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The Chromospheric Telescope (ChroTel) is a small 10‐cm robotic telescope at Observatorio del Teide on Tenerife (Spain), which observes the entire sun in Hα, Ca ii K, and He i 10 830 Å. We present a new calibration method that includes limb‐darkening correction, removal of nonuniform filter transmission, and determination of He i Doppler velocities. Chromospheric full‐disk filtergrams are often obtained...
Narrow‐line Seyfert 1 galaxies are thought to be young AGNs with relatively small black hole masses and high accretion rates. Radio‐loud narrow‐line Seyfert 1 galaxies (RLNLS1s) are very special, because some of them show blazar‐like characteristics, while others resemble compact steep‐spectrum sources. Relativistic jets were shown to exist in a few RLNLS1s based on VLBI observations and confirmed...
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