astropy

I have position (x,y,z) and velocity (Vx,Vy,Vz) vectors in Earth Centered Inertial Coordinates (ECI) for a satellite orbit, and ultimately want to end up with geodetic coordinates (Latitude, Longitude, & Altitude). According to this other Stack Overflow question it seems that I need to convert to Earth Centered Earth Fixed (ECEF) coordinates as an intermediate step (so ECI --> ECEF --> Lat/Lon/Alt). I know ECI and ECEF share the same origin point (the center of mass of Earth) and the same z-axis that points to the North Pole. However, I am not sure what actual equations or adjustments I need

I'm currently working with some fits tables and I'm having trouble with outputting in Astropy.io.fits. Essentially, I am slicing out a bunch of rows that have data for objects I'm not interested in, but when I save the new table all of those rows have magically reappeared. For example: import astropy.io.fits as fits import numpy as np hdu = fits.open('some_fits_file.fits')[1].data sample_slice = [True True True False False True] hdu_sliced = hdu[sample_slice] Now my naive mind expects that "hdu" has 6 rows and hdu_sliced has 4 rows, which is what you would get if you used np.size(). So if I

I have a fits file about an astronomical object. I can plot it like this: from astropy.io import fits from astropy.wcs import WCS hdul = fits.open(fitsfilename)[0] wcs = WCS(hdul.header) fig = plt.figure(figsize=(12,12)) fig.add_subplot(111, projection=wcs) plt.imshow(hdul.data) This works, and produces a nice pic: I would like to add some additional features to this plot, which doesn't work. For example lets try to add a circle to 119°, -67°30'. I expand the code by: plt.scatter([119],[-67.5],c='r',s=500) What I get is: Which is really not what we wanted, the circle is around 118°5', -67°5',

I am tying to get the physical sky coordinates of a given pixel from within a python script. I would like to use astropy's WCS, but I'll do anything from within python. I have tried these two snippets of code. from astropy.io import fits from astropy.wcs import WCS def astropymethod1(img): # from http://astropy.readthedocs.org/en/latest/wcs/ w = WCS(img) lon, lat = w.all_pix2world( 100., 100., 1) print lon, lat def astropymethod2(img): # from http://astropy.readthedocs.org/en/latest/wcs/ hdu = fits.open(img) w = WCS(hdu[0].header) lon, lat = w.wcs_pix2world(100., 100., 1) print lon, lat The