Hello all,

First of all, my best wishes to all of you. And to the developers of 
PovRay: keep up the good work; we're all grateful for the job you're doing.

My 5-year old son is very interested and intrigued by the interplay of 
the sun/earth/moon and how this creates day, night, seasons, ... Also 
the mechanism of a solar and lunar eclipse (who is casting a shadown on 
who) has caught his attention.

Since I lack a mechanical model of this three body system (I remember we 
had this in our geography classroom when I was in secondary school: you 
could turn a handle and then by means of gears the bodies would rotate 
and move), I was planning to do some animations with PovRay.

I don't want to re-invent the wheel, hence my question: is there anybody 
here who has done something similar with PovRay? I would like to end up 
with a small number of input files (or a single one) for which the clock 
variable would both make the bodies rotate and move the camera to show 
the different aspects (night/day, eclipse,...). Do you know of a site or 
reference work where I could get approximate data (good enough for this 
purpose of an educational animation) for the astronomy data?

Thanks for your tips!

bye,
gert

Post a reply to this message

You might want to try Celestia, a real-time planetarium program. 
Certainly, you can do the same things in POV-Ray, but there are several 
caveats:

1) POV-Ray is not a real-time program. You can't preview changes or 
interact with the scene in real-time. The best you can do is render 
individual frames to create a movie--which can be a time consuming 
process, and you'll have to start the process over from the beginning 
each time you make a mistake.
2) POV-Ray can suffer from floating point/rounding errors when the 
objects get too large and/or too distant.
3) POV-Ray takes a long time to master, in general; and creating scenes 
is usually a laborious process.

You could also try GeoGebra, which is a real-time dynamic geometry 
software. You could create representations of the planets as well as the 
shadows they cast on other bodies using geometric objects. This program 
is limited, however, to two dimensions.

Hope that helps.

-Mike

gvdeynde wrote:
> Hello all,
> 
> First of all, my best wishes to all of you. And to the developers of 
> PovRay: keep up the good work; we're all grateful for the job you're doing.
> 
> My 5-year old son is very interested and intrigued by the interplay of 
> the sun/earth/moon and how this creates day, night, seasons, ... Also 
> the mechanism of a solar and lunar eclipse (who is casting a shadown on 
> who) has caught his attention.
> 
> Since I lack a mechanical model of this three body system (I remember we 
> had this in our geography classroom when I was in secondary school: you 
> could turn a handle and then by means of gears the bodies would rotate 
> and move), I was planning to do some animations with PovRay.
> 
> I don't want to re-invent the wheel, hence my question: is there anybody 
> here who has done something similar with PovRay? I would like to end up 
> with a small number of input files (or a single one) for which the clock 
> variable would both make the bodies rotate and move the camera to show 
> the different aspects (night/day, eclipse,...). Do you know of a site or 
> reference work where I could get approximate data (good enough for this 
> purpose of an educational animation) for the astronomy data?
> 
> Thanks for your tips!
> 
> bye,
> gert
> 
>

Post a reply to this message

Hi Mike,

Thanks for the info. I've tried Celestia but thought it might be too 
complex for my son.

Concerning PovRay: I have some experience already (I'm playing with it 
since version 2 or so, have modeled our house in it, did some artwork 
for some websites I made, etc). So I think I can come up with something, 
I was just wondering if somebody already did something close to this and 
I could work further based on that...

I'll have a look at Geogebra...

