Light leaks inside the EUVI telescope optics can also affect the images (EUVI-B 284)

EUVI uses thin metal films to filter out direct sunlight and pass through only the wavelengths of interest. Small holes can develop in these filters, letting stray light through the system. To get around this problem, two sets of filters are used, one at the front of the telescope, and another at the back, to reduce the effect of light leaks. However, some faint leaks are still visible in the images, as shown below for the 284 Angstrom bandpass on STEREO Behind.

[link to youtu.be]

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