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The Saturn Season Begins:
2001-2002 Will Be Spectacular
Photo and article by Jim Scala

Arguably, the amateur's favorite showpiece, Saturn, will make excellent observing during the 2001-2002 opposition that occurs on December 3rd. At 20º 18' declination, where the air is clear, darkest, and above the trees, the opposition will dominate the observing season. Even better, the rings which are tilted 26º are almost at their widest of this current 13.5 year ring cycle. Hence, this is a superb opportunity to study Saturn's rings at their best, and to test your observing skills and understand telescope limits.

The above CCD image taken on August 8th at 0500 PDT (228-mm APO refractor) illustrates a few of the possibilities available with amateur telescopes. Saturn's disk at 17.52" and rings at 39.74" will increase to 20.6" and 46.6", respectively, by December 3rd. Most noticeable on the rings is the dark Cassini division (almost empty space), which was 0.62" wide, even though it seems larger. Test to see how small a telescope allows you to see this division. Although Cassini's division is small at 0.65", on average, it is an extended object (extended dark space), making it possible for small telescopes to seemingly exceed resolution limits. We all experience this when flying at about 30,000 feet and can see a road extending far into the distance well beyond our eyes' resolving ability.

Saturn on August 8th at 0500 (1200 UT) as seen through an inverting telescope. A CCD image acquired with a Santa Barbara Instrument Corporation ST-10E equipped with a CFW-8 color filter wheel. The telescope is a 228-mm F/9 Apochromatic Refractor housed in my backyard observatory in Lafayette CA.

 

 

 

 

 

 

 

 

 

An interesting measure of Saturn's progress toward and then past opposition is the slowly changing shadow of the planet on the rings, which are easily seen just to the left in the image. This shadow will disappear at opposition and then grow again on the opposite side.
In my 228-mm refractor, others and I have seen the Enke division (between Cassini's division and the outer edge) visually and this opposition is an excellent chance to capture it with a CCD that will once again seemingly defy resolution laws. A few amateurs who specialize in high-resolution CCD imaging have captured Enke's division. I will be trying hard to capture it this observing season. With the rings so wide, it's possible to see Saturn's disk through the inner Crepe ring. This elusive ring is seen in the image as the vague inner beginning of the rings themselves. In overly enlarged versions of the above image, a hint of the disk seems to be visible.

On September 10th at 0456, the Moon will occult Saturn in a dark sky. Sky and Telescope and other publications have excellent detailed coverage of this event. With the rings at 26º, this occultation will be the most spectacular in many decades.

 


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