Bias Image

Mode:

Bias

Usage:

Offline, Online

Key:

MegaraBIAS_IMAGE

Product:

MasterBias

Recipe:

BiasRecipe

Recipe input:

RecipeInput

Recipe result:

RecipeResult

Before the Analog-to-Digital conversion is performed a pedestal (electronic) level is added to all images obtained with the MEGARA CCD. This is a standard procedure in CCD imaging and spectroscopy applications for Astronomy and is intended to minimize the ADC errors produced when very low analog values are converted to DUs.

Requirements of the mode

The sequence for this observing mode should include the actions to calibrate the pedestal level of the detectors and associated control electronics by taking images with null integration time. This mode requires having the shutter closed and to readout the detector in a series of exposures with null integration time, being this series the bias image set.

Procedure

The frames in the observed block are stacked together using the median of them as the final result. The variance of the result frame is computed using two different methods. The first method computes the variance across the pixels in the different frames stacked. The second method computes the variance in each channel in the result frame.

Products

Bias image sets are to be obtained both as part of the activities related to the verification of the instrument status and for processing data for scientific exploitation.

Recipe, inputs and results

class megaradrp.recipes.calibration.bias.BiasRecipe(*args, **kwargs)

Process BIAS images and create a MASTER_BIAS product.

This recipe process a set of bias images obtained in Bias Image mode and returns a combined product image, trimmed to the physical size of the detector.

See also

megaradrp.types.MasterBias

description of the MasterBias product

Notes

Images are corrected from overscan and trimmed to the physical size of the detector. Then, they corrected from Bad Pixel Mask, if the BPM is available, Finally, images are stacked using the median.

class BiasRecipeInput(*args, **kwds)

BiasRecipeInput documentation.

Attributes:

master_bpmMasterBPM, requirement, optional

Master Bad Pixel Mask

methodstr, requirement, optional, default=median

Combination method

method_kwargsdict, requirement, optional

Arguments for combination method

obresultObservationResultType, requirement

Observation Result

class BiasRecipeResult(*args, **kwds)

BiasRecipeResult documentation.

Attributes:

master_biasMasterBias, product

RecipeInput

alias of BiasRecipeInput

RecipeResult

alias of BiasRecipeResult

run(rinput)

Execute the recipe.

Parameters:

rinputBiasRecipe.RecipeInput

Returns:

BiasRecipe.RecipeResult

set_base_headers(hdr)

Set metadata in FITS headers.