BBC Focus Magazine

[Colm]

Hi folks... got.. rather the young fella got (ahem) a telescope for Christmas and finally we have a clear night to actually look at something. Anyway, I was looking at Jupiter but I wasn't sure if it was focussed or what. (I think it's Jupiter anyway, in the sky it's not too far from the Moon)

It looks like a bright star to the naked eye, but through the telescope at magnification of 78x, It's a sort of dark blob with a bright halo around it. If I mess with the focusing I can sometimes see just a white blob, or sometimes just a small white spot... What is the "correct" view of Jupiter?

[ChrisH]

At the moment Jupiter is upwards and to the left of the moon. It should appear as a whitish disc with up to 4 points of light nearby, these are the 4 Galilean moons.
When I first saw Jupiter a few years ago with a small telescope I was a bit surprised at how white it was as it appears more orange or brown in most pictures. At the time I noticed 3 of its moons.

[M Paul Lloyd]

A wonderfully clear night out there tonight Colm and Chris, I do so wish I felt up to dragging the old scope out and setting it up but even if the spirit is willing my old bones are saying NO!

Colm try not to worry about magnication too much, its apature that really counts but anyway.

The problem with Jupiter is that it is so far from the Sun that the amount of light available to be reflected back to us is rather limited, so unless you have a telescope with an especially large apature the image is going to appear, either very dim or rather washed out. Plus a lot of the pictures published in books and magazines have, apart from probably been taken from the likes of probes (Voyager and such ) or the Hubble Space Telescope have, to a certain degree, been enhanced so that the colour contrast appears greater than it might through any ground based telescope which will also struggle with the rather inconvenient atmosphere.

Take some consolation from the fact that the image you see is composed of photons which once they have entered your eye and been translated into images will be seen by no-one else... ever.