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Sketching the Sun

A Month of Sun Days—Observing and Sketching the Sun
By Jane Houston Jones

November, 2002

I love observing the sun and sketching sunspots but have never really tracked the rotation over an extended period of time. I decided completing the Astronomical League's Sunspotter Club would be a way for me to improve my knowledge of our nearest star. First, I ordered the Astronomical League's booklet "Observe and Understand the Sun" by ALPO Solar coordinator Richard E. Hill. I used the solar disk and sunspot forms for my sketches. These forms are also available free of charge on the Astronomical League's Sunspotter club website.

On a sunny sun day in October, I set up my homemade f/9 6-inch Dobsonian solar scope on the back deck and had a 54 power look at the sun. I saw 9 active regions -- regions with more than one sunspot (there were actually 12 but I didn't see some of them) and I counted 26 spots (actually 51) for a Wolf sunspot number of 171. My count using this method was 116. Wolf chose to compute his sunspot number by adding 10 times the number of groups to the total count of individual spots, because neither quantity alone completely captured the level of activity.
http://www.ngdc.noaa.gov/stp/SOLAR/SSN/ssn.html

Image: 1021sunspot Flare-producing sunspot group 162, sketched 10/21/02 by the author


Each day I sketched the sun's disk and any active regions that caught my fancy. After sketching them, I used Hill's booklet to classify the spots. The most interesting regions (to me) were the D,E and F classes of sunspots because they produce flares. On days when there were flare-producing spots visible, I also set up our F/6.8 70mm Televue Ranger fitted with a Coronado SolarMax60 H-Alpha filter. I often sketched these h-alpha views too.

Image 1105solardisk
11/05 sunspot activity - 8 active regions and
56 spots counted by the author

New spots rotated on to the eastern limb and others rotated off the western limb. One particularly active region, AR0177, a DKI flare-producing region, first showed its spots on October 31. "D" for a bipolar group with penumbra on both ends and a length of less that 10 degrees. "K" means the largest spot in the region is an asymmetric spot with a diameter greater than 2.5 degrees. And the "I" means numerous umbral spots lie between leader and follower spots. To put this big "K" spot in perspective, 2.5 degrees spans 12,000 miles and the diameter of earth is 7,900 miles. This means the big spot was 1 1/2 times the diameter of the earth...and growing! On November 6 it split in two! Of course that was the first day of our first winter storm, and it rained all day. :-( This sunspot group is still visible today, November 10th, as I write this article! The sketch of 177 was made on November 5th.

Image 1105sunspot
Sunspot group 177's biggest spot split in two 2 days after
the sketch was made on 11/05/02

On October 19, two other amazing active regions caught my eye -- AR0162 and 0165. These regions were visible to the naked eye! AR162 spanned 22 degrees - which is over 13 earth diameters. A few days later it was even bigger, at 27 degrees or 16 earth diameters - comprising over 60 sunspots before it started to decay. Classified FKC -- "F" for bipolar group greater than 15 degrees in length, "K" for the humongous spot larger than 2.5 degrees, and "C" for compact distribution of spots containing many spots with some having their own penumbra. It was visible until November 1st, and I sketched details almost every day. The sketch here was made on October 21st and includes these features:

  • Faculae: relatively large (greater than an arc minute) irregularly shaped light area; sometimes serpentine in shape. Sunspots are usually located in Facula.
  • Granulation: fine grain structure of the solar photosphere. Grains appear to be one to two arc-seconds in diameter.
  • Light bridge: a bright ribbon or band that may appear to connect two sunspots.
  • Penumbra: a gray area which frequently, but not always, appears around an individual sunspot or group of sunspots.
  • Penumbral fibril: fiber like lines that may appear to radiate out from an umbra into the surrounding penumbra.
  • Penumbral grain: granular or small patchy structure that may be visible in the penumbra.
  • Umbra: The dark black area of a Sunspot.

So far I have observed and sketched the sun for 29 of the required 60 days - or two solar rotations. I've had only two rain-outs. Here are two websites I look at on a daily basis to verify my observations, or in the case of a cloud-out, to get my solar fix for the day. I think yu'll enjoy them as much as I do.

More of my sketches can be found at
http://www.whiteoaks.com/sketches/alsunspotter.html

The NOAA Active Regions, including a solar activity report
http://www.bbso.njit.edu/arm/20021107/wl_fd.html

Latest Solar Images
http://sprg.ssl.berkeley.edu/shine/suntoday.html


 



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