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| en:praktikum:photometrie_python [2025/02/17 09:25] – [Magnitude calibration] rhainich | en:praktikum:photometrie_python [2025/07/31 10:08] (current) – [Download calibration data] rhainich |
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| # Images | # Images |
| V_path = 'output/combined_trimmed_filter_V.fit' | V_path = 'output/combined_filter_V.fit' |
| B_path = 'output/combined_trimmed_filter_B.fit' | B_path = 'output/combined_filter_B.fit' |
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| Note: The variable names given here and in the following are only examples and can be replaced by any other name. | Note: The variable names given here and in the following are only examples and can be replaced by any other name. |
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| Note: If the images are not in a subdirectory of the current directory, the path can also refer to the next higher level by means of ''../''. | Note: If the images are not in a subdirectory of the current directory, the path can also refer to the next higher level by using ''../''. |
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| ==== Reading in the images ==== | ==== Reading in the images ==== |
| In the next step we can perform the actual download. For this purpose we use the function ''.query_region''. We have to pass to it the coordinates and the size of the sky region to be queried. Fortunately, both are already known. We know the coordinates from the FIT headers of the star cluster images and the radius of the region is simply the field of view, which we already calculated above. Both values can be taken from the ''V_image'' object. | In the next step we can perform the actual download. For this purpose we use the function ''.query_region''. We have to pass to it the coordinates and the size of the sky region to be queried. Fortunately, both are already known. We know the coordinates from the FIT headers of the star cluster images and the radius of the region is simply the field of view, which we already calculated above. Both values can be taken from the ''V_image'' object. |
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| calib_tbl = v.query_region(V_image.V_image.coordinates_image_center, radius=V_image.field_of_view_x*u.arcmin)[0] | calib_tbl = v.query_region(V_image.coordinates_image_center, radius=V_image.field_of_view_x*u.arcmin)[0] |
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| The table ''calib_tbl'' now comprise all objects contained in the **APASS** catalog that are in our field of view with their ''B'' and ''V'' magnitudes. | The table ''calib_tbl'' now comprise all objects contained in the **APASS** catalog that are in our field of view with their ''B'' and ''V'' magnitudes. |