Copyright (c) 2015, Olaf Frohn
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Catalog sources and conversion notes:
# Data Formats

For GeoJSON, all coordinates need to be given in degrees, longitude as [-180...180] deg, latitude as [-90...90] deg

## Stars

`stars.6.json`, `stars.8.json`, `stars.14.json`: the number indicates limit magnitude  

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",        // Hipparcos number
    "properties": {
      "mag": "",     // Apparent magnitude
      "bv": ""       // b-v color index
    },
    "geometry": {  
      "type": "Point",
      "coordinates": [lon, lat]
    }
  }, { } ]
}
```

## Starnames

`starnames.json`: Magnitude independent, all stars with a name/designation other than HIP/HD  

```js
{"id": {         // Hipparcos number  
   "name": "",      // Proper name  
    ...             // and names in 17 further languages (see list in main readme)
   "desig": "",     // Standard designation, first from list below  
   "bayer": "",     // Bayer  
   "flam": "",      // Flamsteed  
   "var": "",       // Variable star  
   "gliese": "",    // Gliese  
   "hd": "",        // Henry Draper
   "hip": ""        // Hipparcos number again   
  }, "id": {...}  
}
```
  
##Traditional Chinese star and DSO names  

`starnames.cn.json`, `dsonames.cn.json`:  
```js
{"id": {         // Hipparcos number  
   "name": "",      // Chinese name  
   "desig": "",     // IAU designation  
   "en": "",        // English translation  
   "pinyin": ""     // Pinyin transcription  
  }, "id": {...}  
}
```

## DSOs

`dsos.6.json`, `dsos.14.json`: the number indicates limit magnitude  
`dsos.bright.json`: hand selected  
`lf.json`: Local group  
`messier.json` Messier objects

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",       // Short designator
    "properties": {
      "desig": "",  // Designator
      "type": "",   // Object type: gg, g, s, s0, sd, i, e, oc, gc, dn, bn, sfr, rn, en, pn, snr
      "morph": "",  // Morphology classification depending on type  
      "mag": "",    // Apparent magnitude, 999 if n.a.  
      "dim": "",    // Angular dimensions in arcminutes  
      "bv": ""      // Blue minus visual magnitude color inder (b-v)    
    },
    "geometry": {  
      "type": "Point",
      "coordinates": [lon, lat]
    }
  }, { } ]
}
```

___Object type:___ _gg_: galaxy cluster, _g_: galaxy, _s_: spiral galaxy, _s0_: lenticular gal., _sd_: dwarf spheroidal gal., _i_: irregular gal., _e_: elliptical gal., _oc_: open cluster, _gc_: globular cluster, _dn_: dark nebula, _bn_: bright nebula, _sfr_: star forming region, _rn_: reflection nebula, _en_: emission nebula, _pn_: planetary nebula, _snr_: supernova remnant

___additional lg.json properties:___  
_sub_: Sub group membership: \[MW|M31|N3109|LG\]  (Milky Way, Andromeda, NGC 3109, gen. LG)  
_pop_: MW populations \[OH|YH|BD\] (Old halo, young halo, bulge & disk), M31 populations \[M31|GP\]  (gen. M31, great plane)  
_str_: Tidal streams \[Mag|Sgr|CMa|FLS\] (Magellanic Stream, Sagittarius Stream, Canis Major/Monoceros Stream, Fornax-Leo-Sculptor Great Circle)
  

## DSOnames

`dsonames.json`: Magnitude/dimension independent, all DSOs with a proper name  

```js
{"id": {      // most common designation (NGC, IC, M, ...)
  "name":"",  // Proper name (in English)
    ...       // and names in up to 17 further languages (see list in main readme)
}
```

## Constellations

`constellations.json`

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",           // 3-letter designator
    "properties": {
      "name": "",       // full IAU name
      "desig": "",      // 3-letter designator again
      "gen": "",        // genitive for naming stars, not yet used
      "rank": "",       // 1-3 for differential name display by size/brightness
      "en": "",         // english name
      ...               // and names in 18 further languages (see list in main readme)
      "display": []     // [ra,dec,scale], for single constellation display 
    },
    "geometry": {  
      "type": "Point",
      "coordinates": [lon, lat]  // Position of const. name
    }      
  }, { } ]
}
```

## Constellation lines

`constellations.lines.json`, `constellations.lines.cn.json`

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",           // 3-letter designator of constellation
    "geometry": {  
      "type": "MultiLineString",
      "coordinates": [[[lon, lat],[lon, lat],..],[[]lon, lat,[lon, lat],..],..]
    }
  }, { } ]
}
```

## Constellation boundaries

`constellations.bounds.json`, `constellations.bounds.cn.json`

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",           // 3-letter designator of constellation
    "geometry": {  
      "type": "Polygon",
      "coordinates": [[[lon, lat],[lon, lat],..]]
    },
  }, { } ]
}
```

##Traditional Chinese constellations

`constellations.cn.json`  

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",           // numerical id
    "properties": {
      "name": "",       // chinese name
      "en": "",         // english translation
      "pinyin": "",     // pinyin transcription
      "desig": "",      // also chinese name, for compatibility
      "rank": "",       // so far only 1; differential name display by size/brightness
      "display": []     // [ra,dec,scale], for single constellation display 
    },
    "geometry": {  
      "type": "Point",
      "coordinates": [lon, lat]  // Position of const. name
    }      
  }, { } ]
}
```

## Milky way

`mw.json`

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",       // ol 1-5
    "properties": {},
    "geometry": {
      "type": "MultiPolygon",
      "coordinates":[[[[lon, lat],[lon, lat],..],[[lon, lat],[lon, lat],..],..]]
    }
  }, { } ]
}
```

## Special Planes

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",       
    "geometry": {  
      "type": "LineString",
      "coordinates": [[lon, lat],[lon, lat]]
    }
  }, { } ]
}
```

## Asterisms

```js
{
  "type": "FeatureCollection",
  "features": [{
    "type": "Feature",
    "id": "",       // Name without spaces
    "properties": {
      "n": "",      // Proper name
      "es": "",     // Proper name in spanish
      "loc": [lon,lat], // Center location of name string
      "p": n        // Priority 1..6 (~Average brighness)
                    // p=6: Guiding line
    },
    "geometry": {  
      "type": "MultiLineString",
      "coordinates": [[[lon, lat],[lon, lat],..],[[]lon, lat,[lon, lat],..],..]
    }
  }, { } ]
}
```

## Planets

Not geojson, because positions need to be calculated by date from keplerian elements  
All element values in degrees, except a (AU|km) and e (dimensionless)  

```js
"id":{                // (usually) 3-letter id
  "name": "",         // full name
  "trajectory": bool, // show trajectory (tbi)
  "H": n,             // absolute magnitude
  "elements":[{
    "a": "da": Semimajor axis / change per century (all 'dx' fields)
    "e": "de": Eccentricity
    "i": "di": Inclination
    "L": "dL": or "M": "dM": mean longitude (M*Q) or mean anomaly
    "W": "dW": or "w": "dw": longitude of periapsis (w*N) or argument of periapsis
    "N": "dn": longitude of the ascending node
    "ep":"2000-01-01" epoch, default date
  }],
  "desig": "",        // 3-Letter designation
  ...                 // Names in 14 different languages, see list in main readme
  }
```