Sunspots are one of the most accessible and rewarding features to observe on the Sun. With safe filtration and tools like the Baader AstroSolar film and the Seestar S50, it’s possible to capture detailed views of the solar surface from home. This page introduces what sunspots are, how they form, and how I observe and photograph them, illustrated with images from my own back garden.
All of the images here are taken with the superb smart telescope from ZWO - the Seestar S50. These scopes make imaging so simple and accessible to everyone with automatic tracking, a goto system for finding sky objects, and an imaging and stacking system for astrophotography. I use two different filters which are covered later on.
Sunspots are cooler, darker patches on the Sun’s photosphere created by intense magnetic fields rising through the surface. These magnetic fields suppress convection, reducing the upward flow of heat and producing the distinctive dark umbra and lighter penumbra structure.
They are still extremely bright — thousands of degrees — but appear dark only in contrast to the hotter surrounding surface.
Typical features visible in white‑light images:
For more information and a great read - Colin Stuart's Rebel Star is an excellent book, written in an accessible style, but containing all you need for a primer in solar observations and physics.
Sunspots are markers of solar activity and follow a roughly 11‑year cycle. Their number and complexity rise and fall as the Sun’s magnetic field strengthens and reorganises. Active regions can produce flares and coronal mass ejections (CME's), making sunspot monitoring important for both science and space weather forecasting. Spots are numbered according to a numbering system which also denotes certain qualities of the area.
For observers, they offer:
There are some current projects running in space to monitor and observe solar activity, furthering our knowledge all the time. To see how the experts do it, follow them here:
Solar observing must always be done with proper filtration. Even a moment of unfiltered sunlight through optics can cause permanent eye damage and destroy equipment.
Safe methods include:
Unsafe methods include improvised filters, stacked sunglasses, smoked glass, or anything not certified for solar use - never look at the sun without the right protection, and never point your camera or scope at the sun without filters!
Without a doubt the Baader Astrosolar film is the most affordable and solution that produces better results than the Seestar S50 supplied filter.
Baader Astrosolar film Filter (From First Light Optics):
Seestar S50 ND 5.0 Filter:
My workflow varies depending on conditions and equipment:
Sunspots evolve constantly, making them ideal for time-lapse sequences or comparison sets - tracking a spot across the sun's surface makes for some great imagery!
My main method is the Seestar S50 and filters. Although the Baader white light filter produces a better resolved image, with more details and is clearly sharper, there are benefits to the orange disc you get when using the Seestar's own filter:
The image above shows the "orange" disc that you get when using the supplied ND 5.0 solar filter - it's not unpleasant, just not what you want. It also lacks the photosphere's granulation where convection occurs - it all looks very smooth. Although the sunspots AR4374 and 4373 are well represented, although no umbra or penumbra can be seen on them in any sort of detail.
The above image is using the Baader Astrosolar filter on the S50 - so the same sensor, aperture and focal length as the first image. Sunspots 4378 (upper region), 4379 and 4380 (lower region) are clearly visible, and the umbra and penumbra are clearly defined. The white light of this filter also shows the granulation of the photosphere in good detail.
This is the 4X optically zoomed version - showing the active regions in more detail. The granulation is very visible in the image, and fascinating to see from your own back garden!
As time progresses, sunspots will appear and disappear on the surface - it will be great to track them as they move around the sun's observable disc, and it always amazes me that we can view a star in such detail as this in relative comfort.