Solar Observing at Mount Wilson Observatory

“It cannot too often be repeated that the Sun is the only star whose phenomena can be studied in detail.” ~ George Ellery Hale

Vivid image of the Sun’s surface and outer atmosphere, showing swirling plasma, solar flares, and coronal loops in bright orange and white. Captures the dynamic energy and magnetic activity studied during solar observing at Mount Wilson Observatory.

With this statement, George Ellery Hale explained the importance of establishing a solar astrophysical observatory, a dream which became a reality with the founding of the Mount Wilson Solar Observatory in December 1904. Our founder, George Ellery Hale was particularly interested in the Sun, as it is the easiest object in which to study astrophysics – the purpose of Mount Wilson Observatory. And as it is the source of energy for most of the life on our planet, the Sun is worth a little of our attention.

The Snow Telescope at Mount Wilson — The Snow telescope, a coelostat donated by Helen Snow of Chicago to the Yerkes Observatory, was brought to Mount Wilson in 1904.

The 60-foot solar telescope tower at Mount Wilson — The 60-foot solar telescope tower was completed in 1908 and became the world’s greatest tool for solar research.

The 150-foot solar telescope tower at Mount Wilson — The 150-foot solar telescope tower was completed in 1912 to study the position, strength, and polarity of magnetic fields on the Sun.

You can read more about the history of solar observing at Mount Wilson Observatory here.

If you purchase a ticket for one of our weekend public tours, you will usually be able to go inside the Snow telescope and the 150-foot Solar telescope, which was the largest instrument for studying the Sun for 50 years.

The Sunspot Record

The Sunspot Record has been drawn every sunny day at the 150-foot solar telescope tower on Mount Wilson since January 4, 1917. Volunteer Steve Padilla, who worked here for many years as a UCLA solar astronomer keeps this invaluable record going. The spots are hand drawn in pencil, and are marked with magnetic field strength data. It is the longest continual record of sunspot activity with magnetic data ever made.

To see what’s happening on the Sun today (or any sunny day since 1917!), see our daily sunspot drawing archive.

A high-angle shot on a tabletop shows various items related to astronomical observation or study. On the left, a sheet of white paper displays a hand-drawn diagram resembling a cluster of sunspots, with various points labeled with "R" and "V" numbers. Above this diagram, handwritten notes include "+5∘ " and "LONG=246∘ ".

Watch this video on YouTube

The first of the sunspot drawings done at the 150-foot solar tower telescope at Mount Wilson Observatory was drawn by Ferdinand Ellerman on January 4, 1917. Sunspots are darker, cooler areas on the surface of the sun in a region called the photosphere. Sunspots occur over regions of intense magnetic activity, and when that energy is released, solar flares and big storms called coronal mass ejections erupt from sunspots. This video shows every sunspot drawing of the year, from January 4 – December 31, 1917.