Is there a way to scan each pixel of a photo to look for coordinates with python? ( find RA and Dec coordinates through pixels )

Question

I was wondering if there was a way to use python to look through an image to find coordinates. Basically I just need to find the pixel values ( x,y ) for a target star by matching it to its correct right ascension and declination values. However, I have zero idea how to do this, so I thought I'd ask. I'd really appreciate any help or guidance. Thank you!

Answer 1

If we have the image centre in degrees such as (RA, Dec) and the pixel scale with units (deg/px) then we can calculate the pixel co-ordinates as follows:

img = <2D image array>

t_ra = <target star RA in degrees>
t_dec = <target star Dec in degrees>
c_ra = <image centre RA>
c_dec = <image centre Dec>
ps = <pixel scale in deg/px>

H, W = img.shape
x = int((t_ra - c_ra) / ps + W / 2)
y = int((t_dec - c_dec) / ps + H / 2)

# To extract a small square patch from the image
patch_size = 50
img_patch = img[x - patch_size:x + patch_size, y - patch_size:y + patch_size]