
2014.10.28

Going over the sequence of steps in relastro.  I'm concerned that the
iteration is not modifying the measure.R,D values, preventing any
actual iterative improvements.

* UpdateObjects : takes measure.R,D to calculate average.R,D and
  motion terms

* ImageOps : 
  * getImageRaw : takes measure.X,Y, applies image.coords to get (L,M),
    		  (P,Q), etc, calculates 
  * getImageRef : takes average.R,D, applies image.coords to get
    		  (P,Q), (L,M), etc
  * FitChip : fit raw.X,Y to ref.L,M, plus residual map (dX,dY)
  
  *** modified raw.L,M values are then dropped and not used to update measure.R.D

2014.07.03

Thinking some more about the galactic rotation / solar motion based
tie of relastro.  What do I need in the db to do this process?  Here
is an outline:

* generate the PS1 + 2MASS (+ other) database

* ingest the stellar distances from greg.  this boils down to distance
  (or parallax) + error.  These values exist for ~500M objects, so a
  non-trivial fraction of the db.  I suppose the easiest way to handle
  this is as an extra 2 fields in average.d.  The correct (database)
  way to do this would be to define another table with objID, par,
  dpar, refID

* a stand-alone process like setastrom would run through the database
  and set the RoffGAL,DoffGAL offsets.

** I have a model for the motion, but I will need to choose a
   reference date.  I suppose it does not matter too much in detail,
   but obviously I should not choose J1900.  I assume I should choose
   something like the mean epoch (but it needs to be a single epoch
   for the survey).  so, eg, 2012.01.01.  So, I use the model to
   predict the offset for the given distance in the dR,dD direction.  

ref: R,D -> P,Q -> L,M -> X,Y (average)
raw: X,Y -> L,N -> P,Q -> R,D (measure)

* fit is raw.X,Y -> ref.L,M

* KHE : apply correction to raw.X,Y (I can calculate it for all stars

* DCR : apply correction to raw.X,Y (need more than one color, can
  calculate up front). choose a median color and airmass?  

* GAL : I want the transformation of a given image to convert X,Y to
  R,D for that epoch. This really says I need to apply the proper
  motion offset to the ref.R,D so ref.L,M is a prediction of the true
  position.

* QSO : I have the QSO coordinates in the db as specific measurments
  with their own photcode(s).  During the iteration, extract all
  average.R,D for the QSOs and their specific measurements.  Fit
  Y(l,m) to dR,dD.  Find the significant entries (how).  Subtract the
  offsets from ALL average.R,D values??

---------------------------------------------------

* external steps:

  * set the KHE X,Y offset values
  * set the DCR X,Y offset values
  * ingest the GAL P,dP values, set the GAL dR,dD values

* relastro loop
  * update objects
  * fit & apply the QSO correction
  * update chips

  ** I need to do a better job of tracking the change from each
     iteration.

  ** add a bunch of visualizations to demonstrate the quality  

2014.07.01

I had a nice conversation with Valeri Makarov about astrometric
calibration.  I have committed to send them the qsos matched to ps1
positions.

some things Valeri raised:

1) if I make the QSOs into hard points, then they will drive the
solution have to a peak consistency at that location.  thus errors
will build up away from those points, with potential ringing.  His
suggestion is to use a set of spherical harmonics to fit the residual
between the QSO positions and relastro fitted position and to correct
based on this model fit. 

How exactly that works is not completely clear to me.  I imaging doing
something iteratively.  my sequence is basically:

1) fit the image parameters
2) determine the per-epoch R,D values
3) determine mean positions
4) fit the Ylms between QSO radio positions (selected subset only)
   and the new fitted R,D values 
5) identify the significant Ylm terms, the negative of this is the
   correction (actually, I'm fitting dR,dD = Y^D_lm, Y^R_lm
6) adjust the mean positions for all objects based on the correction
7) re-fit the images to these new positions
8) back to step 2 and repeat...

Clearly I can only do this (consistently) if I fit the entire sky (or
as much as possible) in a single pass. I'll need to put some smarts
into the relastro_parallel_regions to get this right.  But, also note
that having the technology in place to apply the Ylms means that I can
apply a correction from Valeri, if supplied.

** What new fields do I need to handle this?  

2) regarding the application of the Galactic rotation / solar motion
model, Valeri raise the concern that different populations follow
different rotation curves.  This is a good point, and an obvious one
in retrospect.  In fact, we would like to be able to measure this.  

Now, clearly Pop I and Pop II stars are very different in terms of
rotation / stellar motions.   How much does this matter?
Specifically, how much does solar motion matter vs the galactic
rotation model?  Also, what fraction of my reference stars are likely
to be giants instead of MS stars?  

Some mitigation strategies:  

1) attempt to use only stars in a modest range of colors and predicted
distances? 
2) ??

NOTE: I need to get the QSOs from bertrand

