Last Sunday morning (July 20, 2025) Pope Leo XIV paid a visit to the historic telescopes of the Vatican Observatory at Castel Gandolfo, south of Rome. He was not just sightseeing. He was there to look through some telescopes!
Study carefully this video from Vatican Media (via ABS-CBN in the Philippines):
First, Pope Leo visits the dome of the Double Astrograph. The VO’s Fr. David Brown, S.J. is showing him the place.
While there, Pope Leo asks Fr. Brown something. There’s a lot of echoing so it’s hard to hear exactly what is being said, but you can make out the following exchange (at the 0:17 mark):
Fr. Brown: “We can’t do it. If we [something] the next one, that’s…” (Poor Fr. Brown — having to tell the Pope “no”.)
Pope Leo: “All right.”
Fr. Brown: “…that’s the better one to….”
Pope Leo: “The one right next door here?”
The next one, next door. That’s the 16-inch Refractor. They go over to the dome housing it. Note that the pope is the first one through the door.
I think the Pope was wanting to use the Astrograph to look at something. I have shown many people around telescopes. Some are mildly interested. They follow you. They look politely and nod. Maybe something you show them strikes their interest and they engage a little more.
But then there are the people who are itching to see stuff, who you have to disappoint by saying “we can’t do that with this telescope; we can do it with the other telescope”, and they already know what telescope you mean because they have enough interest to have familiarized themselves with the basics of the place — “Oh, you mean the other telescope right over there?” And when they get to the other telescope, they are through the door before you are, and are ready to see stuff. They have ideas.
Once everyone gets into the 16-inch’s dome and Fr. Brown gets the dome slit open, Pope Leo gestures out the slit and mentions (at the 1:15 mark), “the crescent moon.” Fr. Brown, operating in “Italy” mode, responds in Italian, “Ah, si si si!” (Yes yes yes!) He hasn’t been thinking of that. The Moon is Pope Leo’s idea. You can see his interest in his expression.
Let’s consider for a moment what the sky looked like at the time. The Palazzo Pontificio that is home to these telescopes is oriented about 10° from due north-south, as indicated by the arrow below (the dome at center is the 16-inch).
From the shadows people were casting as they walked toward the first dome, we can see that the Sun was not quite aligned with that arrow then. But by the time they got into the second dome, the Sun was probably pretty close to the direction the arrow is showing, namely 10° east of south, or azimuth 170°.
So here is the sky at Castel Gandolfo on July 20, with the sun at an azimuth of 170° (thanks, Stellarium). Obviously, the Moon is up.
And here is what the Moon might have looked like through the telescope.
The thing is, while the Moon obviously was visible at the time, it can be hard to see a crescent Moon at that position relative to the Sun with the Sun being so high in the sky. It would not be prominently visible. Pope Leo probably had some idea ahead of time — probably before he even headed up to the observatory — that it was there, and he knew to look for it. He was not just at the scopes to see the scopes. He was there to use the scopes to see the Moon.
Anyhow, Brown gets the Moon in view, and Pope Leo checks it out (1:32 mark). He messes with the eyepiece, “Ah! It’s changing the focus, right?” “Yes,” says Brown. Pope Leo is not squinting, not struggling to see. This is not his first time at a telescope.
Fr. Brown was quoted in L’Osservatore Romano as saying that, “the Holy Father showed genuine interest, wanting to know the history and functioning of the telescope we were preparing to use and whether the images of the celestial bodies observed were upside down”.
Elsewhere in the video you can see that Pope Leo clearly understands what a glass plate is and that it would be held in the Astrograph (0:28 mark).
Let me offer the disclaimer that I have no inside information here. (I bugged Fr. Brown to give me the full details, but it turns out he’s not supposed to do that, and that makes sense.) But from all this video, it seems clear to me that, while Pope Leo might have been a math major, he also has some interest in astronomy.
I’d bet a few pizzas on it. Like I said, I’ve seen a lot of people at telescopes.
