Is there any simple experiment that can be done with an H-alpha telescope, for example to estimate the Sun's mass, size, distance, temperature or intensity?

I give lessons about renewable energy and it would be nice to somehow integrate a telescope (PST Coronado + double stack) to the chapter about photovoltaics and solar thermal energy.

  • Right now, the only "experiment" I could come up with was to show that there's often nothing to see because of the solar minimum. But we also wouldn't see any feature if the telescope was not focused or not well calibrated.

  • With some luck, it should be possible to follow the movement of a sunspot over a few days and estimate how fast the sun is rotating, possibly at different latitudes.

  • I suppose that in order to calculate many sun characteristics, it is mandatory to know the average distance between Earth and the Sun. It seems to be relatively hard to estimate 1 AU.

Is it possible to use the telescope for any experiment and estimate an order of magnitude for any of the Sun characteristics, assuming that the distance to the Sun is approximately 150 000 000km?

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    $\begingroup$ Prominences are still visible quite regularly, even under the current solar conditions. The Gong H alpha network gives real time views of what's on offer - halpha.nso.edu/index.html $\endgroup$
    – Dr Chuck
    Commented Sep 8, 2019 at 8:51
  • $\begingroup$ @DrChuck: Thanks for the link. I love looking at prominences and some were really beautiful, e.g. with complete loops. Is it possible to measure anything while looking at them? $\endgroup$ Commented Sep 8, 2019 at 9:25
  • $\begingroup$ @DrChuck: With some luck, it should be possible to follow the movement of a sunspot over a few days and estimate how fast the sun is rotating. $\endgroup$ Commented Sep 8, 2019 at 11:41
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    $\begingroup$ yes, if you can find any at the moment. If you are lucky you may be able to detect the fact that the sun's rotation rate varies with latitude. You may find that some national astronomy societies (eg the British Astronomy Association to name only one) have observing programs. $\endgroup$
    – Dr Chuck
    Commented Sep 8, 2019 at 13:56
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    $\begingroup$ How many filters do you have at your disposal, is it only $\rm H\alpha$? $\endgroup$ Commented Sep 12, 2019 at 8:47

1 Answer 1


If you have the right filters and equipment you can make doppler measurements of the $H_\alpha$ line from the sun. Since an H-alpha telescope directly detects this you can use this to measure the doppler shift. Using this you can measure the rotation rate of the sun. This has been done before with a different telescope and the paper is here.

It should also be noted that if you don't find an adequate experiment just seeing the sun thru your telescope makes a profound impact on the viewer. One writer wrote that " I watched with a mix of awe and fear. Ever since that time, I've seen the Sun not so much as a sunny companion but as a star to be reckoned with." Reference is here. That link and this one discuss viewing the doppler effect using an H-alpha telescope.

  • $\begingroup$ Thank you very much. I especially like how the author restricted the amount of needed equipment in order to let small labs replicate the experiment. It would still be out of scope for our department but this experiment definitely goes in the right direction. As for the second paragraph, you're preaching to the choir. I love looking at the sun in $H\alpha$ but I've seen some people who were completely unimpressed. It might get better close to the solar maximum. $\endgroup$ Commented Sep 16, 2019 at 12:31
  • $\begingroup$ Apparently I'm too stupid to award bounties on time. At least you got half of it! $\endgroup$ Commented Sep 19, 2019 at 7:13
  • $\begingroup$ Thank you very much. Just happy that I helped you really. Several things on the site are not obvious so I sure wouldn't worry about it! $\endgroup$
    – Natsfan
    Commented Sep 19, 2019 at 15:44

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