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The active sun
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uncarollo
May 22, 2012, 12:42:32 PM5/22/12
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Image taken with Astro-Physics 160 EDF refractor and Solarscope H-
alpha filter (single stacked for this photo) showing the huge killer
scorpion prom:
http://cosmosimages.net/pictures/20120519_stiched%20color%20invert%20with%20proms.jpg
alpha filter (single stacked for this photo) showing the huge killer
scorpion prom:
http://cosmosimages.net/pictures/20120519_stiched%20color%20invert%20with%20proms.jpg
Chris.B
May 22, 2012, 2:20:54 PM5/22/12
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Absolutely stunning! The harder one stares the more detail seems to
jump out.
May I ask why the limb appears lighter? Rather than the converse
typical of white light observation?
Paul Schlyter
May 22, 2012, 5:41:42 PM5/22/12
to
In article <0d5c0f1b-fce0-4aa0-8598-
d74dcf...@z19g2000vbe.googlegroups.com>, chr...@nypost.dk says...
That's because the solar radiation in H-alpha originates from near the
temperature minimum in the solar atmosphere. White light originates
from a layer a few thousand kilometers below the temperature minimum.
It works like this: the Sun has no solid surface but is a "ball of gas"
which is mostly non-transparent (= opaque). When we look at the center
of the solar disk, we see somewhat deeper down in the "ball of gas" of
the Sun compared to when we look near the limb of the solar disk. This
is because of geometrical reasons combined with the fact that we can see
through a certain number of atoms (that number is wavelength dependent)
before the gas becomes too non-transparent for us to see any further
down.
Now, do we get limb darkening or limb brightening? That depends on how
the temperature changes with altitude at the region where most of the
light we see originates. At the photosphere, where the white light
originates, the temperature drops with altitude. Near the solar limb we
don't see as far down as at the center of the solar disk. That means
near the solar limb we see somewhat cooler gases. Cooler gases radiate
less, and therefore we see a limb darkening.
The light at H-alpha originates from a higher layer in the Sun, in the
chromosphere near the temperature minimum. Therefore, the temperature
rises above where H-alpha originates. Again, near the solar limb we
don't see as far down as at the center of the solar disk. But in this
case it means we see somewhat hotter gases near the solar limb in H-
alpha (as well as in the center of any dark spectral line in the Sun's
spectrum), i.e. we see a limb brightening.
This effect is even more pronounced in the Lyman-alpha spectral line in
the far ultraviolet: Lyman-alpha is even an emission (= bright) line in
the solar spectrum, as opposed to H-alpha which is an absorption (=
dark) line. That's because Lyman-alpha originates from an even higher
altitude in the solar atmosphere.
If you want to know more about how this works, read about Plank's Law
and Kirchoff's Laws -- Wikipedia is a good starting point. You could
also read about Radiative Transfer.
d74dcf...@z19g2000vbe.googlegroups.com>, chr...@nypost.dk says...
temperature minimum in the solar atmosphere. White light originates
from a layer a few thousand kilometers below the temperature minimum.
It works like this: the Sun has no solid surface but is a "ball of gas"
which is mostly non-transparent (= opaque). When we look at the center
of the solar disk, we see somewhat deeper down in the "ball of gas" of
the Sun compared to when we look near the limb of the solar disk. This
is because of geometrical reasons combined with the fact that we can see
through a certain number of atoms (that number is wavelength dependent)
before the gas becomes too non-transparent for us to see any further
down.
Now, do we get limb darkening or limb brightening? That depends on how
the temperature changes with altitude at the region where most of the
light we see originates. At the photosphere, where the white light
originates, the temperature drops with altitude. Near the solar limb we
don't see as far down as at the center of the solar disk. That means
near the solar limb we see somewhat cooler gases. Cooler gases radiate
less, and therefore we see a limb darkening.
The light at H-alpha originates from a higher layer in the Sun, in the
chromosphere near the temperature minimum. Therefore, the temperature
rises above where H-alpha originates. Again, near the solar limb we
don't see as far down as at the center of the solar disk. But in this
case it means we see somewhat hotter gases near the solar limb in H-
alpha (as well as in the center of any dark spectral line in the Sun's
spectrum), i.e. we see a limb brightening.
This effect is even more pronounced in the Lyman-alpha spectral line in
the far ultraviolet: Lyman-alpha is even an emission (= bright) line in
the solar spectrum, as opposed to H-alpha which is an absorption (=
dark) line. That's because Lyman-alpha originates from an even higher
altitude in the solar atmosphere.
If you want to know more about how this works, read about Plank's Law
and Kirchoff's Laws -- Wikipedia is a good starting point. You could
also read about Radiative Transfer.