thanks again,
gert

On 2009-01-06 14:33, SharkD wrote:
> You might want to try Celestia, a real-time planetarium program. 
> Certainly, you can do the same things in POV-Ray, but there are several 
> caveats:
> 
> 1) POV-Ray is not a real-time program. You can't preview changes or 
> interact with the scene in real-time. The best you can do is render 
> individual frames to create a movie--which can be a time consuming 
> process, and you'll have to start the process over from the beginning 
> each time you make a mistake.
> 2) POV-Ray can suffer from floating point/rounding errors when the 
> objects get too large and/or too distant.
> 3) POV-Ray takes a long time to master, in general; and creating scenes 
> is usually a laborious process.
> 
> You could also try GeoGebra, which is a real-time dynamic geometry 
> software. You could create representations of the planets as well as the 
> shadows they cast on other bodies using geometric objects. This program 
> is limited, however, to two dimensions.
> 
> Hope that helps.
> 
> -Mike
> 
> gvdeynde wrote:
>> Hello all,
>>
>> First of all, my best wishes to all of you. And to the developers of 
>> PovRay: keep up the good work; we're all grateful for the job you're 
>> doing.
>>
>> My 5-year old son is very interested and intrigued by the interplay of 
>> the sun/earth/moon and how this creates day, night, seasons, ... Also 
>> the mechanism of a solar and lunar eclipse (who is casting a shadown 
>> on who) has caught his attention.
>>
>> Since I lack a mechanical model of this three body system (I remember 
>> we had this in our geography classroom when I was in secondary school: 
>> you could turn a handle and then by means of gears the bodies would 
>> rotate and move), I was planning to do some animations with PovRay.
>>
>> I don't want to re-invent the wheel, hence my question: is there 
>> anybody here who has done something similar with PovRay? I would like 
>> to end up with a small number of input files (or a single one) for 
>> which the clock variable would both make the bodies rotate and move 
>> the camera to show the different aspects (night/day, eclipse,...). Do 
>> you know of a site or reference work where I could get approximate 
>> data (good enough for this purpose of an educational animation) for 
>> the astronomy data?
>>
>> Thanks for your tips!
>>
>> bye,
>> gert
>>
>>

Post a reply to this message

This may not help much, but here goes...

I wanted to do something similar but not for the Earth/Moon/Sun system. 
  It was for a science fiction story I was working on that takes place 
on a planet that orbits a star 20 lightyears away.  This is actually a 
binary planet where two approximately equal mass planets orbit each 
other (or around the center of mass of the two planets) and both orbit 
the star.  The two planets are tidally locked to each other.  I wanted 
to discover the dynamics of this world.

I wrote a simple model in POVRay and created an animation that captured 
one frame per hour for one year (143 Earth days) and clearly showed the 
geometry and timing of eclipses.

Notes:
	- as was mentioned, you have to be careful about scale
	- I didn't try modeling the elliptical nature of orbits - all orbits 
are simple circles
	- since I'm creating the world as a work of fiction, I have some  room 
to adjust the parameters to my suiting.

I can make this model available to you if you wish.  It could be 
adjusted to give an "impression" of the Earth/Moon system but couldn't 
be used to give accurate predictions of eclipses, etc.

David Buck

gvdeynde wrote:
> Hi Mike,
> 
> Thanks for the info. I've tried Celestia but thought it might be too 
> complex for my son.
> 
> Concerning PovRay: I have some experience already (I'm playing with it 
> since version 2 or so, have modeled our house in it, did some artwork 
> for some websites I made, etc). So I think I can come up with something, 
> I was just wondering if somebody already did something close to this and 
> I could work further based on that...
> 
> I'll have a look at Geogebra...
> 
> thanks again,
> gert
> 
> On 2009-01-06 14:33, SharkD wrote:
>> You might want to try Celestia, a real-time planetarium program. 
>> Certainly, you can do the same things in POV-Ray, but there are 
>> several caveats:
>>
>> 1) POV-Ray is not a real-time program. You can't preview changes or 
>> interact with the scene in real-time. The best you can do is render 
>> individual frames to create a movie--which can be a time consuming 
>> process, and you'll have to start the process over from the beginning 
>> each time you make a mistake.
>> 2) POV-Ray can suffer from floating point/rounding errors when the 
>> objects get too large and/or too distant.
>> 3) POV-Ray takes a long time to master, in general; and creating 
>> scenes is usually a laborious process.
>>
>> You could also try GeoGebra, which is a real-time dynamic geometry 
>> software. You could create representations of the planets as well as 
>> the shadows they cast on other bodies using geometric objects. This 
>> program is limited, however, to two dimensions.
>>
>> Hope that helps.
>>
>> -Mike
>>
>> gvdeynde wrote:
>>> Hello all,
>>>
>>> First of all, my best wishes to all of you. And to the developers of 
>>> PovRay: keep up the good work; we're all grateful for the job you're 
>>> doing.
>>>
>>> My 5-year old son is very interested and intrigued by the interplay 
>>> of the sun/earth/moon and how this creates day, night, seasons, ... 
>>> Also the mechanism of a solar and lunar eclipse (who is casting a 
>>> shadown on who) has caught his attention.
>>>
>>> Since I lack a mechanical model of this three body system (I remember 
>>> we had this in our geography classroom when I was in secondary 
>>> school: you could turn a handle and then by means of gears the bodies 
>>> would rotate and move), I was planning to do some animations with 
>>> PovRay.
>>>
>>> I don't want to re-invent the wheel, hence my question: is there 
>>> anybody here who has done something similar with PovRay? I would like 
>>> to end up with a small number of input files (or a single one) for 
>>> which the clock variable would both make the bodies rotate and move 
>>> the camera to show the different aspects (night/day, eclipse,...). Do 
>>> you know of a site or reference work where I could get approximate 
>>> data (good enough for this purpose of an educational animation) for 
>>> the astronomy data?
>>>
>>> Thanks for your tips!
>>>
>>> bye,
>>> gert
>>>
>>>

