我正在嘗試實現一個非常簡單的天體測量代碼。我已經手動在我的照片中找到了幾個星星的坐標(RA/DEC和x/y像素)。

一切似乎都是直截了當的，但我還是得到了奇怪的結果，偏離了幾度。在

我正在嘗試求解我拍攝的一張CCD圖像的板常數，在那里我用手找到了照片中的恒星坐標和位置，現在我想嘗試找到(0，0)點的真實世界坐標。在

我希望有人能幫助我的代碼或告訴我如何正確地做。

提前謝謝你！在

這是我的代碼：import numpy as np

import os

def astrometry(star_pos, xpix, ypix, focallength, target_RA, target_DEC):

pi = np.pi

DegToRad = pi / 180

RadToDeg = 180 / pi

n = len(star_pos)

(target_RA, target_DEC) = (target_RA, target_DEC)

print(target_RA, target_DEC)

# 1) Obtain star coordinates in pixel and RA/DEC

x_pix = [row[0] for row in star_pos]

y_pix = [row[1] for row in star_pos]

ra_star = [row[2] for row in star_pos]

dec_star = [row[3] for row in star_pos]

# 2) Calculate the standard coordinates of the stars

X_star = np.zeros(n)

Y_star = np.zeros(n)

for i in range(n):

X_star[i] = -(np.cos(DegToRad*dec_star[i])*np.sin(DegToRad*(ra_star[i] - target_RA)))/(np.cos(DegToRad*target_DEC)*np.cos(DegToRad*dec_star[i])*np.cos(DegToRad*(ra_star[i]-target_RA)) + np.sin(DegToRad*target_DEC)*np.sin(DegToRad*dec_star[i]))

Y_star[i] = -(np.sin(DegToRad*target_DEC)*np.cos(DegToRad*dec_star[i])*np.cos(DegToRad*(ra_star[i]-target_RA)) - np.cos(DegToRad*target_DEC)*np.sin(DegToRad*dec_star[i]))/(np.cos(DegToRad*target_DEC)*np.cos(DegToRad*dec_star[i])*np.cos(DegToRad*(ra_star[i]-target_RA)) + np.sin(DegToRad*target_DEC)*np.sin(DegToRad*dec_star[i]))

# 3) Calculate the plate constants (Check my notes)

def calc_plate_const(k,x,y,X):

c_down = ((x[k+1]-x[k])*(y[k]*x[k+2]-y[k+2]*x[k])-(x[k+2]-x[k])*(y[k]*x[k+1]-y[k+1]*x[k]))

c_up = (X[k]*x[k+1]*(y[k]*x[k+2]-y[k+2]*x[k])-X[k+1]*x[k]*(y[k]*x[k+2]-y[k+2]*x[k])-X[k]*x[k+2]*(y[k]*x[k+1]-y[k+1]*x[k])-X[k+2]*x[k]*(y[k]*x[k+1]-y[k+1]*x[k]))

c = c_up/c_down

print('c',c)

b = ((X[k]*x[k+1]-X[k+1]*x[k])-(x[k+1]-x[k])*c)/(y[k]*x[k+1]-y[k+1]*x[k])

print('b',b)

a = (X[k]-b*y[k]-c)/x[k]

print('a', a)

return(a,b,c)

(a,b,c) = calc_plate_const(0,x_pix,y_pix,X_star)

(d,e,f) = calc_plate_const(0,x_pix,y_pix,Y_star)

print(target_RA,target_DEC)

# 4) Calculate the standard coordinates for the object

# HIER object at (0,0)

(x_ob, y_ob) = (0,0)

X_ob = a*x_ob + b*y_ob + c

Y_ob = d*x_ob + e*y_ob + f

print('x', x_pix, x_ob, 'y', y_pix, y_ob)

print('X', X_star, X_ob, 'Y', Y_star, Y_ob)

print('RA', ra_star, 'DEC', dec_star)

# 5) Calculate the RA/DEC of the objects standard coordinates

a = target_RA + np.arctan(DegToRad*((-X_ob)/(np.cos(DegToRad*target_DEC)- Y_ob*np.sin(DegToRad*target_DEC))))

d = target_DEC - np.arcsin(DegToRad*((np.sin(DegToRad*target_DEC) + Y_ob*np.cos(DegToRad*target_DEC))/(np.sqrt(1 + X_ob**2 + Y_ob**2))))

print('RA in rad', a, 'DEC in rad', d)

print('RA',a,target_RA, 'DEC',d, target_DEC)

return(a,d)

例如，輸入是一個數組，其中以圖像像素表示的星星位置和真實世界的度數

^{pr2}$

我預計(0,0)點RA在133°左右，12月-5.75°

總結

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