Programming Question The moon size?

[Alexw95]

hey i was just wondering i was looking at pictures from the real apollo missions and the moon and earth size from eachother are so much bigger than in orbiter some times the moon is even star like in orbiter is this correct?

 

[Izack]

Here is the Earth and the Moon to scale for both distance and size.

In Orbiter, the Moon appears smaller from Earth's surface because it does not model the optical illusion that makes the Moon seem larger in real life than it really is.
Orbiter's Moon is exactly the same size. To demonstrate, land on the Moon and take a look at the Rad number in OrbitMFD. It will read 1.738M (1 738 km) near the equator, which is exactly what it is in real life.

By the way, to Orbiter-Forum! It's nice to see another Canadian.

 

[Piper]

The number one reason for the apparent different sizes, is because of field of view. Most people regularly use a FOV of 40 or 50 degrees for Orbiter. So picture taking 40 or 50 degrees of your natural field of vision, and compressing it to fit on your screen. In real-life, the width of your screen probably only takes between 10 or 20 degrees of your natural vision (depending on the size of your screen, and how close you sit to it). So in other words, it's like your vision being compressed 2 to 5 times.

 

[Chupacabra]

Or rather your vision expanded 2 to 5 times, considering you see much more than you normally would. This personally always made it difficult for me to enjoy 3d cockpits.

 

[statickid]

another way to look at it is that you need to figure out what feild of vision makes things natural size on YOUR monitor. with my monitor, (not sure of the size) i figured out that using a fov of 20 degrees makes the moons apparent size look right when i sit in my chair if i had a way bigger monitor, say the size of a large panel flat screen tv, i might only have to make the field of view 30 or 40 degrees, if i had a tiny little monitor, i might have to make the FOV all the way down to 10 degrees. i'm pretty sure a rough estimate of the apparent size of the moon to the naked eye is about half a degree. this means that if you put your monitor on my setting for realistic seeing at 20degrees, then 40 moons would fit nicely across the monitor laid end to end.

(edit) so in other words just what piper said... oops didn't read all the replys hahaha

 

[RisingFury]

In Orbiter, the Moon appears smaller from Earth's surface because it does not model the optical illusion that makes the Moon seem larger in real life than it really is.

Exactly. Along side with the FOV and monitor size.

The illusion he's referring to is that as light enters the atmosphere, it slows down somewhat and because the atmosphere is curved, it acts like a lens. The effect is even more apparent when the object rises and sets, that's why the Sun looks huge when setting above the sea.

Another little trick is that as the light travels through the atmoshere's different layers, it bends. When you're seeing the Sun set, it is actually already about half way under the horizon, but because light bends when it travels through the atmosphere, it allows you to kind of "peek around the cordner".

 

[Hielor]

Exactly. Along side with the FOV and monitor size.

The illusion he's referring to is that as light enters the atmosphere, it slows down somewhat and because the atmosphere is curved, it acts like a lens. The effect is even more apparent when the object rises and sets, that's why the Sun looks huge when setting above the sea.

Another little trick is that as the light travels through the atmoshere's different layers, it bends. When you're seeing the Sun set, it is actually already about half way under the horizon, but because light bends when it travels through the atmosphere, it allows you to kind of "peek around the cordner".

Not quite. The illusion is a result of the moon/sun being low to the horizon and "near" to objects which you recognize. Your mind automatically wants to compare it to those objects, so it appears to be larger. If you were to measure the visual size of the moon when it's at the horizon, and re-measure it when it's higher up, you would find that they're the same.

 

[Moach]

also, most other games and sims, and even movies have miseducated our perception of the moon and sun sizes onscreen...

such scenes are often filmed with narrow FOVs, or have some form of exaggeration to add some dramatic effect... and since this is so common, we have kinda "leaned" to expect the moon to look a certain size on movies and games...


so when you see it as it would look like for real, it feels strange... although it's correct

 

[RisingFury]

Not quite. The illusion is a result of the moon/sun being low to the horizon and "near" to objects which you recognize. Your mind automatically wants to compare it to those objects, so it appears to be larger. If you were to measure the visual size of the moon when it's at the horizon, and re-measure it when it's higher up, you would find that they're the same.

