Starship Asterisk*

Ann wrote:I note that the color of the corona is shown as orange, while the integrated color of the solar flash spectrum is likely white.

Or am I wrong to assume that the integrated color of the flash spectrum of the Sun would be white?

Chris wrote:

/the corona/ is orange with this particular sensor.

Guest wrote:
I thought alpha/Lyman emissions of hydrogen line spectra were in the UV. The visible emissions are Balmer line emissions. i.e. the Lyman Alpha are drops from higher electron excited states to level 1 and the the Balmer lines are drops to level 2.
John

http://en.wikipedia.org/wiki/H-alpha wrote:
<<H-alpha (Hα) is a specific red visible spectral line in the Balmer series created by hydrogen with a wavelength of 656.28 nm, which occurs when a hydrogen electron falls from its third to second lowest energy level. It is difficult for humans to see H-alpha at night, but due to the abundance of hydrogen in space, H-alpha is often the brightest wavelength of visible light in stellar astronomy.>>

Czerno ohoh wrote:
What element and transition is responsible for the 3rd brighter (green) line, please?

• Magnesium ("triplet" : 516, 517, 518 nm)

http://www.eurastro.de/webpages/MRSPECT.HTM wrote:
The Solar Eclipse 1999 From Hungary
EurAstro Team Szeged I (Manfred Rudolf, Alfred Jakoblich, Franz Michlmayer, Carmen Ortega)

The spectra have been recorded with a 2" spectroscopic grating (200 grooves/mm) which was mounted in front of a 500 mm telephoto lens.

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Some prominent emission lines are:

Hydrogen:
. Ha (657nm), H b (486 nm), Hg (434 nm), Hd (410 nm)
He I: 668, 588, 502, 492, 447 nm
Ba II: 650, 614, 493, 455 nm
Na I: 589 nm
Mg I: 553, 516-518 nm ("triplet")
Sr II: 422, 408 nm
Ca I: 586, 423 nm
Ca II: 397,393 nm
Fe I: many lines between 520-570 and 413-430 nm

Spectrum of the chromosphere:

The bright lines in red and turquoise, and two of the blue lines correspond to hydrogen, whereas the yellow line is indicative of helium. Helium was first discovered in 1868 by its yellow emission line in the flash spectrum recorded during a solar eclipse. The wavelength of the emission lines is indicative of the composition (chemical elements) while the intensity of the lines reflects the abundance of the elements (ca. 70% hydrogen, 28% helium, the rest heavier elements). See the emission lines of: Hydrogen (656, 486, 434, 410 nm; indicated by white lines), Helium (587 nm (white line), 502, 447 nm), Sodium (589 nm, close to the yellow helium line), Magnesium (516, 517, 518 nm), Calcium (397, 393 nm). Many of the green lines are due to the presence of iron.

Coronal spectrum

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In the spectrum you can distinguish a red, yellow, a faint green, turquoise, and several blue circles. Each of them represents an image of the solar corona in a different wavelength. The red, turquoise, and some of the blue images again are due to the hydrogen emissions, and the yellow image corresponds to helium. The bright dots on the circumference of the solar images represent the prominences. The green emission at a wavelength of 530 nm was first discovered at an eclipse in 1869. An emission line at that wavelength was unknown in laboratory spectra, and a new element was suspected, named "coronium". Later it turned out that this green emission was due to iron atoms from which 13 electrons have been stripped off (FeXIV), and which can only be found under the extreme conditions of the corona at temperatures of 2,000,000 Kelvin or higher. This also makes clear why there are no green "dots" (images of prominences) on the circumference of the green solar image. The temperature of the prominences is about 4000-6000 K only and thus far too low to allow the formation of the highly ionized FeXIV.>>

geckzilla wrote:I am pretty confused about filters and H-alpha and NII. When I look at Hubble images a lot of times H-alpha will come through the 658 filter and NII through the 656, yet both are called H-alpha filters. Sometimes they look very similar and other times they are quite different, which is really surprising to me considering how close they are. I can't figure out if light gets redshifted slightly or if the filters are just named slightly off or something else I haven't managed to think of.

geckzilla wrote:Yup, I've been through multiple lists of those. The list doesn't always match up with the descriptions for HubbleSite releases.

geckzilla wrote:I am pretty confused about filters and H-alpha and NII. When I look at Hubble images a lot of times H-alpha will come through the 658 filter and NII through the 656, yet both are called H-alpha filters. Sometimes they look very similar and other times they are quite different, which is really surprising to me considering how close they are. I can't figure out if light gets redshifted slightly or if the filters are just named slightly off or something else I haven't managed to think of.

