CODEWITHSUNDEEP
pythonastronomyastropyastroquery
Matt-Mac-Muffin
Matt-Mac-Muffin

Reputation: 177

Astroquery VizieR UCAC4 full download

I would like to have a local (offline) ASCII version of UCAC4 star catalogue in order to have an isolated work environment.

I am having issues trying to retrieve this specific full catalog. Downloading small parts is pretty straightforward using topcat VO->Vizier service option or even the CdS web interface, but I did not manage full catalogue retrieval.

My best shot was using Python scripting astroquery but the following function call does not return nearly enough stars when it should download half the catalogue (Northern part of celestial sphere):

ucac4 = v.query_region(coord.SkyCoord(ra=0, dec=45, unit=(u.deg, u.deg), frame='icrs'), 
                       width=90, height=360, catalog= 'I/322A')

width and height seem to refer to declination/ra in this order (am I wrong with this assumption?)

I also tried to iterate on smaller parts of the sky and it improves the density, but I still seem to have missing objects and cannot figure out why. For instance, I tried to iterate on 0.2° declination steps so I could cross check with this file : ftp://cdsarc.u-strasbg.fr/pub/cats/I/322A/UCAC4/u4i/zone_stats but still the query_region function does not return the expected amount of stars...

And I also tried Astrosurf links but I cannot just use these files because I want it in an ASCII format.

Upvotes: 2

Views: 1019

Answers (2)

Seb
Seb

Reputation: 26

Fastest solution : get the cdsclient package. Run the finducac4 program with -whole option, for example : finducac4 -whole -m 115000000 > myUcac4.dat

Upvotes: 1

keflavich
keflavich

Reputation: 19225

To download large data sets, you need to increase the ROW_LIMIT. The default is only 50 because we wanted to limit the load on the vizier servers unless users know what they're doing.

from astroquery.vizier import Vizier
Vizier.ROW_LIMIT = 100000000000

Upvotes: 3

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