• G. Parmeggiani

      Articles written in Journal of Astrophysics and Astronomy

    • An analytical approximation of the hubble space telescope monochromatic point spread functions

      O. Bendinelli G. Parmeggiani F. Zavatti

      More Details Abstract Fulltext PDF

      A mixture of off-centred Gaussians is used to approximate the predicted monochromatic point spread functions (PSFs) of Hubble space telescope (HST) at long wavelengths, and also, with a reduced number of parameters, the wide-band PSFs. The usefulness of the approximation in simulation and analysis of HST data is shown by means of application to image centring and convolution-deconvolution problems.

    • CCD star images: On the determination of Moffat’s PSF shape parameters

      O. Bendinelli G. Parmeggiani F. Zavatti

      More Details Abstract Fulltext PDF

      Among the variety of empirical models of optical Point Spread Function used in the astronomical environment, only the Moffat’s (1969) one is able to describe by means of two parameters (in the circular case) both the inner and the outer star image regions. In view of this very important feature, the problem of the simultaneous estimates of Moffat’s PSF shape parameters, off-centring, and the background level in CCD star images has been investigated. The problem does not seem to be rigorously resolvable, but an approximate way to calculate all the parameters except off-centring is shown. It must be stressed that, the Moffat’s PSF model being a softened power law belonging to the family of modified King and Hubble models, the present discussion can be of aid in many other research fields. Also, the integral equation enabling us to convolve a spherical source with Moffat’s PSF is given and applied for comparison to Multi-Gaussian convolution.

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      Posted on January 27, 2016

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