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Costantino Sigismondi

Publications and source records attributed to Costantino Sigismondi.

At least 37 records · Page 2Linked to original sources
arXiv2014

Measures of the Earth Obliquity during the 1701 Winter Solstice at the Clementine Meridian Line in Rome

The great meridian line in the Basilica of Santa Maria degli Angeli in Rome was built in 1701/1702 with the scope of measuring the obliquity of the Earth's orbit in the following eight centuries, upon the will of Pope Clement XI. During the winter solstice of 1701 the first measurements of the obliquity were taken by Francesco Bianchini. He was the astronomer who designed the meridian line, upgrading the similar instrument realized by Giandomenico Cassini in San Petronio, Bononia. The accuracy of the data is discussed from the point of view of the use of the pinhole.

physics.hist-ph↗
arXiv2014

Photometry of Delta Scorpii from 1996 to 2013 using SOHO LASCO C3 coronograph

The variabile star Delta Scorpii is in conjunction with the Sun at the end of November each year. We studied its magnitude by averaging the observations of 28 Nov - 1 Dec from 1996 to 2013 using the coronograph LASCO C3 on-board the SOHO Satellite and we extended of four years, i.e. 25 % of the total light curve, back to 1996, with respect to the present AAVSO dataset on this star. The 0.2 magnitude scatters of the single measurements have been studied and the sources of such disturbances are vignetting and diffraction patterns from the coronograph. The new data collected on Delta Scorpii show its minimum at mv=2.5 magnitudes for 1996 and 1997, confirming the values observed during the minimum of 2009, and the main periodicity of 11 years in the stellar variability.

astro-ph.SR↗
arXiv2014

Data analysis of 2005 Regulus occultation and simulation of the 2014 occultation

On March 20, 2014 at 6:06 UT (2:06 New York time) Regulus, the 1.3 magnitude brighter star of Leo constellation, is going to be occulted by the asteroid 163 Erigone. The unusual event, visible to the naked eye over NYC, can allow to measure the shape of the asteroid, with reaching a space resolution below the diffraction limit of the eye, and of all instruments not based on interferometry. Ultimately the aperture of the instrument is related to the amount of scintillation affecting the light curve of the occultation, limitating the accuracy of video recorded data. The asteroid profile scans the surface of the star at a velocity of 6 mas/s; the diameter of the star is about 1.3 mas and the detection of the stellar limb darkening signature is discussed, taking into consideration also the Fresnel fringes. New data reduction with R-OTE software of the 2005 Regulus occultation and simulations of the 2014 occultation with Fren_difl software are presented.

astro-ph.SR↗
arXiv2014

Callisto III e la Cometa di Halley: la ricerca di Johan Stein SJ tra leggenda e storia

The Dutch Jesuit astronomer Johan Stein published in 1909 a text about the legend on a papal bull of Pope Callixtus III against the comet of 1456. This comet happened to be the Halley's one. The original documents, either chronicles and observations, and coeval testimonies are deeply investigated by Stein and the falsity of that legend is clearly demonstrated. In the occasion of the 200 years of the restoration of the Societas Jesu made in 1814 by Pope Pius VII an Italian edition of the full text of Johan Stein is here presented.

physics.hist-ph↗
arXiv2014

The solar diameter series of the CCD Solar Astrolabe of the Observatório Nacional in Rio de Janeiro measured during cycle 23

The interest on the solar diameter variations has been primary since the scientific revolution for different reasons: first the elliptical orbits found by Kepler in 1609 was confirmed in the case of the Earth, and after the intrinsic solar variability was inspected to explain the climate changes. The CCD Solar Astrolabe of the Observatório Nacional in Rio de Janeiro made daily measurements of the solar semi-diameter from 1998 to 2009, covering most of the cycle 23, and they are here presented with the aim to evidence the observed variations. Some instrumental effects parametrizations have been used to eliminate the biases appeared in morning/afternoon data reduction. The coherence of the measurements and the influence of atmospheric effects are presented, to discuss the reliability of the observed variations of the solar diameter. Their amplitude is compatible with other ground-based and satellite data recently published.