Post a reply to this message

David Buck <dav### [at] simberoncom> wrote:
>   It was for a science fiction story I was working on that takes place
> on a planet that orbits a star 20 lightyears away.  This is actually a
> binary planet where two approximately equal mass planets orbit each
> other (or around the center of mass of the two planets) and both orbit
> the star.  The two planets are tidally locked to each other.  I wanted
> to discover the dynamics of this world.

Out of curiosity: Would such a system actually be stable in reality?

Post a reply to this message

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Hash: SHA1

clipka wrote:
> David Buck <dav### [at] simberoncom> wrote:
>>   It was for a science fiction story I was working on that takes place
>> on a planet that orbits a star 20 lightyears away.  This is actually a
>> binary planet where two approximately equal mass planets orbit each
>> other (or around the center of mass of the two planets) and both orbit
>> the star.  The two planets are tidally locked to each other.  I wanted
>> to discover the dynamics of this world.
> 
> Out of curiosity: Would such a system actually be stable in reality?
> 
	It is: look at the Pluto-Charo pair of planets (planetoids?) in the
solar system.

		Jerome

PS: Of course, Pluto and Charo aren't 20 ligth-years away from their
sun, but that's probably just me being obtuse ;)

- --
mailto:jeb### [at] freefr
http://jeberger.free.fr
Jabber: jeb### [at] jabberfr
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Post a reply to this message

On Wed, 07 Jan 2009 09:51:15 +0100, gvdeynde <gvd### [at] gmailcom> wrote:

>I was just wondering if somebody already did something close to this and 
>I could work further based on that...


Hi Gert,
Out of interest I started to model an Earth Moon Sun system in a modeller and
quickly found that it not really easy to see what is happening when you use
proper scaling. For a five year old I assume that a non realistic model would
do.
Using a modeller you can show how the moon moves round the earth before
rendering. The modeller I used is Bishop3D and as it is in Beta it is free
http://www.bishop3d.com/ 
 
http://uk.youtube.com/watch?v=wsh6l7KpMEg

OK I know that the Earth should be moving but it is just a demonstration of a
shadow :)

-- 

Regards
     Stephen

Post a reply to this message

clipka wrote:
> David Buck <dav### [at] simberoncom> wrote:
>>   It was for a science fiction story I was working on that takes place
>> on a planet that orbits a star 20 lightyears away.  This is actually a
>> binary planet where two approximately equal mass planets orbit each
>> other (or around the center of mass of the two planets) and both orbit
>> the star.  The two planets are tidally locked to each other.  I wanted
>> to discover the dynamics of this world.
> 
> Out of curiosity: Would such a system actually be stable in reality?
> 
> 
> 

You need to have the two planets separated more than the Roche Limit 
otherwise the tidal forces will tear them apart.  In this case, they are 
about 10x the Roche Limit.  Within that range, it should be fine over 
long periods of time (billions of years) but I haven't done the 
simulations to verify that.

David Buck

Post a reply to this message

Jérôme M. Berger nous illumina en ce 2009-01-07 15:13 -->
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> clipka wrote:
>> David Buck <dav### [at] simberoncom> wrote:
>>>   It was for a science fiction story I was working on that takes place
>>> on a planet that orbits a star 20 lightyears away.  This is actually a
>>> binary planet where two approximately equal mass planets orbit each
>>> other (or around the center of mass of the two planets) and both orbit
>>> the star.  The two planets are tidally locked to each other.  I wanted
>>> to discover the dynamics of this world.
>> Out of curiosity: Would such a system actually be stable in reality?
>>
> 	It is: look at the Pluto-Charo pair of planets (planetoids?) in the
> solar system.
> 
> 		Jerome
> 
> PS: Of course, Pluto and Charo aren't 20 ligth-years away from their
> sun, but that's probably just me being obtuse ;)
> 
> 
It's 20 lightyears away from HERE.

