hi wondering if i could get a little advice?

[DavidSimon]

hi i'm just wondering if any one around here is into active research?

has anyone used data from the big sky surveys like SDSS(Sloan) or 2DF?

ok. here is what i'm trying to do:

i'm trying to extract H_aplha line widths for a sample of galaxies from the SDSS survey from the SQL interface at their data release website.
i have the coordinates of each of the galaxies and i want to be able to extract the H_aplha data from the catalogue. i've worked out(i think) how to make a 'square box' search centred a specific set of coordinates by defining min and max values for he Ra and Dec.

what i want to know is, is it possible to run a search that will find the closest match to the specified coordinates? at the moment is i make the square of the search box too small i get no results and if it is too big i get thousands.
if it is not possible to make a 'best match' search then i would still like to know if it is possible to do a radius search because i have the option of checking for the best match after if i can get a catalogue of results from the fixed radius search.

i anyone has any advice or anything i'd be really greatfull

oh, by the way i'm not big (or anything)0 on pragramming so that's not an option for getting the data.


thanks

[btimsah]

No, but I can send you to:

http://sdss2df.ncsa.uiuc.edu/2df/hel...249C20160EF9AD

If you've allready tried that, then I dunno.

[Jolly Rodger]

sick

[Pete]

Hi David,
I'd attack it by intriducing a calculated field to give the angular distance of each object from your specified coordinates, then sorting the results in ascending order of that calculated field.

To improve the performance, it would be sensible to limit the search to a box of reasonable size, so that the server doesn't have to calculate angular distances to every object in the database.

[Pete]

If you post your 'square box' query SQL, I can add the necessary changes for you.