[AstroPy] Issues in DR14/DR15 headers read using astropy.io.fits

[Peter Dzwig]

I am looking for some general help with FITS Headers



I have two (SDSS) files:

(1) remote_filename =
'https://dr15.sdss.org/optical/spectrum/view/data/format=fits/spec=lite?plateid=0425&mjd=51898&fiberid=0440'

(2)remote_filename =
'https://dr15.sdss.org/optical/spectrum/view/data/format=fits/spec=lite?plateid=7512&mjd=56777&fiberid=0396'

I wrote some Python code using astropy which extracted the spectrum of
an object from the second HDU of the appropriate .fits file. In
particular I wanted to extract certain fields

For example:

f = fits.open(remote_filename)

specdata2 = f[2].data

RA = specdata2[0][59]
Dec = specdata2[0][60]

# Classification

Class = specdata2[0][61]

# Redshift and error

redshift = specdata2[0][63]
redshift_error = specdata2[0][64]

used to work fine. In the case of (1) above, it does. In the case of (2)
it just produces junk. I used the formulation for a large number of
files from DR12

FWIW I am running Python 3.7 over Ubuntu 18.04. I think that is probably
irrelevant as a colleague who is running in another configuration has
the same sort of problem

Any ideas why?

It seems that there might be the following reasons:

(i) there is a change in the formats (somewhere) in DR15

(ii) something has changed in the way io.fits treats some HDUs that I
have missed.

Is there perhaps a cleaner way of getting this info?

I have posted this to the Skyserver Helpdesk without any response. Am
happy to take this offline if people want.

Thanks for any help,

Peter



-- 

Dr. Peter Dzwig