250
Secchi saw a teaching opportunity in gnomonics, so much so that he dedicated
an appendix to it in his Principi di Astronomia (Principles of Astronomy). For him,
sundials and solar clocks were a means to promote astronomy, and with this in
mind, he built a number of them near educational facilities. In addition, to promote
the acceptance of a national mean time, he augmented some of them with an analemma, the curve shaped like a figure “8” that is the graphical expression of the
equation of time.
15
Making these educational instruments provided a diversion for
him during breaks and holidays.
Noting that in the future we may well discover additional sundials attributed to
Secchi, in the meantime let us examine those already identified:
15.4.1 Sezze Sundial (1852)
Secchi went to Sezze (in the province of Latina) on September 20, 1852 to make a
sundial in the De Magistris palace. He recorded this in the Annual Report of the
Roman College Observatory in 1856, as a part of the report of observations of
Comet Biela, which he had followed with the Cauchoix telescope on 16 August.
16
Secchi wrote:
I could not follow [the comet] until the end of its apparition, because on the 20th of
September I left for Sezze where I been invited by the kindness of Professor Regnani. It is
important to note that the city’s latitude and longitude have now been determined with a
greater precision than had been done up until now.
In the note, Secchi reports the outcome of his measurements:
Here are the results of this little scientific expedition. The observation site was the interior
terrace of the courtyard of the Valletta de Magistris family estate in the aforementioned city
of Sezze. Latitude is 41° 29′ 38“ Longitude 2′ 18.4” east of the Obs. Coll. Roma, sea level
height 330.9 meters. Magnetic decl. is about 13°0.40 west.
This sundial was created for an educational purpose, in connection with the new
physics teaching lab or “cabinet.” The will of Superio De Magistris had, in fact,
provided for the De Magistris Charity by allocating funds for the establishment of
three new professorships in the seminary to which eight young people supported by
the institution were assigned. The chair of philosophy was provided with a physics
cabinet equipped with instruments, and for this reason, Francesco Regnani, priest
15 Solar time has a variable rhythm throughout the year as a result of the eccentricity of the Earth’s
orbit and the tilt of its axis on the orbital plane. Mean time moves at a constant rate. The two times
differ at most by 16 min, agreeing on 4 days of the year: April 16, June 14, September 2, and
December 26.
16 Angelo Secchi, Memoria sopra alcuni lavori fatti al nuovo osservatorio del Collegio Romano
durante il primo anno della sua erezione fino al 31 dicembre del 1855. (A record of some work
done at the new observatory of the Roman College from the first year of its construction up to 31
December 1855.) This reference was identified by Maria Luisa Tuscano.
M. L. Tuscano
Secchi saw a teaching opportunity in gnomonics, so much so that he dedicated
an appendix to it in his Principi di Astronomia (Principles of Astronomy). For him,
sundials and solar clocks were a means to promote astronomy, and with this in
mind, he built a number of them near educational facilities. In addition, to promote
the acceptance of a national mean time, he augmented some of them with an analemma, the curve shaped like a figure “8” that is the graphical expression of the
equation of time.
15
Making these educational instruments provided a diversion for
him during breaks and holidays.
Noting that in the future we may well discover additional sundials attributed to
Secchi, in the meantime let us examine those already identified:
15.4.1 Sezze Sundial (1852)
Secchi went to Sezze (in the province of Latina) on September 20, 1852 to make a
sundial in the De Magistris palace. He recorded this in the Annual Report of the
Roman College Observatory in 1856, as a part of the report of observations of
Comet Biela, which he had followed with the Cauchoix telescope on 16 August.
16
Secchi wrote:
I could not follow [the comet] until the end of its apparition, because on the 20th of
September I left for Sezze where I been invited by the kindness of Professor Regnani. It is
important to note that the city’s latitude and longitude have now been determined with a
greater precision than had been done up until now.
In the note, Secchi reports the outcome of his measurements:
Here are the results of this little scientific expedition. The observation site was the interior
terrace of the courtyard of the Valletta de Magistris family estate in the aforementioned city
of Sezze. Latitude is 41° 29′ 38“ Longitude 2′ 18.4” east of the Obs. Coll. Roma, sea level
height 330.9 meters. Magnetic decl. is about 13°0.40 west.
This sundial was created for an educational purpose, in connection with the new
physics teaching lab or “cabinet.” The will of Superio De Magistris had, in fact,
provided for the De Magistris Charity by allocating funds for the establishment of
three new professorships in the seminary to which eight young people supported by
the institution were assigned. The chair of philosophy was provided with a physics
cabinet equipped with instruments, and for this reason, Francesco Regnani, priest
15 Solar time has a variable rhythm throughout the year as a result of the eccentricity of the Earth’s
orbit and the tilt of its axis on the orbital plane. Mean time moves at a constant rate. The two times
differ at most by 16 min, agreeing on 4 days of the year: April 16, June 14, September 2, and
December 26.
16 Angelo Secchi, Memoria sopra alcuni lavori fatti al nuovo osservatorio del Collegio Romano
durante il primo anno della sua erezione fino al 31 dicembre del 1855. (A record of some work
done at the new observatory of the Roman College from the first year of its construction up to 31
December 1855.) This reference was identified by Maria Luisa Tuscano.
M. L. Tuscano