RX J0439.0+0715.-ObsID 526 was rejected due to a very high background level,
leaving ObsID 3583.
RX J0439.0+0715 (z = 0.24): RX J0439.0+0715 is a single, elliptical cluster.
The core is offset a bit from the center of the cluster, but otherwise it
appears fairly symmetric. This cluster had three observations in the archive.
However, one of these observations was for less than a kilosecond, and another
observation had a high background rate. We only used the longest of the three