ChroTel is a 10 cm aperture
telescope to observe the chromosphere of the Sun. It was developed
at the Leibniz-Institut for Solar Physics (KIS) Freiburg together with the High
Altitude Observatory (HAO) in Boulder, USA. With a spatial
resolution of about 2 arcsec it observes the solar chromosphere in
its most prominent lines un the near UV, the red and the infrared
(Ca II K, Hα and He I) using a 2048x2048 pixel CCD. ChroTel uses a
two mirror system ("turret") next to the VTT building that relays
a stabilized image of the solar disc into a laboratory within the
VTT building. The heart of the optical lab is a filter system
consisting of three narrow-band Lyot filters, of which one is
tunable. The He I filter is tunable and observations are taken at
seven wavelength positions fully covering the whole spectral line,
giving full-disk chromospheric Doppler maps. Images in all
channels (and the seven He I bands) can be taken with a cadence of
below one minute. The operation of ChroTel is automatic, as far as
possible. ChroTel also serves live images for VTT and Gregor. The
scientific data of ChroTel are freely available for scientific and
educational use. Observing campaigns together with the Tenerife
Infrared Polarimeter (TIP) at the VTT enabled us to calibrate the
Doppler shift maps derived from the seven filtergrams of ChroTel
in the Helium I channel. The main goals of the science operations
of ChroTel are to study the dynamic response of the chromosphere
to photospheric driving especially in the chromospheric network,
large-scale structures and their disturbance such as flares and
CMEs and the chromospheric source of the fast solar wind.
An overview of the available data products and the header structure of the individual fits files can be found here.