From owner-fitsbits at tarsier.cv.nrao.edu Tue May 7 22:03:53 1996 Received: (from majdom at localhost) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.7 $) id WAA16822; Tue, 7 May 1996 22:03:53 -0400 Received: from fits.cv.nrao.edu (fits.cv.nrao.edu [192.33.115.8]) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.7 $) with ESMTP id OAA13768; Tue, 7 May 1996 14:44:03 -0400 Received: from solitaire.cv.nrao.edu (news at solitaire.cv.nrao.edu [192.33.115.79]) by fits.cv.nrao.edu (8.7.5/8.7.1/CV-2.1) with SMTP id OAA04074 for ; Tue, 7 May 1996 14:43:57 -0400 (EDT) Received: by solitaire.cv.nrao.edu (4.1/DDN-CV/1.9) id AA08803; Tue, 7 May 96 14:43:54 EDT To: fitsbits at fits.cv.nrao.edu Date: 7 May 1996 14:20:41 GMT From: timmyd at netcom.com (Tim DeBenedictis) Message-Id: <4mnm7n$pf at pecos.msfc.nasa.gov> Organization: MSFC X-Ray Astronomy's InterNetNews site Path: solitaire.cv.nrao.edu!hearst.acc.Virginia.EDU!news-server.ncren.net!taco.cc.ncsu.edu!lll-winken.llnl.gov!nntp.coast.net!zombie.ncsc.mil!news.mathworks.com!newsfeed.internetmci.com!news.msfc.nasa.gov!pecos.msfc.nasa.gov!not-for-mail Reply-To: timmyd at netcom.com Subject: Std. date/time/RA/Dec FITS keywords? Newsgroups: sci.astro.amateur,sci.astro.research,sci.astro.fits,alt.sci.astro.fits Sender: owner-fitsbits at tarsier.cv.nrao.edu Precedence: bulk Greetings all- I am writing some astrometry software which needs to run with a variety of different FITS-format images. It would be nice to use the R.A., Dec., date, and time information stored in the images' FITS headers, but unfortunately there does not seem to be any standard FITS keywords which provide this information. I read the defining FITS paper, which describes the DATE-OBS keyword; however, there is no corresponding TIME-OBS keyword, and one-day time resolution is not sufficient. I also read about the CRVAL, CRPIX, CRDEL, and CROT keywords, which sem to specify the coordinates, rotation, and image scale. However, as far as I can tell, no one actually seems to use these in practice! I've worked with a variety of images from institutions like Kitt Peak, Lowell Observatory, as well as amateur images from SBIG cameras. The only thing I've seen is keywords like RA and DEC which then list an R.A. and Dec. in hours/minutes/seconds as an ASCII string. Is there any standard way of handling these things? What is the "correct" way to do it? Please send e-mail, as I am not able to check responses to all the groups I've posted this to. -Tim DeBenedictis timmyd at netcom.com From owner-fitsbits at tarsier.cv.nrao.edu Thu May 9 16:02:40 1996 Received: (from majdom at localhost) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.7 $) id QAA30981; Thu, 9 May 1996 16:02:40 -0400 Received: from fits.cv.nrao.edu (fits.cv.nrao.edu [192.33.115.8]) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.7 $) with ESMTP id PAA30198; Thu, 9 May 1996 15:12:11 -0400 Received: from solitaire.cv.nrao.edu (news at solitaire.cv.nrao.edu [192.33.115.79]) by fits.cv.nrao.edu (8.7.5/8.7.1/CV-2.1) with SMTP id PAA08508 for ; Thu, 9 May 1996 15:12:00 -0400 (EDT) Received: by solitaire.cv.nrao.edu (4.1/DDN-CV/1.10) id AA23315; Thu, 9 May 96 15:11:57 EDT To: fitsbits at fits.cv.nrao.edu Date: 9 May 1996 16:20:44 GMT From: Peter Bunclark Message-Id: <4mt60p$1pn at pecos.msfc.nasa.gov> Organization: Royal Greenwich Observatory Path: solitaire.cv.nrao.edu!hearst.acc.Virginia.EDU!news-server.ncren.net!news.duke.edu!news.mathworks.com!newsfeed.internetmci.com!news.msfc.nasa.gov!pecos.msfc.nasa.gov!not-for-mail Reply-To: psb at ast.cam.ac.uk Subject: Re: Std. date/time/RA/Dec FITS keywords? Newsgroups: sci.astro.amateur,sci.astro.research,sci.astro.fits,alt.sci.astro.fits Sender: owner-fitsbits at tarsier.cv.nrao.edu Precedence: bulk Tim DeBenedictis wrote: > > Greetings all- > > I am writing some astrometry software which needs to run with a variety > of different FITS-format images. It would be nice to use the R.A., Dec., > date, and time information stored in the images' FITS headers, but > unfortunately there does not seem to be any standard FITS keywords which > provide this information...