Starship Asterisk*

I would enjoy seeing some of the images, or perhaps an inset image, of the subject in visible light. This would allow me to see how the photograph has been enhanced with the many different spectrum levels. Perhaps a similar image in visible light on a following day after a particularly stunning image. But then, most of the images seen on APOD are stunning.

Thanks for the chance to speak

MadcityTraveler

MadcityTraveler wrote:I would enjoy seeing some of the images ... of the subject in visible light.

This may be a useful suggestion in general.

If you are referring to Central IC 1805 (APOD 2008 July 26) ...

APOD wrote:A composite of narrow and broad band telescopic images, the view ... includes emission from hydrogen in green, sulfur in red, and oxygen in blue hues.

I think they are saying this composite is made of several photos, all in visible light. I think the "broad band" image includes most if not all of the spectrum of visible wavelengths, and that the listed elements' appearance is accentuated by adding photos taken with filters that only pass the desired emission wavelengths, also in the visible range. Or there could be non-visible wavelengths shown as color - the text doesn't say specifically.

Here's a false-color view of IC 1805:

http://antwrp.gsfc.nasa.gov/apod/ap040917.html

Here's a futher explanation of a common color mapping scheme:

"The final image depicts red light from hydrogen atoms as green, red light from sulfur ions (sulfur atoms with one electron removed) as red, and green light from doubly-ionized oxygen (oxygen atoms with two electrons missing) as blue."

So I guess that makes the color in this picture visible but false.

MadcityTraveler wrote:I would enjoy seeing some of the images, or perhaps an inset image, of the subject in visible light.

IC1805, APOD 20080725

Try this black and white image from japan. In the dark the human eye looses its ability to see in colour, so a B/W image is rather appropriate. The same website has a colour image of IC1805 as well.

henk21cm wrote:IC1805, APOD 20080725

Shouldn't that be IC1805, APOD 20080726?

The caption to the APOD contained a link to a natural color plate of The Heart Nebula.

bystander wrote:Shouldn't that be IC1805, APOD 20080726?

Quite right. 25th is the blue pinwheel.

______________
Errare humane est et nil humane mihi rarum est.
 Henk