@@ -60,6 +60,9 @@ signal. This patten is then subtracted from the original image and saved to
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a FITS file for usual data reduction processing (preferably with PypeIt) to
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yield an extracted 1D spectrum for analysis.
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+ Example Pre- and Post-Scrubbed Data Products
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+ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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+
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To illustrate the need for and utility of this tool, :numref: `spec1d_comps `
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shows a comparison of the extracted 1D spectra for two different object types
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from two different programs (and nights) from both the original and scrubbed
@@ -81,6 +84,36 @@ from the spectra.
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estimates a mean :math: `SNR = 4.8` for the scrubbed galaxy spectrum and
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a mean :math: `SNR = 7.2` for the scrubbed white dwarf spectrum.
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+ Of equivalent interest to the quality of the extracted spectra is the noise
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+ remaining after extraction of sky and objects. Shown in :numref: `prepost_noise `
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+ are the noise analysis plots from PyepIt for the pre- and post-scrubbed
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+ versions of the 2D spectral image shown in :numref: `raw_frame `. The images and
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+ pixel histograms are of the residual noise image, which is the science image
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+ minus the object and sky models, and then divided by the uncertainty image.
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+ The ideal pixel histogram would be a gaussian with width :math: `\sigma =1 `.
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+
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+ .. _prepost_noise :
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+ .. subfigure :: A|B
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+ :gap: 2px
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+ :class-grid: outline
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+
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+ .. image :: figures/pypeit_spec2d_noise_prescrub.png
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+ :alt: Pre-scrubbed noise analysis plot
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+
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+ .. image :: figures/pypeit_spec2d_noise_postscrub.png
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+ :alt: Post-scrubbed noise analysis plot
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+
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+ -- Noise analysis of the pre- (top) and post-scrubbed (bottom) versions of
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+ the frame shown in :numref: `raw_frame `. Image values are residual image
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+ divided by uncertainty, so the ideal pixel histogram would be a gaussian
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+ with width :math: `\sigma =1 `. Note the improvement in both the visual
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+ quality of the scrubbed frame and the width and shape of the pixel histogram
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+ compared to the pre-scrubbed frame.
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+
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+
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+ Outline
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+ ^^^^^^^
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+
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This document begins with a description of how to use this tool to clean the
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EMI pickup noise from your data, and moves on to lay out the details of what
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the tool does to your data and other points to consider.
@@ -493,11 +526,11 @@ than that predicted from the FFT (green dashed line in the second panel of
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Pickup Noise Pattern Construction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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- Finally, we use the sinusoid fits to produce a pattern image. This is the
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+ The final result of sinusoid fits is a constructed pattern image. This is the
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zero-mean sinusoid (sans quadratic polynomial) that *should * represent only the
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- EMI pickup noise (as an additive AC-only signal). Subtract that and make
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- additional QA plots to show how totally awesome this is!!!
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-
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+ EMI pickup noise (as an additive AC-only signal). :numref: ` image_comparisons `
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+ shows the process of pattern construction and its effect on the processed
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+ science image.
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.. _image_comparisons :
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.. figure :: figures/scrubber_image_comparisons.*
@@ -629,3 +662,14 @@ panel in :numref:`image_comparisons`). The result is shown in
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discussed above) from artifacts and ringing in the FFT. The peak at 169.1
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pixels, indicating the frequency with the most power in the flattened array:
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most likely the period of the AC EMI pickup noise.
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+
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+ Also, say something about the actual line-by-line fits in terms of how good a
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+ sinusoid fits each one. Show a figure like :numref: `line_by_line `.
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+
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+ .. _line_by_line :
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+ .. figure :: figures/scrubber_line_fitting.png
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+ :class: with-shadow
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+ :alt: Line-by-line fitting examples
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+
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+ -- Examples of individual line fits for 4 randomly selected lines from the
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+ image shown in :numref: `raw_frame`.
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