telescope - Who invented the blink comparator?

It would appear to have been developed by Carl Pulfrich working for Zeiss in 1904.

Alternatively Max Wolf in 1900 again working with the Zeiss company.

Looks like the idea was Wolf's and the realisation Pulfrich's. From the second link we have:

Wolf was a codeveloper of the stereo comparator together with Carl
Pulfrich from the Zeiss company. The stereo comparator consists of a
pair of microscopes arranged so that one can see simultaneously two
photographic plates of the same region taken at diff erent times. Wolf
seems to have experimented with such techniques as early as 1892, but
without success. When Pulfrich approached him to adapt the technique
from geodesy to astronomy, Wolf was delighted. A steady exchange of
letters followed. Wolf and Pulfrich then worked together to analyze
the rapidly growing accumulation of photographic plates. Tragically,
Pulfrich lost one eye in 1906, preventing him from using the
stereographic tool from then on.