A planet orbiting it's sun at a 20 lightyears radius would need to have an 
extra-galactic sun, or get snatched away by nearby stars. Such a planet would 
also be frozen solid, with, maybe, sone seas of liguid hydrogen and helium. It's 
"year" would last several 100's of millenias.


-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when your source files are starting to 
get bigger than the image files.
     -- Matt

Post a reply to this message

David Buck wrote:

> You need to have the two planets separated more than the Roche Limit 
> otherwise the tidal forces will tear them apart.  In this case, they are 
> about 10x the Roche Limit.  Within that range, it should be fine over 
> long periods of time (billions of years) but I haven't done the 
> simulations to verify that.
> 
> David Buck

Based on my undergraduate level physics education, I would say the other stability
limit is that the separation of the two planets should be substantially less than the
separation of the center of mass from the star.

Stability issues primarily occur with 3-body systems: they have a habit of ejecting
one of their members.  So as long as the system is a 2-body system, where one of these
bodies is itself a 2-body system, you're okay.

Dan

Post a reply to this message

Alain wrote:
> Jérôme M. Berger nous illumina en ce 2009-01-07 15:13 -->
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> clipka wrote:
>>> David Buck <dav### [at] simberoncom> wrote:
>>>>   It was for a science fiction story I was working on that takes place
>>>> on a planet that orbits a star 20 lightyears away.  This is actually a
>>>> binary planet where two approximately equal mass planets orbit each
>>>> other (or around the center of mass of the two planets) and both orbit
>>>> the star.  The two planets are tidally locked to each other.  I wanted
>>>> to discover the dynamics of this world.
>>> Out of curiosity: Would such a system actually be stable in reality?
>>>
>>     It is: look at the Pluto-Charo pair of planets (planetoids?) in the
>> solar system.
>>
>>         Jerome
>>
>> PS: Of course, Pluto and Charo aren't 20 ligth-years away from their
>> sun, but that's probably just me being obtuse ;)
>>
>>
> It's 20 lightyears away from HERE.
> 
> A planet orbiting it's sun at a 20 lightyears radius would need to have 
> an extra-galactic sun, or get snatched away by nearby stars. Such a 
> planet would also be frozen solid, with, maybe, sone seas of liguid 
> hydrogen and helium. It's "year" would last several 100's of millenias.
> 
> 


Um, yea :-).

The star (Delta Pavonis) is about 20 lightyears from our Sun.  I don't 
think a planet could orbit a star at a distance of 20 light years.  The 
planets orbit their sun at a distance of 93.5 million km and the two 
planets are about 47,000 km apart from each other and rotating 19.7 
degrees off the ecliptic.  The Roche Limit is about 5900 km so they 
won't tear each other apart.   The binary planets have a 33.6 hour day 
and a year of 182 Earth days or 130 planet days.  Acceleration due to 
gravity is 7.2 m/s^2 (compared to 9.8 m/s^2 on Earth).  If you're on one 
planet, the other appears fixed permanently in the sky and is just over 
13.6 times the size of the Earth's moon in the sky. Every year, there 
are two periods (one in the spring and one in the fall) when the two 
planets eclipse each other for several days in a row.

(Ok, I'm a geek :-)  )

Back to the IRTC software.

David Buck

Post a reply to this message

David Buck wrote:

> Um, yea :-).
> 
> The star (Delta Pavonis) is about 20 lightyears from our Sun.  I don't 
> think a planet could orbit a star at a distance of 20 light years.

v^2/r = Mg/r^2 relates orbital speed to distance and solar mass.  v = 2 pi r / tau,
where tau is the orbital period, so 4 pi^2 r / tau^2 = M g / r^2 =>

tau = 2 pi * sqrt(r^3 / M g)

The Earth's orbital radius is 1.58e-5 light years.  20 light years is a factor 1.26e6
larger.  For comparable solar mass, this would yield an orbital period of 1.4 billion
years.  The age of the universe is 13.7 billion years.  So classically there's been
time for at least a few such orbits...

The problem is there could be no massive objects of comparable mass to the star within
the neighborhood defined by the length scale of the orbital radius, for example within
100 light years, or the orbit wouldn't be stable.

Dan

Post a reply to this message

gvdeynde <gvd### [at] gmailcom> wrote:Do you know of a site or
> reference work where I could get approximate data (good enough for this
> purpose of an educational animation) for the astronomy data?

