We simulate the actions of a coronagraph matched to diffraction-limited adaptive optics (AO) systems on the Calypso 1.2m, Palomar Hale 5m and Gemini 8.lm telescopes, and identify useful parameter ranges for AO coronagraphy on these systems. We model the action of adaptive wavefront correction with a tapered, high-pass filter in spatial frequency rather than a hard low frequency cutoff, and estimate the minimum number of AO channels required to produce sufficient image quality for coronagraphic suppression within a few diffraction widths of a central bright object (as is relevant to e.g., brown dwarf searches near late-type dwarf stars). We explore the effect of varying the occulting image-plane stop size and shape, and examine the trade-off between throughput and suppression of the image halo and Airy rings. We discuss our simulations in the context of results from the 241-channel Palomar Hale AO coronagraph system, and suggest approaches for future AO coronagraphic instruments on large telescopes.

This paper describes the wave-front correction system developed for the Sunrise balloon telescope, and it provides information about its in-flight performance. For the correction of low-order aberrations, a Correlating Wave-Front Sensor (CWS) was used. It consisted of a six-element Shack -Hartmann wave-front sensor (WFS), a fast tip-tilt mirror for the compensation of image motion, and an active telescope secondary mirror for focus correction. The CWS delivered a stabilized image with a precision of 0.04 arcsec (rms), whenever the coarse pointing was better than ± 45 arcsec peak-to-peak. The automatic focus adjustment maintained a focus stability of 0.01 waves in the focal plane of the CWS. During the 5.5 day flight, good image quality and stability were achieved during 33 hours, containing 45 sequences, which lasted between 10 and 45 min.

We describe the design of the Sunrise Filter Imager (SuFI) and the Image Stabilization and Light Distribution (ISLiD) unit onboard the Sunrise balloon borne solar observatory. This contribution provides the necessary information which is relevant to understand the instruments' working principles, the relevant technical data, and the necessary information about calibration issues directly related to the science data.

The Sunrise balloon-borne solar observatory, consisting of a 1 m aperture telescope that provided a stabilized image to a UV filter imager and an imaging vector polarimeter, carried out its second science flight in June 2013. It provided observations of parts of active regions at high spatial resolution, including the first high-resolution images in the Mg ii k line. The obtained data are of very high quality, with the best UV images reaching the diffraction limit of the telescope at 3000Å after Multi-Frame Blind Deconvolution reconstruction accounting for phase-diversity information. Here a brief update is given of the instruments and the data reduction techniques, which includes an inversion of the polarimetric data. Mainly those aspects that evolved compared with the first flight are described. A tabular overview of the observations is given. In addition, an example time series of a part of the emerging active region NOAA AR 11768 observed relatively close to disk centre is described and discussed in some detail. The observations cover the pores in the trailing polarity of the active region, as well as the polarity inversion line where flux emergence was ongoing and a small flare-like brightening occurred in the course of the time series. The pores are found to contain magnetic field strengths ranging up to 2500 G and, while large pores are clearly darker and cooler than the quiet Sun in all layers of the photosphere, the temperature and brightness of small pores approach or even exceed those of the quiet Sun in the upper photosphere.