Planet Distances

[christoria]

Hello,

I'm currently working on an excellent script that will show what planets look like at a fixed distance - in comparison to the sun at that same distance. I've got up to mars done. My question is, can I set the distance any easier than this:

select { object "Mercury" }
wait { duration 3 }
changedistance { duration 3 rate 1.6 }
wait { duration 5 }

I'd rather put the exact km's than try to figure on a rough estimate using "rate". Each planet has a different "rate". Is it possible to do that?

Thanks for your time,

christoria

[Harry]

I'm currently working on an excellent script that will show what planets look like at a fixed distance - in comparison to the sun at that same distance. I've got up to mars done. My question is, can I set the distance any easier than this:

select { object "Mercury" }
wait { duration 3 }
changedistance { duration 3 rate 1.6 }
wait { duration 5 }

I'd rather put the exact km's than try to figure on a rough estimate using "rate". Each planet has a different "rate". Is it possible to do that?

You probably can use the various goto-commands, which have differing means to set the distance to an object. For example, if you select a planet and then use "goto { distance x }", you set the distance to x times the planets radius (still not in km, but easy to compute). For more precise control over the location where this will end, you can use the gotoloc command, and set a vector in relation to the selected object (finally in km, but needs vector-arithemtic). For details, see the Don's Scripting Guide at
http://www.donandcarla.com/Celestia/

(though rereading the part about the position argument to gotoloc I am not sure if there really is a distinction between Altitude and Distance - probably should be checked)

Is this what you had in mind?

Harald

[christoria]

Hello Harry,

Thank you for answering. This is exactly what I wanted to do. I can now write the whole script without making sure my guesses are pretty close.

However, it seems the formula is just a little off. I experimented some and came up with a different way. Check this out:

goto { distance x }

x = distance divided by planet radius

My example: I want to goto 2,000,000 km away. So Mercury would be:
2,000,000 divided by 2440 (Mercury's radius) = 819
x = 819

goto { distance 819 }

Add the decimals for more accurate distance, but this worked perfectly.

Thanks again.

christoria

[don]

Howdy christoria,

Welcome to the forums and to Celestia scripting!

Thank you very much for this easy calculation. I just added it to the scripting guide, which is still being worked on.

Hope all goes well ...

-Don G.

[christoria]

Excellent don,

Glad to help. Without Harry's help, I would not have found it though. I'm finding scripting to be quite the teaching/learning aid. I'll upload what I've done so far if anyone's interested. I've got a "solar system tour" done and a "planet comparison to the sun" about 95% complete.

See ya,

christoria

PS - Trivia question (anyone): How much does Earth weigh?

[Harry]

PS - Trivia question (anyone): How much does Earth weigh?

According to http://seds.lpl.arizona.edu/nineplanets/nineplanets/earth.html:
it has a mass of: 5.972e24 kg

But right now I'm gonna eat a bar of chocalate, and then it will only be

5971999999999999999999999.9 kg



Now weight would probably depend on the suns gravitation, right?

[Added later:] Thinking about it: what is actually the definition of weight? Does the centrifugal (?) force have to be considered (which would make earth weigh nothing)?

Harald

[steffens]

I'll upload what I've done so far if anyone's interested. I've got a "solar system tour" done and a "planet comparison to the sun" about 95% complete.

Yes, please upload everything! I love these scripts, its just nice to sit back and watch celestia at work. Sadly I have not found many real scripts showing off some fancy locations and views yet. So please, everyone, show us your shows .

Thanks for your hard work!
steffens

[jamarsa]

According to http://seds.lpl.arizona.edu/nineplanets ... earth.html:
it has a mass of: 5.972e24 kg

But right now I'm gonna eat a bar of chocalate, and then it will only be

5971999999999999999999999.9 kg

Not true. Applying some Universe Law I heard of, Actually it weights 4 lbs more.

[christoria]

OK, try this one. Let me know how it turns out on your system. I wrote it for mine, which is a little slower than some. Also, let me know if you like it. The facts, I believe, are all correct.


Feel free to change this in any way. Just upload whatever you do. I, too, like to see Celestia just run with it sometimes.

----------------------------------------------------------------------------------

{
# Setup section
timerate { rate 1 }
labels { clear "planets|minorplanets|stars|constellations|spacecraft|asteroids|moons" }
renderflags { set "stars|planets|clouds"
clear "constellations|orbits|galaxies|boundaries" }
print { text "Beginning planet size/distance comparison in 5 seconds. . . Press ESC to end."
row -3
column 5
duration 3 }
set { name "AmbientLightLevel" value 0.4 }
set { name "FOV" value 25.0 }
setvisibilitylimit { magnitude 6.5 }
wait { duration 5 }

# Visit Sun
timerate { rate 1 }
select { object "Sol" }
center { time 10 }
goto { time 10 distance 10 }
follow {}
wait { duration 10 }
print { text "The Sun, our base point for measuring distance. We're at 7 million km away."
row -3
column 5
duration 5 }
wait { duration 5 }
print { text "Let's zoom in to 2 million km - our base number."
row -3
column 5
duration 5 }
select { object "Sol" }
wait { duration 3 }
changedistance { duration 3 rate -0.5 }
wait { duration 5 }
print { text "We'll observe all of the planets from this distance."
row -3
column 5
duration 5 }
wait { duration 5 }

