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| en:praktikum:photometrie [2022/10/13 08:14] – [Reduction pipeline: darkframes, flatfields, and image addition] rhainich | en:praktikum:photometrie [2023/09/19 06:52] (current) – rhainich |
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| ====== N2 - Photometry of open star clusters ====== | ====== N2 - Photometry of open star clusters (GDL) ====== |
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| /* | /* |
| ==== Reduction pipeline: darkframes, flatfields, and image addition ==== | ==== Reduction pipeline: darkframes, flatfields, and image addition ==== |
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| The analysis of this observation requires the handling of a larger amount of data. Therefore, the reduction is performed with a //GDL// routine which performs the darkframe and flatfield correction and subsequently adds up the individual exposures in each filter. The routine contains no quality control unit, so bad exposures need to be sorted out before (see above). | The analysis of this observation requires the handling of a larger amount of data. Therefore, the reduction is performed with a //GDL// routine __which performs the darkframe and flatfield correction and subsequently adds up the individual exposures in each filter__. The routine contains no quality control unit, so bad exposures need to be sorted out before (see above). |
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| === Preparation === | === Preparation === |
| The script can be executed in the terminal with the following command | The script can be executed in the terminal with the following command |
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| ./plot_cmd.py | python plot_cmd.py |
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| Afterwards, a figure, showing the CMD, can be found in the current directory. The file type of this figure can be set via the variable ''filetype''. | Afterwards, a figure, showing the CMD, can be found in the current directory. The file type of this figure can be set via the variable ''filetype''. |
| Afterwards, recompile and run your //GDL// program once more. Then save and run the //Python// script from a console: | Afterwards, recompile and run your //GDL// program once more. Then save and run the //Python// script from a console: |
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| ./plot_stars.py | python plot_stars.py |
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| An image "starmap.png" will be the result if all went well. It shows the image (e.g. ''vadd.fit'') as color-inverted background and all identified stars as overlays **(please include or attach this image to your report)**. This image can be compared with the calibration stars mentioned in the beginning. After one of the star's from the "starmap" has been matched to a calibration star, the number of the corresponding mark on the "starmap" can be looked up in the file ''stars.dat'' to obtain the corresponding magnitude. The stars in the ''stars.dat'' file are ordered by increasing Y values. So you can search for the position of the star in your image which you used as background image for the star map and then you can search for the coordinates in the ''stars.dat'' file. The difference between this magnitude and the value given in //Simbad// is the calibration shift. Repeat this procedure for 5-6 stars and calculate the average of the calibration shifts. The variance should not be larger than 0.1 mag. | An image "starmap.png" will be the result if all went well. It shows the image (e.g. ''vadd.fit'') as color-inverted background and all identified stars as overlays **(please include or attach this image to your report)**. This image can be compared with the calibration stars mentioned in the beginning. After one of the star's from the "starmap" has been matched to a calibration star, the number of the corresponding mark on the "starmap" can be looked up in the file ''stars.dat'' to obtain the corresponding magnitude. The stars in the ''stars.dat'' file are ordered by increasing Y values. So you can search for the position of the star in your image which you used as background image for the star map and then you can search for the coordinates in the ''stars.dat'' file. The difference between this magnitude and the value given in //Simbad// is the calibration shift. Repeat this procedure for 5-6 stars and calculate the average of the calibration shifts. The variance should not be larger than 0.1 mag. |
| As previously described, the file ''cmd.dat'' can be plotted with the script ''plot_cmd.py'', which can be run with | As previously described, the file ''cmd.dat'' can be plotted with the script ''plot_cmd.py'', which can be run with |
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| ./plot_cmd.py | python plot_cmd.py |
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| It also offers the possibility to include isochrones, which can be downloaded from the websites of various stellar evolution projects. The variables of the script ''plot_cmd.py'' need to be adjusted according to the requirements of the downloaded isochrone files. The script expects that the isochrones are given as individual files, which should be located in a single directory (''isoDir''). | It also offers the possibility to include isochrones, which can be downloaded from the websites of various stellar evolution projects. The variables of the script ''plot_cmd.py'' need to be adjusted according to the requirements of the downloaded isochrone files. The script expects that the isochrones are given as individual files, which should be located in a single directory (''isoDir''). |