely go above 900mm focal length these days it seems.

Is there any other suggestions? I don't have much budget to play with, and it is only the Moon so not sure it justifies enormous expense.

Maybe I should be looking at something other than a refractor to bump up the focal length, but I can see that would probably get prohibitively expensive.

Regards,
Roger.