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Solar Hydrogen Alpha Gallery
Solar Hydrogen Alpha Animation
Our nearest and dearest star is not particularly significant in the grand scheme of things. It is neither particularly bright nor faint and if all stars were placed at the same distance from us, it would pale into insignificance besides celestial powerhouses like Rigel and Deneb. However, it does give us an opportunity to see a star in close-up, less than a hundred million miles away.
Observing the sun can cause blindness but can also be extremely rewarding if undertaken safely. Simply looking through binoculars at the sun will make you go blind. At least with a telescope you’ll still have the use of the other eye. Don’t be tempted to take a look when the sun is partially obscured by cloud or low down and red either, as it still presents a danger. Also be aware of the finderscope, too.
You are probably already familiar with viewing sunspots by using solar projection. You may also be familiar with some of the problems and difficulties that you will encounter. You may either use a finderscope to project a small solar image onto a piece of card or you may try aligning the sun’s shadow onto it. If you are fortunate, you will see several spots on the image of the card and you may even be able to take photographs. My preferred method of recording the sunspots is to draw them. If you like to be accurate you can even trace them with a pencil. You can then keep them in a book or scan them into a computer or reproduce them using drawing tools.
After a few weeks, you will hopefully notice that you are almost getting a separate hobby of solar astronomy. This is particularly useful if you live 50 degrees latitude or more, as you don’t get a lot of useful darkness during the summer. You will notice how sunspots apparently move across the solar disk. Firstly, if you watch the sun throughout the day, you will see that the sunspots rotate, with the motion of the earth, in a similar way in which the constellations do at night. If you record the sun at about the same time each day you will notice that sunspots rotate across the solar disk. They also grow, shrink, change shape and disappear. Unlike faint galaxies, the sun is a very forgiving object. You can see sunspots under some conditions that you would probably not believe. Yet, you may notice that some of the fainter sunspots may fade from view on very poor days or require larger instruments. Also, there are many days where you can get a good telescopic view of the whole solar disc at around 50x magnification but any attempt to boost the magnification will result in a blurred image and no more detail.
I use full aperture filters. You can spend anything from about £15 to £80. The idea is that you cover the objective of your telescope and use it exactly as you would for night viewing. If you really want the easiest option, you cover your finderscope as well. It’s also safer and saves the sort of lining up using shadows that is difficult when using projection. I have made up full aperture filters for each of my telescopes and my largest binoculars. By making my own filters, I have been able to cover all of my telescopes and binoculars for less than £30.
My 127mm Synta Maksutov fitted with a full aperture solar filter.
Some filters come ready-made and are available from many suppliers. I haven’t tried them, mostly due to a quirk of fate. However, I’ve seen some of the photos in books and magazines and they looked quite impressive.
The advantages of full aperture filters are ease of use and clarity of view. I am able to see limb darkening (sun brighter in the centre) and umbral/penumbral shading of sunspot groups. Also, with a given telescope, the shapes of the spots are much clearer. I’ve occasionally seen faculae (brighter patches). This is a noticeable improvement over solar projection.
You should be able to use any eyepiece/Barlow lens combination that you can use on the moon. On my refractor, I can go up to 240x on a clear day. I can also use up to 300x on my Maksutov.
In theory, full aperture filters carry some risk. Fortunately, these can be avoided by sensible precautions. Firstly, make sure the filter is firmly secured to the objective, with no risk of it slipping off. In case a filter has been cracked or scratched, always test it first, especially before any sort of public viewing. It is best done at low magnification. Rather than aiming the telescope directly at the sun, aim a little bit to the side. If there is too much glare, you could have a problem. Move the telescope slowly towards the sun. If you are able to view its image in comfort, you are OK.
I’ve been using filters since late 2001 now, with no (known) ill effects. Being lazy, I often do a quick scan of the sun using my binoculars. Being 15x70s, I achieve good resolution and limb darkening is very clear. However, only the larger sunspots and the groups appear but it gives a good guide as to whether carrying a telescope out is worth the effort or not. Also, I find that in winter I only get to see the sun at lunchtime from work, so only have time for a quick “bin scan”. It is often possible to view daily changes by viewing the sun around lunchtime or before starting work each day.
After a few years of watching the rise and fall in numbers of sunspots, you may want more from your solar viewing. For about £500 in the UK ($500 in the USA) you can buy a hydrogen alpha telescope, albeit at entry level. This enables you to see solar flares and more structure in the solar disc than you can see with an ordinary telescope. It works by blocking out all of the sun’s light except for a narrow wavelength band. Although the novelty of using this could wear off and you could be wishing you’d spent the money on something else, the great advantage is that you can see prominences and solar structures grow, change and disappear on timescales of hours or even minutes, so you can make several interesting observations in a single day. Also, as the filters are built into the telescope, it is completely safe.
My Coronado Personal Solar Telescope piggy backed onto an EQ1 mount with my Skywatcher Startravel 80.
One disadvantage, though, is that you need a reasonably clear day, especially
if you use an entry level, small aperture instrument. Conventional “white
light” viewing is more forgiving of bad weather.
