Messier/type:M23/open cluster
mag/dia/dist:5.5 / 30' / 2,100 ly
constellation:Sagittarius
date/time/place:May 24, 01 / 02:26 / bangkok
trans'y/seeing/l-poll:fair-poor / fair / medium
telescope:newtonian 4.5" f8.8
eyepieces/power:25mm / 40x
sky atlas page:22
Start from the lagoon nebula, M8; hop to stars 13 & mag5.5. M23 locates at the top of imaginary triangle which star 13 & mag5.5 forms the base line. Also, close to M23, there is one star mag6.5 as an indicator. At eyepiece M23 appeared as faint, small open cluster, couldn't resolve some faint stars, which appeared as faint nebulosity.
Refer to text: 150 stars; detached, max mag9.2, extend 16 ly; age 220 million years. Home
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