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DES Document 6560-v1

The impact of camera optical alignments on weak lensing measures for the Dark Energy Survey

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Document type:
Journal Publication
Submitted by:
Sarah Bridle
Updated by:
Sarah Bridle
Document Created:
26 Jun 2012, 04:34
Contents Revised:
26 Jun 2012, 04:34
Metadata Revised:
26 Jun 2012, 04:36
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Telescope Point Spread Function (PSF) quality is critical for realising the potential of
cosmic weak lensing observations to constrain dark energy and test General Relativity.
In this paper we use quantitative weak gravitational lensing measures to inform the
precision of lens optical alignment, with specific reference to the Dark Energy Survey
(DES). We compute optics spot diagrams and calculate the shear and flexion of the
PSF as a function of position on the focal plane. For perfect optical alignment we verify
the high quality of the DES optical design, finding a maximum PSF contribution to
the weak lensing shear of 0.04 near the edge of the focal plane. However this can be
increased by a factor of approximately three if the lenses are only just aligned within
their maximum specified tolerances. We calculate the E and B-mode shear and flexion
variance as a function of de-centre or tilt of each lens in turn. We find tilt accuracy to be
a few times more important than de-centre, depending on the lens considered. Finally
we consider the compound effect of de-centre and tilt of multiple lenses simultaneously,
by sampling from a plausible range of values of each parameter. We find that the
compound effect can be around twice as detrimental as when considering any one lens
alone. Furthermore, this combined effect changes the conclusions about which lens is
most important to align accurately. For DES, the tilt of the first two lenses is the most
Files in Document:
  • arxiv pdf (antonik_bacon_bridle_doel_ea_1206.5320v1.pdf, 319.5 kB)
Notes and Changes:
Version uploaded to arxiv (v1) and submitted to MNRAS.
Publication Information:
Submitted to MNRAS
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