The Best Views in the Solar System (Handy-Dandy Reference Chart)

NOTE: The following originally appeared on Solar System Heritage. I am reposting it here taking some feedback/corrections into account, and also cleaning up formatting, etc.

I am working on a story whose opening scene is planned to be on Callisto with a view of Jupiter. When writing this scene, I thought, wouldn’t it be nice to know about how large Jupiter looms in Callisto’s sky in real life, to give my story just a touch of extra-gritty realness? Or, for that matter, to know how big all the various bodies of the Solar System appear when viewed from the other bodies?

Unfortunately, I couldn’t find a reference chart with this info. So, I have started putting one together myself. I am not a math person by any stretch of the imagination, but I know how to google haha. I found that to calculate the apparent size of something, one uses this fairly simple formula…

arctan(diameter/distance) 

“Diameter” is the diameter of the object you are looking at. “Distance” is how far away it is. “Arctan” is a trigonometry function (inverse tangent); just look for a website that will calculate arctan for you. Easy-peasy, space-lemon-squeezy.

Applying this formula will get you a number in degrees (or radians if you prefer), and one can get a sense of how this big or small something appears by using the same formula on common objects seen at arm’s length and comparing your results to each other.

Below is a table of views of various objects in the Solar System by vantage point and approximate apparent size when viewed therefrom, using the formula. As noted above, math is not my strong suit, so my calculations may very well be far off of the reality. (Note: I added a few inches to the average length of the human arm to account for the fact that "arm's length", in this context, is the distance from your eyes to your fingertips rather than shoulder to fingertips.) 

One thing to keep in mind is that, in real life, most people grossly overestimate the apparent size of objects in the sky. If you ask a random person how big the moon appears in the Earth's night sky, they will frequently say something like “a dinner plate” or “a softball” or even “a basketball”, but that isn’t even close to correct. In fact, you can easily hide the moon behind the tip of your pinkie finger held at arm’s length. One can only imagine what people would think of seeing something that actually does hang in the sky like a basketball, like Mars as seen from Deimos, let alone larger, like Saturn as seen from Mimas!

View of the Sun (865,000 miles diameter)

• from Vulcan (assuming ~20 million miles from the Sun): about two and a half degrees -- a ping-pong ball held at arm's length
• from Mercury (~42 million miles from the Sun): slightly more than one degree -- a U.S. penny (one-cent coin) or euro two-cent coin held at arm's length
• from Venus: can't see the Sun on account of the thick clouds (in fiction, the Sun is generally assumed to cause a diffuse glow in the sky at least)
• from Earth (~92 million miles from the Sun): about half a degree -- your pinkie fingernail held at arm's length (coincidentally, the Moon and the Sun have very nearly the same apparent size from Earth)
• from Mars (~138 million miles from the Sun): about a third of a degree -- an average-sized green pea held at arm's length
• from Ceres (~258 million miles from the Sun): about a fifth of a degree -- the head of a pin held at arm's length
• from Neptune or Pluto (~3 billion miles from the Sun): about a sixth of a degree -- at this point, the Sun is not much bigger than a star, though still much brighter than a star (in fact, still bright enough to cause a twilight "day" in this part of the Solar System)
• from Ultima Thule or Planet X (~4 billion miles from the Sun): about an eighth of a degree -- the Sun appears to be a bright star

View of Earth (7,926.3 miles diameter)

• from Luna (about 238,000 miles from Earth): slightly less than two degrees -- the Earth appears about the size of a U.S. half-dollar coin or British 50p coin held at arm's length

View of Mars (4,212 miles diameter)

• from Phobos (3,700 miles away): about 49 degrees -- about as big as a giant (90cm) beach ball held at arm's length
• from Deimos (14,600 miles away): about 16 degrees -- a small watermelon held at arm's length

View FROM Mars 

• of Phobos (diameter 14 miles): takes up about a fifth of a degree, or about as big as a pinhead held at arm's length (fun fact: Phobos rises and sets about twice per Martian day due to its crazy fast orbital speed)
• of Deimos: it looks much like a star
• of Earth and Luna: they can be seen, individually, with the naked eye from Mars (just as Mars can be seen from Earth with the naked eye); they look much like stars (fun fact: Luna is the only moon in the Solar System that can be seen with the naked eye from the surface of a planet other than its host)

View of Jupiter (~89,000 miles diameter)

• from Io (about 217,000 miles away): about 22 degrees -- a big watermelon held at arm's length
• from Europa (about 414,000 miles away): about 12 degrees -- a cantaloupe held at arm's length
• from Ganymede (about 665,000 miles away): about 7 degrees -- a softball held at arm's length
• from Callisto (about 1.1 million miles away): about 4 degrees -- a baseball or cricket ball held at arm's length

View of Saturn (74,500 miles diameter excluding rings; outer diameter of the "A" ring is about 170,000 miles) NOTE: Saturn's closest moons are lined up with the rings (indeed are part of the ring system), hence viewing them edge-on and from within, spoiling the view

• from Mimas (115,000 miles from Saturn): Saturn itself takes up about 32 degrees of sky -- equivalent to a 55cm pilates balance ball held at arm's length
• from Enceladus (148,000 miles from Saturn): Saturn itself takes up about 27 degrees -- equivalent to a medium-sized (45cm) beach ball held at arm's length
• from Titan: Titan's thick atmosphere would probably obscure the view from Titan
• from Iapetus (2,213,000 miles from Saturn):
• Saturn itself takes up slightly less than two degrees in the sky -- about like a U.S. half-dollar coin or British 50p coin held at arm's length
• The rings should appear to take up about 4 degrees of sky -- the diameter of a baseball or cricket ball held at arm's length (but disk-shaped instead of spherical, of course)
• The orbit of Iapetus is such that it should get a decent view of the rings (i.e. not edge-on)
• from Phoebe (~8 million miles from Saturn):
• Saturn itself takes up about half a degree -- your pinkie fingernail held at arm's length
• The rings should appear to take up about one and a quarter degree -- a bit smaller than a U.S. nickel (5-cent coin) or euro five-cent coin held at arm's length
• The orbit of Phoebe is such that it should get a decent view of the rings (i.e. not edge-on), though it is kind of far away

View of Uranus (~32,000 miles diameter)

• from Miranda (80,000 miles away): about 22 degrees -- a big watermelon held at arm's length
• from Ariel (119,000 miles away): about 15 degrees -- a small watermelon held at arm's length
• from Umbriel (165,000 miles away): about 11 degrees -- a cantaloupe held at arm's length
• from Titania (271,000 miles away): about 7 degrees -- a softball held at arm's length

View of Neptune (~34,000 miles diameter)

• from Triton (220,000 miles away): about 9 degrees -- a shot-put held at arm's length

View of Pluto (~1,473 miles diameter)

• from Charon (3,161 miles away): about 25 degrees -- a medium-sized (45cm) beach ball held at arm's length

View FROM Pluto 

• of Charon (750 miles diameter): about 13 degrees --a cantaloupe held at arm's length