The SST is a vacuum telescope, meaning that it is evacuated internally to avoid disruption of the image from air inside. This is a particular problem with solar telescopes because of the heating from the large amounts of light collected being passed on to any air causing image degradation.
As of 2005 the SST has produced the highest resolution images on the Sun of any telescope. This is largely thanks to its adaptive optics system,[4] which was upgraded to an 85-electrode monomorph deformable mirror from CILAS[5] in 2013.
There are two modes of operation, selected by switching the beam from one optical table to another. One mode is a spectrograph mode, using the TRIPPEL spectrograph. The other mode is an imaging mode, where the beam is split up in a red and a blue part by a 500-nm dichroic beamsplitter. Both beams have dual Fabry-Pérot-based tunable filters,[6]CRISP in the red and CHROMIS in the blue. The image data are usually compensated for residual wavefront aberrations by use of the MOMFBD image reconstruction method.[7][8]
The CHROMospheric Imaging Spectrometer[10] (CHROMIS) was installed in 2016. It is similar to CRISP (but so far without polarimetry) and designed for use at wavelengths in the range 380–500 nm. In particular, CHROMIS is optimized for use in the Ca II H and K lines, which are formed in the upper chromosphere. The total system uses three 1920×1200-pixel Grasshopper 3 CMOS cameras from Point Grey (now FLIR). One camera is used for direct narrow-band observations and two, in a phase-diversity configuration, are collecting simultaneous wide-band image data.
The CRisp Imaging SpectroPolarimeter[11][12][13] (CRISP) was installed in 2008. It operates from 510 to 860 nm and is able to measure polarization by using liquid crystal modulation combined with a polarizing beam splitter. The total system uses three 1k × 1k Sarnoff CCDs, two are used for direct narrow-band observations and the third is collecting simultaneous wide-band images.
The TRI-Port Polarimetric Echelle-Littrow[14] (TRIPPEL) is a Littrow spectrograph using a 79 grooves/mm echelle grating with a blaze angle of 63.43 degrees. TRIPPEL's wavelength range is about 380–1100 nm, and it has a moderate resolution for a solar telescope, with R being approximately 200,000. This corresponds to about 1.3 km/s on the solar surface.
TRIPPEL has a number of key useful features. It allows simultaneous observations at 3 different wavelengths, can in principle exploit the full spatial resolution of the SST, and has good polarimetric properties.
^Scharmer, Göran; Owner-Petersen, M.; Korhonen, T.; Title, A. (1999). T. R. Rimmele; K. S. Balasubramaniam; R. R. Radick (eds.). "The New Swedish Solar Telescope". High Resolution Solar Physics: Theory, Observations, and Techniques. Astronomical Society of the Pacific Conference series. 183: 157–168. Bibcode:1999ASPC..183..157S.
^van Noort, Michiel; Rouppe van der Voort, Luc; Löfdahl, Mats G. (2005). "Solar Image Restoration By Use Of Multi-frame Blind De-convolution With Multiple Objects And Phase Diversity". Solar Physics. 228 (1–2): 191–215. Bibcode:2005SoPh..228..191V. doi:10.1007/s11207-005-5782-z.
^"CHROMIS". SST wiki. Institute for Solar Physics. Retrieved 26 September 2017.
^"SST CRISP images". SST website. Institute for Solar Physics. Retrieved 28 May 2011.
^Scharmer, G. B.; Narayan, G.; Hillberg, T.; de la Cruz Rodriguez, J.; Löfdahl, M. G.; Kiselman, D.; Sütterlin, P.; van Noort, M.; Lagg, A. (December 2008). "CRISP Spectropolarimetric Imaging of Penumbral Fine Structure". The Astrophysical Journal. 689 (1): L69–L72. arXiv:0806.1638. Bibcode:2008ApJ...689L..69S. doi:10.1086/595744.
^"CRISP". SST wiki. Institute for Solar Physics. Retrieved 26 September 2017.
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