Saturn with Rhea Shadow Transit

On Wednesday night I captured Saturn in above average seeing – the second time that week! When I’d finished processing the images, I noticed a faint Moon near the edge of Saturn, and a dark feature just under the ring plane.

When blinking between the two images, I saw that the feature had moved, so I check Starry Night Pro planetarium software and found that the small Moon was Rhea and the dark spot on Saturn’s disc was Rhea’s shadow.

You can see the animation of the two frames below.

Saturn with Rhea Shadow Animation

Saturn with Rhea Shadow Animation

Continue reading to see the two colour images.

The difference in brightness between the two red channel images is due to the capture settings. In the first image, I had gamma at 110 and in the second, 120. The blue channel was so faint, I bumped up the gamma to capture all 3 channels at 15fps rather than dropping blue back to 7.5fps.

Saturn and Rhea's shadow

Saturn and Rhea's shadow

I recorded for 2 minutes (approx 2000 frames) in each channel, and stacked 650 frames from each. ME deconvolution was performed in AstraImage, followed by colour, contrast and saturation adjustment in Photoshop.

Saturn, Rhea and Rhea's Shadow

Saturn, Rhea and Rhea's Shadow

Saturn’s rings are really getting dark now, as they tilt towards edge on with the Sun, so they don’t get illuminated as much – even though we’re above the ring plane looking down.

It’s only going to get more difficult over the next few months as the rings get dimmer, and Saturn heads towards superior conjunction with the Sun.

Thanks for looking.

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