Hi All,
I have a current version of the Meade MA (modified achromat) 1.25 inch eyepiece which came with the scope, and it looks exactly the same as the one sold per link below (note, my eyepiece came with the scope, so did not buy from this seller):
https://www.telescopehouse.com/meade...iece-1-25.html
When I disassembled this Meade MA 25mm to clean the dust and blacken the lens edge (which does make a difference), I learnt the following:
1. The eye lens is an achromat doublet (glued together) made of glass.
2. The field lens is a bi-convex lens made of
plastic (easily scratched)
The design is almost the same as a Kellner, barring the plastic bi-convex field lens instead of one made of glass which is somewhat more plano-convex.
I was keen to see why the MA 25mm eyepiece spacing between the eye lens and field lens elements being much closer than the other 25mm Kellner eyepieces I have, the answer unfortunately lies in the curvature of the plastic field lens, plus its refractive index being plastic and not glass.
What disappointed me the most is to learn that a plastic lens being used as a Meade telescope eyepiece element (albeit a low end eyepiece for Meade) when other brands’ 25mm eyepieces use glass lens elements for their field lens.
Cost cutting in Chinese suppliers have crept into Meade’s eyepiece inventory (by design or by stealth)… so buyers beware…
PS:
Given I have other 25mm eyepieces already with glass lens elements, to save this dud MA eyepiece to having more practical use for me, I have increased the spacing between the field lens by moving the plastic field lens further away from the eye lens (which is easily achievable in this MA design).
That is, I now place this plastic field lens just before the field stop for the field lens, and changed this MA 25mm to around 37.5mm instead, a 1.25 inch eyepiece which I don’t have at this focal length.
The field of view is narrow, probably 35 degrees (but still better than the cheap Huygens that is marked with a silver lettering H sticker coming out of China, which comprised of two identical plano convex lens). It does now have a lower power than 25mm, which is something I like to have in my collection. And low power won't magnify the plastic scratches and optically flaw as readily inherent in this plastic field lens.
Thanks.
Kind regards,
Bill