Starship Asterisk*

geckzilla wrote:I was wondering if the spikes of light to the right of the normal visible spectrum were infrared or just some internal lens reflections of some sort. I'm leaning toward reflections, but I'm not sure.

The Balmer series.

Ann wrote:

geckzilla wrote:I was wondering if the spikes of light to the right of the normal visible spectrum were infrared or just some internal lens reflections of some sort. I'm leaning toward reflections, but I'm not sure.

There is no reason why infrared flashes would look purple in a "true-color" image like this, I think. So I believe they are reflections.

I find the APOD quite beautiful and fascinating. Imagine the Sun as an emission-line star!

geckzilla wrote:I was wondering if the spikes of light to the right of the normal visible spectrum were infrared or just some internal lens reflections of some sort. I'm leaning toward reflections, but I'm not sure.

https://en.wikipedia.org/wiki/Helium#Scientific_discoveries wrote:

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[color=#00FF00][size=150]Spectral lines of helium[/size][/color]

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<<The first evidence of helium was observed on August 18, 1868 as a bright yellow line with a wavelength of 587.56 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was initially assumed to be sodium. On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the solar spectrum, which he named the D3 Fraunhofer line because it was near the known D1 (589.59 nm)and D2 (589.00 nm) lines of sodium. He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος (helios).

In 1882, Italian physicist Luigi Palmieri detected helium on Earth, for the first time, through its D3 spectral line, when he analyzed the lava of Mount Vesuvius.

On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare earth elements) with mineral acids. Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas liberated by sulfuric acid, he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun. These samples were identified as helium by Lockyer and British physicist William Crookes. It was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight. Helium was also isolated by the American geochemist William Francis Hillebrand prior to Ramsay's discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen. His letter of congratulations to Ramsay offers an interesting case of discovery and near-discovery in science.>>

Chris Peterson wrote:

geckzilla wrote:I was wondering if the spikes of light to the right of the normal visible spectrum were infrared or just some internal lens reflections of some sort. I'm leaning toward reflections, but I'm not sure.

Diffraction gratings produce orders of spectra- that is, the spectra repeat at increasingly wide angles as the ruling spacing matches integral multiples of the wavelength of the light. The main spectrum we're seeing here is the first order spectrum (the zeroth order is the direct light of the Sun itself). I think the purple and blue bands to the right are the much dimmer second order spectrum. So, not IR and not a reflection.

alter-ego wrote:

Chris Peterson wrote:

geckzilla wrote:I was wondering if the spikes of light to the right of the normal visible spectrum were infrared or just some internal lens reflections of some sort. I'm leaning toward reflections, but I'm not sure.

Diffraction gratings produce orders of spectra- that is, the spectra repeat at increasingly wide angles as the ruling spacing matches integral multiples of the wavelength of the light. The main spectrum we're seeing here is the first order spectrum (the zeroth order is the direct light of the Sun itself). I think the purple and blue bands to the right are the much dimmer second order spectrum. So, not IR and not a reflection.

My first thought was the 2nd order too, but the 2nd set does not satisfy the dispersion of a 2nd (or higher) order. The angular separations between the lines should be twice that of the 1st order. In fact, the angular separations are equal to those in the first set so that would most likely make the 2nd set a duplicate artifact of the first set, e.g. by reflection. Therefore the 2nd set is not a higher spectral order (and I agree, not IR either).

Chris Peterson wrote:

alter-ego wrote:

Chris Peterson wrote: Diffraction gratings produce orders of spectra- that is, the spectra repeat at increasingly wide angles as the ruling spacing matches integral multiples of the wavelength of the light. The main spectrum we're seeing here is the first order spectrum (the zeroth order is the direct light of the Sun itself). I think the purple and blue bands to the right are the much dimmer second order spectrum. So, not IR and not a reflection.

My first thought was the 2nd order too, but the 2nd set does not satisfy the dispersion of a 2nd (or higher) order. The angular separations between the lines should be twice that of the 1st order. In fact, the angular separations are equal to those in the first set so that would most likely make the 2nd set a duplicate artifact of the first set, e.g. by reflection. Therefore the 2nd set is not a higher spectral order (and I agree, not IR either).

It looks to me like the spectrum I'm identifying as second-order does, in fact, have the doubled angular separations. (Secondary on the top, aligned with primary on bottom.)

orders.jpg

alter-ego wrote:You did a nice job at capturing the 2nd set for comparison (color, contrast). You're saying that the primary cyan-colored line corresponds to the last line visible in the 2nd set?