It's good for a lot more than rough approximations, but to the best of my
knowledge, ephemeris data is the definitive source:

http://eclipse.gsfc.nasa.gov/TYPE/TYPE.html

You might try searching for interactive simulations too.  I know I've seen
models you can fly around in before, but I can't remember the name.

 - Ricky

Post a reply to this message

Hi all,

Thanks to all for your input.

David, yes, if you don't mind, I would like to have a look at your code.

Stephen, great simulation. Any chance of sending me the Bishop3d 
file/PovRay file?

all the best,
gert

Post a reply to this message

On Thu, 08 Jan 2009 09:36:04 +0100, gvdeynde <gvd### [at] gmailcom> wrote:

>
>Stephen, great simulation. Any chance of sending me the Bishop3d 
>file/PovRay file?

I'll just have to cut down the sizes of the image maps, they total about 6 megs.
The Bishop3D file is only 2K, zipped.
-- 

Regards
     Stephen

Post a reply to this message

gvdeynde wrote:
> Hi all,
> 
> Thanks to all for your input.
> 
> David, yes, if you don't mind, I would like to have a look at your code.
> 
> Stephen, great simulation. Any chance of sending me the Bishop3d 
> file/PovRay file?
> 
> all the best,
> gert
> 
> 

See the article "Delta Pavonis Celestial Mechanics" in 
povray.binaries.scene-files.

David Buck

Post a reply to this message

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Alain wrote:
> Jérôme M. Berger nous illumina en ce 2009-01-07 15:13 -->
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> clipka wrote:
>>> David Buck <dav### [at] simberoncom> wrote:
>>>>   It was for a science fiction story I was working on that takes place
>>>> on a planet that orbits a star 20 lightyears away.  This is actually a
>>>> binary planet where two approximately equal mass planets orbit each
>>>> other (or around the center of mass of the two planets) and both orbit
>>>> the star.  The two planets are tidally locked to each other.  I wanted
>>>> to discover the dynamics of this world.
>>> Out of curiosity: Would such a system actually be stable in reality?
>>>
>>     It is: look at the Pluto-Charo pair of planets (planetoids?) in the
>> solar system.
>>
>>         Jerome
>>
>> PS: Of course, Pluto and Charo aren't 20 ligth-years away from their
>> sun, but that's probably just me being obtuse ;)
>>
>>
> It's 20 lightyears away from HERE.
> 
	I know that's what he *meant*, hence the smiley and the second part
of my sentence, but that's not what he *wrote*...

		Jerome
- --
mailto:jeb### [at] freefr
http://jeberger.free.fr
Jabber: jeb### [at] jabberfr
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Post a reply to this message

On Thu, 08 Jan 2009 09:50:45 +0000, Stephen <mcavoysAT@aolDOTcom> wrote:

>On Thu, 08 Jan 2009 09:36:04 +0100, gvdeynde <gvd### [at] gmailcom> wrote:
>
>>
>>Stephen, great simulation. Any chance of sending me the Bishop3d 
>>file/PovRay file?
>
>I'll just have to cut down the sizes of the image maps, they total about 6 megs.
>The Bishop3D file is only 2K, zipped.

Bishop3D file
http://www.geocities.com/mcavoys/Bishop3D/Earth02K_4.zip

Image maps for B3D file.
http://www.geocities.com/mcavoys/Bishop3D/Maps.zip

If you unzip both files into the same directory and add that directory to the
PovRay library path it should work (I tested them) Any problems just ask either
here of at the Bishop3D forums
-- 

Regards
     Stephen

Post a reply to this message

Stephen nous illumina en ce 2009-01-08 15:05 -->
> On Thu, 08 Jan 2009 09:50:45 +0000, Stephen <mcavoysAT@aolDOTcom> wrote:
> 
>> On Thu, 08 Jan 2009 09:36:04 +0100, gvdeynde <gvd### [at] gmailcom> wrote:
>>
>>> Stephen, great simulation. Any chance of sending me the Bishop3d 
>>> file/PovRay file?
>> I'll just have to cut down the sizes of the image maps, they total about 6 megs.
>> The Bishop3D file is only 2K, zipped.
> 
> Bishop3D file
> http://www.geocities.com/mcavoys/Bishop3D/Earth02K_4.zip
> 
> Image maps for B3D file.
> http://www.geocities.com/mcavoys/Bishop3D/Maps.zip
> 
> If you unzip both files into the same directory and add that directory to the
> PovRay library path it should work (I tested them) Any problems just ask either
> here of at the Bishop3D forums
Just unzip in a sub-folder of the POV scene folder. No need to add any new path 
this way.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you have ever brought your 
computer to its knees by mistakenly launching 64 simultaneous frames to be 
traced, while trying to maximizing the benefits of parallelizing them.
Carsten Whimster

