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Observer's Challenge – Saturn vs Pluto

At the 2019 Winchester week-end, Paul Abel and Pete Lawrence presented a series of observing challenges which members might like to have a go at during the year. Some are relatively easy, some really are quite challenging indeed.

There are actually two challenges here; read on...

The first challenge is to try and observe Saturn and Pluto at the same time. Saturn is an easy target and currently resides in Sagittarius. Pluto is also in Sagittarius and on 1st June 2019 the two planets are just 3.3 degrees apart. The pair will be low in the southern sky as viewed from the UK. Despite the vast differences in brightness (Saturn magnitude 0.28 and Pluto magnitude 14.3) will anyone be able to capture them on an image in the same field of view?

The second part of this challenge is observing the variation of Iapetus. Iapetus is a 3rd largest moon of Saturn. It has an interesting two tone surface - one hemisphere is rather bright, the other is covered in a dark reddish material. As a result, Iapetus changes in magnitude considerably as it orbits Saturn. Iapetus is brightest when on the western side of Saturn and faintest when on the eastern side. Iapetus takes about 79 days to complete one complete orbit of Saturn, so about 40 days from one elongation to the opposite one. A good time to start this challenge is in early June when the moon is at it greatest eastern elongation, and again in mid July when it is at its greatest western elongation. Saturn comes to opposition on 9th July 2019, when it will appear no higher than about 16 degrees above the horizon as viewed from London.

Please do post any observations you make to your BAA Member Page

Paul G. Abel & Pete Lawrence

[Thumbnail image by Peter Tickner]

BAA Members can access the 2019 BAA Handbook here.

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