Combine Frames

Description

The step CombineFramesStep combines a stack of frames.

Algorithm

A data cube is created from the input frames. The cube is then reduced according to the input argument method. If method='sigma_clip', bad pixels are iteratively flagged before reduction. Currently only the sigma clipping method only implements cenfunc=’median’ and stdfunc=’mad_std’.

The error is calculated in one of two ways:

1. error_calc='measure' : The error is calculated from the standard deviation of the values of the input frames.

2. error_calc='propagate' : The error is calculated from the propagation of the errors of the input frames:

   \[\sigma = \big( \sum_i \sigma_i^{-2} \big)^{-1/2}\]

where \(\sigma\) is the error of the combined frame and \(\sigma_i\) is the error of the input frames.

Arguments

inputlist[str | LigerIRISDataModel ]

The input data to combine.

methodstr

Method for combining the frames:

• ‘mean’: Unweighted mean.

• ‘wmean’: Weighted mean.

• ‘median’: Unweighted median.

• ‘wmedian’ : Weighted median.

• ‘sigma_clip’ : Sigma clipping, see arguments sigma, cenfunc, stdfunc, maxiters. Currently, only cenfunc=’median’ and stdfunc=’mad_std’ are supported.