Man...this certainly isn't easy.
For full length recordings, I'd say:
Time Fragments Vol. 2: Requiem for the Green Planet
Celestial Geometries (w/ Tau Ceti)
The Rustling of Leaves
Archaic Oceans (w/ Tau Ceti)
There are a lot of great Penumbra EPs too:
Leteph (w/ L.E.M.)
The Sun is Falling in a Sea of Blood
Lifting the Veil (w/ Tau Ceti)
The Gates of Aldebaran (w/ L.E.M.)
As We Slip Away to Dream
A Call, an Echo (w/ Klaus Wiese)
The whole Dreams collection is amazing too.