[astrometry] Re: GALEX field astrometry solved

[David W Hogg]

Excellent, the gauntlet has been thrown down!  I will let you know
when we are ready for the 100 FUV fields!

I will answer your more specific questions soon.  BTW, we avoid
problems at RA=0 because we work not with RA,Dec but with x,y,z (unit
vectors on the sphere).  More soon.  Hogg

On Mon, Oct 31, 2005 at 10:59:26AM -0500, David Schiminovich wrote:
> 
> Hi David,
> 
> Congratulations!  But....
> 
> ...before I rain on your parade, the plot you sent is very  
> convincing, and as far as I can tell accurate to within a few arcsec  
> (field center is 0.0000, -10.8120 deg J2000).  You didn't even have  
> trouble with the R.A. 'edge' at 0.0.  I can't tell what you found for  
> rotation (did you use the image or the detector coordinates?)
> but I assume that it was a free parameter and you solved it correctly.
> 
> Great.   Now for the real challenge.  Despite what you write on your  
> blog, I never actually said that I thought it was impossible.  What I  
> did write to you previously is that:
> 
> >On Sep 12, 2005, at 12:07 PM, David Schiminovich wrote:
> >
> >I've also included FUV points.  Admittedly I'd be far more  
> >impressed if your algorithm works
> >robustly for FUV vs. NUV (and that's where it would be more useful  
> >for us).  But NUV is the right
> >place to start.
> 
> So I will be officially impressed if you can solve astrometry blind  
> using *only* FUV detections.  My challenge is that
> 
> a) I give you FUV-only data from 100 all-sky-survey images selecting  
> fields with a relatively uniform distribution in Galactic latitude.
> b) You obtain a correct automated solution (field center within 3"  
> and rotation within 5') in all but two fields (pathological cases  
> will be removed).
> 
> Achieving this goal will win you beer.  Solving all fields (no  
> failures) will win you good beer.
> 
> When you're ready to try it out I'll generate the 100 catalogs.
> 
> Cheers,
> 
> David
> 
> 
> 
> o----
> 
> David Schiminovich    Assistant Professor of Astronomy
> Columbia University   (o) 212-854-7819  (c) 626-319-5991
> 
> 
> 
> On Oct 30, 2005, at 1:31 PM, David W Hogg wrote:
> 
> >David,
> >
> >If you have been reading my blog, you know that we solved the
> >astrometry for that GALEX field blind.  We used only the brightest 100
> >(dstn, is that correct?) sources in the NUV channel, and a
> >B-band-selected subset of USNO-B1.0.  As you will recall, we had no
> >idea, going in, the RA, and Dec of the field, nor orientation (we did
> >know that GALEX fields are about 1 deg in diameter).  The QA plot (2
> >pages) is at this URL:
> >
> >  http://cosmo.nyu.edu/hogg/research/2005/10/27/
> >
> >It might not appear super convincing, but if you look carefully on the
> >second page (where crosses show ALL USNO stars and boxes show ALL
> >GALEX sources), there are lots of crosses inside the boxes.
> >
> >The x and y axes are RA and Dec respectively in degress J2000.
> >
> >Do you have any GALEX images for which you do *not* know the pointing
> >or rotation?  Also, is there any use for you all for us to re-solve
> >all your astrometry?  I ask because for a small fee (like a beer
> >sometime), we could in principle do it...
> >
> >Hogg
> >-- 
> >David W. Hogg        *  assistant professor
> >Center for Cosmology and Particle Physics
> >Department of Physics, New York University
> >4 Washington Pl, New York, NY 10003
> >david.hogg at nyu.edu   *  http://cosmo.nyu.edu/hogg/
> >
> 

-- 
David W. Hogg        *  assistant professor
Center for Cosmology and Particle Physics
Department of Physics, New York University
4 Washington Pl, New York, NY 10003
david.hogg at nyu.edu   *  http://cosmo.nyu.edu/hogg/