[Observing Sunspots]
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Observing Sunspots

By Jim Scala


Bay Area weather generally offers fair astronomical seeing and occasionally, good to excellent, but much of the year our superb maritime climate produces skies with moisture aloft that degrades nighttime seeing. However, during the day, the Sun cuts right through this “scud,” which helps steady solar observing. Since we’re in a sunspot maximum, it’s an excellent time to view the ever-changing surface of our nearest star and enjoy the convenience of daytime astronomy.

Observing sunspots doesn’t require expensive equipment; however, like anything, you can go as far as your pocketbook will allow. A good two-inch telescope will do just fine, and four inches is overkill. Many sunspot groups exceed 60 arc seconds in size. Since a two-inch telescope will resolve 2.3 arc seconds, a plethora of sunspot detail awaits the small scope owner. For example, figure one is a sunspot group that covered just under four arc minutes and was visible on November 15, 1999 when Mercury’s 9 arc second disk transited the Sun. In a two-inch scope, Mercury was a just a round black speck, but this sunspot group was clearly visible in a one-inch scope.

November 15, 1999 Sunspot Group. This sunspot group was prominent when Mercury transited and added to the viewing. This group is 200,203 km at its longest dimension. It could easily hold 16 earth-sized planets!

CCD images taken through a 355 Maksutov using a Thousand Oaks Type Two solar filter. Additionally two ND-1 filters were required to reduce light intensity enough for the CCD.



Take Correct Precautions
Anyone who has ever experimented with a magnifying glass knows that concentrated sunlight creates enough heat to start a fire. Indeed, a telescope is really just a large magnifying glass (light bucket) that concentrates light and heat. So, if you look at the Sun through a telescope, you will burn out your eye before you can turn away. Consequently, you have to observe in one of two ways: either cut down light by a factor of about a 1,000 before it enters the scope; or let it into the scope and then project the Sun’s image on an appropriate viewing screen. This latter method has drawbacks since in a compound scope, such as an SCT or Maksutov, internal heat can cause damage to the scope.

Caution is essential!

Variety Awaits
Here is a sampling of sunspots that have graced the surface over the past few months and illustrates their variety and how much they change. Each grouping usually lasts for several weeks, if not months. They start at upper or lower (temperate) latitudes and migrate toward the equator. The Sun rotates in about 10 days, so if you observe every three to five days, you can watch a group as it takes shape, then decays, and disappears.

March 11, 2000. (Left) The longest dimension of this group is 3 arc minutes; that’s 125,381 km. It is just below naked-eye visibility. Some keen-eyed people could probably have seen this spot. (Right) This is the second group visible on March 11. It was 94,040 km at its longest dimension. It was easily visible in a small scope.

June 2, 2000. This grouping of spots (Left) was near the Sun’s edge. It is 84,761 km at its longest dimension. Still not large enough for naked-eye visibility. This single sunspot (Right) was near the center of the solar disk. 

A Small Scope Will Do
The following images illustrate what you can do with a small scope. Ellis Myers, using Kodak Gold 200 film through a 70 mm (2.7") scope equipped with a solar filter, took the general view from Moraga on June 12, a day with misty clouds. Jim Scala, atop Mt. Diablo, took the other images on June 10th with a 2.5-inch scope (at f/42) using Ilford XP-2 film. The close-up was taken with a 2× Barlow lens, giving a focal ratio of f/84! Both negatives will stand much enlargement, illustrating what a small scope can do with ample sunlight.

(Left) June 12, 2000. TeleVue Oracle telescope (f.l.= 560 mm) with Thousand Oaks solar filter.

(Below Left) June 10, 2000. General view of the sunspots taken with a 64-mm solar filter reducing aperture of a 7" (178 mm) telescope with a 2540 focal length. (Below Right) The same scope equipped with a 2× Barlow giving a final focal length of 5080 mm.

 

 

 

 


Get Started Now
The June 1999 and January 2000 issues of Sky and Telescope have superb articles on making sunspot scopes, or converting your present scope, from readily available materials. First, purchase a two- or three-inch objective lens from one of the many suppliers (choose a high focal ratio) listed in S&T; then, after a couple of trips to the hardware store and some pleasant work at the bench, you will have a fine sunspot telescope.

For those who own a telescope, the easiest course is to purchase a solar filter from one of the suppliers listed in S&T; then, you can observe the Sun directly. To really cut costs, you can purchase aluminized Mylar and make your own full-aperture solar screen.


Universe 2000
The dawn of the new millennium is an unbelievably exciting time for astronomy. Giant planets have been discovered orbiting nearby Sun-like stars. Recent spacecraft observations of Mars show conclusively that water once flowed freely on the red planet’s surface, perhaps giving life a chance to take hold there. And bacteria have been found thriving deep in the crust of the Earth, suggesting that other subsurface environments among the planets and moons of our solar system could be comfortable habitats for living organisms.

Universe 2000, the 112th Annual Meeting of the Astronomical Society of the Pacific, will focus on the developments taking place in the new interdisciplinary field of astrobiology. Leading researchers at the cutting edges of astronomy, planetary science, geology, and biology will give keynote addresses on Saturday, July 15th and Sunday the 16th in Pasadena, California. Four programs will meet the varied interests of attendees:
Universe 2000 Expo; Cosmos in the Classroom Symposium; Universe in the Classroom: A Workshop on Teaching Astronomy in Grades 3-12; and an Astrobiology Symposium: “From Dust to Life: Surviving the First Billion Years of the Solar System.”

The research symposium will provide interdisciplinary links between astronomy and the other academic disciplines related to astrobiology, at a level that is appropriate for professional researchers who are being introduced to other fields. We anticipate an audience that is made up of astronomers, geologists, biologists, chemists, and other scientists representing a host of other related disciplines.

The focus of the symposium will be the formation of the solar system and the first billion years of Earth’s history, from the accretion of planetesimals to the first life. A variety of perspectives will be offered on this first phase of Earth’s evolution, i.e., what can the fields of astronomy, planetary science, geology, oceanography, chemistry, and biology tell us about this remarkable period? The symposium will endeavor to develop as complete a picture as possible of our current understanding of this unknown era, with emphasis on what information is needed across disciplinary boundaries.

Topics covered and issues to be explored include: the chemical and radiation environments of the early solar system; the formation of the Earth; the biochemistry of life; the anaerobic Earth; our earliest living ancestor (the tree of life); life in extreme environments and bacterial survival.

The program is intended to provide a meaningful and engaging experience for all. Everyone is encouraged to attend the public symposium, which complements the other symposia. Four interdisciplinary panels exploring the relationship between astronomy, the arts, and other areas of human endeavor should be of particular interest to members’ families and guests. Field trips to the Mount Wilson Observatory, Griffith Park Observatory, and other engaging destinations are also being planned. The ASP Awards dinner on Saturday, July 15, will feature Bill Nye, the Science Guy, as a guest speaker!

Join us at ASP 2000 as we kick off the next millennium of astronomy and space exploration! More information, and a registration form are available at www.aspsky.org.



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