Solar activity during May 2001

(near the maximum of the cycle 23)

This page describes the impressive solar activity of the cycle 23, which is very irregular since the beginning of the millennium. Sporadic large sunspots are visible between quiet periods of the solar activity. All images presented on this site have been taken by the authors. Most of them have required telescopes and special filters!

Relatively large sunspot near the limb of the Sun
(To see the full resolution, click on the image)

Instrumentation : Schmidt-Cassegrain telescope with F = 2030 mm, f/10 + Astrosolar foil (density 5) + IR BG39
Camera : Philips Vesta Pro Scan (WEBCAM !), mounted at the prime focus, exp. 0.4 ms
Time : May 27, 2001, 13H24 (UT), from Affoltern am Albis (Switzerland), © M. Willemin

The raw image is taken in VGA format (640 x 480) and on an 8 bits greyscale. The contrast and the intensity have been slightly enhanced. The color has been introduced by modifying the weight of the three RGB channels. The theoretical resolution limit of the instrumentation is 500 km (on the Sun). For the best image obtained this day, a resolution of the order of 1000 km was achieved. Especially for solar photography, the resolution is often limited by the atmospheric turbulence. This is clearly the case here, because the telescope was located on a balcony. In principle, it is not recommended to use instruments with a too large optical diameter, the effects of the turbulence will be enhanced and the image quality reduced. An example of poor resolution during a observation of the Sun is shown on the following movie.

Turbulence during sunspot observation

This movie has been taken with exactly the instrumentation as mentioned above and with the same atmospheric conditions! The resolution of the webcam has been intentionally reduced in order to limit the size of the files! The frame rate is about 15 Hz.

If you like to see a larger field, please select the format you prefer :

Open a new window with the full resolution

(*.gif) (2021 kB)
(Can take more than 6 min. with a 56k modem)

Video File and click on the image for starting the sequence with the full resolution
(*.avi) (670 kB)

WARNING: Never view the Sun through optical instruments like telescopes or binoculars without reducing light intensity with appropriate filters. Irreversible eye damage may result!

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