2MASS6X color J (1.23um) & K (2.16um) HiPS

During the final months of 2MASS observatory operations, a campaign of targeted "long exposure" observations was carried out during times when no previously unscanned parts of the sky were available for the main survey. These observations used the same freeze-frame scanning technique employed for the survey, but with READ2-READ1 exposures six times longer than was used for normal survey observations (hence they are referred to as "6x" observations). The 2MASS 6x measurements were intended to probe ~1 magnitude deeper than the main survey in unconfused regions. Approximately 590 deg2 of sky distributed in 30 targeted regions were scanned at least once using the long exposures. Most of this area is concentrated in two large, comprehensive surveys of the Large and Small Magellanic Clouds, 383 deg2 and 127 deg2, respectively. Twenty-eight additional smaller fields were mapped in the 6x mode from both observatories, covering targets that include the Pleiades open cluster, galactic star formation complexes, M31, nearby galaxy clusters and the Lockman Hole.

在2微米全天巡天（2MASS）项目的观测运行末期，当此前未被扫描的天区已无剩余可供主巡天使用时，团队开展了针对特定目标的“长曝光”观测计划。此次观测沿用了主巡天所采用的冻结帧扫描技术，但将READ2-READ1曝光时长设置为常规巡天观测的六倍，因此这类观测被称为“6倍曝光（6x）”观测。2MASS 6倍曝光观测数据旨在在无源混淆区域中实现比主巡天高约1个星等的探测深度。本次长曝光观测覆盖30个目标区域的天区，总覆盖面积约590平方度，且所有区域均完成了至少一次扫描。该天区的绝大部分集中于大麦哲伦云和小麦哲伦云的两项大型全覆盖巡天中，对应面积分别为383平方度与127平方度。此外，两台观测站还通过6倍曝光模式测绘了28个小型天区，覆盖目标包括昴星团、银河系恒星形成复合体、M31、邻近星系团以及洛克曼空洞。