Celestia Forums

<LOL> Now that we've been sufficiently anal in defining our terms, I'll agree that we're both right. :) Seriously, the distinction between luminosity and magnitude is that luminosity is an absolute, while magnitude (absolute /or/ apparent) is only relative to some other reference star. If you toss m...

A shorter answer is that any work that specifically requires the use of a GPL'd program in order to function is a derivative work and must be GPL'd, unless the owner of the program declares that he will not enforce the GPL with respect to that particular derivative work.

I should probably disclaim that I'm not a copyright lawyer, and this is not legal advice, so don't sue me. :) I do have a clue, tho. Revent, Thanks for your attempt at clarification, which seems to make sense. Unfortunately, it means that many existing Addons probably are illegal. Not really illegal...

We've been through this before: all addons are copyrighted by their authors unless they explicitly state otherwise . That's the law. Wishful thinking won't change it. Many people have put a lot of work into their products and are not about to let anyone else make money off their efforts. If you wan...

Yea, I was looking at his later calculations where he stated that definition of D that way, but was looking at D in the original equation as just distance (though it would still really be D/Do with either equation, so that you get a dimensionless quantity. Dividing by one is pretty simple, tho :) )....

<sighs> I spent about 15 minutes typing a long reply to this, and then lost it because I got disconnected (invalid session). Maybe in a few days I'll re-explain the difference between luminosity and brightness, or a real astronomer will tackle this. The brief version is that root(L/Lo)=D is wrong, a...

The average distance to the moon is 384400 kilometers. A circle of that radius has a circumference of 2415256 kilometers. The diameter of the moon is 3475 kilometers, or 0.001439 of the circumference of the orbit. Thus, the moon should span approximately that proportion of a full circle in the sky,...

I'll get back to you on the eclipse thing ... seems interesting. But planetary temperature wouldn't necessarily plummet - there's a fair old thermal inertia to something the size of a planet, and we don't all freeze to death during the night. :wink: My thermo prof would rap you on the knuckles, Gra...

FYI, as of the current Satellite Boxscore (12/8/03) there are 9231 objects in orbit in the NORAD database. Of those, 2947 are payloads, and 6284 (68%!!!!) are orbital debris. I've been working for several weeks on a SSC that'll list ALL of the objects in the NORAD database, and generate it in such a...

Hank It's been suggested before, but i reckon the best way to find out how many points you need would be to work out the angle between 3 of them. If the angle is greater than (say) one degree, then you need more points to fill in this space. If not, then you can reduce the number of points in this ...

The average distance to the moon is 384400 kilometers. A circle of that radius has a circumference of 2415256 kilometers. The diameter of the moon is 3475 kilometers, or 0.001439 of the circumference of the orbit. Thus, the moon should span approximately that proportion of a full circle in the sky, ...

1) If you look at solarsys.ssc, you'll see something like... "Mercury" "Sol" Change Sol the the name of the star you want the planet to orbit. Also, don;t edit extrasolar.ssc. Put your planet in a new file (whatever.ssc) in the extras directory. 2) "Bob's Moon" "whatever planet/whatever star" 3) It'...

Luminosity and magnitude are not the same thing. Luminosity is the rate at which an object emits energy. Magnitude is a logarithmic scale of how bright an object appears (at one parsec, for absolute magnitude). Not the same thing, not even similar. Luminosity is linear, magnitude is logmarithmic. Fo...

I've been thinking about David Stevenson's paper on Interstellar Planets (see this link for the PDF), and am puzzled by something he says on page 6. Rather than bug him about what may (for all I know) be a very silly question, I thought I'd try asking here first :) He's talking about how some world...

I have an OIG account. It's where Celestrak gets their TLEs.
http://oig1.gsfc.nasa.gov/
You can get historical tles from 'Jonathon's Space Report' here...
http://host.planet4589.org/space/

Er, that's not right, then (I gave the TLE, but didn't install it). That's what happens when you use a TLE from the wrong epoch, I guess. An orbit that low would be essentially IN the atmosphere, and not at all stable. When Skylab was operational, it was in a 268.1x269.5 mile (431.5x433.7 km) orbit,...

It'd be nice if this feature worked for other types of objects. It'd make it possible to list and search for satellites by common name, SCC, and COSPAR (i.e Hipparcos, 20169, 1989-062B), it'd let you use any of the names of a moon or minor planet, (i.e. Adrastea, 2002J1, or Jupiter XXXII, which are ...

Hipparcos
1 20169U 89062B 03328.20883033 -.00000035 +00000-0 +32591-3 0 07738
2 20169 006.8009 273.1479 7202398 179.9484 180.6437 02.25908999082865

03328 was Monday, FYI. That's the most recent TLE NORAD has generated.

Enjoy!

Even with current elements, pass predictions with Celestia will never be as accurate as with SatTrak or some other specialized program. It's because the NORAD TLEs are really designed for and meant to be used with a specific algorithm, the 'SGP4 model', that most satellite prediction programs use bu...

Shrox's Skylab add-on is in the extras dir on CVS, but without the correct orbital elements (as he notes in the file). Here they are, with launch and deorbit dates. SKYLAB 1 Launched: 1973/05/14 Decayed: 1979/07/11 1 06633U 73027 A 79185.88914720 .01109374 +00000-0 +00000-0 0 00194 2 06633 050.0279 ...