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Planetary viewing and distance from Earth


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How big a difference does the distance of a planet make when viewing?  I got my first glimpse of Saturn last night and it was awesome, but very small.  I checked Stellarium and apparently it's just under 10.5 AU from Earth right now, and at its closest is closer to 7 AU.  Would that make a huge difference for viewing, or just a slight difference?

I also checked out Mars and it was just a very small reddish dot that I could not make out detail on.  Do I need to wait for it to be closer?  I'm viewing at 240x (10mm + 2x barlow) and plan on getting a 6mm eyepiece soon for planetary viewing that will put me at 400x with my barlow.  I think that's as high as I want to go with my 8" Dob, or for planets could I go higher?  They seem very bright, so I'm wondering if I can take the magnification higher.

Thanks,

Steven

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you might be able to use 300x on Mars, the moon and occasionally Saturn but main the first two (plus double stars).

the best thing to compare is angular diameter. saturn varies between about 14.5 and 20 arc seconds. mars between 3.5 and 25.1 arc seconds (about max of 15 arcseconds in April 2014)  and for comparison, Jupiter is currently 46.8 arc seconds

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It can make quite a difference, though perhaps less so for Saturn.  The angular diameter of Saturn varies from about 15 arcseconds at its furthest from Earth to 21 arcseconds when it is closest.  Jupiter varies from about 30 to 50 arcseconds and Mars from 3.5 to 25.

I'm not sure how large Mars is now in terms of angular diameter, but it should reach 15 arcseconds at opposition in April this year.  I'd guess it could be about half that at the moment.

James

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Thank you.  Seems like Jupiter is prime right now.  My next question was going to be if anyone had a bird's eye view of the solar system that showed the positions of the planets, but I found one here.  Is that one pretty good, or are there better representations elsewhere?

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Mars is difficult at any time. Even at its historic closest some years ago I was able to make out very little detail in my then 4.5" scope. I could see a reddish disk with a little white button at the poles, and with long observing managed a couple of surface features. It makes a great difference how close it is. Jupiter and Saturn can yield some detail at almost any time you can see them, but are best when they are closest, naturally. It takes good skies, good eyepieces, and patience to tease out detail in these planets. You can see Uranus and Neptune with your scope, but they will appear as a bluish or greenish star, not much more.

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This one for the planets is fun and easy: Simulation

To see Saturn you have to hit the "-" a couple of times to get Saturm in, just once for Jupiter.

You can let it run or hold the button resembling a diode down then release to stop it when the planet in question is closest to us - generally Sun. Earth and Planet in a line.

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