Quote: I was wondering what, if any, benefit I may get from an H-alpha filter designed for viewing nebula emissions. It's about 7nm wide FWHM. I understand that's really wide by solar viewing standards, will there be any benefit with even say flares or prominences?
Quote:If we look closely at the bright continuous spectrum of the sun, we observe many "spectral lines" corresponding to the various elements of the gases in the photosphere -- the "absorption spectrum." Relatively cool (6000 degrees C) hydrogen gas in the photosphere absorbs light coming up from below, and we see a very dark line – the Hydrogen alpha absorption line -- in the continuous spectrum. It is the darkest line, and relatively wide, because the sun is mostly hydrogen, and it is this gas that predominates the layers of the photosphere.
Quote:The sun's chromosphere lies above the photosphere, and is much hotter -- 20,000 degrees C. At these higher temperatures we see what is know as an "emission spectrum". Here light is being given off instead of absorbed, corresponding to the energy given off when the electron shifts back down to a lower energy state, and at the same frequency or "color" of light which is absorbed in the photosphere.
Quote:This is why you can't use a white light solar filter with a nebula filter and see chromospheric features like flares and prominences: The white light filter reduces the H alpha emission from the chromosphere by the same amount it reduces all the other wavelengths from the photosphere. The wide bandwidth of a nebula filter only lets you see the photospheric features from light coming from either side of the photospheric absorbtion line, and the chromosphere emission itself is reduced by the white light filter to invisibility.
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Quote:It might be a little more general to say that the reason broader "nebula" H-alpha filters won't show the chromospheric detail is that they are letting in a little too much off-band light from the photosphere. That light is basically "drowning out" the weaker chromosphere... With a regular white-light solar filter, you would, of course, dim the chromospheric emission, but the H-alpha filter would still be letting in too much light from wavelengths well away from the H-alpha centerline, and that is the crux of the problem.
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Quote:The off-band contamination of a broad-band H alpha nebula filter used with a white light filter is irrelevant and only adds insult to injury: chromospheric details and prominences will be invisible with a white light filter because they are rendered 100,000 to 1,000,000 times fainter than they otherwise would be.
Quote:If it worked why would any of us spend so much on our Solar equipment?
Quote:Has anyone tried using a night time H alpha or any other filter with a Herschel wedge? If the image was too dim, has a long exposure CCD cam been used with this setup? Thanks.
Quote: Comparing the 1nM (10 Angstrom) band to the 1.00 Angstrom band the 1nM band has 31.4 times the light, more than enough to mask the H-alpha emission spectrum.
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Quote:What do you think it will do?
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Quote:I SAID behind the white light filter. Not gonna consider otherwise.
If it worked 25% as well as dedicated solar scopes, it would still be worth me doing, and would still be worth your buying the good stuff.
Quote:Unfortunately, it won't work. The passband width of even imaging H-alpha filters (those used for emission nebulae) have a band width of between 30 and 100 angstroms (FWHM). This is much much too broad to see any solar H-alpha detail, as you need something around 1.5 angstroms or less just to pick up the prominences without an occulting disk being used. To get chromospheric disk detail requires a passband that is less than one angstrom wide, so again, adding the H-alpha "nebula" filter after a white light filter just won't work.
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