Creatures of the Night 

Low frequency radio astronomers do it at night.

I was re-reading my post from last month and I realized something.  For years, astronomers using radio telescopes have been accustomed to observing, day or night, rain or shine. Of course there are always exceptions, but as a rule, if your desired source was up during the day, this did not present any particular difficulty because the giant dishes could focus away from the sun. Those were the days!

Now, as we push the boundaries with wider fields of view, like the MWA which looks at almost a third of the sky at a time, we find that we can must limit out observing to times when the sun is set, effectively cutting the telescope time in half!  In fact, as we continue to build sensitivity we might be further restricted to times during the night when the ionosphere has settled down and the “seeing” is good enough.

Ironically this all happened because we got rid of the steerable dish, that last vestige of similarity to traditional optical telescopes,in favor of dipole antennas that see the entire sky at once.