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AO on AR 8970

Observations of AR8970 using Adaptive Optics

On April 27 the large sunspot in Active Region 8970 was observed using the Adaptive Optics system at the Swedish Vacuum Solar Telescope at La Palma. The observations are a succesful demonstration of the ability of the AO system to reach the diffraction limit of the telescope under excellent seeing conditions. It showed to give a significant improvement of the image quality under less favorable conditions.

Click on the image to get a high resolution version.
This image is rich in fine scale structures and is a good example of the complexity of active regions. It shows umbral dots and two light bridges in the dark umbra, bright grains, dark clouds and bright and dark filaments in the penumbra, pores, disconnected penumbrae, granules and Gband bright points in the surroundings of the spot. Tick marks are 1 second of arc (approx. 700 km on the Sun).
This image was the Astronomy Picture of the Day at May 22!

Here is an MPEG movie of the whole spot in low resolution. (1.6 Mb)
If you want better image quality than MPEG and you have a fast connection, you could download this animated GIF movie (15 Mb).

The images were recorded with the Swedish Vacuum Solar Telescope (diameter 47.5 cm) using a 1.1 nm filter centered on 430.8 nm wavelength (G Band). The adaptive optics system consists of a 19-electrode bimorph mirror from Laplacian Optics and a 19-element Shack-Hartmann micro-lens array. Cross-correlations are used to determine the relative positions of the 16x16 pixel sub-images and the required computations are done with a single 500 Mhz Compaq Alpha workstation using a EV6 processor running at 500 Mhz with a frame rate of 955 frames/s. The images were recorded using a Kodak Megaplus 1.4 CCD camera with 6.8 micron pixels, exposure time: 20 ms. The observation sequence consists of 108 images and correspond to 55 minutes on the Sun (13:16 - 14:11 UT). At April 27, Active Region 8970 was of magnetic type beta-gamma and was near disk center (observing angle is 13 degrees).

High Resolution Movies

The small boxes in the picture below indicate the location of the high resolution movies. Click on the corresponding thumbnails below to view the high resolution image and to download the movie.



Download Data

Download the data in FITS format and read it with your favorite data analysis software (IDL, ANA, etc).

The data cube is cut in three pieces to get manageable file sizes, you can glue them together to restore the whole 108 images cube.
gband_ao.01_36.cube.fits 36.5 Mb: image 1 - 36
gband_ao.37_72.cube.fits 36.5 Mb: image 37 - 72
gband_ao.73_108.cube.fits 36.5 Mb: image 73 - 108
(if you do not want to download the data via your browser, go to ftp.astro.su.se/pub/rouppe)

gband_ao.120.fits 1.3 Mb: single image.

gband_ao.README
More information about the adaptive optics system at the SVST.
Luc Rouppe van der Voort
Last modified: Fri May 12 16:19:30 MET DST