It seems the lens are indeed made of lanthanum glass.
I was referring to the information from the Pentax website,
http://www.pentaxwebstore.com/product/9588
It says below,
- High-refraction, low dispersion lanthanum glass to provide high resolution images with minimal aberrations
ion:
- Designed for use with Pentax PF 65 Series Spotting Scopes, provides 20x-60x magnification when used with them.
- 60 degree apparent field of view
- Rubber eyepiece ring designed for viewing comfort
- Also recommended for use with astronomical telescopes with 1 1/4" focuser
- Pentax SMC full-surface multi-layer coated optics reduce glare while providing maximum light transmission and color quality
- High-refraction, low dispersion lanthanum glass to provide high resolution images with minimal aberrations
- Advanced computer simulation design technology to reduce internal reflections, producing brighter, clearer images.
- Weatherproof construction for greater durability.
So, there should not be any doubt. Also, these eps are weatherproof....I am not sure if it means waterproof?