astro-ph.SR↗
arXiv2014

The Figure of the Sun from Ground-based Experiments

The figure of the Sun reflects its inner structure and dynamics, influencing also the perihelion precession of close orbiting bodies, like Mercury. To study the solar figure from ground, the deformation on the solar image induced by the atmosphere has to be known up to one part over a million, and this is done through differential refraction models: a historical review of them is drafted. The solar oblateness has been investigated in order to validate alternative theories to General Relativity and to understand the internal dynamics of our star. The solar figure should possess only micro departures from sphericity according to the standard stellar structure theory and helioseismology data, though variations along the cycle has been observed. Ground-based and satellite data show contrasting observational results. The oblateness measured onboard RHESSI satellite, the one of SDS onboard a stratospheric ballon and that one of the Astrolabe of Rio de Janeiro are presented with their implications in classical and relativistic gravitation. The perspectives offered by the reflecting heliometer in the future measurement of the oblateness are depicted.

astro-ph.SR↗
arXiv2014

Ipotesi astronomiche sul foro della colonna augustea di Santa Maria in Aracoeli

The third column of the left row in the Basilica of Santa Maria in Aracoeli in Rome, has a hole carved in it, of probable astronomical use. The tube aims at a point a 116 degrees of azimut, East-South-East and 17.3 degrees of altitude, the Sun could be aimed in that direction at 07:00 UTC of 12 october and 7:25 UT of march 2, but the view is obstructed by the church's building. Same situation for the 3.9 magnitude alpha Monocerotis, visible 2000 years ago, taking into account the precession. Other hypotheses on the meridian astronomical use of this hole are here reviewed. In the case of solar observations it cannot be for meridian transits in Rome, since the lower transits occurs now at 24.5 degrees at winter solstice; we investigate the case of stellar transits, of declination 30.8 degrees South. Many alignments are possible leaving the azimut as free parameter, being the columun not in its original collocation, but here we investigate only the meridian transits, and no bright stars could have been seen through that hole, taking also into account the precession 2000 years ago. We conclude that this hole was probably not used for meridian observations.

physics.hist-ph↗
arXiv2013

Nova Centauri 2013 broad maximum from visual observations calibrated with same altitude stars

A bright Nova in Centaurus was discovered on Dec 2, 2013 at magnitude V=5.5. Its luminosity reached mv=3.8 from Dec 5 to 7, becoming the brightest Nova of 2013 and of the last decades. On Dec 14 it brightened at mv=3.2. The observations of the author contributed to the compilation of the IAU Circular 9265 which announced the Nova as V1369 Cen and are here described. The first observations have been made with naked eye, and the use of same altitude calibration stars of similar color allowed an accuracy within 0.1 magnitudes. The method of selecting stars on the same almucantarat (altitude circle) even farther than 20 degrees, reduces the effects of differential atmospheric extinction. Its application is useful not only for bright Novae but also for luminous variable stars like the supergiant Betelgeuse and Antares and some bright Miras.

astro-ph.SR↗
arXiv2013

Solar astrometry with Rio Astrolabe and Heliometer

Monitoring the micro-variations of the solar diameter helps to better understand local and secular trends of solar activity and Earth climate. The instant measurements with the Reflecting Heliometer of Observatorio Nacional in Rio de Janeiro have minimized optical and thermal distortion, statistically reducing air turbulence effects down to 0.01 arcsec. Contrarily to satellites RHRJ has unlimited lifetime, and it bridges and extends the measures made with drift-scan timings across altitude circles with 0.1 arcsec rms with Astrolabes. The Astrolabe in Rio operated from 1998 to 2009 to measure the solar diameter and the detected variations have statistical significance.

astro-ph.IM↗
arXiv2013

The occultation of Arcturus in the Vatican

The dome of Saint Peter's Basilica plays the role of the Moon during a stellar occultation and Arcturus is the target star. This occultation-like phenomenon is useful for introducing to occultation astronomy a class of student up to university level. It can be organized very easily at the convenience of the audience. Techical and didactical aspects are discussed; the video is available at http://www.youtube.com/watch?v=hIfsj7t-u-c and has been realized with an ordinary camcorder.