Chris Peterson wrote:

alter-ego wrote:

Chris Peterson wrote: Diffraction gratings produce orders of spectra- that is, the spectra repeat at increasingly wide angles as the ruling spacing matches integral multiples of the wavelength of the light. The main spectrum we're seeing here is the first order spectrum (the zeroth order is the direct light of the Sun itself). I think the purple and blue bands to the right are the much dimmer second order spectrum. So, not IR and not a reflection.

My first thought was the 2nd order too, but the 2nd set does not satisfy the dispersion of a 2nd (or higher) order. The angular separations between the lines should be twice that of the 1st order. In fact, the angular separations are equal to those in the first set so that would most likely make the 2nd set a duplicate artifact of the first set, e.g. by reflection. Therefore the 2nd set is not a higher spectral order (and I agree, not IR either).

It looks to me like the spectrum I'm identifying as second-order does, in fact, have the doubled angular separations. (Secondary on the top, aligned with primary on bottom.)

orders.jpg

Ann wrote:

Chris Peterson wrote:It looks to me like the spectrum I'm identifying as second-order does, in fact, have the doubled angular separations. (Secondary on the top, aligned with primary on bottom.)

Your interpretation seems absolutely right to me.

The colors of the second order spectrum do not correspond one-to-one to the colors of the primary spectrum. Nevertheless, even in the second order spectrum, there is a progression from violet to longer wavelength blue. The cyan-colored Hβ flash in the primary spectrum thus corresponds to a shorter-wave blue flash in the secondary spectrum. It would have been interesting to see what the yellow-orange helium flash would have looked like in the secondary spectrum. Perhaps it would have been green?

Chris Peterson wrote:EDIT: here's a more carefully composed comparison between the first- and second-order spectra. And the spacing is quite close to two-to-one, within reasonable measurement error and considering some likely lens distortion.

orders2.jpg

alter-ego wrote:
Yup. Last night had I looked closely at the violet lines, the higher resolution of the split in the 2nd set would have cinched the 2nd order dispersion requirement for me.

The Ca II [397,393 nm] doublet :

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)

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In the image [at right] the emission lines of the flash spectrum have been straightened by "bending" the image along a curve. So the assignment of the spectral lines is considerably simplified.

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

neufer wrote:

alter-ego wrote:
Yup. Last night had I looked closely at the violet lines, the higher resolution of the split in the 2nd set would have cinched the 2nd order dispersion requirement for me.

...

The Ca II [397,393 nm] doublet :

Chris Peterson wrote:

Ann wrote:

Chris Peterson wrote:It looks to me like the spectrum I'm identifying as second-order does, in fact, have the doubled angular separations. (Secondary on the top, aligned with primary on bottom.)

Your interpretation seems absolutely right to me.

The colors of the second order spectrum do not correspond one-to-one to the colors of the primary spectrum. Nevertheless, even in the second order spectrum, there is a progression from violet to longer wavelength blue. The cyan-colored Hβ flash in the primary spectrum thus corresponds to a shorter-wave blue flash in the secondary spectrum. It would have been interesting to see what the yellow-orange helium flash would have looked like in the secondary spectrum. Perhaps it would have been green?

I think you might be misunderstanding the secondary spectrum a bit. The colors (really, wavelengths) of each band are identical, all that changes is the distance between them. So the yellow-orange helium flash will look identical in the secondary spectrum (except for being dimmer). It will just be twice as far from the leftmost violet line.

EDIT: here's a more carefully composed comparison between the first- and second-order spectra. And the spacing is quite close to two-to-one, within reasonable measurement error and considering some likely lens distortion.

orders2.jpg

Ann wrote:I think I understood you correctly. I just thought that the cyan color of Hβ looks different than the color of the Hβ flash in the secondary spectrum.

Chris Peterson wrote:

Ann wrote:I think I understood you correctly. I just thought that the cyan color of Hβ looks different than the color of the Hβ flash in the secondary spectrum.

Well, I had to change the intensity to make the secondary spectrum more visible, and that means I changed the color as well. To really see it properly we'd need a spectroscope, not a color camera. It would be difficult to perfectly balance the primary and secondary such that the colors appear identical. But I think it's close enough to show what's going on.