And so, as the King of Sweden plunged deeper and deeper into the heart of Germany, from Brandenburg to Saxony, then headlong through Thuringia and on to Bavaria, the miners and herdsmen put their hands on their hearts and pledged their devotion to the astronomer, and he demanded from Vienna tubes a hundred eighty, a hundred ninety, two hundred feet long, and what choice did the Emperor have but to provide them? Ferdinand’s gambit, however ingenious it was, had failed. He would have to formulate another.

Yet none of this made the astronomer happy. The tube now made sense to the goatherds, perhaps, “but it was making less and less sense to me.” Thousands of the astronomer’s tubes had flooded the continent ever since Galileo had popularized it with his fanciful tale about the Doge of Venice atop the Campanile di San Marco, but “no one, I thought, understands how it truly works, and neither do I.” If he truly understood how the tube worked, he thought, he should be able, whenever he wished, not to look through it, to stop looking through it, to curb the compulsion to look through it, complete star catalogue or no, even for the rest of his life if he wished, and that was something he was manifestly unable to do.

And along with that thought, and linked to it in some obscure way he could not comprehend, came another: he wanted his son back.

How badly he wanted his son back!

And then one day, around the time Gustavus Adolphus traversed the Lech, and seized Augsburg, and conquered Munich, and threatened in fewer than three weeks to appear at the gates of Vienna with forty thousand men, the astronomer’s son did come back.

“Ten minutes,” said the astronomer, peering into his telescope, picking up his quill, and writing down a string of numbers. “Be ready, my friend! It is nearly upon us.”