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No, no, Alex, every Galilean eye lens that I have seen in sextant telescopes has been a single biconcave lens. It is the "inverting scopes" that have colour-corrected eye pieces, usually two or more positive lenses.

And if Noell buys an achromatic negative lens for his Galilean telescope
he may well find that it is a strange aspheric compound lens for some special purpose. I suggest he sticks to a nice simple biconcave lens.

<<Your computation looks correct to me, but take into account that
your telescope will probably have lower quality than a factory made one.
They usually use the eyepiece consisting of several lenses, to remove the
chromatic aberration. One-lens eyepiece will probably have somewhat
lower quality of the image.>>

Bill Morris
Pukenui
New Zealand

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