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Friday, January 29, 2010


Opposition of Mars (and a blue Moon), Saturday January 30 2010

The "Blue" Moon and Mars, looking north-east at 10:00 pm local daylight saving time as seen from Australia.

This Saturday Mars is at opposition, where it is biggest and brightest as seen from Earth. It is also the night of the "Blue" Moon, and the Moon this night will have the largest apparent diameter of the year. So all in all a good night.

Mars will be easy to spot, it rises not long after the Moon and will be the bright red object left of the Moon.

Mars through binoculars. A few nights after opposition, Mars and the beautiful Beehive Cluster will be within the same binoculars filed of view.

Most of you remember the Mars Hoax email back in August, whch has circulated every two years since the Great opposition in 2003, which claimed that Mars would look as big as the Moon. Well, as you can clearly see tomorrow night it is not, Mars will just be a bright dot next to the Full Moon.

In binoculars (see image left) Mars will still be a bright dot. You will only see Mars as a disk in a telescope, and then you will need a medium to large telescope to see any detail. Still, even if you are just seeing a small disk, you are looking at an alien world, sister to our own, where robots are ceaselessly braving the harsh environment to gain knowledge. That's got to be impressive.

Mars as seen at this opposition through a 6" telescope with a 12 mm eyepiece.

So why is the opposition of Mars so rubbish this year. Basically because Mars is nearly at its furthest from the Sun, and Earth is nearly at its closest. Amongst other things it means light takes nearly 9 hours to reach Earth from Mars, while in 2003, it took only 5 hours.

Yeah, Okay you say, but why does it vary, why isn't Mars at the same distance each opposition? Because Mars's Orbit is not a whole number of earth orbits long, so the dates of perihelion and aphelion for Mars and Earth drift with respect to each other. (see the Hoax page for a more detailed description and this page for a better description).

So the upshot is that 2010 and 2012 are pretty poor oppositions, and we have to wait until 2018 fro a really good one (although 204 and 2016 won't be too bad).

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Hi Ian. I was out with my C6-SGT observing this grouping, and you revealed some interesting facts for me. I've also linked to your post from my blog at www.orion-xt10/blog where I write up my amateur astronomy experiences!
Looking at the moon now, 7:33 p.m. est. from near Niagara Falls, NY, USA. It looks like a second moon hanging below it, almost like you clicked a picure of the moon, moved the camera a little and took a second photo. Never seen anything like it before. I went outside thinking it was the window, it was the same outside. Figure it might be the storm to the East of here, near Washington, D.C., or the extreme cold as it is 8 degrees f. here.
Hi Jim! An interesting observing blog.

Hi Anonymous! What you have seen is most likely a mirage, caused by a difference in temperature between the ground and the air layer above it. It's pretty amazing to see one of that quality.
Do you mean 9 minutes for light to travel to us? Surely not hours?
Thanks Ian for explaining what I saw the other night. I tried taking photos of the moon and its reflection that made it look like a moon on a moon, but the second moon would not come through with my camera. It was neat to see, and I am 56 and have never previously seen such a moon, so figured it was not common.

Thanks again,
G'Day Molly

Photographing these things can be very difficult, because of the big intensity difference between the reflection and the bright Moon, or yes can see it quite clearly, but film/pixels just don't have the dynamic range our eyes do. Photographing coloured halos around the Moon can also be very disappointing.
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