Some more Astrometry questions

[gusciora@…]

psCellinChip() What is the proper way to determine if an (x,y) pair is valid
for a cell? Can I simply check if (x,y) is between 0 and however many
rows/columns that image has? Can I assume all readouts for the cell are the
same size, and therefore, that I only have to check one readout?

psCoordChiptoCell(): The psFPA struct has two transformation members:

fromTangentPlane
toTangentPlane

The psChip struct has two similar transformation members:

toFPA;
fromFPA;

However the psCell struct only has one such member

toChip

Can we add a "fromChip" member to the psCell struct? This is needed by
psCoordChiptoCell().

When I transform between the FP and TP, I must use a 4-D transformation with
the magnitude and color of the object being additional elements. Where do I
get the magnitude and color from? Do these vary at each coordinate in the
focal plane? Or, is this a constant for an entire exposure?

There is an element of the psCell struct:

psPlaneTransform* toSky;

This is of type "psPlaneTransform", however the intent is to produce sky
coordinates which are, of course, spherical coordinates. That doesn't seem
right. But since it's a "quick" transform, I'm not sure. Can you expand on that?

psCoordCelltoSkyQuick(): uses the "toSky" transformation in the psCell struct
that I mentioned above, which is a linear transformation. If that transform
should indeed be linear, how should I produce the spherical coordinates from
it that this function requires?

psCoordSkytoCell(): where do I get the grommit info?

psCoordSkytoCellQuick(): this transform is not specified anywhere, as far
as I can tell.

psCoordCelltoSky(): I implement by doing:

1: cell to FPA transformation.
2: FPA to tangent plane transformation.
3: tangent plane to sky transformation.

In order to do step 3, I have to create a grommit for this function which is
only used once, then discarded. Maybe we should make the grommit a member
in the psFPA structure?

[Paul Price]

I think most of these questions have been answered elsewhere. If there are any
outstanding, please let me know.

[Paul Price]

I assume this is resolved after our meeting at MHPCC a month ago.