[deletia - mod.] Read : FITS Documents [moral: check the 'net before pressing "post" - mod.] From owner-fitsbits at tarsier.cv.nrao.edu Tue May 14 11:23:40 1996 Received: (from majdom at localhost) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.8 $) id LAA05385; Tue, 14 May 1996 11:23:40 -0400 Received: from fits.cv.nrao.edu (fits.cv.nrao.edu [192.33.115.8]) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.8 $) with ESMTP id RAA01403; Mon, 13 May 1996 17:29:49 -0400 Received: from solitaire.cv.nrao.edu (news at solitaire.cv.nrao.edu [192.33.115.79]) by fits.cv.nrao.edu (8.7.5/8.7.1/CV-2.1) with SMTP id RAA15347 for ; Mon, 13 May 1996 17:29:46 -0400 (EDT) Received: by solitaire.cv.nrao.edu (4.1/DDN-CV/1.10) id AA08849; Mon, 13 May 96 17:29:42 EDT To: fitsbits at fits.cv.nrao.edu Date: 13 May 1996 14:36:56 GMT From: sla at umbra.ucolick.org (Steve Allen) Message-Id: <4n7he5$3m8 at pecos.msfc.nasa.gov> Organization: UCO/Lick Observatory, Santa Cruz Path: solitaire.cv.nrao.edu!bofh.dot!hearst.acc.Virginia.EDU!caen!uwm.edu!math.ohio-state.edu!usc!howland.reston.ans.net!newsfeed.internetmci.com!news.msfc.nasa.gov!pecos.msfc.nasa.gov!not-for-mail Reply-To: sla at ucolick.org Subject: Re: Std. date/time/RA/Dec FITS keywords? Newsgroups: sci.astro.amateur,sci.astro.research,sci.astro.fits,alt.sci.astro.fits Sender: owner-fitsbits at tarsier.cv.nrao.edu Precedence: bulk In article <4mt60p$1pn at pecos.msfc.nasa.gov>, Peter Bunclark wrote: >Tim DeBenedictis wrote: >> of different FITS-format images. It would be nice to use the R.A., Dec., >> date, and time information stored in the images' FITS headers, but >> unfortunately there does not seem to be any standard FITS keywords which >> provide this information...[deletia - mod.] >Read : >FITS >Documents This reply may give the impression that there is a definitive answer to the question. There is not. There are no adopted standards specifying the keyword name or format of RA and Dec in a FITS header. There exists decimal degrees, decimal hours, and hexadecimal strings in hours and degrees. The given RA and Dec may be expressed in a catalog reference frame or as notably inaccurate telescope encoder readings. Similarly there is no adopted standard specifying the keyword name or format of observation time in a FITS header. Again, existing practice varies rather widely as do the accuracies of the clocks used to obtain the time. There is a draft document at http://fits.cv.nrao.edu/documents/wcs/wcs.html whose adoption should solve this problem, but its recommendations are not generally found in any existing FITS headers. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 sla at ucolick.org Voice: +1 408 459 3046 FAX: +1 408 454 9863 WWW: http://www.ucolick.org/~sla PGP public keys: see WWW From owner-fitsbits at tarsier.cv.nrao.edu Wed May 15 10:09:54 1996 Received: (from majdom at localhost) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.8 $) id KAA20482; Wed, 15 May 1996 10:09:54 -0400 Received: from fits.cv.nrao.edu (fits.cv.nrao.edu [192.33.115.8]) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.8 $) with ESMTP id UAA08398; Tue, 14 May 1996 20:07:27 -0400 Received: from solitaire.cv.nrao.edu (news at solitaire.cv.nrao.edu [192.33.115.79]) by fits.cv.nrao.edu (8.7.5/8.7.1/CV-2.1) with SMTP id UAA20423 for ; Tue, 14 May 1996 20:07:23 -0400 (EDT) Received: by solitaire.cv.nrao.edu (4.1/DDN-CV/1.10) id AA01719; Tue, 14 May 96 20:07:20 EDT To: fitsbits at fits.cv.nrao.edu Date: Tue, 14 May 1996 08:46:58 +0100 From: Peter Bunclark Message-Id: <31983A72.2310 at ast.cam.ac.uk> Organization: Royal Greenwich Observatory Path: solitaire.cv.nrao.edu!bofh.dot!hearst.acc.Virginia.EDU!news-server.ncren.net!news.duke.edu!news.mathworks.com!newsfeed.internetmci.com!usenet.eel.ufl.edu!bofh.dot!warwick!lyra.csx.cam.ac.uk!news References: <4n7he5$3m8 at pecos.msfc.nasa.gov> Subject: Re: Std. date/time/RA/Dec FITS keywords? Newsgroups: sci.astro.fits Sender: owner-fitsbits at tarsier.cv.nrao.edu Precedence: bulk Steve Allen wrote: > > In article <4mt60p$1pn at pecos.msfc.nasa.gov>, > Peter Bunclark wrote: > >Tim DeBenedictis wrote: > >> of different FITS-format images. It would be nice to use the R.A., Dec., > >> date, and time information stored in the images' FITS headers, but > >> unfortunately there does not seem to be any standard FITS keywords which > >> provide this information...