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Grab your sextant, swing in some shades, point it at the Sun, and see its imperfection. There is a very large sunspot group active right now. It will be moving around to the back side of the Sun soon, and even before then it will be foreshortened as it heads toward the limb, so today is your best chance. We had a brief window in the clouds this morning... I had little trouble seeing this sunspot group a few minutes ago using an ordinary Davis Mk. 15 plastic sextant with the standard low-power scope. Do be sure that your scope is properly focused! The group is easy in a higher-power, higher-quality sextant scope.

Note: this will not look like a black spot, not like Venus in transit. It's a clump, and in any case sunspots are not actually dark. They're darker than the normal face (photosphere) of the Sun, but still very bright. It's the contrast that makes them look dark through the right solar filters. Can anyone find a number on that (I could not with a little searching just now)? How bright is the central face of the Sun (photosphere) in MPSAS (magnitudes per square arc second) and how bright is the center of a "dark" sunspot in comparable units?

The image here is a current SOHO satellite image. This is about what you could see, direct with a filter or by eyepiece projection, with about 50x magnification using a backyard telescope.

Note also that there is a major geomagnetic storm underway and predicted to intensify late today. Look for aurorae in high latitudes, and expect interference with radio transmission at some frequencies. This storm, like the sunspot group, is a symptom of the Sun's peak activity. We are near sunspot maximum in its roughly eleven-year cycle.

Frank Reed

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