Lunar Occultation of Saturn (APOD 16 Mar 2007)

[goredsox]

http://antwrp.gsfc.nasa.gov/apod/ap070316.html

It appears that the Saturns don't quite line up in a straight line. I am holding a straight edge (printer paper) right up to the flat screen monitor.

Could it be "camera giggle"? Or perhaps lunar gravitational distortion? Maybe at this magnification Saturn's path is a pronounced curve? Just an optical illusion? Any other theories?

-GRS
"Maybe next year.."

[cosmo_uk]

I'm going with optical illusion due to the curved shape of the moon as when I put my ruler through a point on saturn it lines up all the way to the other end of the line. Although it could be my monitor!

[BMAONE23]

This illusion is most likely caused by slight shaking in the video camera during filming. Someone walking around the camera during the 21 minutes of taping time needed to track this much of Saturns path would possibly shake the camera causing imperfections in the image. Or an imperfect recombination of images used to create this fantastic view might be another possibility.
On close examination, the 5th frame of Saturn lies farther out than the rest. If you put a straight edge against the outer edge of the rings, it will only contact the 5th and last frames of Saturn.

[orin stepanek]

I wonder it the fact that Saturn's orbit around the sun and The moon's around the Earth may have something to do with some curvature of the occultation?
Orin

[ebow]

I wonder why so many photos are rotated for general audiences? In this case, the APOD shows a scene where south is up. The image under the link "summary" (http://www.digitalsky.org.uk/occultatio ... ummary.jpg) shows the true orientation. Nothing is really lost in the original perspective, and I don't think anything is gained by turning it over.

[Andy Wade]

This illusion is most likely caused by slight shaking in the video camera during filming. Someone walking around the camera during the 21 minutes of taping time needed to track this much of Saturns path would possibly shake the camera causing imperfections in the image. Or an imperfect recombination of images used to create this fantastic view might be another possibility.
On close examination, the 5th frame of Saturn lies farther out than the rest. If you put a straight edge against the outer edge of the rings, it will only contact the 5th and last frames of Saturn.

I thought it might also be because the image is a three frame mosaic?

Incidentally the same image was shown on LPOD on 5th March 2007:

http://www.lpod.org/?m=20070305

[Dr. Skeptic]

Any optical aberrations would be due to tracking errors (telescope or computer monitor), no gravitational lensing here.

[NoelC]

I suspect the image was assembled digitally, without excessive regard to the position in the moon in the frames other than those where it is partially occulted. It may not have even been possible to discern the features of the moon in most of the Saturn exposures.

On another topic, related to this same image set...

Both the Moon and Saturn are sunlit, right?

Is Saturn showing up in the non-normalized images so much dimmer than the moon because it is just much farther away from the sun than is the Moon? I have always been under the impression that the surface brightness of two things equally bright will be the same at any distance; the further object will just look smaller. So this implies Saturn is less brightly lit, which makes sense.

I know the Moon isn't very reflective; it's reflectivity has been compared to an asphalt roadway. And Saturn's rings ARE supposed to be quite reflective, being comprised of ice crystals.

I think I've answered my own question here.

-Noel