“Astropy”的版本间差异
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*很好的教程网站 [https://learn.astropy.org/] |
*很好的教程网站 [https://learn.astropy.org/] |
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:比如星际红化的 [https://learn.astropy.org/tutorials/color-excess.html] |
:比如星际红化的 [https://learn.astropy.org/tutorials/color-excess.html] |
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[http://docs.astropy.org/en/stable/io/fits/] |
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>>> hdulist = fits.open('input.fits') |
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>>> hdulist.info() |
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===header=== |
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*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. |
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>>> hdulist[0].header['targname'] |
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*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)): |
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*It’s also possible to view a slice of the header: |
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>>> header[:2] |
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*Another way to either update an existing card or append a new one is to use the Header.set() method: |
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>>> prihdr.set('observer', 'Edwin Hubble') |
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===fits table 的读与写=== |
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*写 |
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from astropy.table import Table |
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t=Table([Bage,fzbin,Age_weight2],names=('Age','z','weights')) |
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t.write('SFH_LMC3_out.fits',format='fits') |
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*读 |
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hdu = fits.open('SFH_LMC3_out.fits') |
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hdu.info() #看看哪些hdu |
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data=hdu[1].data |
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data.columns #看看有那些列 |
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Bage=data.field('Age') |
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===fits文件打开过多错误=== |
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* [https://docs.astropy.org/en/stable/io/fits/appendix/faq.html#i-am-opening-many-fits-files-in-a-loop-and-getting-oserror-too-many-open-files] |
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* fits.close() |
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* 可能还根系统设置有关 |
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ulimit -a |
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ulimit -n 100000 |
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vim /etc/security/limits.conf |
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* 把python的软限制编程硬限制,参见 [https://bbs.huaweicloud.com/blogs/108323],下面方法貌似也不管用 |
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import resource |
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soft, hard = resource.getrlimit(resource.RLIMIT_NOFILE) |
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resource.setrlimit(resource.RLIMIT_NOFILE, (hard, hard)) |
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*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 |
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* 实测这两个效果不好（python 3.8） |
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:*del hdu.data |
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:*hdu = fits.open(fits_name,memmap=False) #打开fits文件数目比较多的情况下 |
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==fits image读写== |
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n = np.arange(100.0) |
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hdu = fits.PrimaryHDU(n) |
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hdu.writeto('new2.fits') |
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hdu.writeto('new2.fits') |
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*如果超过一个hdu |
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>>> hdul = fits.HDUList([hdu]) |
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>>> hdul.writeto('new1.fits') |
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==astrometry== |
==astrometry== |
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2023年7月9日 (日) 01:22的版本
- 很好的教程网站 [1]
- 比如星际红化的 [2]
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)