“Astropy”的版本间差异
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>>> c = SkyCoord(ra=ra1*u.degree, dec=dec1*u.degree) |
>>> c = SkyCoord(ra=ra1*u.degree, dec=dec1*u.degree) |
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>>> catalog = SkyCoord(ra=ra2*u.degree, dec=dec2*u.degree) |
>>> catalog = SkyCoord(ra=ra2*u.degree, dec=dec2*u.degree) |
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>>> idx, d2d, d3d = c.match_to_catalog_sky(catalog) |
>>> idx, d2d, d3d = c.match_to_catalog_sky(catalog) #d3d是假设距离为1的地方的3维距离，因此是以弧度为单位 |
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>>> sel=np.where(d2d.degree < 0.00002) |
>>> sel=np.where(d2d.degree < 0.00002) |
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>>> Nsel=len(sel[0]) |
>>> Nsel=len(sel[0]) |
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2022年11月1日 (二) 01:52的版本
- 很好的教程网站 [1]
- 比如星际红化的 [2]
astropy.io.fits
>>> hdulist = fits.open('input.fits')
>>> hdulist.info()
header
- each element of an HDUList is an HDU object with .header and .data attributes, which can be used to access the header and data portions of the HDU.
>>> hdulist[0].header['targname']
- To see the entire header as it appears in the FITS file (with the END card and padding stripped), simply enter the header object by itself, or print(repr(header)):
- It’s also possible to view a slice of the header:
>>> header[:2]
- Another way to either update an existing card or append a new one is to use the Header.set() method:
>>> prihdr.set('observer', 'Edwin Hubble')
fits table 的读与写
- 写
from astropy.table import Table
t=Table([Bage,fzbin,Age_weight2],names=('Age','z','weights'))
t.write('SFH_LMC3_out.fits',format='fits')
- 读
hdu = fits.open('SFH_LMC3_out.fits')
hdu.info() #看看哪些hdu
data=hdu[1].data
data.columns #看看有那些列
Bage=data.field('Age')
fits文件打开过多错误
- [4]
- fits.close()
- 可能还根系统设置有关
ulimit -a ulimit -n 100000 vim /etc/security/limits.conf
- 把python的软限制编程硬限制,参见 [5],下面方法貌似也不管用
import resource soft, hard = resource.getrlimit(resource.RLIMIT_NOFILE) resource.setrlimit(resource.RLIMIT_NOFILE, (hard, hard))
- lsof -p 进程id > openfiles.log命令，获得当前占用句柄的全部详情进行分析
- 实测这两个效果不好（python 3.8）
- del hdu.data
- hdu = fits.open(fits_name,memmap=False) #打开fits文件数目比较多的情况下
fits image读写
n = np.arange(100.0)
hdu = fits.PrimaryHDU(n)
hdu.writeto('new2.fits')
hdu.writeto('new2.fits')
- 如果超过一个hdu
>>> hdul = fits.HDUList([hdu])
>>> hdul.writeto('new1.fits')
astrometry
- match 两个星表
>>> from astropy.coordinates import SkyCoord >>> from astropy import units as u >>> c = SkyCoord(ra=ra1*u.degree, dec=dec1*u.degree) >>> catalog = SkyCoord(ra=ra2*u.degree, dec=dec2*u.degree) >>> idx, d2d, d3d = c.match_to_catalog_sky(catalog) #d3d是假设距离为1的地方的3维距离，因此是以弧度为单位 >>> sel=np.where(d2d.degree < 0.00002) >>> Nsel=len(sel[0]) >>> print(ra1[sel][0],ra2[idx[sel][0])
宇宙学
http://docs.astropy.org/en/stable/cosmology/
- 从红移到年龄
>>>from astropy.cosmology import FlatLambdaCDM >>>cosmo = FlatLambdaCDM(H0=70, Om0=0.3)
>>> lum_dis=cosmo.luminosity_distance(redshift) #计算光度距离
- 从年龄到红移
>>> import astropy.units as u >>> from astropy.cosmology import z_at_value >>> z_at_value(cosmos.age, 2 * u.Gyr)
单位转换
dL=lum_dis.to(u.cm)