The three channel optical-near-infrared imager 3kk has been developed and build in our group to serve for simultaneous imaging records of a selected science target in a blue, red, and infrared band. Project manager was F. Lang-Bardl. Typical science applications are e.g. the monitoring of variable sources in three bands to obtain colour information like needed for a secure classification of exo-planet candidates (see below/link) or so-called photo-redshifts where multiple band observations of a galaxy compared to standard spectral energy distribution enable the determination of its redshift and thus distance.
The telescope light passes two custom-designed beam splitters that send the light into a blue arm, into a red one, and into a near-infrared one. This beam splitter system is designed to keep the full imaging quality (SPIE 3kk 2010). The blue and the red beam are both equipped with Bonn shutters (Reif et al. 2007), followed by filter wheels, and Fairchild-2k optical CCD cameras (Apogee). For more details see the table below.
The NIR camera is built in cooperation with the IfA in Hawaii. It is build around an HAWAII-2RG 2k * 2k detector and a SIDECAR ASIC detector control system, operated at 80 K. The camera housing is designed as a dewar cooled with liquid nitrogen which is produced by a facility at the observatory. The infrared camera operates without shutter, is coupled by reimaging optics, and includes a cold stop and a cold filter wheel. For more details see the table below. A full design description can be found in our SPIE 2016 contribution.
Three-channel imager at the Wendelstein 2-m Telescope (3KK)
|Field of view||3 channels on same f.o.v.:
blue and red CCDs, WNIR
7 × 7 arc min (blue, red)
8 × 8 arc min (WNIR)
|Number of pixels||2048 × 2048 each channel|
|Pixel scale||0.2003 arc sec/pixel blue CCD
0.2012 arc sec/pixel red CCD
0.2516 arc sec/pixel WNIR
|Detector type CCD||Fairchild|
|Detector type WNIR||HAWAII-2RG|
|Channel separation||beam splitters 695 nm, 970 nm|
|Filter positions||12+2 in 2 wheels|
|Filters blue CCD||Sloan u′, g′, r′; [O I], Hα, [S II]|
|Filters red CCD||Sloan i′, z′|
|Filters WNIR||Y, J, H, Ks; H2, Brγ|
|Auto guiding||not implemented|