https://github.com/zfedoran/astrometry.js
Extract star pixel coordinates from a FITS image using JavaScript
https://github.com/zfedoran/astrometry.js
astrometry astrophotography emscripten fitsio stars
Last synced: 5 months ago
JSON representation
Extract star pixel coordinates from a FITS image using JavaScript
- Host: GitHub
- URL: https://github.com/zfedoran/astrometry.js
- Owner: zfedoran
- License: bsd-3-clause
- Created: 2018-02-13T22:29:28.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2018-02-22T21:23:05.000Z (over 8 years ago)
- Last Synced: 2025-09-14T23:19:45.408Z (9 months ago)
- Topics: astrometry, astrophotography, emscripten, fitsio, stars
- Language: C
- Size: 15.5 MB
- Stars: 7
- Watchers: 1
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# astrometry.js
Extract star pixel coordinates from a FITS image using JavaScript (supported on Node.js and your Browser)
## image2xy
A port of the blind image2xy solver utility from [astrometry.net](http://astrometry.net/) using [Emscripten](http://emscripten.org).
----------------------------------------------------------
#### Install (Node.js)
```
npm install astrometry.js
```
#### Usage
Read a FITS image file into a buffer (or `Uint8Array` in the browser, see browser example below))
``` js
const fs = require('fs');
const buf = fs.readFileSync('./example.fits');
const image2xy = require('astrometry.js').image2xy;
const result = image2xy(buf, { verbose: true, extension: 0 });
```
----------------------------------------------------------
#### Install (Browser)
``` html
```
#### Usage
You'll need to do a little bit of work to get a file buffer on the browser. Live [example](https://jsfiddle.net/cj5sf2h2/17/).
``` js
var reader = new FileReader();
reader.onload = function (e) {
// Get the image file as a buffer
var buf = new Uint8Array(e.currentTarget.result);
// Get a fits file buffer containing a star list
const results = astrometry(buf, { verbose: true, extension: 0 });
};
reader.readAsArrayBuffer(file);
```
----------------------------------------------------------
### Example
The following shows an example output.
``` js
const result = image2xy(buf, { verbose: true, extension: 0 });
> infile=fits_buf.fits
outfile=fits_buf.xy.fits
nhdus=1
Got naxis=2, na1=4096, na2=4096
simplexy: nx=4096, ny=4096
simplexy: dpsf=1.000000, plim=8.000000, dlim=1.000000, saddle=5.000000
simplexy: maxper=1000, maxnpeaks=10000, maxsize=2000, halfbox=100
simplexy: median smoothing...
simplexy: measuring image noise (sigma)...
Sampling sigma at 42025 points
Nsigma=0.7, s=13.132
simplexy: found sigma=13.132.
simplexy: finding objects...
simplexy: found 734 blobs
simplexy: finding peaks...
simplexy: found 743 sources.
```
### Options
You may use the same options that image2xy supports by providing the flags directly, or you may use the following human friendly versions.
##### Options List
|Option|Flag|Type|Description|
|------|----|----|-----------|
|**help**|'h'| boolean | Print available options and usage instructions|
|**verbose**|'v'| boolean | Print verbose messages|
|**extension**|'e'| number | Read from a single FITS extension|
|**downsampleFactor**|'D'| number | Downsample, if necessary, by this many factors of two|
|**medianFilteringScale**|'s'| number | Set median-filter box size (default 100 pixels)|
|**psfWidth**|'w'| number | Set Gaussian PSF sigma (default 1 pixel)|
|**noiseLevel**|'g'| number | Set image noise level|
|**peakSigma**|'p'| number | Set significance level of peaks (default 8 sigmas)|
|**saddleLevel**|'a'| number | Set saddle level joining peaks (default 5 sigmas)|
|**disableBackgroundSubtraction**|'b'| boolean |Don't do (median-based) background subtraction|
|**backgroundLevel**|'G'| number | Subtract this 'global' background value; implies -b|
|**outputFilename**|'o'| filename | Write XYlist to given filename.|
|**backgroundSubtractedImageName**|'S'| filename | Save background-subtracted image to this filename (FITS float image)|
|**backgroundImageName**|'B'| filename | Save background image to filename|
|**smoothedImageName**|'U'| filename | Save smoothed background-subtracted image to filename|
|**maskImageName**|'M'| filename | Save mask image to filename|
|**blobImageName**|'C'| filename | Save connected-components image to filename|