# Mercury
timerate { rate 1 }
select { object "Mercury" }
center { time 10 }
print { text "On to Mercury."
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "Mercury. We are only 17 thousand km away."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "Let's go to 2 million km away, like we just did at the sun."
row -3
column 5
duration 5 }
select { object "Mercury" }
wait { duration 3 }
goto { time 6 distance 819.672 }
# changedistance { duration 3 rate 1.6 }
wait { duration 5 }
print { text "Woah! This is the same distance as from the sun!"
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Venus
timerate { rate 1 }
select { object "Venus" }
center { time 10 }
print { text "Let's check out Venus. Watch Mercury go bye bye."
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "Here we are - now we are 42 thousand km away."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "Let's go to 2 million km away again."
row -3
column 5
duration 5 }
select { object "Venus" }
wait { duration 3 }
goto { time 6 distance 330.469 }
# changedistance { duration 3 rate 1.29 }
wait { duration 5 }
print { text "Almost gone! Small compared to the sun, wouldn't you say?"
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Earth
timerate { rate 1 }
select { object "Earth" }
center { time 10 }
print { text "Now let's go home."
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "Beautiful - at a distance of 44 thousand km away."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "And at 2 milliom km. How many earths can fit inside the sun?"
row -3
column 5
duration 5 }
select { object "Earth" }
wait { duration 3 }
goto { time 6 distance 313.571 }
# changedistance { duration 3 rate 1.28 }
wait { duration 5 }
print { text "At a radius of about 25,000 miles, about a million earths could fit in the sun."
row -3
column 5
duration 5 }
wait { duration 8 }
print { text "A little bit of trivia for you..."
row -3
column 5
duration 4 }
wait { duration 5 }
print { text "Earth weighs about 6,600,000,000,000,000,000,000 (6.6 sextillion) tons."
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Mars
timerate { rate 1 }
select { object "Mars" }
center { time 10 }
print { text "Now we set off to the red planet."
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "Right now we are 23 thousand km away."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "2 million km - shall we?"
row -3
column 5
duration 5 }
select { object "Mars" }
wait { duration 3 }
goto { time 6 distance 588.928 }
# changedistance { duration 3 rate 1.48 }
wait { duration 5 }
print { text "Still not seeing much at this distance."
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Jupiter
timerate { rate 1 }
select { object "Jupiter" }
center { time 10 }
print { text "On to some bigger planets. Much bigger. First is Jupiter."
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "We are 500 thousand km away! Remember Mercury at 17 thousand km?."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "How big will this look at 2 million km? Let's see."
row -3
column 5
duration 5 }
select { object "Jupiter" }
wait { duration 3 }
goto { time 6 distance 27.975 }
# changedistance { duration 3 rate 1.29 }
wait { duration 5 }
print { text "This is much bigger planet. Actually this is the biggest planet!"
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Saturn
timerate { rate 1 }
select { object "Saturn" }
center { time 10 }
print { text "And the planet with the best rings. Saturn."
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "422 thousand km away. What a cool planet!"
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "Could watch this one for a while, but, 2 million km coming up."
row -3
column 5
duration 5 }
select { object "Saturn" }
wait { duration 3 }
goto { time 6 distance 331.785 }
# changedistance { duration 3 rate 1.29 }
wait { duration 5 }
print { text "Still looks cool. And you can see it. Also a big one!"
row -3
column 5
duration 5 }
wait { duration 8 }
print { text "Want some more trivia?"
row -3
column 5
duration 5 }
wait { duration 8 }
print { text "Saturn is the only planet, that if put in water, would float!"
row -3
column 5
duration 5 }
wait { duration 10 }
print { text "Tell me that aint cool. Saturn is cool."
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Uranus
timerate { rate 1 }
select { object "Uranus" }
center { time 10 }
print { text "Now, we chek out Uranus. That's 'your-in-iss'"
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "All blue and everything at 179 thousand km."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "Betcha it stays blue at 2 million km."
row -3
column 5
duration 5 }
select { object "Uranus" }
wait { duration 3 }
goto { time 6 distance 78.25 }
# changedistance { duration 3 rate 1.29 }
wait { duration 5 }
print { text "Still blue. Told ya. Did you notice the planet is sideways?"
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Neptune
timerate { rate 1 }
select { object "Neptune" }
center { time 10 }
print { text "OK. Two to go. Here comes Neptune. Isn't this fun?"
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "173 thousand km. The closest we've started with the gas giants."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "Here we go - 2 million km."
row -3
column 5
duration 5 }
select { object "Neptune" }
wait { duration 3 }
goto { time 6 distance 80.762 }
# changedistance { duration 3 rate 1.29 }
wait { duration 5 }
print { text "Neptune is about 4 times bigger than Earth."
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }

