IRIS Movie of the Day
At least once a week a movie of the Sun taken by NASA's Interface Region Imaging Spectrograph (IRIS) is posted by one of the scientists operating the instrument.
Solar eclipse observed with IRIS
Credit: IRIS, LMSAL/NASA, Juan Martinez-Sykora
In July 2018 the moon passed in front of the Sun as seen by IRIS, producing a solar eclipse. These observations are of interest for calibration of how the light in our instrument is focused. Like in any optical instrument, the light passing through IRIS is not perfectly focused onto the detector, with some low levels of light scattered (caused by imperfections in the optical path) making the images a tiny bit fuzzier than the ideal conditions. By measuring the light levels in the locations where the Moon is passing through, we can estimate how much light is scattered (since the Moon should be be completely dark) and correct images and spectra for this effect. Such a point-spread-function correction leads to data with even higher contrast than our raw data.