The Night Sky: Sunspots

Sunspots are increasing in numbers to the delight of solar observers.

Attached are test images of the Sun taken with a telescope and a digital camera. A very special solar filter was used. The only safe way to take pictures of the Sun is with a filter designed to do so.

Sunspots are massive magnetic storms on the Sun. They form from a complex process that twists and contorts the Sun’s magnetic field. They are 9000 degrees F, but are cooler than the brighter 10,000 degree areas surrounding them. Thus they appear black, but if sunspots could be viewed away from the rest of the Sun they would look blindingly bright. Sunspot numbers vary from minimum to maximum in an 11-year cycle. The next sunspot maximum is predicted to be May of 2013. Studies have found that Earth’s temperature varies slightly with the sunspot cycle.

Galileo was among the first to observe sunspots with a telescope. He was also one of the first to begin to understand what he was seeing on the sun’s surface. Others before him mistakenly thought they were seeing planets passing in front of the Sun. Galileo observed that sunspots moved from day to day. This proved the Sun rotated in about 25 days. He also noted that sunspots grow, their shapes evolve and then they fade away, proving the Sun was not static and that it was dynamic and changing.


The full solar disk image shows a scattering of sunspots on the Sun’s surface and a large group of sunspots just below center. This large group of sunspots is cataloged as AR 11476. AR stands for ‘Active Region’.

A close up of AR11476 is also attached. The close up shows the darker central sunspot areas called umbra and the lighter outer regions called penumbra. The Earth is about the same size as the large umbra just below center in this picture.

Image Technical details:

Acquired at the Bowman Observatory May 12, 2012

80mm refractor telescope at 1200mm FL

Baader solar filter

Canon T2ia camera

Data acquisition using EOS Movie Record software

Processed in RegiStax and PhotoshopCS5

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Rick Bria May 28, 2012 at 04:31 PM
Bill, You are correct... and I have to laugh every time I write about something that occurs during the daylight hours, because I also see the irony. But the same can be said about ‘Sunset’ or ‘Sunrise’. It is only from our perspective on Earth. Night sky, day sky, it is really all the same thing. Rick
Rick Bria May 28, 2012 at 04:36 PM
Forgot to mention... all this daytime stuff stems from preparation for the upcoming Venus Transit on June 5th. My next blog will speak of that rare event... If it is clear, the Bowman Observatory will be the place to see it... stay tuned. Rick Bria
Zeena Nackerdien May 31, 2012 at 01:20 AM
Hi Rick: Mark Anderson wrote a very interesting book about "The transit of Venus" in the 1760s. Since the upcoming transit is a once-in-a-lifetime event, this fan is eagerly awaiting the details. Do we have to bring special glasses to Bowman or can we just peer through your telescope?
Rick Bria May 31, 2012 at 03:21 AM
Zeena, There is no need for people to bring any equipment or viewing glasses to the Bowman Observatory. We will use two methods to view the transit. The first will use a camera. It will send live video to a laptop computer that all will be able to see. That is the 21st century method. We will also use the projection method. Just as the first people to view transits did in 1631, we will have the telescope project an image of the Sun and Venus onto a screen for all to see Both methods are completely safe, but I like the projection method best because of the history, and in my view, it is the most rewarding. Rick
Zeena Nackerdien May 31, 2012 at 01:25 PM
Excellent, Rick. I am looking forward to the event.


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