Star maps.

[dr-spangle]

Here is the list of the star maps, Eventually there will be a MAS area of the site for this stuff, but I lost a lot of data since I started work on the MAS site so I'm going to start again...

Rectangular star map:
http://micras.org/maps/star_map.png

Rectangular star coordinates:
http://micras.org/maps/star_coords.txt

North polar star map:
http://micras.org/maps/north_polar_stars.png

South polar star map:
http://micras.org/maps/north_polar_stars.png

[Scott Alexander]

Any chance you could vary the magnitudes a little more? Most uses for this I can imagine would mostly involve a few very bright stars, but it's very hard to determine which ones that would be on these maps.

EDIT: Or does the third coordinate express the magnitude? If so, I think you should switch from a linear scale to a logarithmic scale. Real magnitude works something like each level being three times as dim as the one before it, so there's a several hundred fold difference between the brightest and dimmest visible stars that's just not reflected there.

[Orion]

Spangle: Thank you!

[dr-spangle]

Any chance you could vary the magnitudes a little more? Most uses for this I can imagine would mostly involve a few very bright stars, but it's very hard to determine which ones that would be on these maps.

EDIT: Or does the third coordinate express the magnitude? If so, I think you should switch from a linear scale to a logarithmic scale. Real magnitude works something like each level being three times as dim as the one before it, so there's a several hundred fold difference between the brightest and dimmest visible stars that's just not reflected there.

It would have been nice if you had raised this issue back when i first released the map, but it's fine, we can make edits to the coords file and the others should slot together...

The third coordinate is apparent magnitude on a scale of 0-255

We're somewhat limited in a could factors... computer monitors can only handle 256 shades of grey (although some should be varied off grey really...) PHP doesn't like it much when I use too many colours, but I think I've beat that issue now.

[Scott Alexander]

Well, I don't think I saw this when you first released it.

A quick look at Wikipedia confirms that magnitude is logarithmic. There's a 25-fold difference between Sirius (mag -1.5) and Polaris (mag 2), and a 1500-fold difference between Sirius and the faintest visible stars.

Also, and this is just a guess, the distribution of magnitudes probably follows a power law. So there are probably many, MANY more faint stars than there are bright stars. That means a random number generator just doesn't cut it.

Your options are either to use an algorithm that artificially clusters most greys into the 40s and 50s while also having a few outliers of 100s and 200s, or to think up a better way. I recommend a better way, but I'm not sure what it would be. Maybe some stars should be more than one pixel?

And while you're altering star appearance, give a few of them some color! Where's the Betelguese of Micras?

[dr-spangle]

They're clustered around 255 , because that made it look rather nice

you could make a formula to move a random number to those numbers in the right ratio?


with the last one I told one PHP file to open a blank text file then write "1" into it once then start a new line and write "2" twice (on new lines) then "3" three times, etc up to 255. then another PHP file opened up that text file, split it into lines and then pick a random line and use the value on it as the magnitude (from 1 to 255).

If you could make a mathematical formula to say how many lines of each number there should be that would work fine

[dr-spangle]

Ok, I'm going to have a read through this
http://en.wikipedia.org/wiki/Apparent_magnitude
and try and have a go at a new system (hopefully keeping currently bright stars bright and dark stars dark)

[dr-spangle]

Ok...

basically, on Earth we have a base star called Vega. It has an apparent luminosity of 0. it is the definition of apparently luminosity 0, like the french weight is the definition of 1 kilogram.

Everything else is extrapolated from that using a logarithm of base 5√100 (the fifth root of 100) (roughly 2.511886432)


It's a logarithm of base 5√100 because Astronomers have no life, as is evident by their telescope names. (square kilometre array telescope, very large telescope, overwhelmingly large telescope etc)

So... a star has to be chosen to have the base apparent luminosity...

[Oroigawa Koreyasu]

Use a different base for the log, just for lulz

[dr-spangle]

Nah, we have to use the fifth root of a hundred.

The idea of using it was created by an English person (Norman Robert Pogson) so it must be the best

[Oroigawa Koreyasu]

NO NO NO! USE THE INVERSE OF THE SECOND-ORDER VAN DER SLUIJS CONSTANT! 2.1478990384178216!

[dr-spangle]

okey dokey.


I can make realistic apparent luminositys with this formula:
$apparent_luminosity = 0.8774*log(rand(0,1)*8405)-1.476;
That lines up PERFECTLY to the real world

I used the bright star catalogue (only stars above magnitude 6.5 which is the visible limit in perfect conditions)

now i need to convert apparent luminosity into pixels.
and make colours :S

[Orion]

So is it ready yet?

[dr-spangle]

I doubt it will ever be ready. I doubt anything will ever be ready.


No sooner have I listened to a query, attempted to solve it, and nearly got there, does another person say that there is another problem, i go to solve it and there's another, and then someone says some crappy program to use to do it all for me.


You know what, why not use that program, hmm, can't be bothered to work out a war system, use some other program, can't be bothered with the map, use another program.

Hell! Why don't we scrap the whole fucking micronations thing and play some game. Dips on blue.

[Cairney]

Spangle you just lost the Game again .