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I have an astronomical image of the entire night sky (the galactic plane in gamma rays) opened on ds9 in galactic coordinates. I would like to have ds9 draw circles over a list of coordinates that I provide, and draw these circles on top of the night sky image I already have. I know there must be a simple way of doing this, scratching my head over here....

theasucksatpython
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  • In the edit menu, select region. Then in the region menu, check that your shape is a circle. Finally, click on the image where you want the circle. –  Feb 14 '18 at 00:35
  • If you have a list of coordinates, you can write a little script to turn these into a region file and load that into DS9 (region -> load regions). To figure out the format, manually create a few regions and save those to a file, to see the actual file format (it can be useful to switch the WCS format from sexagesimal to degrees, depending on your input list format: wcs -> degrees). –  Feb 14 '18 at 00:38

1 Answers1

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if you have a catalog of objects

import pandas as pd
from astropy.table import Table

# read catalog
candels_catalog = 'cat.csv'
df = pd.read_csv(candels_catalog)

# CSV to Astropy Table
table = Table.from_pandas(df)

# prepare .reg f=ile
reg_filename = "cat.reg"
with open(reg_filename, 'w') as regfile:
    regfile.write("# Region file format: DS9 version 4.1\n")
    regfile.write("global color=green dashlist=8 3 width=2 font=\"helvetica 10 normal roman\" select=1 highlite=1 dash=0 fixed=0 edit=1 move=1 delete=1 include=1 source=1\n")
    regfile.write("image\n")

    # over table'objects
    for obj in table:
        x, y = obj['X_IMAGE'], obj['Y_IMAGE']
        a, b = obj['A_IMAGE'], obj['B_IMAGE']
        theta = obj['THETA_IMAGE']

        # write.reg（use pixel coor）
        regfile.write("ellipse({},{},{},{},{})\n".format(x, y, a, b, -theta))
Mei
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