Sample interview questions: How do you ensure accurate sky subtraction and removal of instrumental artifacts during observations?
Sample answer:
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Dark Frame Subtraction:
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Regularly acquire dark frames with the same exposure time and operating conditions as science data.
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Subtract dark frames from science images to remove fixed pattern noise, thermal and electronic offsets.
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Flat Field Correction:
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Obtain flat field images by observing a uniformly illuminated source (e.g., twilight sky or a calibration lamp).
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Divide science images by flat field images to correct for pixel-to-pixel sensitivity variations.
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Bias Frame Subtraction:
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Acquire bias frames with zero exposure time to estimate the instrument’s readout noise.
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Subtract bias frames from science images to remove the electronic bias level.
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Sky Subtraction:
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Select regions of the science image free of sources (background regions).
- Determine the median pixel value in the background regions to estimate the sky brightness.
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Subtract the sky brightness from th… Read full answer