It was the last day of February. Posts on Facebook were talking about an astronomical parade of planets that would be happening that evening. Like so many things posted on FB, I didn’t have any real desire to see it. I knew that 3 of the planets would be setting soon after sunset and two of the others would be visible only with optical aid. It always sounds so much more interesting than it turns out to be.
Instead of watching the parade of planets, I decided to watch an occultation instead. Io, one of Jupiter’s moons was going to be disappearing behind the planet. I always enjoy seeing an object in space moving in real time! The occultation of a star that is light years away will be almost instantaneous. The star is a mere pinprick of light, gone as soon as it passes behind whatever covers it. When a planet’s moon crosses behind the planet, it might take a few minutes for it to completely disappear since the moon is an actual disc that we can see through a telescope. The increased time makes the movement that much more obvious and that much more exciting.
The day was clear but of course as evening approached, while I was setting up my telescope in the front yard, patches of clouds started drifting in. The majority of the sky was clear but this is Pittsburgh, I knew that the sky will be covered soon.
After everything was set up I watched Jupiter and its moons. Io was close to the planet and on the far side, Callisto sat a bit further away. Ganymede and Europa sat further out on either side. With Io disappearing behind the planet and Callisto soon to be crossing in front of it, I could imagine how they were all orbiting the planet. The seeing was steady and I was able to add a doubler to the eyepiece to increase power without getting any distortion.
Io slowly got closer and closer as I watched until it seemed to touch the planet’s surface. Clouds came and went as I watched and they actually helped me out. The planet’s disc was bright yellow and the moon was both smaller and a fainter orange. The brightness of the planet made it difficult to accurately see the moon as it neared. The clouds would change the color of the planet to grey and as the color faded, the moon became easier to see. This helped when the moon’s disc was partially covered! I thought a couple times that the moon had disappeared only to see it again as the seeing changed.
The moon was drifting behind the planet in line with northern cloud band. It was sometime after 7:29 that I lost sight of it. I then turned the telescope to the moon and enjoyed just roaming across the lunar landscape. The craters alongside the terminator were exciting to explore.
I was wearing only a sweatshirt and the temperature was dropping. The clouds were also increasing so I decided it was time to call it quits. I didn’t need a flashlight to tear my set-up down. The moon was 93% illuminated; I could see my shadow as I was carrying things into the house.
I missed the planetary parade, but then again, I wasn’t out there to see it. I saw the event I wanted to see and the clouds held off, for the most part, until I was tearing things down. My neighbors generously left their porch lights off and no cars drove by, shining their lights on me. I talked with some of them as they walked their dog and got to pet him for a bit. Petting the dog was "almost" as exciting as watching the moon disappear.
All in all, not a bad way to end a short month! Come on March, bring it on!
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