There are other mentionings in Revelation
to the sun being affected (the darkening of
the sun and moon).

This happens in Revelation 8:12, at the
time of the Fourth Trumpet. But here the
sun, moon and stars are only partly
darkened. So it can't be the fulfillment of
Matthew 24:29, when the sun is turned
to complete darkness.

So the event taking place at the Fourth
Trumpet has to be ruled out.