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During the 1860s and 1870s, pioneering stellar spectroscopist Father Angelo Secchi created the Secchi classes in order to classify observed spectra. By 1866, he had developed three classes of stellar spectra:[1][2][3]
In 1868, he discovered carbon stars, which he put into a distinct group:[4]
- Class I: white and blue stars with broad heavy hydrogen lines, such as Vega and Altair. This includes the modern class A and early class F. Class I, Orion subtype: a subtype of class I with narrow lines in place of wide bands, such as Rigel and γ Orionis. In modern terms, this corresponds to early B-type stars.
- Class II: yellow stars-hydrogen less strong, but evident metallic lines, such as Arcturus and Capella. This includes the modern classes G and K as well as late class F.
- Class III: orange to red stars with complex band spectra, such as Betelgeuse and Antares. This corresponds to the modern class M.
In 1877, he added a fifth class:[5]
- Class IV: red stars with significant carbon bands and lines (carbon stars.)
In the late 1890s, this classification began to be superseded by the Harvard classification, which is discussed in the remainder of this article.[6][7]
- Class V: emission-line stars, such as γ Cassiopeiae and β Lyrae.
Star colors are usually subtle, ranging from a warm orange red to a hint of blue on white depending on the viewer's eyes. But put a star of one color next to one of another, and the eye seems to exaggerate both, delighting the follower of double-star astronomy. Waxing romantic, astronomers have called the pair topaz and sapphire.
You say photos do not prove it, and then you yourself use photos ???
Your afterglow and forglow, still have the sun visible
The diagram has the geometry which works in the inverse manner of a satelite dish.
Not so. The color of the sun itself changes because of perspective, as the 'blue sun phenomenon' quite clearly shows.
Also from wiki : Stellar classification - Wikipedia, the free encyclopedia
The Conventional color descriptions are traditional in astronomy, and represent colors relative to Vega, a star that is perceived as white under naked eye observational conditions, but which magnified appears as blue.
Now do this again and selectively depict directional angles that bounce off the moon away from the earth ... the fact of the matter is that there are innumerably more directional angles that you can draw that do not reflect the light toward earth than there are directional angles that do reflect the light toward the earth ... and that's simply because there is no concentration.
1. The cosmological theory holding that the universe is expanding, based on the interpretation of the color shift in the spectra of all the galaxies as being the result of the Doppler effect and indicating that all galaxies are moving away from one another.
As I think about it, the solar eclipse that I saw over a decade or so ago, was about a 90% eclipse. The part I am unsure of was the extent to which it was a partial/complete eclipse. That the sky went red, I am completely certain.
To conclude:
The moon is red during a lunar eclipse, because the universe is expanding.
These are solar eclipses on cloudy days.
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The system includes a red pre-filter ...
Are you calling me a lier?
If they used a red filter, then the sun would also be red.
Bob Sandy used a Nikon digital camera with a 3X telephoto lens and a red filter to record this lovely image of the crescent Sun setting over Virginia.
And I did see the sky go red on a cloudy day with a solar eclipse.
