cosmicrays
Mao yewei wrote on Apr 14, 2008
Hi, I have a question that when using COSMICRAYS task to remove cosmicrays for 2d-spectra before extracting, is there any possibility to recede some strong emission lines? That is IRAF may identify a little strong emission lines as cosmicrays occasionally, may it? Some strong emission lines get weak through this task during my reduction, so I think of this idea.
Owen
Owen
Francisco Valdes wrote on Apr 14, 2008
The short answer to your question is "Yes this is possible".
Separating cosmic rays from real features (emission lines in spectra or the cores of stars in imaging) is very hard. The best way to deal with cosmic rays is with multiple exposures. For single 2D spectra a somewhat better way is during extraction to 1D using APALL. The advantage of this is that it will recognize when something has the same spatial profile (profile across the dispersion) as the spectrum and so cosmic rays have to have a different shape. The problem is that very strong cosmic rays in this algorithm can cause problems.
Yours,
Frank Valdes
Separating cosmic rays from real features (emission lines in spectra or the cores of stars in imaging) is very hard. The best way to deal with cosmic rays is with multiple exposures. For single 2D spectra a somewhat better way is during extraction to 1D using APALL. The advantage of this is that it will recognize when something has the same spatial profile (profile across the dispersion) as the spectrum and so cosmic rays have to have a different shape. The problem is that very strong cosmic rays in this algorithm can cause problems.
Yours,
Frank Valdes
Mao yewei wrote on Apr 14, 2008
Thank you so much, Frank! I'm now removing cosmicray events by dealing with multiple exposures!
Owen
Owen
Jason Quinn wrote on Apr 14, 2008
owen
Hi, I have a question that when using COSMICRAYS task to remove cosmicrays for 2d-spectra before extracting, is there any possibility to recede some strong emission lines? That is IRAF may identify a little strong emission lines as cosmicrays occasionally, may it? Some strong emission lines get weak through this task during my reduction, so I think of this idea.
You may also wish to investigate this website (http://www.astro.yale.edu/dokkum/lacosmic/). The cosmic ray code there works really well.
Jason
Last post on Apr 14, 2008