def solar_velocity_shift(imagelist, restwave):
"""Opens the images of a data cube and shifts the wavelength planes
so they are shifted to the solar frame. This is accomplished using the
IRAF task 'rvcorrect'.
It does it in a really really stupid way, which is to temporarily redirect
IRAF's output to a string, because IRAF doesn't actually save the output
anywhere (that I know of), it only prints it to the terminal. Then this
routine searches through that string for the necessary value. It's a bit
backwards, but it works!
Note that the boost here is a Lorentz boost, not a Galilean boost, though
values for either will be similar (i.e. the relativistic formula is used)
Inputs:
imagelist -> List of strings, the paths to wavelength images to be
updated.
restwave -> The rest wavelength of the line you're interested in.
"""
c = 299792.458 # in km/s
for i in range(len(imagelist)):
sys.stdout = iraf_output = StringIO()
image = FPImage(imagelist[i], update=True)
iraf.rvcorrect(header="N",
input="N",
imupdate="N",
observatory="SAAO",
year=float(image.datestring.split("-")[0]),
month=float(image.datestring.split("-")[1]),
day=float(image.datestring.split("-")[2]),
ut=image.ut,
ra=image.ra,
dec=image.dec,
vobs=0,
mode="a")
image.solarvel = float(iraf_output.getvalue().split()[-6])
iraf_output.close()
beta_earth = (((image.wave/restwave)**2-1) /
((image.wave/restwave)**2+1))
beta_shift = image.solarvel/c
beta_helio = (beta_earth+beta_shift)/(1+beta_earth*beta_shift)
image.wave = restwave*(1+beta_helio)/np.sqrt(1-beta_helio**2)
image.wave[np.isnan(image.wave)] = 0
image.close()
sys.stdout = sys.__stdout__
return
