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So what does "opposition" mean in terms of viewing?


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Saturn will come into opposition, I'm informed April 3rd, which I won't be able to enjoy as I will be packing my bags and returning from a trip to the US of A.

What difference does opposition make to what you see in the scope compared to a non opposed object? I'm rather curious..

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In terms of observation it means:

a) The planet (whatever) is opposite the sun - and thus rises when the sun sets and sets when the sun rises - thus its theoretically visible all night.

On a practical point of view if you have a normal job that roughly translates as a month or so before opp and for quite sometime thereafter its a great time to view it.

:) Its when the planet is at its closest.

Which means its at its brightest, and when its at its largest apparent diameter- so the details on it are clearest and you need the min magnification. The size effect diminishes the further a planet is away from the pkanet you are observing from (the earth in our case). So Mars shows this effect the greatest, Jupiter less so, Saturn less than that - cos the difference in size is caused by our earths orbit from one side of the sun to the other relative to where the object is. Eg planet at 5AU (jup)... 5-1AU=4 to 5+1=6 AU

c) When at opposition the planet is fully illuminated (eg the Moon is full), rather than partially (somewhat gibbous). Just how gibbous a planet shows at maximum (which occurs when its at right angles to the sun), depends again on its distance out from the sun. In the case of Saturn the effect is well shown as before Opposition the shadow of the planet on the rings behind the planet is at one side before opposition, and at the other side after. Have a look!

Hope this helps and happy observing!

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For most planets there is little practical difference in distance for a couple of months either side of opposition. Mars is the exception even so the actual date of opposition is nothing special, conditions are almost equally good for 3-4 weeks either way.

Saturn is unusual in that there is a very marked increase in the brightness of the rings - but not the globe - for a few days either side of opposition, this is due to the reduced mutial shadowing of the ring particles (the heilgenschein effect).

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Correct, although you can use an intricate counter balance system of shoes and handbags to prevent that effect.

You could also play the old look what i found in the loft routine....:) it's more cost effective and more kit can be purchased :p, if all else fails then try the about .

Edited by Si W
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Just back home and set up the scope as it looks like it will be a clear night! Sat here with coffee and iPad in tow.

@Kev, thankyou very much for a wonderfully clesr account of opposition, that was very useful and I look forward to seeing a Mars opposition one day!

@Everyone, thankyou for your posts, this forum is a fantastic place for practical help and humour!

I rarely get opposition, the occasional tut, and look that says "3am? Really? This is worse than golf and fishing!"

As a twenty something guy I expected most of my friends to be more interested in the pub, however - I get resl genuine interest from friends and occasional gstherings as they look at the Moon.

Tonight is from the backyard as my lift into a dsrk site has cancelled on me, hoping to see the cone Nebula, Stellarium suggests that that area is only marginly fainter than the Great Orion etc.

Anyhow, before I ramble, thankyou all!

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