Post a reply to this message

Among other things, triple_r saw fit to write:

> You might try searching for interactive simulations too.  I know I've seen
> models you can fly around in before, but I can't remember the name.

Slightly off topic...

Has anyone seen a picture (ideally a photograph) of how a lunar eclipse
looks from the Moon (from there, it would be a solar eclipse). In total
lunar eclipses the Moon usually gets a reddish tint, apparently from
sunset-like light all around the Earth (as seen from the Moon), I'd like to
see this.

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

Post a reply to this message

Jellby wrote:

> Has anyone seen a picture (ideally a photograph) of how a lunar eclipse
> looks from the Moon (from there, it would be a solar eclipse).

I think the last camera on the moon itself was actually
with Lunochod 2 spending 5 months there in 1973, and the
images doesn't seem to be easily available (not sure if
they even had color).

So any photo would probably be taken from orbit by more
recent missions such as SMART-1, Kaguya or Chang'e-1. Being
solar powered and all that they may well have been in power
saving mode during lunar eclipes though ;)

By the way, googling for Lunochod, I arrived
at the following russian moon page:

   http://selena.sai.msu.ru/Home/Moon.htm

It contains an animation which looks distinctly POV-ish ;)

   http://selena.sai.msu.ru/Home/svechka.gif

Post a reply to this message

Jellby <me### [at] privacynet> wrote:
> Has anyone seen a picture (ideally a photograph) of how a lunar eclipse
> looks from the Moon (from there, it would be a solar eclipse). In total
> lunar eclipses the Moon usually gets a reddish tint, apparently from
> sunset-like light all around the Earth (as seen from the Moon), I'd like to
> see this.

I doubt whether a photograph of such an event exists:

- To date, manned missions to the moon (i.e. Apollo 8 and 10-17) have never been
carried out during lunar eclipses, and to all my knowledge, traversal of earth
shadow during Apollo missions has only occurred in earth orbit; other manned
missions have never even come close to similar distances from earth.

- To date, only very few sattelites have carried photographic film cameras
onboard, and those that did probably never left earth orbit (problem of
retrieval of the exposed film material).

- Satellites leaving earth orbit often had much farther destinations, requiring
trajectories optimized for efficiency, with not much room for the beauty of
lunar eclipses.

- Although some satellites have been deliberately "parked" on the "shadow" side
of earth at the so-called "Lagrangian Point 2" (one of 5 points at which
satellitest can be kept at a stable position relative to earth and sun with
very little effort), this point is at five times the distance of the moon. As
it happens, this is about the distance at which the sun starts to appear bigger
than the earth, probably spoiling the whole effect.

- As for any satellites that might have more or less "accidentally" happened to
cross the earth's shadow at a fitting distance, pointing any optical cameras
towards earth (and sun) during that time would have posed the danger of failing
to turn them away again in time, putting the equipment at high risk of damage.


So probably the only thing we can do to enjoy the beauty of such a sight is to
do what we're best at anyway: Fire up our imagination and inventiveness, and
then fire up POV-Ray.

(BTW, If done right, I guess this could make a tremendous scene for that
planetarium showreel project...)

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"Jellby" <me### [at] privacynet> schreef in bericht 
news:c5e### [at] badulaqueunexes...
> Has anyone seen a picture (ideally a photograph) of how a lunar eclipse
> looks from the Moon (from there, it would be a solar eclipse). In total
> lunar eclipses the Moon usually gets a reddish tint, apparently from
> sunset-like light all around the Earth (as seen from the Moon), I'd like 
> to
> see this.
>

There is a subject for an awesome POV-Ray scene.... As said already by 
others, I don't think there are any photographs available.

