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Mark your calendar for 23 hours. on the night of July 19th. The sun sets around 9 pm EDT, there is a beautiful first quarter moon high in the sky and you will see shining Jupiter to the left of the moon. Still in the western sky, there is Venus, even brighter than Jupiter, but for the purposes of this column, we will ignore Jupiter and Venus.
Fun things start around 11:10 pm EDT and involves the Moon and the most expensive and largest spacecraft ever built (with six humans on board) called the International Space Station or ISS. The event we will see (weather permitting) is a transit of the ISS across the face of the moon. You can not miss it because on July 19, while it is crossing the sky, the ISS will be as bright as the planet Venus!
You may have been lucky enough to have seen a plane cross the moon, and although the ISS is a very small object 500 km away, it shines in the sunlight and can easily be spotted with the naked eye (and even followed with binoculars). The ISS rotates around the Earth 15 times in 24 hours, and periodically, by chance, it passes in front of the Sun or the Moon. In July, for example, there are seven solar transits and six lunar transits. Solar transits require special filters to see the sun safely and without them, solar transits are not safe to watch. However, lunar transits can be seen at the naked eye because the ISS is often visible as a very bright satellite moving in the sky like dozens of others. In fact, on July 19 only, there are six visible passes of the ISS across the sky during the dark hours. One of them, the passage of 11:10 p, m. at 23:20 EDT crosses the Moon.
To successfully see this lunar transit, find a flat horizon to the west and start looking towards the ISS around 11:10 pm. look below the moon and watch a point of light go up. You should be able to see the ISS before 11:12 pm. and it just gets brighter from there. Finally, when directly above it will be as bright as Venus! For 2.8 seconds just after 23:13 EDT, ISS will cross the Moon from the bottom up. The key is to spot it before crossing the moon and following its path up. The ISS does not get much brighter than this and it should be relatively easy to spot early in its path. The entire passage from horizon to horizon takes more than 10 minutes.
There is only one catch. To see the ISS cross the Moon, you have to be at the right place on the planet. The trail is about 10 km wide, the central line running from the north of Sauble Beach to the White Cloud Island, on the Georgian Bay side. Throughout the central line, you will see the ISS cross the center of the Moon. If you are a mile or two on either side, this will move the path across the moon to the edge, and if you are outside the blue track shown, ISS will completely miss the moon. Even a failure is an interesting experience especially since the space station is so bright, but being in the "shadow" of the ISS on Earth is like a kind of eclipse but it is the space station that eclipses a more distant body. This is not a total eclipse because ISS is too far to cover, but a tiny fraction of the Moon's face.
The west end of the July 19 runway falls on the other side of the Sauble Falls Drive, so no matter where with not too many trees in the west would be suitable. Wiarton would also work and anywhere along Gray Road 1 from Wiarton to Big Bay would also be a good location for observation.
The track may change slightly as the time approaches, so check your information on www.transit-finder.com. You absolutely need up-to-date information. There are also several good apps for smartphones that do the job as well. There will be other opportunities to see the transits, but start with the lunar transits before attacking the solar transits. Safe sunscreens are absolutely necessary for these, but lunar transits are completely safe.
Good luck with your spotting!
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