Starship Asterisk*

Ann wrote:Was it a blue or perhaps an ultraviolet filter?

starstruck wrote:

Ann wrote:
I find the brightness contrast between Titan and Dione fascinating. Is Titan actually so dark? Of course Dione is very bright, with its ice cliffs. But its albedo, reflectivity, still can't match that of Enceladus, which is perhaps my favorite moon in the solar system. Can the darkness of Titan be explained by the filter used to take this picture? Was it a blue or perhaps an ultraviolet filter? I didn't check out the caption of today's APOD carefully enough to know.

The first link provides some more information; it says they took the picture in visible blue light. I believe that would mean that if Titan has more red hues in it's colouration then it would appear darker in such an image.

• Titan Albedo: 0.22
  Dione Albedo: 0.998 ± 0.004
  Enceladus Albedo: 1.375 ± 0.008 (geometric)

http://en.wikipedia.org/wiki/Geometric_albedo wrote:
<<The surface materials (regoliths) of airless bodies (in fact, the majority of bodies in the Solar system) are strongly non-Lambertian and exhibit the opposition effect, which is a strong tendency to reflect light straight back to its source, rather than scattering light diffusely. The geometric albedo of an astronomical body is the ratio of its actual brightness at zero phase angle (i.e., as seen from the light source) to that of an idealized flat, fully reflecting, diffusively scattering (Lambertian) disk with the same cross-section. Diffuse scattering implies that radiation is reflected isotropically with no memory of the location of the incident light source. Zero phase angle corresponds to looking along the direction of illumination. For Earth-bound observers this occurs when the body in question is at opposition and on the ecliptic.

For very bright, solid, airless objects such as Saturn's moons Enceladus and Tethys, whose total reflectance (Bond albedo) is close to one, a strong opposition effect combines with the high Bond albedo to give them a geometric albedo above unity (1.4 in the case of Enceladus). Light is preferentially reflected straight back to its source even at low angle of incidence such as on the limb or from a slope, whereas a Lambertian surface would scatter the radiation much more broadly. The geometric albedo above unity means that the intensity of light scattered back per unit solid angle towards the source is higher than is possible for any Lambertian surface.>>

neufer wrote: it says they took the picture in visible blue light.

islader2 wrote:Robot asks us to find a "spec" that is Pan. I found no "spec"==but several specks; which, it turned out to be dirt on my screen and some "floaters" in my vitreous fluid from searching for Pan. Wish I could make a ditty of the search for spec. Well, we have a sci-fi movie 'Search for Spock' with light travel and such.

redskyatnight wrote:Was this a planned picture or was it just a random photograph?

redskyatnight wrote:Was this a planned picture or was it just a random photograph?

kidvid wrote:It seems like there is a fifth moon unless it is an artifact.
In the rings below Dione there is a thin ring gap and it appears to have a bright spot just at the outter gap edge.
So with Massive Titan; Bright Dione; Pandora to the far right and Pan to the far left and possibly the other even smaller moon than Pan; maybe Pan's Flute?