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Hi Vin,
I'm not expert, so bear this in mind, but I do go back a few years.
"H" is for Huygens, a simple 2 lens design, with the focal point within the eyepiece, (between the two lenses). I have three Huygen eyepieces made by Zeiss, for the Zeiss scopes.
Ordinarily the Huygens is synonomous with cheap and nasty, sorry. (The Zeiss don't really fall into the C&N category though!!!)
One benefit of the Huygens is that they can be used for solar projection, as there is no cement used to join the lenses, this cement being vunerable to the heat build up when solar projecting.
The "SR" is a Ramsden derivative, and I believe the "S" is for symetrical. It is slightly better than the Huygens, and the focal plane is in front of the field lens. The SR and the H series were common in my earlier days, but mostly have been superseeded by the Plossl and orthos.
If they perform well, use them. There is a lot to be said for less elements as opposed to the multi element designs in vogue these days.
Gary
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