How do I observe the Sun safely, with tools I could build myself and without breaking the bank? If I wanted to build a Sun funnel on my own and use it on my enthusiast grade telescope, how would I do that?

What supplies and tools would I need, how do I attach it to my telescope so it can be applied to it at will, and are there any other, simpler yet safe ways to observe the Sun and its activity with my telescope? This is approximately what I had in mind:

    Sun funnel

How do I build something like that? I'm primarily interested in observing sunspots, but would also like to know, if there is any way for me to safely observe Sun's coronal activity to any appreciable detail with an enthusiast grade newtonian/dobsonian telescope?

Additionally, could I project the telescope's image directly on some screen behind it, without having to use any intermediary digital equipment, like a recording camera and a digital light projector?


1 Answer 1


As for projecting the Sun onto a screen at a low cost, I would recommend starting with a ~50-200$ sunspotter box, which is basically a lens mounted on a wooden box, that projects the sun onto a white piece of card. The advantage of using a telescope is that it can be programmed to track the Sun, so that if you want to trace sunspots, for instance, you can do so at leisure, instead of having to race to finish before the Sun moves off of the page.

As for observing coronal features- this is a very difficult task. A H-alpha filter (expensive) can be purchased for a home telescope outfitted for solar observing. This would allow you to see filaments/prominences, which is low T (10^4 K) chromospheric material that extends into the corona, suspended by magnetic field and buoyancy forces.

To observe coronal material from Earth, you would need a coronagraph, which blocks out light from the central disk of the Sun. This is because coronal features are extremely dim, as compared with the photosphere. From Earth, coronal features are best observed with during a total eclipse. Using a telescope mounted coronagraph at home is not ideal (and probably not feasible) because a lot of light from the Sun would leak into your field-of-view, due to both diffraction, as well as sky brightness. The University of Hawaii takes these sorts of observations, but even with all of their expensive equipment, the space-based LASCO instrument is able to do far better.


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