我正在努力寻找从坐标列表中删除不需要的目标的最佳方法。我的坐标(Ra,Dec)是使用形成的,astropy.coordinates.SkyCoord
但是我有很多不可观测的目标,它们的磁偏角都太小,所以我想要做的就是对我的列表进行排序,并删除所有磁偏角小于-10的目标例如,度数(例如我的望远镜位于北半球)。
这是我的代码行,它生成列表,它被radecs
简化以从天球坐标获得Ra&Dec。
radecs = astropy.coordinates.SkyCoord(ra=phi*u.rad, dec=(0.5*np.pi - theta)*u.rad)
这是如何在Python中输出列表坐标的示例。
<SkyCoord (ICRS): (ra, dec) in deg
[(45.0, 60.0), (135.0, 45.0), (225.0, 25.0), ...,
(135.0, 55.0), (225.0, 70.0), (315.0, -20.0)]>
我将仅说明如何在一些任意坐标上将numpy索引与布尔掩码一起使用:
from astropy.coordinates import SkyCoord
import astropy.units as u
import numpy as np
phi = np.linspace(0,2*np.pi,20)
theta = np.linspace(0, np.pi, 20)
radecs = SkyCoord(ra=phi*u.rad, dec=(0.5*np.pi - theta)*u.rad)
radecs
给我radecs
:
<SkyCoord (ICRS): (ra, dec) in deg
[(0.0, 90.0), (18.94736842, 80.52631579), (37.89473684, 71.05263158),
(56.84210526, 61.57894737), (75.78947368, 52.10526316),
(94.73684211, 42.63157895), (113.68421053, 33.15789474),
(132.63157895, 23.68421053), (151.57894737, 14.21052632),
(170.52631579, 4.73684211), (189.47368421, -4.73684211),
(208.42105263, -14.21052632), (227.36842105, -23.68421053),
(246.31578947, -33.15789474), (265.26315789, -42.63157895),
(284.21052632, -52.10526316), (303.15789474, -61.57894737),
(322.10526316, -71.05263158), (341.05263158, -80.52631579),
(0.0, -90.0)]>
要获得您的dec
(偏度),您radecs
可以访问该属性:
radecs.dec
[90, 80.526316, 71.052632, 61.578947, 52.105263, 42.631579, 33.157895, 23.684211, 14.210526, 4.7368421, −4.7368421, −14.210526, −23.684211, −33.157895, −42.631579, −52.105263, −61.578947, −71.052632, −80.526316, −90]
因此我们可以-10
通过创建遮罩来访问所有度数大于零度的目标:
radecs.dec > - 10 * u.degree
然后索引满足此掩码的所有目标:
radecs2 = radecs[radecs.dec > - 10 * u.degree]
给我以下内容radecs2
:
<SkyCoord (ICRS): (ra, dec) in deg
[(0.0, 90.0), (18.94736842, 80.52631579), (37.89473684, 71.05263158),
(56.84210526, 61.57894737), (75.78947368, 52.10526316),
(94.73684211, 42.63157895), (113.68421053, 33.15789474),
(132.63157895, 23.68421053), (151.57894737, 14.21052632),
(170.52631579, 4.73684211), (189.47368421, -4.73684211)]>
本质上,您要做的只是最后一步(radecs2 = radecs[radecs.dec > - 10 * u.degree]
),其他所有步骤仅是说明性的。
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