arXiv subjects

Richard Nugent

Publications and source records attributed to Richard Nugent.

5 recordsLinked to original sources

arXiv2012

The Measurement of Solar Diameter and Limb Darkening Function with the Eclipse Observations

The Total Solar Irradiance varies over a solar cycle of 11 years and maybe over cycles with longer period. Is the solar diameter variable over time too? We introduce a new method to perform high resolution astrometry of the solar diameter from the ground, through the observations of eclipses by reconsidering the definition of the solar edge. A discussion of the solar diameter and its variations must be linked to the Limb Darkening Function (LDF) using the luminosity evolution of a Baily's Bead and the profile of the lunar limb available from satellite data. This approach unifies the definition of solar edge with LDF inflection point for eclipses and drift-scan or heliometric methods. The method proposed is applied for the videos of the eclipse in 15 January 2010 recorded in Uganda and in India. The result shows light at least 0.85 arcsec beyond the inflection point, and this suggests to reconsider the evaluations of the historical eclipses made with naked eye.

astro-ph.SR↗

arXiv2012

Eclipse, solar limb darkening function and diameter measurements: toward a unified approach

In order to perform high resolution astrometry of the solar diameter from the ground, through the observations of eclipses, the study of the limb darkening profile is described. Knowing the profile of the solar limb is useful both to monitor the solar radius over time, and to define the oblateness, which is interesting for the classical tests of general relativity. The Limb Darkening Function (LDF) is studied in order to find the inflexion point, to which the measurements of the solar diameter are referred. The proposed method is applied to the videos of the annular eclipse in January, 15, 2010. This new method might solve the ambiguity of some eclipse obervations made with different instruments, where the measured solar diameter was clearly dependent on the aperture of the telescope and on the density of the filter used.

astro-ph.SR↗

arXiv2012

Solar limb darkening function and solar diameter with eclipses observations

We introduce a new method to perform high resolution astrometry of the solar diameter from the ground, through the observations of eclipses. A discussion of the solar diameter and its variations is linked to the Limb Darkening Function (LDF) using the luminosity evolution of a Baily's Bead and the profile of the lunar limb available from satellite data. The inflexion point of the LDF is defined as the solar limb. The method proposed is applied for the videos of the eclipse in January, 15, 2010 recorded by Richard Nugent in Uganda and Andreas Tegtmeier in India. An upper limit for the inflexion point position has been set for that eclipse.

astro-ph.SR↗

arXiv2011

Measuring solar disk shape up to relativistic accuracy: the role of scintillation in ancient naked eye data

The orbital displacement of the Moon is known to a precision on the order of centimeters from the lunar laser ranging data, while the lunar profile's confidence level is still only about 200 m. The lunar motion is used to measure the solar diameter during central eclipses with accurate timing of Baily's beads at the umbral path limits. The onset or disappearance of a Baily's bead is due to the alignment between lunar limb's valleys and solar photosphere: this timing is determined outside our atmosphere. Due to scintillation, naked eye evaluations of such phenomena can be systematically different with respect to telescopes. We analyze the case of Venus' occultations as bead-like situation, in order to infer considerations on naked eye reports in historical total eclipse reports.

astro-ph.SR↗

arXiv2011

Towards a unified definition of solar limb during central eclipses and daily transits

The diameter of the Sun has been measured using Baily's beads during central eclipses, observed with portable telescopes. A blend of tiny emission lines produced in the first several hundred kilometers above the photosphere gives a light signal which prolonges the light curves of the beads. The simple criterion of light OFF/ON adopted in the previous approaches to define the timing of photosphere's disappearance/reappearance is modified. The technique of the limb darkening function reconstruction from the Baily's beads light curves is introduced here.

astro-ph.SR↗