[1] He was director of the observatory at the Pontifical Gregorian University (then called the Roman College) for 28 years.

[2] During his stay in America, he met Commander Matthew Fontaine Maury, the first director of the United States Naval Observatory in Washington.

On the recommendation of his late colleague Francesco de Vico, he became head of the observatory of the college at age 32.

In 1853, under his direction, the crumbling observatory was relocated to a new facility on top of the Sant'Ignazio Church (the chapel of the college).

He was offered important scientific positions and political dignities by the government, but refused to pledge allegiance to the Kingdom in place of the Pope.

Through analysis of this data, he discovered that the stars come in a limited number of distinct types and subtypes, which could be distinguished by their different spectral patterns.

He invented the Secchi disk, which is used to measure water transparency in oceans, lakes and fish farms.

He studied the climate of Rome and invented a "Meteorograph" for the convenient recording of several categories of weather data.

Secchi also performed related technical works for the Papal government, such as overseeing placement of sundials and repair or installation of municipal water systems.

The two STEREO (Solar TErrestrial RElations Observatory) spacecraft each carry an instrument package called SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation).