aperture_trace - igrins/plp GitHub Wiki

Aperture for each order is traced from the master FLAT_ON image.

The y-derivative of the flat image created, and its minima and maxima are traced to from an aperture for each order.

Here is an example of y-derivative images for H & K.

aperture/flat_on_y_derivative_20140525_HK.png

Tracing the minima & maxima of these image results in following apertures.

aperture/aperture_trace_20140525_HK.png

Traces of all orders (but separately for maxima and minima) are fitted with 2-d Chebyshev polynomial, which results in typical error of 0.5 pixel. Currently, the error seems to be dominated by the centroiding algorithm, which need to be investigated if necessary.