One way to capture the sunspots, without having a solar filter, is to draw them by projecting the Sun onto a screen. This is the safest way to observe our star, and you don’t need to buy a filter. This is probably the best, and most inexpensive, way to track the solar activity during its 11-year cycle.
To draw the Sun is not as easy as it may seem. The telescope shakes (how much would depend on the sturdiness of your system) when the pencil touches the screen, or when the wind blows. The good thing is that you don’t need to be an artist to draw the Sun. Your skills will also increase with practice.
Since there is no filter, all the light passes through the optical system, which causes heating. You would see some turbulence of the image (and if you do not see it, it is there!) a few minutes after you point the telescope at the Sun. That’s why you should draw for no more than 5 minutes, move the telescope away from the Sun to cool down, and than start again.
Sunspots are generally found in groups, but not always. You could find a small isolated sunspot. Most large sunspots are surrounded of smaller ones, and sometimes you could see a few sunspots in the penumbra (the shaded regions).
How to draw the Sun?
First, grab a sheet of paper (letter or A4) and draw a circle with radius 2 inches (10 cm) diameter. You may also include inner circle with radius 1 inch (5 cm) if you want. Put it on a screen attached to the telescope. I would recommend that you have a motorized mount, or else you have to track manually the Sun, while you’re drowning it, and that won’t be easy.
After your screen is set and the projected solar disk is adjusted to fit the drawn circle, you can begin to draw the sunspots. Don’t try to reproduce them exactly to the last detail. This is not necessary at the beginning, and you’ll become better with time. Quickly mark the center of a spot, and then draw the shaded region without filing it in. At the end put down the small sunspots (if you see such), which surround the big once.
Finally, what you need to do is choose one small sunspot, and turn off the power of the telescope. When the entire image will start moving, quickly mark the path of the sunspot you’ve chosen with a few dots. That way you can draw a line, which will determine the East direction. Record the sky conditions and the turbulence of the image. You could use scale of 1 to 5, and you are almost done for today. Don’t forget to include the day and time in UT (GMT) preferably.
The last thing you have to include in your drawing is the Wolf number (or the sunspot number). The idea for computing such number belongs to Rudolf Wolf, thus Wolf number. This number is used to track the solar activity. It’s calculated by the following equation:
W = 10 x G + S
where G is the number of groups and S is the number of sunspots. With that your observing session is done.
More information you can find on the SIDC (Solar Influence Data Analysis Center) website.
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