Sample interview questions: Can you explain the process of calibrating and characterizing the instruments attached to a telescope?
Sample answer:
Calibration
- Flat-fielding: Captures images of a uniform light source to correct for pixel-to-pixel variations in sensitivity.
- Bias: Acquires images with the shutter closed to subtract electronic noise from subsequent science images.
- Dark: Records images with the telescope pointed at a dark area to measure and subtract thermal and dark current noise.
- Wavelength calibration: Uses known emission lines from standard stars or lamps to determine the wavelength response of spectrographs and other instruments.
- Photometric calibration: Employs reference stars with known magnitudes to calibrate the instrument’s sensitivity and determine its photometric zero point.
Characterization
- Optical alignment: Verifies that the telescope and instruments are aligned correctly, minimizing coma, astigmatism, and other optical aberrations.
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