Who takes up the gauntlet?  :-)

Thomas

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"Thomas de Groot" <tDOTdegroot@interDOTnlANOTHERDOTnet> wrote:
> There is a subject for an awesome POV-Ray scene.... As said already by
> others, I don't think there are any photographs available.
>
> Who takes up the gauntlet?  :-)

I would if I had the time these days: That earth model I used in the "Not!" shot
still needs a bit of polish anyway, improving the atmosphere colors,
realistically modelling the IOR gradient and all.

My fingers are itching like hell to jump on this, actually. If I wasn't working
on radiosity code these days, that's what I'd spend the nights on: Lunar
eclipse as seen from the moon... astronauts and all included! Digging up that
half-finished Apollo spacesuit model again, polishing up the finished Apollo
Lunar Module... ah, what better setting to revive the heroes of my childhood!


Vade! Tempt me not, if you want the radiosity code to come to completion any
time soon...!

(... Man, you're lucky that realistic lunar scenes *need* radiosity, with all
that indirect light reflecting from the moon's surface...)

Post a reply to this message

"clipka" <nomail@nomail> schreef in bericht 
news:web.496b1d304590b7f02c9ab000@news.povray.org...
> "Thomas de Groot" <tDOTdegroot@interDOTnlANOTHERDOTnet> wrote:
>> Who takes up the gauntlet?  :-)
>
> I would if I had the time these days: That earth model I used in the 
> "Not!" shot
> still needs a bit of polish anyway, improving the atmosphere colors,
> realistically modelling the IOR gradient and all.
>
> My fingers are itching like hell to jump on this, actually. If I wasn't 
> working
> on radiosity code these days, that's what I'd spend the nights on: Lunar
> eclipse as seen from the moon... astronauts and all included! Digging up 
> that
> half-finished Apollo spacesuit model again, polishing up the finished 
> Apollo
> Lunar Module... ah, what better setting to revive the heroes of my 
> childhood!
>
>
> Vade! Tempt me not, if you want the radiosity code to come to completion 
> any
> time soon...!
>
> (... Man, you're lucky that realistic lunar scenes *need* radiosity, with 
> all
> that indirect light reflecting from the moon's surface...)
>

[Satanas retreats a few steps, grinning]

Well, there is an incentive for you... :-)

Thomas

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"Thomas de Groot" <tDOTdegroot@interDOTnlANOTHERDOTnet> wrote in message 
news:496b0649$1@news.povray.org...
>
> "Jellby" <me### [at] privacynet> schreef in bericht 
> news:c5e### [at] badulaqueunexes...
>> Has anyone seen a picture (ideally a photograph) of how a lunar eclipse
>> looks from the Moon (from there, it would be a solar eclipse). In total
>> lunar eclipses the Moon usually gets a reddish tint, apparently from
>> sunset-like light all around the Earth (as seen from the Moon), I'd like to
>> see this.
>>
>
> There is a subject for an awesome POV-Ray scene.... As said already by others, 
> I don't think there are any photographs available.
>

Actually, Surveyor II took a picture of a solar eclipse from the moon.
Images were retrieved by Apollo 12 crew who also snapped a nice picture
in space (not on the moon's surface).

There is a page with good math data at 
http://star-www.st-and.ac.uk/~awc/eclipse.html
(part 2).

Theory says the earth will be quite a sight as earthshine will center an
image of a planet surrounded by all the world's sunsets at the same time.

Post a reply to this message

"pan" <pan### [at] syixcom> wrote:
> Actually, Surveyor II took a picture of a solar eclipse from the moon.
> Images were retrieved by Apollo 12 crew who also snapped a nice picture
> in space (not on the moon's surface).

Hum - I forgot about the Surveyor probe indeed (it was Surveyor 3 though, not
2). That would have been a chance to get some nice shots of a "lunar solar
eclipse".

Unfortunately, you are a bit misinformed: Apollo 12 did not retrieve any
photographic images from the probe, neither did the probe carry any
photographic camera in the first place. It had been sitting around on lunar
soil for three years already, and when it had been built, probably nobody had
expected a manned mission to land anywhere close. So all the Apollo 12 crew
took home was some parts of the probe, probably to examine some problems
experienced (including the TV camera) and learn some lessons from it.

The eclipse shot from Surveyor 3 is actually a very bad black-and-white shot,
that had been transmitted years earlier already, and - as the beautiful Apollo
12 shot indicates - does the event no justice whatsoever.

The Apollo 12 shot, on the other hand, was taken comparatively close to earth,
so it, too, can only hint at how it might look in reality from the moon.

Post a reply to this message

[sorry! 1st emailed instead of reply here. Out of practice using 
newsgroups.]

