Wecome Khodd! I'll second Geoff's advice. A good barlow and a 12mm plossl in addition to what you have will give you a lot more flexibility. But you don't need these to see Cassini. It should be easily visible with your 15mm and 9mm. Just go and look a again a few times. Here is a preview courtesy of Asimov
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http://www.iceinspace.com.au/forum/s...ead.php?t=9040