The Blink

Two astronomers were experimenting with a black hole in sight.
Fired a powerful laser to try to communicate that night.
Tried this way and that with their powerful feed.
At points in the dark hole to see what they need.
Nothing was happening, nothing came back.
Then to one side there was a blink, so they had to backtrack.
By deviating send and receive which was quite an art.
They had a reliable message to decode for a start.
It took ages to determine all the English characters to chart.
Finally decoding it said “planet crash...you must immediately depart !!”