<p>If you have the right filters and equipment you can make doppler measurements of the <span class="math-container">$H_\alpha$</span> 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 <a href="http://articles.adsabs.harvard.edu//full/2012SASS...31..225G/0000226.000.html" rel="nofollow noreferrer">here</a>. </p>

<p>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."
<a href="https://www.skyandtelescope.com/observing/guide-to-observing-the-sun-in-h-alpha092321050923/" rel="nofollow noreferrer">Reference is here</a>. That link and <a href="http://www.ianmorison.com/h-alpha-solar-telescopes-an-in-depth-discussion-and-survey/" rel="nofollow noreferrer">this one</a> discuss viewing the doppler effect using an H-alpha telescope. </p>

CC BY-SA 4.0
2019-09-16T12:31:58.890Z
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.
Eric Duminil
CC BY-SA 4.0
2019-09-19T07:13:06.617Z
Apparently I'm too stupid to award bounties on time. At least you got half of it!
Eric Duminil
CC BY-SA 4.0
2019-09-19T15:44:08.137Z
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!
Natsfan
CC BY-SA 4.0
2019-09-12T16:30:12.660Z
2019-09-12T16:30:12.660Z
Natsfan
<p>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?</p>

<p>I give lessons about renewable energy and it would be nice to somehow integrate a telescope (<a href="https://www.meade.com/coronado-personal-solar-telescope-pst.html" rel="nofollow noreferrer">PST Coronado</a> + double stack) to the chapter about photovoltaics and solar thermal energy.</p>

<ul>
<li><p>Right now, the only "experiment" I could come up with was to show that there's often nothing to see because of the <a href="https://en.wikipedia.org/wiki/Solar_minimum" rel="nofollow noreferrer">solar minimum</a>. But we also wouldn't see any feature if the telescope was not focused or not well calibrated.</p></li>
<li><p>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.</p></li>
<li>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 <a href="http://curious.astro.cornell.edu/about-us/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate" rel="nofollow noreferrer">relatively hard</a> to estimate 1 <a href="https://en.wikipedia.org/wiki/Astronomical_unit" rel="nofollow noreferrer">AU</a>.</li>
</ul>

<p>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?</p>

CC BY-SA 4.0
2019-09-08T08:51:38.997Z
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  - http://halpha.nso.edu/index.html
Dr Chuck
CC BY-SA 4.0
2019-09-08T09:25:41.000Z
@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?
Eric Duminil
CC BY-SA 4.0
2019-09-08T11:41:16.627Z
@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.
Eric Duminil
CC BY-SA 4.0
2019-09-08T13:56:02.043Z
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.
Dr Chuck
CC BY-SA 4.0
2019-09-11T19:21:08.137Z
For what it's worth I googled "coronado telescope forum" and "solar telescope forum". The searches resulted in many potentially interesting sites. You will at least find people that have used the telescope and may have already done the sort of experiments you are interested in
L d Bonnie
CC BY-SA 4.0
2019-09-11T19:36:01.377Z
@LdBonnie: I could only find reports of visual observation for prominences, flares, filaments, granulation and sunspots using those keywords. I find those *really* cool and beautiful, but they're few and far between. And I'm not sure I could sell a "Look at how cool this small prominence is!" as an experiment. :-/ If you find any site specifically for solar experiments, please feel free to share.
Eric Duminil
CC BY-SA 4.0
2019-09-12T08:47:22.433Z
How many filters do you have at your disposal, is it only $\rm H\alpha$?
AtmosphericPrisonEscape
CC BY-SA 4.0
2019-09-12T08:52:48.300Z
@AtmosphericPrisonEscape: Yes, just $H\alpha$, either with 1.0 Å or 0.5 Å bandpass when using the double stack. As far as I know, I cannot remove any filter. I wouldn't want to anyway, for security purposes. I have a dobsonian with a white light filter at home, but I'd never show it to any student. I'd be one filter away from jail. What do you have in mind?
Eric Duminil
CC BY-SA 4.0
2019-09-12T09:37:44.990Z
As all ideas involving prominences are doomed to fail often, I thought along the lines of measuring properties of something you always can see - the solar atmosphere. First, you could establish where the $\rm H\alpha$ in the atmosphere is coming from, by observing the limb, and noting the difference to the visual photosphere. Then, depending on the capabilities of your students, you could go and estimate the relative level populations of the hydrogen you see, from this you'd get a temperature.
AtmosphericPrisonEscape
CC BY-SA 4.0
2019-09-12T09:55:19.627Z
Other things like using the optically thin emission to estimate the solar atmospheric mass could be possible. But this depends on the equipment you have, e.g. if you're using a CCD or only visual observations etc. If your focus should remain on renewable energy, then the combination with $H\alpha$ is however a bit unclear. This is because in photovoltaics, to my knowledge, one uses the visible continuum to generate energy, not necessarily the lines.
AtmosphericPrisonEscape
CC BY-SA 4.0
2019-09-12T11:08:04.810Z
@AtmosphericPrisonEscape: Thanks. I might have to accept the fact that there really isn't any link between $H\alpha$ and photovoltaics. Too bad, I'd have liked to get fundings for a new t̶o̶y̶ instrument.
Eric Duminil
CC BY-SA 4.0
2019-09-12T11:34:09.783Z
You can always, correctly, argue that the bulk wattage of the sun has to pass first through its atmosphere before reaching Earth. Hence the existence of the Fraunhofer lines, of which $\rm H\alpha$ is one. In this context it would make a lot of sense to study up a bit more on the solar atmosphere, and hence, buy more filters! Those issues are however very interconnected with radiative transfer, so that might overwhelm your students a bit, depending on their background.
AtmosphericPrisonEscape
CC BY-SA 4.0
2019-09-12T13:12:04.883Z
@AtmosphericPrisonEscape: Ooooh. That's an excellent point. I already show spectrum diagrams (e.g. https://www.solarquotes.com.au/blog/wp-content/uploads/2017/08/spectrum.jpg), I just need to find one that is large enough to show both Frauenhofer lines and the atmospheric absorption bands of our atmosphere. I'm afraid buying more filters isn't an option yet. In the meantime, I could just show https://sdo.gsfc.nasa.gov/data/ for an interesting day.
Eric Duminil
<the-sun><amateur-observing><h-alpha>
Any simple experiment with an H-alpha telescope?
Eric Duminil
# Any simple experiment with an H-alpha telescope?