Ann wrote:

So is the corona orange in optical light?

Ann wrote:
So is the corona orange in optical light?

Chris Peterson wrote:

geckzilla wrote:I am pretty confused about filters and H-alpha and NII. When I look at Hubble images a lot of times H-alpha will come through the 658 filter and NII through the 656, yet both are called H-alpha filters. Sometimes they look very similar and other times they are quite different, which is really surprising to me considering how close they are. I can't figure out if light gets redshifted slightly or if the filters are just named slightly off or something else I haven't managed to think of.

The lines for [NII] and Ha are only 2nm apart. The camera has very narrow band filters which reasonably isolate the two, as well as a somewhat wider filter between the two that gets both lines. As you note, however, redshift is a factor (or in the case of Doppler shift, blueshift as well). It doesn't take much to shift either line into an adjacent filter. In many cases researchers must use some other information than just the filter to determine what is an [NII] emission area and what is an Ha emission area.

neufer wrote:

Ann wrote:
So is the corona orange in optical light?

It can be provided the sun is low enough in the sky: http://apod.nasa.gov/apod/ap110115.html

geckzilla wrote:Ah, so it's not easy to make the determination or at least it requires one to be careful about it. What about local objects? I know for planetary nebulas both the filters are used a lot. I have no idea whether 2 nm is a lot or a little for nearby things.

geckzilla wrote:

Chris Peterson wrote:

geckzilla wrote:
I am pretty confused about filters and H-alpha and NII. When I look at Hubble images a lot of times H-alpha will come through the 658 filter and NII through the 656, yet both are called H-alpha filters. Sometimes they look very similar and other times they are quite different, which is really surprising to me considering how close they are. I can't figure out if light gets redshifted slightly or if the filters are just named slightly off or something else I haven't managed to think of.

The lines for [NII] and Ha are only 2nm apart. The camera has very narrow band filters which reasonably isolate the two, as well as a somewhat wider filter between the two that gets both lines. As you note, however, redshift is a factor (or in the case of Doppler shift, blueshift as well). It doesn't take much to shift either line into an adjacent filter. In many cases researchers must use some other information than just the filter to determine what is an [NII] emission area and what is an Ha emission area.

Ah, so it's not easy to make the determination or at least it requires one to be careful about it. What about local objects? I know for planetary nebulas both the filters are used a lot. I have no idea whether 2 nm is a lot or a little for nearby things.

http://www.sao.ru/hq/lsfvo/devices/scorpio-2/filters_eng.html wrote:

[b][color=#0000FF]The narrow band filters for observation with scanning FPI [/color][/b]

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Code: Select all

name	 CWL(Å) FWHM  Tmax(%)
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FN655	 6559	97	92
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#76B	  6560	15	71
#77B	  6571	14	76
#78B	  6580	13	69 

Middle-band filters: The set of passband filters with band width 70-200 A is available for observations in the Н-alpha, [SII], [OIII] emission line and in the continuum. The majority of the filters were made by Asahi Spectra USA Inc., the FN674 filter was made by NIIPP (Moscow).

The narrow band filters for observation with scanning FPI : The sets of narrow-band (FWHM=12-25 A) filters are available for observations of galaxies in the [OIII], H-alpha, [NII], [SII] emission limes. You can use this IDL-program to choose the optimal filters for desired systemic velocities.

wikipedia wrote:Helios was imagined as a handsome god crowned with the shining aureole of the Sun, who drove the chariot of the sun across the sky each day to earth-circling Oceanus and through the world-ocean returned to the East at night.