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Last updated on April 19, 2014 at 5:20 EDT
Galaxy Cluster Abell 370
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Galaxy Cluster Abell 370

May 17, 2005
J band image (1.25 micron) of the galaxy cluster Abell 370 (A370; redshift z = 0.375), obtained in 'jitter' mode, showing the famous gravitational arc just below the centre. The observations consisted of 24 exposures of 2 min each, made on randomly generated telescope positions within a sky region of 30 x 30 arcsec. The individual exposures have been sky subtracted using a running average determined from the same data and then re-centred and combined.

The scale is 0.29 arcsec/pixel; the field is about 5 x 5 arcmin with North at the top and East to the left. The seeing was less optimal, about 1.2 arcsec. A J = 22 mag point source yields a signal-to-noise ratio of 4 within a 3 arcsec diameter aperture.