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Changes between Version 9 and Version 10 of Ask_an_expert


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Timestamp:
Aug 10, 2009, 2:10:08 PM (17 years ago)
Author:
pitts
Comment:

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  • Ask_an_expert

    v9 v10  
    2323
    2424 * How do I make a lightcurve for a given object?
     25        '''Answer from Mark Pitts:'''
     26            1) You can use "mextract" to pull individual measurements, including magnitude (using the proper photcode) and time of the measurment (using the "time" keyword). Eventually, you will be able to use the "OBJID" keyword to pull all the measurements associated with a given object, but for now you can use the RA and DEC keywords to isolate the object (i.e., use boolean logic to pull out all measurments within about 1 arcsec of the object):
     27             -> catdir (data catalog)
     28             -> region (ra) (dec) (radius)
     29             -> define values for object's position obj_ra and obj_dec
     30             -> mextract -region (photcode),(photcode):err,time where (sqrt(((RA-obj_ra)*cos(DEC))^2 + (DEC-obj_dec)^2) <= 0.0003)
     31            2) Now you can plot up the data:
     32             -> set xvec = time; set yvec = (photcode); set zvec = (photcode):err
     33             -> device -n lightcurve
     34             -> labels -fn times 14 -x "time (sec)" -y "mag" +x "Lightcurve"
     35             -> limits xvec yvec; box -lw 2
     36             To plot points:
     37             -> plot -x 2 -pt 1 -sz 1.5 -c black xvec yvec -dy zvec
     38             To connect the points:
     39             -> plot -x 0 -lt 0 -lw 1 -c green xvec yvec
    2540
    2641 * We want to find dropout objects, which may involve identifying