# Pluto
timerate { rate 1 }
select { object "Pluto" }
center { time 10 }
print { text "Lastly, we will go to Pluto. A small one you will see."
row -3
column 5
duration 5 }
goto { time 10 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 10 }
print { text "Only 8 thousand km away. At Mercury, we started at 17 thousand km."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "Say bye. 2 million km coming up."
row -3
column 5
duration 5 }
select { object "Pluto" }
wait { duration 3 }
goto { time 6 distance 1737.619 }
# changedistance { duration 3 rate 1.29 }
wait { duration 5 }
print { text "There you have it. Sun = Huge. Pluto = Where'd it go?"
row -3
column 5
duration 5 }
wait { duration 8 }
timerate { rate 1 }
wait { duration 10 }
print { text "We're done. Planets vary greatly in size."
row -3
column 5
duration 8 }
wait { duration 10 }
print { text "However, none compare to the sun. What a magnificent solar system!"
row -3
column 5
duration 8 }
wait { duration 10 }
timerate { rate 1 }
select { object "Earth" }
center { time 10 }
print { text "Let's head home to end all of this."
row -3
column 5
duration 5 }
goto { time 15 distance 8 }
follow {}
timerate { rate 1 }
wait { duration 16 }
print { text "And here is our planet - Earth. So go home already."
row -4
column 5
duration 5 }
wait { duration 10 }
print { text "You can press -D- to watch it again."
row -3
column 5
duration 8 }
wait { duration 10 }
}

--------------------------------------------------------------------------------

I used a base model script from somewhere here. I modified it a lot though. Someone gets the credit for that much, but I have neglected to account for him/her. Sorry. If you know who, please let me know, so I can give the credit appropriately.

Thank you,

christoria

[don]

Howdy christoria,

WOW! What a fun (and educational) script! I LOVE IT! I loved the trivia and comments too. Very well done christoria! Thank you for sharing it with us.

Some notes, when running on my system (I also do editing on the side, so I included some text edit notes, especially since kids will love this one):

* "The Beginning planet size/distance comparison in 5 seconds. . ." text went bye bye faster than I could read it.

* "We are 500 thousand km away! Remember Mercury at 17 thousand km?." -- You could probably remove the ending period.

* "This is much bigger planet. Actually this is the biggest planet!" -- Maybe add the word "a", "This is a much...".

* "Tell me that aint cool. Saturn is cool." -- Apostrophe for "ain't".

* "Now, we chek out Uranus. That's 'your-in-iss'":
- "chek" to "check"
- 'your-in-iss', maybe 'YOUR-in-iss' to show where the emphasis is?

* "You can press -D- to watch it again." -- Actually, you can only press "D" if you saved your existing demo.cel file and named this script demo.cel.

* For some examples of how you could "spice up" the display of the planets, see Chris' original demo.cel script. He speeds up time, sets Saturn at a wobbling orbit, and some other fun things that might work with your script too.

Excellent work christoria! Keep 'em coming!

-Don G.

[christoria]

Thank you very much don.

Perhaps longer on the intro is a better idea.

I did a lot of copy and paste - hence the question mark with period.

I meant to put the "a" there.

You know, aint aint a word, so how could it be wrong?

"YOUR" right. Emphasis is always a better idea.

I was unaware of the proper "D" function. Like I mentioned, I used a base script and changed it all. Thank you for pointing that out. Is there a way to replay the last played script without reloading it?

I plan on bringing this one to a higher level. Spinning planets, time changes (which I just learned how to do), maybe a comet or two. I've got another one almost ready that tours the solar system - planets and moons. I used the same base script. Come to think of it, I think it was the web page cel script generator I used as a base script.

Thank you,

christoria

[don]

Howdy christoria,

You know, aint aint a word, so how could it be wrong?

Well, ya got me thar, young lady (in my best John Wayne imitation voice).
(Edit: OOOps - christoria is a lad, not a lass - sorry dude! Ya REALLY got me -- Just like Andrea, he's a lad also.)

"YOUR" right. Emphasis is always a better idea.

Just an idea I've seen used in some on-line medical dictionaries I've accessed lately.

I was unaware of the proper "D" function. Like I mentioned, I used a base script and changed it all.

Ahhhh, then if the "D" is left over from the base script, then it was the one that came with Celestia, called demo.cel.

Is there a way to replay the last played script without reloading it?

Not to my knowledge. Good idea for an "Enhancement" though! Bop on over to the Developer forum and post a note so someone (like me) remembers it beyond this message.

In addition to the demo script, there is one other built-in (hardcoded) script used by Celestia: start.cel. This one is run every time you start Celestia. The demo.cel script is run anytime by pressing "d".

I plan on bringing this one to a higher level. Spinning planets, time changes (which I just learned how to do), maybe a comet or two.

KEWEL! Looking forward to seeing it!

I've got another one almost ready that tours the solar system - planets and moons. I used the same base script. Come to think of it, I think it was the web page cel script generator I used as a base script.

I think that one hits every single non-man-made object in the solar system (except maybe the asteroid belt), which would give you a good way to begin a complete tour indeed.

Thank you,

You are quite welcome cristoria. It really is more fun having lots of folks playing with scripting, sharing their scripts, and coming up with good ideas for enhancements.

Happy Scripting...

-Don G.