10 replies to this topic

[lighttrap]

I wouldn't be surprised if those aren't .965" rather than 1.25".

[jwaldo]

They appear to both be Huygens, an old, outdated design with every abberation you cann imagine, so no, probably not good

[matt]

May I add that the Huygens is also notable for its very narrow fov (in the 30° range!). Charles Huygens is forgiven because he actually invented the eyepiece design business, and there was very little competition from Televue and Takahashi back then.
Some people say, though, that the H is very good for solar projection, so as you can get nada resale value on astromart for this thing, you could as well keep it for solar observing. The Huygens design is actually the simplest possible - two lenses, one converging and one diverging, which create an achromatic lens; just like an achro objective on a refractor. Good news, you can see stars with them. Bad news (or good news for eyepiece designers and salesmen), it works only on axis - whenever your go across the fov (which is narrow anyway), you're in trouble. Add to that that the manufacture of such an eyepiece is rarely done to very high standards.

As for the "SR", it's a Symetrical Ramsden, another primitive design favored by department store telescope designers, which could serve proudly as a dust plug on your focuser.

[Greg K.]

Well, did you try them?

[erik]

even today, many department store scopes come with hyugens. the 4mm is probably like looking through a pinhole...

[LivingNDixie]

Yeah those look like great solar projection eyepieces

[erik]

...and even the longer f/lengths hyugens are like looking through a plossl with a thick brown film over the lens elements...

[John Jarosz]

Hey, I just used my Ramsden eyepiece from 1966. I think it cost $3.00. I used it for a new adaptor barrel for a .965 eyepiece. I threw the lenses away. So there!

john