Comparing simultaneous measurements by two high-resolution imaging   spectropolarimeters: the `Goettingen' FPI@VTT and CRISP@SST
  In July 2009, the leading spot of the active region NOAA11024 was observed simultaneously and independently with the 'Goettingen' FPI at VTT and CRISP at SST, i.e., at two different sites, telescopes, instruments and using different spectral lines. The data processing and data analysis have been carried out independently with different techniques. Maps of physical parameters retrieved from 2D spectro-polarimetric data observed with 'Goettingen' FPI and CRISP show an impressive agreement. In addition, the 'Goettingen' FPI maps also exhibit a notable resemblance with simultaneous TIP (spectrographic) observations. The consistency in the results demonstrates the excellent capabilities of these observing facilities. Besides, it confirms the solar origin of the detected signals, and the reliability of FPI-based spectro-polarimeters. 
N. Bello Gonz\'alez, L. Bellot Rubio, A. Ortiz, R. Rezaei, L. Rouppe   van der Voort and R. Schlichenmaier
astro-ph.SR