APOD: A Filament Across the Sun (2012 Aug 20)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4074
Joined: Fri Dec 04, 2009 3:27 am

APOD: A Filament Across the Sun (2012 Aug 20)

Post by APOD Robot » Mon Aug 20, 2012 4:07 am

Image A Filament Across the Sun

Explanation: Is that a cloud hovering over the Sun? Yes, but it is quite different than a cloud hovering over the Earth. The long light feature on the left of the above color-inverted image is actually a solar filament and is composed of mostly charged hydrogen gas held aloft by the Sun's looping magnetic field. By contrast, clouds over the Earth are usually much cooler, composed mostly of tiny water droplets, and are held aloft by upward air motions because they are weigh so little. The above filament was captured on the Sun about two weeks ago near the active solar region AR 1535 visible on the right with dark sunspots. Filaments typically last for a few days to a week, but a long filament like this might hover over the Sun's surface for a month or more. Some filaments trigger large Hyder flares if they suddenly collapse back onto the Sun.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

Mactavish
Ensign
Posts: 76
Joined: Tue Dec 13, 2011 8:56 pm
Location: California

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by Mactavish » Mon Aug 20, 2012 4:55 am

I assume that “color-inverted” means converted from color to black and white. So, why was this image color-inverted? Was there something to be gained? Can someone explain please? Personally, I would prefer to see the original color image.

Boomer12k
:---[===] *
Posts: 2691
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by Boomer12k » Mon Aug 20, 2012 6:09 am

The Chinese believed a Dragon ate the Moon for a Solar Eclipse explanation....NOW I SEE WHY....There IS a Dragon on the Sun.... :D

:---[===] *

User avatar
starstruck
Science Officer
Posts: 177
Joined: Sat Sep 17, 2011 9:37 am

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by starstruck » Mon Aug 20, 2012 7:34 am

I don't think this is a color-inverted image. It may be an inverted monochrome image, in which case it could be described as a negative, done to emphasise different tonal details. Also, I am intrigued by when clouds above the Earth are not much cooler; usage of the term "usually" would seem to imply sometimes they are not . . a mushroom cloud maybe? Good image of an interesting phenomenon though.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17513
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by neufer » Mon Aug 20, 2012 11:50 am


starstruck wrote:
Mactavish wrote:
I assume that “color-inverted” means converted from color to black and white. So, why was this image color-inverted? Was there something to be gained? Can someone explain please? Personally, I would prefer to see the original color image.
I don't think this is a color-inverted image. It may be an inverted monochrome image, in which case it could be described as a negative, done to emphasise different tonal details.
Filaments seen with an H-alpha filter normally appear as dark features in the chromosphere (literally, "sphere of colour"). :arrow:

However, the APOD cannot be described as a simple negative because the background space is still dark.
Art Neuendorffer

User avatar
starstruck
Science Officer
Posts: 177
Joined: Sat Sep 17, 2011 9:37 am

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by starstruck » Mon Aug 20, 2012 12:22 pm

Thanks neufer. The background space has obviously been treated and added as a layer on this photo to make it look more acceptable. However, if you follow the link to the flickr page in the "above color-inverted image" link in the text, you can see the untreated negative image with the background space showing as white.

MyName

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by MyName » Mon Aug 20, 2012 1:03 pm

1 - Why do you have to include pictures of cats in suglasses in your links, I mean come on, isn't tham meme dead and buried by now, and did it really have to infiltrate APOD? Aren't you guys better than that?

2 - Clouds on Earth are usually cooler than filaments on the Sun? Usually? Can you give me an example of a cloud on the Earth that comes close to that temperature?

3 - What is the point of the link in the word "right"? Does this have any relavence to the topic?

4 - What do you mean by "charged hydrogen gas"? Are you trying to say "plasma"?

I love APOD but it appears that the quality of the descriptions are starting to slide.

User avatar
Chris Peterson
Abominable Snowman
Posts: 15317
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by Chris Peterson » Mon Aug 20, 2012 2:27 pm

Mactavish wrote:I assume that “color-inverted” means converted from color to black and white. So, why was this image color-inverted? Was there something to be gained? Can someone explain please? Personally, I would prefer to see the original color image.
The image is described as made through a hydrogen-alpha filter, and is therefore a monochrome image. There is no color. (As noted elsewhere, "inverted" is used correctly to refer to inverting the black/white endpoints, effectively making what is commonly called a negative... although in this case with the background masked out of processing.)

Color could be added in post processing- for instance, by simulating the red color of Ha, but that would show less detail to the eye than this grayscale image. A pseudocolor palette could be used to enhance detail over the grayscale, of course, although that would alter the aesthetics.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Bikepharm

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by Bikepharm » Tue Aug 21, 2012 1:59 am

"because they are weigh so little" Really?

biddie67
Science Officer
Posts: 483
Joined: Sun Jan 31, 2010 9:44 am
Location: Possum Hollow, NW Florida

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by biddie67 » Tue Aug 21, 2012 2:45 am

For a beginner in this complex arena, I found this APOD with its description and the many links an exciting introduction to ideas and things that I hadn't known about before. Thanks !!!

User avatar
DavidLeodis
Perceptatron
Posts: 1169
Joined: Mon May 01, 2006 1:00 pm

Re: APOD: A Filament Across the Sun (2012 Aug 20)

Post by DavidLeodis » Tue Aug 21, 2012 10:44 am

starstruck wrote:Thanks neufer. The background space has obviously been treated and added as a layer on this photo to make it look more acceptable. However, if you follow the link to the flickr page in the "above color-inverted image" link in the text, you can see the untreated negative image with the background space showing as white.
In the information in Flickr that is brought up through the 'above color-inverted image' link in the explanation to the APOD it states the image was taken on August 5 2012 but very confusingly in the information with the 'untreated negative image' in Flickr it states it was taken on August 1 2012. I wonder which date is correct? I regularly see dates in Flickr accounts for when a photo was taken that must be wrong yet they never seem to be corrected.