I had made a few attempts to show the solar system or parts of it in POV-Ray
over the years. As I read others saying here, scale modeling and getting
the view right can be trouble... for me anyhow.

When I first read your post last week I was going to look for what I might
have done before but decided to start fresh again. Idea this time being to
create an "orrery" of various scales fit together into one scene file. Not
sure I succeeded but I'm posting it anyway at povray.binaries.scene-files,
less the image maps since you could easily replace them with textures or
images found online. Low resolutions okay and faster to render, I down-sized
mine to 720X360 from hi-res ones I already had.
(example: earth-map.jpg, jupiter-map.jpg)

While going to post this I saw David Buck's fictional scene at p.b.s-f. I
realize now my try at it might seem confusing at first, too. heh-heh-heh.
:^)  Since the topic of atmosphere during eclipses was brought up as I
returned to read here while refining the orrery I tried adding that without
success. Poorly done so ignoring that part might be best-- unless someone
wants to fix it.

I can't be certain I got all the elements of the orbits right, I fumbled
with the sizes and angles until it looked like the animations kept the
correct orbital inclinations; and all along writing the file out in such a
way that made sense to me yet not sure it will to everyone else. No doubt
better methods or implementations exist than what I chose.

Again, it's being posted at povray.binaries.scene-files, under the name
"solar system orrery ver1", since the text line-wrap would be a disaster if
posted here.

Bob

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Among other things, clipka saw fit to write:

> My fingers are itching like hell to jump on this, actually. If I wasn't
> working on radiosity code these days, that's what I'd spend the nights on:
> Lunar eclipse as seen from the moon... astronauts and all included!
> Digging up that half-finished Apollo spacesuit model again, polishing up
> the finished Apollo Lunar Module... ah, what better setting to revive the
> heroes of my childhood!

I've been wondering about this lunar-eclipse-from-the-moon image for some
years, so I'm looking forward to whatever you can get :)

P.S. I'm also glad this raised some interest. Another thing I've been
thinking about for years is how cool a "bird flight simulator" would be.
Think of it, instead of controlling a plane you'd control a bird, the wing
flapping frequency, the tail... there would be different kinds of birds and
different "missions" (a migration with a duck, capturing a pigeon with a
hawk...) And the scenery could be anything from a city full of buildings to
a garden with flowers (for a hummingbird)... and rendered with POV-Ray :D

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

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Alain <ele### [at] netscapenet> wrote:
> >
> It's 20 lightyears away from HERE.
>
> A planet orbiting it's sun at a 20 lightyears radius would need to have an
> extra-galactic sun, or get snatched away by nearby stars. Such a planet would
> also be frozen solid, with, maybe, sone seas of liguid hydrogen and helium. It's
> "year" would last several 100's of millenias.
>

Just for fun, I made the calculation for a star with the same mass as the sun:
following Kepler's thrid law the planet would orbit the star once every 1.4
billion years at a speed of 26 m/s (95 km/h), which IMO is still surprisingly
fast, about 1/1000 of the speed of earth.
Like you said it would have to be a solitary star, but that shouldn't be a
problem, there's a lot of space out there. Pun intended :-)

Post a reply to this message

stevenvh nous illumina en ce 2009-02-05 08:33 -->
> Alain <ele### [at] netscapenet> wrote:
>> It's 20 lightyears away from HERE.
>>
>> A planet orbiting it's sun at a 20 lightyears radius would need to have an
>> extra-galactic sun, or get snatched away by nearby stars. Such a planet would
>> also be frozen solid, with, maybe, sone seas of liguid hydrogen and helium. It's
>> "year" would last several 100's of millenias.
>>
> 
> Just for fun, I made the calculation for a star with the same mass as the sun:
> following Kepler's thrid law the planet would orbit the star once every 1.4
> billion years at a speed of 26 m/s (95 km/h), which IMO is still surprisingly
> fast, about 1/1000 of the speed of earth.
> Like you said it would have to be a solitary star, but that shouldn't be a
> problem, there's a lot of space out there. Pun intended :-)
> 
> 
> 
As I sayd, 100's of millenias. 1.4 billions years is 1400 millenias.

You said "lots of space" out there... You bet! Over all, the galaxys "use" less 
than 1% of the "space".

-- 
Alain
-------------------------------------------------
Agnostic: Shit might have happened; then again, maybe not.

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