Davoud
May 22, 2012, 7:36:45 PM5/22/12
to
uncarollo:
> http://cosmosimages.net/pictures/20120519_stiched%20color%20invert%20with%20pr
> oms.jpg
It's a stunner of a photo, for sure, but it obviously shows that the
sun is angry at us for not accepting that the end of the world is nigh
as revealed by the Mayan calendar. IOW, we're doomed. Doomed, I say.
I'll forward the link to Marty Cohen for a second opinion, but I'm sure
he'll agree with me.
--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.
usenet *at* davidillig dawt cawm
> http://cosmosimages.net/pictures/20120519_stiched%20color%20invert%20with%20pr
> oms.jpg
It's a stunner of a photo, for sure, but it obviously shows that the
sun is angry at us for not accepting that the end of the world is nigh
as revealed by the Mayan calendar. IOW, we're doomed. Doomed, I say.
I'll forward the link to Marty Cohen for a second opinion, but I'm sure
he'll agree with me.
--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.
usenet *at* davidillig dawt cawm
Chris.B
May 23, 2012, 2:55:41 PM5/23/12
to
On May 22, 11:41 pm, Paul Schlyter <pau...@stjarnhimlen.se> wrote:
>
> If you want to know more about how this works, read about Plank's Law
> and Kirchoff's Laws -- Wikipedia is a good starting point. You could
> also read about Radiative Transfer.
Thank you, Paul, for that very thorough explanation.
>
> If you want to know more about how this works, read about Plank's Law
> and Kirchoff's Laws -- Wikipedia is a good starting point. You could
> also read about Radiative Transfer.
Paul Ciszek
May 26, 2012, 11:48:59 AM5/26/12
to
In article <7458888b-ebf3-49e2...@pa10g2000pbc.googlegroups.com>,
Could you please describe what the colors in this image really mean?
(i.e., it doesn't look H-alpha red, nor does it look like a grayscale
image converted to yellow.)
How narrow a bandwidth does one need in order to see convective cells
in the sun? There are some articles showing how to get a sort of H-
alpha filter by combining some other, affordable filters, but the
bandwidth is several nm.
During a total eclipse, can one photograph prominances without an
H-alpha filter?
--
Please reply to: | "We establish no religion in this country, we
pciszek at panix dot com | command no worship, we mandate no belief, nor
Autoreply is disabled | will we ever. Church and state are, and must
| remain, separate." --Ronald Reagan, 10/26/1984
uncarollo
May 26, 2012, 5:04:05 PM5/26/12
to
On May 26, 10:48 am, nos...@nospam.com (Paul Ciszek) wrote:
> In article <7458888b-ebf3-49e2-a6b5-3e1a73cfb...@pa10g2000pbc.googlegroups.com>,
>
> uncarollo <chris1...@aol.com> wrote:
> >Image taken with Astro-Physics 160 EDF refractor and Solarscope H-
> >alpha filter (single stacked for this photo) showing the huge killer
> >scorpion prom:
>
> >http://cosmosimages.net/pictures/20120519_stiched%20color%20invert%20...
> uncarollo <chris1...@aol.com> wrote:
> >Image taken with Astro-Physics 160 EDF refractor and Solarscope H-
> >alpha filter (single stacked for this photo) showing the huge killer
> >scorpion prom:
>
>
> I have to ask some really stupid questions here:
>
> Could you please describe what the colors in this image really mean?
> (i.e., it doesn't look H-alpha red, nor does it look like a grayscale
> image converted to yellow.)
>
> How narrow a bandwidth does one need in order to see convective cells
> in the sun? There are some articles showing how to get a sort of H-
> alpha filter by combining some other, affordable filters, but the
> bandwidth is several nm.
>
> During a total eclipse, can one photograph prominances without an
> H-alpha filter?
The coloration is up to the imager. Yes, H-a is red but yellow is more
> I have to ask some really stupid questions here:
>
> Could you please describe what the colors in this image really mean?
> (i.e., it doesn't look H-alpha red, nor does it look like a grayscale
> image converted to yellow.)
>
> How narrow a bandwidth does one need in order to see convective cells
> in the sun? There are some articles showing how to get a sort of H-
> alpha filter by combining some other, affordable filters, but the
> bandwidth is several nm.
>
> During a total eclipse, can one photograph prominances without an
> H-alpha filter?
pleasing to the eye. It is an artistic choice.
I think you need a very narrow bandwidth to see the H-alpha detail on
the surface. For the granulation (or convective cells) you only need a
white light filter.
During total eclipse you will see the prominances very well without
any kind of filters.
You can also create your own eclipse using an occulting disc at the
focus of your telescope and a wider band H-alpha filter. Baader
Planetarium used to sell such a device. The occulting discs were made
of polished stainless steel, and were sized to the focal length of the
scope - refractor being preferred because of the large amount of
energy going down the tube.
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