Let we have the statements like
We are doing observations by telescopes, by radio-telescopes, by heliometers etc.
But stars do exist independently of
by which (what?) they are (being?) observed (??)
I need the correct ending phrase (emphasized) in the last sentence and its, if any, shorter version;
i.e., without mentioning the noun-verb
they are. What I typed above is likely erroneous, sorry.
That is, I'm looking for something like a question-form to the
by in the 1-st sentence. Here is a guiding analog:
People do something for bla-bla
So the question-form for ending phrase here is
He is doing bla-bla independently of
I see the word
wherewith in a dictionary.
Collins explains the word as, probably, archaic
with or by which. Does it help here?