(Asked by: username_0 on 2019-09-07)

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](https://www.meade.com/coronado-personal-solar-telescope-pst.html) + 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](https://en.wikipedia.org/wiki/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](http://curious.astro.cornell.edu/about-us/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate) to estimate 1 [AU](https://en.wikipedia.org/wiki/Astronomical_unit).

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?

**Tags:** the-sun, amateur-observing, h-alpha

> **Comments:**
> **username_1**: 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  - http://halpha.nso.edu/index.html  
> **username_0**: @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?  
> **username_0**: @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.  
> **username_1**: 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.  
> **username_2**: For what it's worth I googled "coronado telescope forum" and "solar telescope forum". The searches resulted in many potentially interesting sites. You will at least find people that have used the telescope and may have already done the sort of experiments you are interested in  
> **username_0**: @LdBonnie: I could only find reports of visual observation for prominences, flares, filaments, granulation and sunspots using those keywords. I find those *really* cool and beautiful, but they're few and far between. And I'm not sure I could sell a "Look at how cool this small prominence is!" as an experiment. :-/ If you find any site specifically for solar experiments, please feel free to share.  
> **username_3**: How many filters do you have at your disposal, is it only $\rm H\alpha$?  
> **username_0**: @username_3: Yes, just $H\alpha$, either with 1.0 Å or 0.5 Å bandpass when using the double stack. As far as I know, I cannot remove any filter. I wouldn't want to anyway, for security purposes. I have a dobsonian with a white light filter at home, but I'd never show it to any student. I'd be one filter away from jail. What do you have in mind?  
> **username_3**: As all ideas involving prominences are doomed to fail often, I thought along the lines of measuring properties of something you always can see - the solar atmosphere. First, you could establish where the $\rm H\alpha$ in the atmosphere is coming from, by observing the limb, and noting the difference to the visual photosphere. Then, depending on the capabilities of your students, you could go and estimate the relative level populations of the hydrogen you see, from this you'd get a temperature.  
> **username_3**: Other things like using the optically thin emission to estimate the solar atmospheric mass could be possible. But this depends on the equipment you have, e.g. if you're using a CCD or only visual observations etc. If your focus should remain on renewable energy, then the combination with $H\alpha$ is however a bit unclear. This is because in photovoltaics, to my knowledge, one uses the visible continuum to generate energy, not necessarily the lines.  
> **username_0**: @username_3: Thanks. I might have to accept the fact that there really isn't any link between $H\alpha$ and photovoltaics. Too bad, I'd have liked to get fundings for a new t̶o̶y̶ instrument.  
> **username_3**: You can always, correctly, argue that the bulk wattage of the sun has to pass first through its atmosphere before reaching Earth. Hence the existence of the Fraunhofer lines, of which $\rm H\alpha$ is one. In this context it would make a lot of sense to study up a bit more on the solar atmosphere, and hence, buy more filters! Those issues are however very interconnected with radiative transfer, so that might overwhelm your students a bit, depending on their background.  
> **username_0**: @username_3: Ooooh. That's an excellent point. I already show spectrum diagrams (e.g. https://www.solarquotes.com.au/blog/wp-content/uploads/2017/08/spectrum.jpg), I just need to find one that is large enough to show both Frauenhofer lines and the atmospheric absorption bands of our atmosphere. I'm afraid buying more filters isn't an option yet. In the meantime, I could just show https://sdo.gsfc.nasa.gov/data/ for an interesting day.  

---

## 1 answers

### Answer by username_4 on 2019-09-12. Score: 2

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](http://articles.adsabs.harvard.edu//full/2012SASS...31..225G/0000226.000.html).

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](https://www.skyandtelescope.com/observing/guide-to-observing-the-sun-in-h-alpha092321050923/). That link and [this one](http://www.ianmorison.com/h-alpha-solar-telescopes-an-in-depth-discussion-and-survey/) discuss viewing the doppler effect using an H-alpha telescope.

> **Comments:**
> **username_0**: 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.  
> **username_0**: Apparently I'm too stupid to award bounties on time. At least you got half of it!  
> **username_4**: 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!  

---

