如何使用Python将TESScut中的一颗恒星绘制到天空中的正确位置（而不是误差为10度）？

Question

我想使用来自TESScut的数据绘制Beta Dor的TESS测量值。在Gaia DR2 archive中我查找Beta Dor的RA和DEC值，我得到：

RA: 83.40630967798376 DEC:  -62.48977125108528 

我去TESScut，将这两个值放入，选择Sector 1，然后选择Download FFI Cutout。解压缩下载的文件，然后在Python中我做：

import matplotlib.pyplot as plt
from lightkurve import TessTargetPixelFile
import numpy as np

sector1ffi_cutout='tess-s0001-4-4_83.40630967798376_-62.48977125108528_64x64_astrocut.fits'
tpf_s1 = TessTargetPixelFile(sector1ffi_cutout)

fig = plt.figure(figsize=(5,5))
fig.add_subplot(111, projection=tpf_s1.wcs)
plt.pcolormesh(np.log(tpf_s1.flux[0]))
plt.show()

给我：

其中，看坐标（〜-53°，~6h30min）显然是错误的，根据盖亚（以及其他来源），这颗恒星不在这个位置。

我做错了什么，如何将这颗恒星绘制到它应该的位置？

---

为了完整性，当我绘制明星时，我会收到以下警告：

> /home/szabopal/.local/lib/python3.5/site-packages/ipykernel_launcher.py:10:
> RuntimeWarning: divide by zero encountered in log   # Remove the CWD
> from sys.path while we load stuff.
> /home/szabopal/.local/lib/python3.5/site-packages/ipykernel_launcher.py:10:
> RuntimeWarning: invalid value encountered in log   # Remove the CWD
> from sys.path while we load stuff.
> /home/szabopal/.local/lib/python3.5/site-packages/astropy/visualization/wcsaxes/grid_paths.py:73:
> RuntimeWarning: invalid value encountered in greater   discontinuous =
> step[1:] > DISCONT_FACTOR * step[:-1]
> /home/szabopal/.local/lib/python3.5/site-packages/astropy/visualization/wcsaxes/grid_paths.py:73:
> RuntimeWarning: invalid value encountered in greater   discontinuous =
> step[1:] > DISCONT_FACTOR * step[:-1]
> /home/szabopal/.local/lib/python3.5/site-packages/astropy/visualization/wcsaxes/grid_paths.py:73:
> RuntimeWarning: invalid value encountered in greater   discontinuous =
> step[1:] > DISCONT_FACTOR * step[:-1]
> /home/szabopal/.local/lib/python3.5/site-packages/astropy/visualization/wcsaxes/grid_paths.py:73:
> RuntimeWarning: invalid value encountered in greater   discontinuous =
> step[1:] > DISCONT_FACTOR * step[:-1]

---

进一步发展

我认为上面的问题是由wcs引用整个FFI引起的，而不是抠图。

print(tpf_s1.wcs)

得到：

WCS Keywords

Number of WCS axes: 2
CTYPE : 'RA---TAN-SIP'  'DEC--TAN-SIP'  
CRVAL : 90.634460449219  -57.666290283203  
CRPIX : 250.0  -984.0  
PC1_1 PC1_2  : 1.0  1.0  
PC2_1 PC2_2  : 1.0  1.0  
CDELT : 0.00571299832697903  0.005705604460241471  
NAXIS : 81986  1282