astro-ph.IM↗
arXiv2013

Considerations on the light curve of Nova Delphini 2013

It is possible to evaluate the absolute magnitude of the Nova Delphini 2013 with visual observations submitted to AAVSO, following the works of Leonida Rosino at Asiago Observatory on the novae of M31. A naif interpretative model of the light curve is presented, based on the decreasing exponential law, in order to open to amateur astronomers a glimpse on the complex theoretical framework of these phenomena.

astro-ph.SR↗
arXiv2013

The Heliometer of Rio de Janeiro in Operation - 2013 Calibration

Here the preliminary results of the calibration of the heliometric angle of the Heliometer in Rio de Janeiro are presented. They have been made in 2013 with a reference surveying rod, equipped with two metal spheres acting as artificial star, when illuminated by the Sun, and with the method of drift-scan timing.

astro-ph.IM↗
arXiv2013

The Heliometer of Rio de Janeiro in Operation - 2010 to 2013

Out of the three quantities that characterize the state of an isolated gaseous body: pressure, temperature and volume the radius is the only one directly measurable for the Sun, what is specially true in the optical window and for ground base measurements. The Heliometer of Observatorio Nacional, in Rio de Janeiro, measures the distance between two opposite limbs of the Sun in the same field of view, through the reflection on a 10 cm parabolic mirror split on its half and forming an appropriate angle. This configuration is free from optical aberrations and focal variations along the measurement direction. The mirrors are made on CCZ vitro-ceramic and the telescope structure is of carbon steel, resulting that there is no flexion or temperature deformation. The instrument is compact, and can perform hundreds of measurements per duty day, around all heliolatitudes. It attains an accuracy on the solar radius of 0.01 arcsec, becoming the ideal instrument to monitor from the ground the solar diameter, and to bridge satellites and astrolabes historical series of data. We discuss the first years of regular observation, with emphasis on the instrumental calibrations and on the statistic study of the derived time series, attitude series, and solar geometry series. On basis of these series we obtain how well the Heliometer and Solar Astrolabe results are matched.

astro-ph.IM↗
arXiv2013

Pawel Max Maksym (1983-2013) Polish Astronomer and Film-maker

The sudden and untimely death of Pawel Max Maksym will not diminish his contributions to the field of occultation astronomy, and to Polish society in general. Founder of the Pope Silvester II Observatory in Bukowiec, he was also writing a book to introduce children to astronomy. Graduating in Geography with an experimental thesis in Lunar Occultations at Lodz University, Pawel earned a diploma from the prestigious National Film School in Lodz. An expert observer, he mastered the technique of stellar occultations, fostering the scientific activity of the Observatory. A review of his publications in Minor Planet Circulars and on YouTube is presented here.

physics.hist-ph↗
arXiv2013

Transits of Venus and the Astronomical Unit: four centuries of increasing precision

Only seven transits of Venus have been observed and studied up to now since the first astronomical observations with the telescope: 1639, 1761-69, 1874-82 and 2004-12. The measurement of the Astronomical Unit has been one of the main goal of the study of this rare phenomenon, as well as the identification of the planetary atmosphere and its properties, the understanding of the black drop phenomenon and the measurement of the solar diameter. The transit of 1639 observed by J. Horrocks is presented in more detail.

physics.hist-ph↗
arXiv2013

Solar diameter, eclipses and transits: the importance of ground-based observations

The lifetime of a satellite is limited, and its calibration may be not stable, it is necessary to continue ground-based measures of the solar diameter with methods less affected by atmospheric turbulence, and optical aberrations: planetary transits and total eclipses. The state of art, advantages and limits of these methods are considered.

astro-ph.IM↗
arXiv2013

Venus transits: history and opportunities for planetary, solar and gravitational physics

The data of 2012 transit of Venus are compared with the ones of 2004. The thickness of the atmosphere of Venus, its aureole and the effect of oblateness and other asphericities in the figure of the Sun are taken into consideration, as well as the black drop effect. A new extrapolation method for the contact times is presented. The next Mercury transit in 2016 will be fully visible from Europe, and the data will be gathered in view of this new method of analysis, to obtain the solar diameter.

astro-ph.IM↗