Some of the best images of Saturn are shown here. They all used the AO-2 adaptive optics system, and show nearly diffraction-limited images taken during good seeing in San Diego.
These images were taken with a 10" (masked to 9.65") planetary Newtonian, projected to F/60 (14.1 m EFL), and an SBIG ST-7E CCD camera and CFW-8 color filter wheel.
Saturn December 27, 2002
Compare the AO-2 image stabilization; its been a few years since I did this test, so as a sanity check, I took a number of images with the AO-2 turned OFF and the AO-2 turned ON, in average seeing. Here are the best in each series. None of the images with the AO-2 turned OFF came close to the best one with the AO-2 turned ON, validating the continued usefulness of the AO-2 system. The exposures here were 2 seconds through each of the red, green, and blue filters. The image on the left has the AO-2 turned ON, while the image on the right has the AO-2 turned OFF. While this best image in average seeing is not spectacular, it can be used to show the absence of any major storm activity on Saturn.
Saturn December 30, 2002
The seeing was much better this evening, and allowed 4 second long exposures in each of the three colors. Still no storm activity seen.
Good seeing, still no storm activity seen. On all of these images, at least 4 moons can be seen in the original uncropped images, since the exposures are so long (4 seconds).
Seeing was average, so an average image resulted. No hint of features on Saturn. The humidity was so high that the secondary mirror started fogging up, making the image even dimmer and full of scatter. After this session, a longer dewcap was added to the tube to prevent future fogging, and the fan on the back of the mirror was reversed to blow instead of draw air down the tube. The red and green frames were 2 seconds, the blue frame was 4 seconds long.
With a longer dew cap, the secondary did not fog over, and better images are again possible. This image is composed of the sum of several frames, added before maximum entropy processing; the best three red frames (2 second exposures), six green frames (2 second exposures), and two blue frames (3 second exposures). No storms or other features are seen on Saturn. No more time will be spent this season on Saturn - Jupiter will take priority.
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