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We demonstrate that for data recorded with a solar telescope that usesadaptive optics and/or post-processing to compensate for many low- andhigh-order aberrations, the RMS granulation contrast is directly proportionalto the Strehl ratio calculated from the residual (small-scale) wavefront error.We demonstrate that the wings of the high-order compensated PSF for SST arelikely to extend to a radius of not more than about 2 arcsec, consistent withearlier conclusions drawn from straylight compensation of sunspot images. Wereport on simultaneous measurements of seeing and solar granulation contrastaveraged over 2 sec time intervals at several wavelengths from 525 nm to 853.6nm on the red-beam (CRISP beam) and wavelengths from 395 nm to 484 nm on theblue-beam (CHROMIS beam). These data were recorded with the Swedish 1-m SolarTelescope (SST) that has been revamped with an 85-electrode adaptive mirror anda new tip-tilt mirror, both of which were polished to exceptionally highoptical quality. The highest 2-sec average image contrast measured in April2015 through 0.3-0.9 nm interference filters at 525 nm, 557 nm, 630 nm and853.5 nm with compensation only for the diffraction limited point spreadfunction of SST is 11.8%, 11.8%, 10.2% and 7.2% respectively. Similarly, thehighest 2-sec contrast measured at 395 nm, 400 nm and 484 nm in May 2016through 0.37-1.3 nm filters is 16%, 16% and 12.5% respectively. The granulationcontrast observed with SST compares favorably with that of other telescopes.Simultaneously with the above wideband red-beam data, we also recordednarrow-band continuum images with the CRISP imaging spectropolarimeter. We findthat contrasts measured with CRISP are entirely consistent with thecorresponding wide-band contrasts, demonstrating that any additional imagedegradation by the CRISP etalons and telecentric optical system is marginal oreven insignificant.

Is the sky the limit? Performance of the revamped Swedish 1-m Solar Telescope and its blue- and red-beam re-imaging systems