From sla@umbra.ucolick.org Fri Jun 7 12:31:15 1996 Path: solitaire.cv.nrao.edu!bofh.dot!hearst.acc.Virginia.EDU!news-server.ncren.net!concert!rutgers!news.columbia.edu!panix!newsfeed.internetmci.com!news.msfc.nasa.gov!pecos.msfc.nasa.gov!not-for-mail From: sla@umbra.ucolick.org (Steve Allen) Newsgroups: sci.astro.research Subject: Parallactic angle (was Re: Is there a book to teach practical astronomy?) Date: 6 Jun 1996 14:56:42 GMT Organization: UCO/Lick Observatory, Santa Cruz Lines: 26 Sender: astres@pecos.msfc.nasa.gov Approved: astres@pecos.msfc.nasa.gov Message-ID: <4p6rj9$173@pecos.msfc.nasa.gov> Reply-To: sla@ucolick.org NNTP-Posting-Host: pecos.msfc.nasa.gov Summary: Parallactic angle misnomer Keywords: techniques In article <4p46gu$h8@pecos.msfc.nasa.gov>, Andrew Cooke wrote: > - What is parallactic angle? The most common current usage of "parallactic angle" appears to be a misnomer. I've been trying to find out whence this originated. As near as I can find, the origin of parallactic angle lies in the hand application of annual parallax to the catalog coordinates of a star. It is the angle between the direction to ecliptic north and the direction to equatorial north. Looking at Smart's Spherical Astronomy, however, the term is applied to the angle between the local vertical and equatorial north. In the spherical triangles both of these have the same geometry, but the context is very different. In most current cases the angle should be called the "vertical angle". I don't know if Smart is the first instance of this misnomer. But the result is that it has propagated into subroutine libraries and may be too entrenched ever to be undone. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 sla@ucolick.org Voice: +1 408 459 3046 FAX: +1 408 454 9863 WWW: http://www.ucolick.org/~sla PGP public keys: see WWW From tyler@plk.af.mil Fri Jun 28 09:42:55 1996 Path: solitaire.cv.nrao.edu!hearst.acc.Virginia.EDU!caen!spool.mu.edu!uwm.edu!news-res.gsl.net!news.gsl.net!EU.net!news.msfc.nasa.gov!pecos.msfc.nasa.gov!not-for-mail From: tyler@plk.af.mil (David Tyler) Newsgroups: sci.astro.research Subject: Re: psf from image ? Date: 27 Jun 1996 14:50:56 GMT Organization: Air Force Phillips Lab. Lines: 24 Sender: astres@pecos.msfc.nasa.gov Approved: astres@pecos.msfc.nasa.gov Distribution: world Message-ID: <4qu748$6n6@pecos.msfc.nasa.gov> Reply-To: tyler@plk.af.mil NNTP-Posting-Host: pecos.msfc.nasa.gov Keywords: techniques JIANG MING writes: >* Support for extracting PSF from image >Could someone tell me to know how to do such an extracting and if there are >any avaiable references. if the object is *known,* the psf may be estimated by minimizing some cost function, for example ||obj*otf - img||, where obj is the object spatial spectrum, otf is the trial optical transfer function (FT of the psf), and img is the spatial spectrum of the recorded image. if the object is *unknown,* the object and psf may be jointly estimated, although this is a computationally intensive problem. various "blind deconvolution" methods seem to work well when noise is not significant. a good reference for the joint estimation problem is paxman, schulz, and fienup, josa-a 9, p. 1072 (1992). see also the references therein. dave ______________________________________________________________________ -David W. Tyler "It seems you feel our work is not -USAF Phillips Laboratory of benefit to the public." -Albuquerque, New Mexico -tyler@plk.af.mil --Rachel