sci-universe: This summer I’m learning to observe and analyze data with the largest telescope
sci-universe: This summer I’m learning to observe and analyze data with the largest telescope in Northern Europe (Tartu Observatory). The method we’re practicing is called spectroscopy which means our data is represented by a spectrum, a plot as a function of wavelength (or frequency). In the beginning it looks like that in my case: On clear nights, we observe stars of our interest with the telescope connected to an instrument that separates their light into spectrum, and records the signal using a camera. Besides the stellar spectra, we also record spectra of a certain lamp. This is needed for wavelength calibration to later get from camera’s pixels to angstroms. We also take zero and flat-field exposures. After that, it is a lot of work to get the actual “pure“ stellar spectrum from the image because we need to remove instrumental effects, sky background and other noise. So what we have to do now is called data reduction. I’ll be very brief. For that, we use the program IRAF which runs on Linux. The main steps are flat-field correction; stellar spectra extraction which takes us from a 2D image above to a graph: then lamp spectra extraction, line identification, and wavelength calibration. After all that, we get the final spectrum. Here’s the spectrum of star V639 Cassiopeia which lies more than 3500 light-years away from us: I will leave the information behind those lines for an upcoming post -- source link
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