[daip] [#4188]: blanking in GBT maps

[Eric Greisen]

Trisha wrote:
> OK, so let me make sure I understand:
> 
>     * In SDGRD I do not need to add a fake RA and Dec (I can leave APARM
>       blank), and therefor after SDGRD I do not need to change the
>       header to change the reference coordinate to Glong and Glat
>       because SDGRD will be able to handle the coordinate information. 
>     * Blanking the cube will help me get better moment maps (I usually
>       use a channel range; will that be enough?)
>     * In XMOM I should use OPTYPE 'MAX' with ICUT=0 and FLUX=-1000000.  
> 
> Thank you so much for your help!-Trisha

The coordinates are marked as RA and Dec so the image will come out as 
RA and Dec.  If the values attached to the data samples are correct, 
then one can change the image to galactic with the verb CELGAL which 
fixes up the header but only for projective geometries like -SIN.  It 
does not work for -GLS.  If the values attached to the data samples are 
in fact Galactic coordinates then one need only change the strings 
(CTYPE1, and CTYPE2).

I don't know why the data are tagged with RA and Dec, I thought that 
Glon and Glat would also work.  But the header and the data samples and 
the random parameters appear to be RA and DEC.  It will work if they are 
all glon and glat but they have to match in the header and random 
parameters and in the values of those random parameters.

Blanking the cube which can be done in part with ICUT and FLUX helps 
when you are doing proper moments.  The MAX operation is simple and 
usually does not require any blanking.  But it does show different 
things (on my HI cubes it shows peak brightness while a real MOM0 shows 
the integral brightness).

Eric Greisen