Adrian Dening's Stars Over Somerset

Monday 4th to Sunday 10th September 2023

If you venture outside around 11pm on Monday 4th, a 70%-lit Waning Gibbous Moon will have risen above the horizon towards the east with a magnitude -2.5 planet Jupiter just to the right of it.

Take the opportunity to aim your telescope towards Jupiter at that time and it will be possible to see all four of the Galilean Moons - running from left to right - Callisto, Ganymede, Europa and Io. Sometimes it is not possible to see all four of them at once because they are orbiting around Jupiter and are hidden from our view as they pass behind it.

When you look through your telescope's eyepiece, the four moons will be the opposite way around to have I have listed them - because of the way their optics are designed, astronomical instruments always produce an inverted or upside-down view!

If you use binoculars, which are designed for looking at things on the Earth, then the image will be the correct way round. Binoculars incorporate an extra prism to correct the image, but the process loses a little bit of light. This is done because if you're looking at a ship in the distance, it's nice to have the sea at the bottom and the sky at the top! Astronomers don't care if their target is the other way up as it's far more important for them to collect as much light as possible!

There are a couple of great opportunities to spot the International Space Station at the beginning of next week. On Monday 4th it appears over the horizon to the west at 5.23am and reaches an altitude of 77 degrees as it spends 6 minutes heading towards the east. On Tuesday 5th, it will appear in the west at 4.37am and pass directly overhead.

Screenshots courtesy of Stellarium
Copyright Adrian Dening and Radio Ninesprings 2023
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