The Shadow Transit of Titan

I spent the early morning hours of Sunday watching an event along with three other members of the Amateur Astronomers Association of Pittsburgh. (3AP.org) Using the 115 year old, 11” Brashear Telescope at the Wagman Observatory, John Holtz, Mike Miller, Sean Matoon and I watched as the shadow of Titan, one of Saturn’s moons, crossed onto and across the planet’s surface. These transits occur about every 15 years.

    The astronomy club had two star parties this weekend and after the second one, after the public had departed, we aimed the telescope at Saturn. The seeing was pretty steady, the image wasn’t bouncing around at all and we had no problems increasing the magnification.

    Neptune was sitting within a degree or two of Saturn so we swung the scope over to it while we were waiting for the transit to start. The planet first appeared as a faint blue dot but by increasing the magnification we were able to see it as a round disc. We weren’t able to see any features on it. The shadow of Titan would be about 1/3 the size of Neptune, this could be difficult!

    As Saturn orbits the sun, our view of the planet's rings change. We recently passed through the ring’s plane where the rings appear to us as being edge on. This gives us a quite different view of the planet as to what we are familiar with.

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    When the planet is in this orientation, the shadow of Titan, the largest of the planet’s moons, can be observed crossing the planet’s surface. The moon orbits Saturn every 16 days so we have a chance to see this event a couple more times during the next month or two.

    Moving the scope back to Saturn and turning off all the lights in the room, we watched. Titan could be seen sitting below the planet’s rings on the right-hand side. The transit was due to start at 2:25 but we couldn’t see it until 2:30 when John first located it.

    Over the next hour and a half, we watched as the shadow slowly worked it’s way towards the meridian. We experimented with a variety of eyepieces, giving us magnifications between 243 - 939 power! While the viewing at 939X was nice, as would be expected, we opted for a lower power which gave us a much crisper image. We even tried using a binocular viewer which sadly, was difficult to use. It did give me a nice 3-D image of the planet!

    The shadow was dim and I had difficulty seeing it. The other three having much better eyesight could see the shadow much easier.

    We watched it, taking turns at the scope until a bit after 4 when we decided to close things up. Dawn wasn’t far away, our homes seemed even further. I pulled up in front of my house at 5.

    I think it was great seeing this. It is another astronomical event to tuck into my belt. It wasn’t quite as exciting as watching a solar eclipse or watching Mars slip behind the moon but it was right up there with them!