An Islamic astrolabe from medieval Spain, discovered in a museum in Verona, Italy, has been found to contain multiple layers of Hebrew engravings, thought to be additions by various Jewish owners of the object carried out throughout hundreds of years.

Astrolabes were portable circular devices, usually about the size of a small dinner plate, with multiple, engraved moving components used to determine time, distance, height and latitude, among other functions. An aid to navigation, they could also help with astrological readings, and in the Islamic world, had a function to indicate the proper time for the five daily prayers.

The Verona device, datable to the 11th century in southern Spain, likely started out as a purely Islamic astrolabe but different owners subsequently scratched several Hebrew additions into the metal parts, some of which seem to follow guidelines for astrolabe use as laid out by Andalusian Jewish luminary Abraham Ibn Ezra (1089–1167).

In a “massive coincidence,” Ibn Ezra’s treatise on astrolabes, the earliest in Hebrew that has survived, is known to have been written in Verona, explains Dr. Federica Gigante of the University of Cambridge, speaking to The Times of Israel by phone.

“It was so exciting. It fits the picture so perfectly. We have a Jew from Andalusia who gets to Verona who writes about astrolabes, and we have an astrolabe from Andalusia in Verona with markings that someone was following his instructions,” she said, noting that medieval Verona had a thriving and diverse Jewish community.

The astrolabe is described in Gigante’s paper, “A Medieval Islamic Astrolabe with Hebrew Inscriptions in Verona,” published last week in the peer-reviewed journal “Nuncius.”

One of the Hebrew additions is a correction of a latitude marking from 45 degrees to 44.5, which is in line with Ibn Ezra’s writings, Gigante explains.

“He gives a set of instructions, one of which is that you should always check your instruments for accuracy and always check your latitude lines. And then you have the correction in Hebrew, so it’s really like someone checked the astrolabe just like Ibn Ezra said,” she noted.

Ibn Ezra also assumed his readers were using an Islamic astrolabe because he mentioned the settings for determining prayer times and also the Arabic astrological functions.

“He had written about translating the signs to Hebrew and given instructions to do so, and then on the Verona astrolabe, some of the astrological signs are translated into Hebrew,” she continued.

“So it really does seem like someone was following his instructions here,” Gigante said. Most Jews in Verona at the time would not have known Arabic and the Hebrew etchings would have enabled them to use the valuable device.

An earlier inscription found on the device also has a Jewish connection, and likely points to a different Jewish owner of the astrolabe.

“One of the owners of this object, very early on in Andalusia, wrote ‘For Isaac the work of Jonah,’ in Arabic [for Isḥāq […]/the work of Yūnus]. You cannot be sure, but Isaac and Jonah are quintessential Jewish names, but written in Arabic, because Jews in Spain would have used Arabic, so it makes perfect sense” that this owner was also Jewish, according to Gigante.

Gigante, an expert on medieval Islamic astrolabes, explains that about a year ago, she stumbled across a modern photograph of a museum collection that had an astrolabe in the background. At the time she was on an internet search for information about Veronese collector Ludovico Moscardo (1611–1681), a noble who mentions several astrolabes in a catalog of his possessions.

Moscardo likely acquired the astrolabe from another Renaissance-era aficionado, who perhaps had inherited it from an old teacher, so the device had probably not been used for generations by the time it came into his possession, Gigante notes in her article. The item is currently displayed in the Fondazione Museo Miniscalchi-Erizzo museum in Verona.

“The astrolabe had been around for 600 years before entering the collection of Ludovico Moscardo in about 1672. It was in a private museum in Italy, and I discovered it by chance, on the internet,” she marveled.

Visiting the museum several months later, she describes holding the astrolabe, which had not been previously studied, and discovering a series of unusual scratches in the metal parts that stood out in the “breaking light” coming through a window. She later determined that the scratches were Hebrew additions, somewhat faint, put there by several different owners.

Other medieval-era Islamic astrolabes have added Hebrew, Gigante notes, but “in terms of how many different layers you can read over this one, it is pretty unique.”

The astrolabe also has similar additions of so-called Arabic numerals, the same as Western numbers in use today. (Arabic, then and now, uses a separate, distinct system for numerals.)

The Verona astrolabe is covered with later addendums, “lightly scratched markings in Western Arabic numerals translating and correcting the latitude values, some even multiple times,” the article notes. The astrolabe also features the word “Cordoba” in Hebrew characters next to the latitude marking for that famous city in southern Spain.

The Verona device “underwent many modifications, additions, and adaptations as it changed hands and owners over time… a testimony to the contacts and exchanges between Arabs, Jews and Europeans in the medieval and early modern periods,” Gigante wrote.

Astrolabes, often thought of as the forerunners of modern clocks, are a little like contemporary smartphones, Gigante said. They are portable, multiple-use computing devices and have various dials or parts that can be updated or swapped out to provide different functions, much like smartphone apps.

The Verona astrolabe also has an example of this versatility. “There is another plate, added on later, that has two latitudes, 30 and 35, and both of these are not in Europe, because they are too far south… My guess is Morocco, but it could be in Egypt,” Gigante said.

“It shows that someone, at a certain point, modified that astrolabe for travel in North Africa,” she said, a kind of “Morocco travel app.”

For Gigante, these glimpses of real people in history, gleaned from small clues, are one of the most fascinating aspects of her work.

“You can imagine, in Andalusia a Muslim who made it, a Jewish owner who bought it, went to North Africa, and then it had different Jewish owners in Italy, and then it went to the collectors a few hundred years later.”