Dark Image

Mode:

Dark

Usage:

Offline, Online

Key:

MegaraDarkImage

Product:

MasterDark

Recipe:

DarkRecipe

Recipe input:

DarkRecipeInput

Recipe result:

DarkRecipeResult

The potential wells in CCD detectors spontaneously generate electron-ion pairs at a rate that is a function of temperature. For very long exposures this translates into a current that is associated with no light source and that is commonly referred to as dark current.

Requirements

While in imaging or low-resolution spectroscopy this is nowadays a negligible effect thanks to the extremely low dark current levels of state-of-the-art CCDs (typically < 1 e-/hour) when working at intermediate-to-high spectral resolutions where the emission per pixel coming from the sky background and the astronomical source can be very low this is worth considering.

The sequence for this observing mode should include the actions to measure the variation of the intrinsic signal of the system by taking images under zero illumination condition and long integration time. This mode requires that the focal-plane cover is configured (it should be fully closed), the shutter is closed and to expose a certain time and readout the detector a series of exposures, being this series the dark image set.

Procedure

The “User” processes an observing block obtained in the observing mode Dark. This mode includes the required actions to obtain a master dark frame. The master dark generated is used in other stages of the data processing.

Products

Dark 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.

A bidimensional dark image, QA flag, a text log file of the processing and a structured text file containing information about the processing.

Recipe, inputs and results

class megaradrp.recipes.calibration.dark.DarkRecipe(*args, **kwargs)

Process DARK images and provide MASTER_DARK.

class DarkRecipeInput(*args, **kwds)

DarkRecipeInput documentation.

Attributes:
master_biasMasterBias, requirement

Master BIAS image

obresultObservationResultType, requirement

Observation Result

class DarkRecipeResult(*args, **kwds)

DarkRecipeResult documentation.

Attributes:
master_darkMasterDark, product
RecipeInput

alias of DarkRecipeInput

RecipeResult

alias of DarkRecipeResult

set_base_headers(hdr)

Set metadata in FITS headers.