[deletia - mod.] > > >Read : > >FITS > >Documents > > This reply may give the impression that there is a definitive answer > to the question. There is not. > > There are no adopted standards specifying the keyword name or format > of RA and Dec in a FITS header. There exists decimal degrees, decimal > hours, and hexadecimal strings in hours and degrees. The given RA and > Dec may be expressed in a catalog reference frame or as notably > inaccurate telescope encoder readings. > > Similarly there is no adopted standard specifying the keyword name or > format of observation time in a FITS header. Again, existing practice > varies rather widely as do the accuracies of the clocks used to obtain > the time. > > There is a draft document at > http://fits.cv.nrao.edu/documents/wcs/wcs.html > whose adoption should solve this problem, but its recommendations > are not generally found in any existing FITS headers. > > -- > Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 > sla at ucolick.org Voice: +1 408 459 3046 FAX: +1 408 454 9863 > WWW: http://www.ucolick.org/~sla PGP public keys: see WWW I agree that there hasn't been much standardisation up to present; but anyone writing new software should study the available documents on wcs, including the section in NASA's ``A Users's Guide for the Flexible Image Transport System (FITS)'', and apply the recomendations to his instrument/system. The disagreements seem to be in how exactly to represent the image skew, rotation and scale. The actual convention for representing the coordinates of the reference pixel are as laid down in the mystical PAPER I , ie CRVALn in degrees for ra and dec. Meanwhile, most observatories have actually used RA and DEC keywords in more or less human-readable format, but these shouldn't in fact be part of a wcs. Since widely-distributed software (eg SAOTNG) is becoming available to exploit images with wcs, there is much more motivation than previously to exploit the potential. Peter. From owner-fitsbits at tarsier.cv.nrao.edu Fri May 17 08:23:10 1996 Received: (from majdom at localhost) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.8 $) id IAA11686; Fri, 17 May 1996 08:23:10 -0400 Received: from fits.cv.nrao.edu (fits.cv.nrao.edu [192.33.115.8]) by tarsier.cv.nrao.edu (8.6.13/$Revision: 2.8 $) with ESMTP id AAA10047; Fri, 17 May 1996 00:00:59 -0400 Received: from solitaire.cv.nrao.edu (news at solitaire.cv.nrao.edu [192.33.115.79]) by fits.cv.nrao.edu (8.7.5/8.7.1/CV-2.1) with SMTP id AAA12429 for ; Fri, 17 May 1996 00:00:56 -0400 (EDT) Received: by solitaire.cv.nrao.edu (4.1/DDN-CV/1.10) id AA26337; Fri, 17 May 96 00:00:54 EDT To: fitsbits at fits.cv.nrao.edu Date: Fri, 17 May 1996 00:02:48 GMT From: Robert Mutel Message-Id: <319BC228.1E5A at astro.physics.uiowa.edu> Organization: University of Iowa Path: solitaire.cv.nrao.edu!bofh.dot!hearst.acc.Virginia.EDU!news-server.ncren.net!news.duke.edu!news.mathworks.com!news.kei.com!nntp.coast.net!oleane!jussieu.fr!math.ohio-state.edu!news.physics.uiowa.edu!news References: <4n7he5$3m8 at pecos.msfc.nasa.gov> Subject: Re: Std. date/time/RA/Dec FITS keywords? Newsgroups: sci.astro.fits Sender: owner-fitsbits at tarsier.cv.nrao.edu Precedence: bulk Readers of sci.astro.research may be interested in a collection of programs for FITS images called ATFtools. It includes a tool for inserting world coordinates into a FITS image header by pattern matching to the Guide Star Catalog. The program (wcs) uses the nominal ra, dec, keywords (along with keyword crpix for plate scale) to roughly locate the image center and either an online or CD-ROM GSC database to do the pattern matching. The programs have been ported to several UNIX systems (Linux, Solaris, Unixware) and Windows-95. There are also tools for batch photometry, FITS header editing, and multiple image alignment. and cropping. The Windows-95 port is available at