Hmmm, seems you're right.

Is this what you're referring to?
[ame="http://en.wikipedia.org/wiki/Ebbinghaus_illusion"]Ebbinghaus illusion - Wikipedia, the free encyclopedia[/ame]

 

[Hielor]

Hmmm, seems you're right.

Is this what you're referring to?
Ebbinghaus illusion - Wikipedia, the free encyclopedia

Yeah, something like that. There's also a few more possible explanations of the effect at [ame="http://en.wikipedia.org/wiki/Moon_illusion"]Moon illusion - Wikipedia, the free encyclopedia[/ame]

 

[statickid]

i got an old copy of flight simulator and the moon took up like half the screen and i wanted to punch it in the face.

the "illusion" is simply context

 

[statickid]

the ratios should be the same

HAIL !!

 

[Alexw95]

So if i have a 36" monior widescrean what fov should i run it at on orbiter for things to look real

 

[martins]

If your nose touches the screen, you can set the FOV close to 180 degrees.

 

[Alexw95]

what if i am 2 meters or so away

 

[martins]

Then you need trigonometry.

 

[statickid]

whether you know it or not, you've got a pretty good instinct about what size of moon "looks" real to you. nothing real complicated here, just sit in your chair, like you always do, looking at your screen like you always do, then get to someplace in orbiter where you can see the moon from the earth surface or easier, earth orbit. the simplest way is to rotate the camera so that the moon is behind your ship. then zoom into your ship, might as well try 10 degrees to start with. then use the mouse wheel zoom to get some distance so your ship is tiny, and you can see the moon clearly. then just judge for yourself, is it too big? press x. still too big? press x again. my screen is just about as wide as a keyboard, and somewhere between 20 and 30 FOV looks good to me.

---------- Post added at 05:16 PM ---------- Previous post was at 05:13 PM ----------

it would be easier if you measure your monitor size with m or cm if you're going to measure your distance in meters. you REALLY sit 2m from your monitor??? holy smokes! i can't even read my monitor from 2m. do you have really long arms? i guess a 36 inch monitor is pretty big..

 

[Hielor]

whether you know it or not, you've got a pretty good instinct about what size of moon "looks" real to you. nothing real complicated here, just sit in your chair, like you always do, looking at your screen like you always do, then get to someplace in orbiter where you can see the moon from the earth surface or easier, earth orbit. the simplest way is to rotate the camera so that the moon is behind your ship. then zoom into your ship, might as well try 10 degrees to start with. then use the mouse wheel zoom to get some distance so your ship is tiny, and you can see the moon clearly. then just judge for yourself, is it too big? press x. still too big? press x again. my screen is just about as wide as a keyboard, and somewhere between 20 and 30 FOV looks good to me.

The problem with using a very low FOV that emulates the real FOV that your monitor is to your eye is that you're heavily limiting yourself. Imagine trying to drive a car when you can only see out a 22" hole. Using a larger FoV is very standard for games, and unless you have several monitors set up to get you a realistic viewport size, using a smaller FoV is just going to make things difficult for you.

 

[statickid]

Then you need trigonometry.

hahah yeah, and you can hang a ping pong ball from the ceiling to rest your forehead against to make sure your eyes are at exactly the correct distance to get the precise fov/distance/monitor size ratio

 

[Izack]

Also interesting to point out is that the illusion can be recreated somewhat in Orbiter. Have a look at "Views>Moon through atmosphere" from the launchpad. It shows the Moon at a 10 degree FOV above Atlantis on her launchpad. (A scene which I suddenly find myself emotional about as I write this...I just now realised that Orbiter's flagship will probably never fly again.)