Processing Method Effect on Sun Diameter Measurement With CCD Solar Astrolabe

Djafer, Djelloul; Irbah, Abdanour

doi:10.1088/0004-637x/750/1/46

Cited by 2 publications

(2 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We will use the wavelet transform implemented with theà trous algorithm to automatically detect the signatures of clouds and the noise magnitude in the daily solar irradiance. We chose this algorithm since the transform is known at each decomposition level, its evolution is followed from one scale to the other and it is easy to implement [7,9]. The decision if we have or not a clear day is taken from the decomposition analysis considering some 3 We first start by recalling the principle of the wavelet transform decomposition using the Mexican hat wavelet and theà trous algorithm (see Fig.…”

Section: Discrimination Between Clear and Turbid Days Using The Wavelmentioning

confidence: 99%

Identification of clear days from solar irradiance observations using a new method based on the wavelet transform

2017

View full text Add to dashboard Cite

A new method using the wavelet transform properties is developed to determine clear days of solar irradiance. These days are needed to model the solar radiation and to compare the existing empirical models. We use this method to process four years of global solar irradiation data collected at the Research Unit of Applied Renewable Energies at Ghardaïa city in Algeria. We also determine clear days from this data set using a standard method based on the clearness index criteria. The results show that the two methods give different numbers of clear days. The effect of this difference is analyzed by computing the Global Solar Radiation (GSR) with the Iqbal C model but also by the estimation of turbidity parameters using for that a innovative approach. We find that some significant differences are observed in the GSR modeling leading to bad estimation of turbidity parameters. We conclude that using our method is therefore more efficient since it is not dependent of the site and observations.

show abstract

Section: Discrimination Between Clear and Turbid Days Using The Wavelmentioning

confidence: 99%

Identification of clear days from solar irradiance observations using a new method based on the wavelet transform

2017

View full text Add to dashboard Cite

show abstract

“…First of all, however, a filtering process has to remove noise from the temporal series images while preserving solar limb shape so as not to alter the reconstructed PSF. The filtering we use is based on the compact wavelet analysis and the finite Fourier transform definition (Djafer & Irbah 2012;Djafer et al 2008). The solar edge defined by the inflexion point of the limb darkening function given by a CCD line is then determined for each cleaned image.…”

Section: Calculation Of the Experimental Otfmentioning

confidence: 99%

Solar seeing monitor MISOLFA: A new method for estimating atmospheric turbulence parameters

Irbah¹,

Borgnino²,

Djafer

et al. 2016

A&A

View full text Add to dashboard Cite

Aims. Daily observation conditions are needed when observing the Sun at high angular resolution. MISOLFA is a daytime seeing monitor developed for this purpose that allows the estimation of the spatial and temporal parameters of atmospheric turbulence. This information is necessary, for instance, for astrometric measurements of the solar radius performed at Calern Observatory (France) with SODISM II, the ground-based version of the SODISM instrument of the PICARD mission. Methods. We present a new way to estimate the spatial parameters of atmospheric turbulence for daily observations. This method is less sensitive to vibrations and guiding defaults of the telescope since it uses short-exposure images. It is based on the comparison of the optical transfer function obtained from solar data and the theoretical values deduced from the Kolmogorov and Von Kàrmàn models. This method, previously tested on simulated solar images, is applied to real data recorded at Calern Observatory in July 2013 with the MISOLFA monitor.Results. First, we use data recorded in the pupil plane mode of MISOLFA and evaluate the turbulence characteristic times of angle-ofarrival fluctuations: between 5 and 16 ms. Second, we use the focal plane mode of MISOLFA to simultaneously record solar images to obtain isoplanatic angles: ranging from 1 to 5 arcsec (in agreement with previously published values). These images and our new method allow Fried's parameter to be measured; it ranges from 0.5 cm to 4.7 cm with a mean value of 1.5 cm when Kolmogorov's model is considered, and from less than 0.5 to 2.6 cm with a mean value of 1.3 cm for the Von Kàrmàn model. Measurements of the spatial coherence outer scale parameter are also obtained when using the Von Kàrmàn model; it ranges from 0.25 to 13 m with a mean value of 3.4 m for the four days of observation that we analyzed. We found that its value can undergo large variations in only a few hours and that more data analysis is needed to better define its statistics.

show abstract

Processing Method Effect on Sun Diameter Measurement With CCD Solar Astrolabe

Cited by 2 publications

References 21 publications

Identification of clear days from solar irradiance observations using a new method based on the wavelet transform

Identification of clear days from solar irradiance observations using a new method based on the wavelet transform

Solar seeing monitor MISOLFA: A new method for estimating atmospheric turbulence parameters

Contact Info

Product

Resources

About