Retrieve RA and DEC

[Fede]

Hi there, I'm using python to recover the coordinates of an image with nova.astrometry offline.

The results are shown in the picture.

How can I save the values of RA and DEC in a tdms file? 

I tried with 

radec = subprocess.call(...)

   with open("RADEC.tdms","w") as radecw:

   radecsave = radec['Field center']

   radecw.write(radecsave)

but it doesn't work. It returns 'int' object is not subscriptable.

Moreover, how can I solve RA and DEC for other point in the picture? As an asteroid or a satellite not in the center of the image?

Thank you.

[Dustin Lang]

subprocess.call() returns the return code of the program (0), not the text printed by the program.

https://docs.python.org/3/library/subprocess.html#subprocess.call

If you want to convert other pixel locations in the image, not the center, then you should read the WCS file that is created, eg with astropy -- wcs_pix2world

https://docs.astropy.org/en/stable/wcs/

cheers,

--dustin

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[Fede]

Thank you Dustin,

so what should I write in order to get the output as a string of the results of the processing?

Il giorno martedì 23 giugno 2020 16:13:44 UTC+2, Dustin Lang ha scritto:

subprocess.call() returns the return code of the program (0), not the text printed by the program.

https://docs.python.org/3/library/subprocess.html#subprocess.call

If you want to convert other pixel locations in the image, not the center, then you should read the WCS file that is created, eg with astropy -- wcs_pix2world

https://docs.astropy.org/en/stable/wcs/

cheers,

--dustin

On Tue, Jun 23, 2020 at 10:09 AM Fede <federica....@gmail.com> wrote:

Hi there, I'm using python to recover the coordinates of an image with nova.astrometry offline.

The results are shown in the picture.

How can I save the values of RA and DEC in a tdms file? 

I tried with 

radec = subprocess.call(...)

   with open("RADEC.tdms","w") as radecw:

   radecsave = radec['Field center']

   radecw.write(radecsave)

but it doesn't work. It returns 'int' object is not subscriptable.

Moreover, how can I solve RA and DEC for other point in the picture? As an asteroid or a satellite not in the center of the image?

Thank you.

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[Dustin Lang]

Read the subprocess page --

Code needing to capture stdout or stderr should use run() instead:

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[Fede]

Hi Dustin, 

I tried to use wcs_pix2world as you suggested, but the output is exactly the pixels I'm giving as input...

Il giorno martedì 23 giugno 2020 16:13:44 UTC+2, Dustin Lang ha scritto:

subprocess.call() returns the return code of the program (0), not the text printed by the program.

https://docs.python.org/3/library/subprocess.html#subprocess.call

If you want to convert other pixel locations in the image, not the center, then you should read the WCS file that is created, eg with astropy -- wcs_pix2world

https://docs.astropy.org/en/stable/wcs/

cheers,

--dustin

On Tue, Jun 23, 2020 at 10:09 AM Fede <federica....@gmail.com> wrote:

Hi there, I'm using python to recover the coordinates of an image with nova.astrometry offline.

The results are shown in the picture.

How can I save the values of RA and DEC in a tdms file? 

I tried with 

radec = subprocess.call(...)

   with open("RADEC.tdms","w") as radecw:

   radecsave = radec['Field center']

   radecw.write(radecsave)

but it doesn't work. It returns 'int' object is not subscriptable.

Moreover, how can I solve RA and DEC for other point in the picture? As an asteroid or a satellite not in the center of the image?

Thank you.

--
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[Dustin Lang]

You're opening the .wcs file to create the astropy WCS object?

Maybe send your code and example WCS file you're using.

On Thu, Jul 2, 2020 at 8:48 AM Fede <federica.l...@gmail.com> wrote:

Hi Dustin, 

I tried to use wcs_pix2world as you suggested, but the output is exactly the pixel I'm given as input...

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[Leonardo Parisi]

This script work for me:

---------

import numpy as np

from astropy import wcs

from astropy.io import fits

import sys

hdulist = fits.open(sys.argv[1])

w = wcs.WCS(hdulist[0].header)

for coord in sys.argv[2:]:

  pixels = coord.split(',')

  #lon, lat = w.all_pix2world(float(pixels[0])+0.5, float(pixels[1])+0.5, 1) # pixel coord in FITS references frame

  lon, lat = w.all_pix2world(float(pixels[0])-0.5, float(pixels[1])-0.5, 0) # pixel coord in AstroPy references frame

  print(lon, lat)

-----

you can call as:

python3.7 world2pix.py {Astrometry solved fits file} x1,y1 x2,y2 xn,yn

The important part is in which reference frame the pixels coordinate as given.

In my example I use the standard image references frame with the origin in the top left corner

My be Dustin can confirm

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[Fede]

from astropy import wcs
from astropy.io import

fits

hdu_list = fits.open('file')
hdu = hdu_list[0].header
w = wcs.WCS(hdu,hdu_list)
coordRA,coordDEC = w.wcs_pix2world(x,y,1)
print(coordRA,coordDEC)

Where x,y are the px in the fits.

Il giorno giovedì 2 luglio 2020 14:50:51 UTC+2, Dustin Lang ha scritto:

You're opening the .wcs file to create the astropy WCS object?

Maybe send your code and example WCS file you're using.

To view this discussion on the web visit https://groups.google.com/d/msgid/astrometry/6fdb5b0b-d46f-4df7-b91b-61e3f96dada5o%40googlegroups.com.

[Dustin Lang]

what is the 'file' you are opening?

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[Fede]

Ok I found the error, I needed to open the wcs file :) thank you!

[Dustin Lang]

You have to read the staring.wcs file (or wcs.fits from the web site) if you want to run the WCS pixel/world conversions.

On Fri, Jul 3, 2020 at 7:08 AM Fede <federica.l...@gmail.com> wrote:

It is a FITS file, as 'staring.FITS'

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