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# Planetary Persceptive?

Since it is Ice Giant season, I was wondering what I could say to give people perspective on what they are seeing, in terms they could (and I) could understand. Something like, viewing Neptune from Earth is like seeing a pea in Seattle from Newark or something to that effect. Does anyone know where I could get information like this to put things into terrestrial perspective? For all the planets and stars, for that matter, not just U and N.

Charles Sands Observing since 12/29/86 12" f/5 Apertura AD12 Dobsonian 90mm f/13.9 Sky Watcher Mak Cass 70mm f/5 refractor, Orion GoScope 10x50 binos (Bushnell Falcon) 7x35 binos (Sears Discoverer) Orion StarShoot Solar System Imager IV Sky & Telescope's POCKET SKY ATLAS CyberSky 4.0 astronomy software -------------------- Never underestimate the power of stupid people in large groups - Lewis Grizzard (1946-1994)
You already know the angular sizes of the planets at any time. The matter at hand is to determine at what distance a common objects subtends the same angle. We know that an object subtends an angular diameter of 1 arcsecond when it lies at a distance equal to 206,265 times its diameter.

For example, a 1/4" ball bearing would appear 1 arcsecond across when 206,265 * 0.25" = 51,566", or 4297', or 1,432 yd away.

To appear 10" across, the 1/4" ball bearing would have to be 1,432 / 10 = 143.2 yd.

And so your formula for distance at which an object of measured size subtends a given angular diameter (arcseconds):

206,265 * obj. diam. / arcseconds

Home-made and modified binoculars My Gallery (mostly DIY stuff) **UPDATED Jun 22, 2013** Simple minds discuss people. Good minds discuss events. Great minds discuss ideas. - Hyman Rickover
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So, Uranus (4" arc) would be the size of a dime (0.7 inch) at ~1000 yards.

Another interesting site...
http://www.exploratorium.edu/ronh/solar_system/

Norme

150mm MCT f/13, 31% CO

Yellow Zone

"People say I'm in denial. I disagree."

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Oops. Yes, gas giant. lol Thanks guys.

Charles Sands Observing since 12/29/86 12" f/5 Apertura AD12 Dobsonian 90mm f/13.9 Sky Watcher Mak Cass 70mm f/5 refractor, Orion GoScope 10x50 binos (Bushnell Falcon) 7x35 binos (Sears Discoverer) Orion StarShoot Solar System Imager IV Sky & Telescope's POCKET SKY ATLAS CyberSky 4.0 astronomy software -------------------- Never underestimate the power of stupid people in large groups - Lewis Grizzard (1946-1994)
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If something is one arcsecond when it is 206,265x its diameter, does that mean if it is only 1/4 the distance, it will subtend 4 arcseconds or is it not a linear measure?

Charles Sands Observing since 12/29/86 12" f/5 Apertura AD12 Dobsonian 90mm f/13.9 Sky Watcher Mak Cass 70mm f/5 refractor, Orion GoScope 10x50 binos (Bushnell Falcon) 7x35 binos (Sears Discoverer) Orion StarShoot Solar System Imager IV Sky & Telescope's POCKET SKY ATLAS CyberSky 4.0 astronomy software -------------------- Never underestimate the power of stupid people in large groups - Lewis Grizzard (1946-1994)
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Glenn's equation above is linear, so without doing the math the result would have to be linear.

Norme

150mm MCT f/13, 31% CO

Yellow Zone

"People say I'm in denial. I disagree."

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Over these small angles, a linear approach is perfectly valid. Only when going past about 10 degrees or so would non-linearity become worth considering (depending on requirements for accuracy.)

Home-made and modified binoculars My Gallery (mostly DIY stuff) **UPDATED Jun 22, 2013** Simple minds discuss people. Good minds discuss events. Great minds discuss ideas. - Hyman Rickover
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So, working this out, the Earth (7,926 miles) would appear 4" arc (same as Uranus's apparent angular size) at ~409 million miles. Uranus (31,250 miles) appears that same size at 1,610 million miles - 4 times the distance.

"The diameter of Uranus is 51,118 km. Just for comparison, this about 4 times bigger than the diameter of the Earth, at 12,742 km across."

That's it? Uranus is only 4 times the diameter of Earth? I though it was much larger.

Norme

150mm MCT f/13, 31% CO

Yellow Zone

"People say I'm in denial. I disagree."

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It's actually 4.007 Earths wide.

Pete

"I got here the same way the coin did" - Anton Chigurh "Noth doth not noth" PWP “We are the universe contemplating itself” - Carl Sagan 70mm TV Ranger 150mm SCT, Celestron 8" F/9 PARKS reflector, Clements Mirror, Spectrum Coatings Plossls, Orthos, TV Barlows DBK21au http://www.cloudynights.com/photopost/showgallery.php?ppuser=64701&cat=500
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