Solar activity during the year 2000

(close to the maximum of the cycle 23)

An increase of the solar activity was revealed by our observations of the Sun on March 5 and 13, 2000. The eleven-years activity cycle has probably not yet reached its maximum, but the sunspots number is already high. Some sunspots are much larger that the planet Earth, which make them easily observable ! A huge sunspot has been observed during the second part of September 2000. Unfortunately no image of this has been taken. After a relatively quite period, a regain of activity has been reported at the end of December 2000 (see the image below). According to the predictions, the maximum of this cycle should occur around the year 2001. The mean period of a cycle is 11.04 years. Due to fluctuations of this period and strong variations of the solar activity close to its maximum, an exact calculation of the maximum date is impossible.

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

 · Impressive sunspots group on December 31, 2000 (Last Day of the Millennium !)

Instrumentation : Achromat Refractor with f = 910 mm
Sun filter : Astrosolar foil (density 5), optical diameter 72 mm, f/d = 12.6
Additional filter : IR rejection filter BG39 (Schott)
Camera : Philips Vesta Pro Scan (WEBCAM !), mounted at the prime focus
Exposure : 1/250 s
Note that the resolution on this image is about 1400 km or 1.9", which is equivalent to the theoretical limit of the instrument given by 1.22*l/d = 1.9".
This performance is very interesting, because the altitude of the Sun, at this time, was just below 20°, which is far away from ideal conditions !
Time : December 31, 2000, 11H55 (UT), from Affoltern am Albis (Switzerland), © M. Willemin

 · Sun photograph taken on March 13, 2000

Instrumentation : Achromat Refractor with f = 910 mm
Sun filter : Astrosolar foil (density 5) with IR rejection filter B+W 486, optical diameter 72 mm, f/d = 12.6
Film : Conventional Kodacolor Gold 100 Asa
Exposure : 1/1000 s
Time : March 13, 2000, 10H57 (UT), from Affoltern am Albis (Switzerland), © M. Willemin

 · Nice sunspots group on March 13, 2000

Instrumentation : Achromat Refractor with f = 910 mm and eyepiece projection with 18 mm Orthoscopic. Resulting focal length : 6.3 m.
Sun filter : Astrosolar foil (density 5) with IR rejection filter B+W 486, optical diameter 72 mm, f/d = 87.5
Film : Conventional Kodacolor Gold 100 Asa
Exposure : 1/30 s
Time : March 13, 2000, 11H20 (UT), from Affoltern am Albis (Switzerland), © M. Willemin

 · Sun photograph taken on March 5, 2000

Instrumentation : Conventional Newton telescope with f = 1000 mm
Sun filter : Astrosolar foil (density 5) with IR rejection filter B+W 486, optical diameter 72 mm (off-axis), f/d = 13.9
Film : Conventional Kodacolor Gold 200 Asa (not optimal for this specific application !)
Exposure : 1/1000 s
Time : March 5, 2000, 14H01 (UT), from Affoltern am Albis (Switzerland), © M. Willemin

· Details concerning the sunspots

Instrumentation : Conventional Newton telescope with f = 1000 mm and Barlow lens (3 x)
Sun filter : Astrosolar foil (density 5) with IR rejection filter B+W 486, optical diameter 72 mm (off-axis), f/d = 42
Film : Conventional Kodacolor Gold 200 Asa (not optimal for this specific application !)
Exposure : 1/125 s
Time : March 5, 2000, 14H13 (UT), from Affoltern am Albis (Switzerland), © M. Willemin

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