查看“Astropy”的源代码

*很好的教程网站 [https://learn.astropy.org/]
:比如星际红化的 [https://learn.astropy.org/tutorials/color-excess.html]

* [[astropy.io.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)

==bug==
*在anaconda3.8.3升级 astropy 和liberfc之后，astropy.fits出错，解决方法是降级
*安装pytorch之后，自动降级到4.3，但是还是又小问题
*进一步[[conda]]指定降级到4.2才行
*可以看出[[conda]]的版本管理并不好,