WCS problems on Optical Telescopes.

[Bill Owen]

In article <DWELLS.97Sep26171353 at fits.cv.nrao.edu>, dwells at nrao.edu (Don Wells) writes:
> ... A Chebyshev polynomial is a sufficient representation of the pixel
> regularization map; the number of terms needed is essentially the same as
> the number of spline coefficients that would be needed for the same
> precision of representation. The Chebyshev expansion, which is orthogonal
> and has the equi-ripple property, can be converted to the equivalent
> conventional polynomial for interchange. I expect that the alternative FITS
> keyword notation which I mentioned in the BoF at Sonthofen will support up
> to 9999 polynomial coefficients per axis.

True, but it's not the only possible set of basis polynomials.  I use the
Legendre polynomials, because if the reference stars are uniformly distributed
the resulting model coefficients will be uncorrelated.

-- Bill Owen, wmo at wansor.jpl.nasa.gov