Daofind-world coordinates
Lientjie wrote on Jul 23, 2008
Hi!
I used Daofind to extract sources from an Infrared image of a star-forming region with a lot of dust.
1. My output *.coo.1 file just gives the coordinate catalog in pixel coordinates. I need world coordinates to be able to do photometry on the image (for comparison with 2MASS images). I updated the header of the image using ccmap, and could specify in Source Extractor (I previously used for the same purpose as Daofind) whether I wanted the output catalog in pixel or world coordinates. Daofind, however, by default always gives the pixel coordinates, although one has both pixel and world coordinates in the image header. I do not find an option in Daofind to specify that I want the world coordinates, the only place is "wcsout" but there I can just specify "logical", "tv" or "physical" and all three of them still are pixel coordinates. Can someone please tell me how to extract the world coordinates of the image / transform the pixel coordinates (the transformation equation I got with ccmap and originally used for the astrometry is quite complicated and I would prefer another method than just to apply that equation).
2. Is it possible to explicitly specify an aperture diameter for the detection of the sources or does Daofind implicitly calculate the aperture using the "datapars" and "findpars" parameter lists (like the FWHM etc.)?
thanx!
Lientjie
I used Daofind to extract sources from an Infrared image of a star-forming region with a lot of dust.
1. My output *.coo.1 file just gives the coordinate catalog in pixel coordinates. I need world coordinates to be able to do photometry on the image (for comparison with 2MASS images). I updated the header of the image using ccmap, and could specify in Source Extractor (I previously used for the same purpose as Daofind) whether I wanted the output catalog in pixel or world coordinates. Daofind, however, by default always gives the pixel coordinates, although one has both pixel and world coordinates in the image header. I do not find an option in Daofind to specify that I want the world coordinates, the only place is "wcsout" but there I can just specify "logical", "tv" or "physical" and all three of them still are pixel coordinates. Can someone please tell me how to extract the world coordinates of the image / transform the pixel coordinates (the transformation equation I got with ccmap and originally used for the astrometry is quite complicated and I would prefer another method than just to apply that equation).
2. Is it possible to explicitly specify an aperture diameter for the detection of the sources or does Daofind implicitly calculate the aperture using the "datapars" and "findpars" parameter lists (like the FWHM etc.)?
thanx!
Lientjie
Francisco Valdes wrote on Jul 23, 2008
I am not an expert on the IRAF (or non-IRAF for that matter) DAOPHOT tasks. I could investigate further but let me give you a quick answer.
First you could try wcsout=world even though the help doesn't specify that as an option. It might work. If not you can convert the coordinates after the fact with wcsctran (if the WCS is in the header) or cctran (to use the ccmap database directly).
I'll leave it to you or someone else to figure out your question about the aperture size.
Yours,
Frank Valdes
First you could try wcsout=world even though the help doesn't specify that as an option. It might work. If not you can convert the coordinates after the fact with wcsctran (if the WCS is in the header) or cctran (to use the ccmap database directly).
I'll leave it to you or someone else to figure out your question about the aperture size.
Yours,
Frank Valdes
Last post on Jul 23, 2008