For something a little different in the tropics, how about a stargazing trip to the top of one of most sought-after places to star gaze in the world--Mauna Kea. First, the small van takes you, at mid-afternoon, to the Visitors Center at 9,200 feet elevation where you are regaled by a short talk on what you are about to see and the itinerary for the evening, and treated to something to eat. You then go to the top of Mauna Kea to watch the sun go down and look at the West coast of the island and Maui or the clouds below you, depending on the weather. Please see more pictures on my Mauna Kea page.
As dusk turns to dark at the top of Mauna Kea, the tour vans descend to the visitor's center, or nearby, where the tour company takes out its own telescopes and sets them up for an evening of stargazing. On the trip I took, I clearly saw the rings of Saturn and the moons of Jupiter. We also had a good gander at Venus which was in a "new moon" phase and appeared as a brilliant crescent. We had a good look at the Southern Cross and the brilliant Sirius, as well as the Milky Way and many other astronomical constellations that could be seen in the evening sky that night. Our guides used lasers to point out the various star groups, making them easy to identify, as well as setting up their telescopes to view specific star groups and planets much more closely.
If you don't want to pay for a tour like the one I've described, please visit this Mauna Kea Visitor's Center page for information on free stargazing available at the center.