Re: Soliciting criticism

[Chris Albertson <chrisalbertson90278@yahoo.com>]

Just looking at the thumbnail pictures of the two graphs
I can see the slopes are diferent.  I think you have a good,
graphic and intuitive way to compare data reduction pipelines.
You want all the green and red points to lie on a straight
horizontal line on the bottom of the graph.
sps2x uses,sps2x uses, I think PSF fitting while sextrator does aperature
photometery.   I think PSF fitting while sextrator does aperature
photometery.  
One thing required by the psf fitting technique is a good psf
model.  

"Creager, Robert S" wrote:
> 
> > Hey folks,
> >
> > I'm hoping some of you have the desire to critique, and offer suggestion
> > about the graphs here: http://robertcreager.mystarband.net/ .  The are all
> > from Tom's data, night 2157 (from a few weeks ago).  As the graph titles
> > imply, one is reduced from source extractor, and one from sps2x.
> >
> > Speaking of source extractor, does anyone have a set of values which might
> > be appropriate for reducing Mark IV images?  I grabbed Glenn Gombert setup
> > from 1996, but at this point, I'm shooting in the dark as to how to
> > improve the reduction.  If anyone wants to direct, I'll be happy to make
> > changes and keep re-running the reduction.  It takes about 4 hours from
> > start to finish for reducing night 2157, so I can get two runs per day at
> > home.
> > The basic steps are:
> > *     Create master dark and flats from median data
> > *     Adjust the object data by: mean * (object[i][i] - dark[i][j] ) /
> > flat[i][j] where mean is the mean of a central box of the flat field
> > *     Do the reduction (sps2x, source extractor) in V-I pairs
> > *     Match the reduction data to transform into ra/dec
> > *     Try to match both to subset of Tycho2 data
> > *     If both match, use in next step
> > *     If only one matches, match other band to the matching one to
> > calculate ra/dec
> > *     Collate the V-I pairs from previous
> > *     Solve for magnitude adjustment from collated data
> > *     Use stars which match the Tycho2 subset
> > *     Fit a line to the raw color (V-I) vs. magnitude delta (Tycho2 -
> > measured) for each V and I
> > *     Iterate over the line fit, removing 4 sigma data, until either no
> > more data was removed, we've removed too much data (10% removed) or the
> > RMS error is below 0.05
> > *     Import star list into database, and match stars within 0.004
> > degrees.
> > *     Produce graphs included from the previous data
> > The majority of the stars in the graph have 30+ measurements.

-- 

--
   Chris Albertson             
   Redondo Beach, California
   home:   310-376-1029   chrisalbertson90278@yahoo.com
   cell:   310-990-7550
   office: 310-336-5189   Christopher.J.Albertson@aero.org