more on Libra, and a star cluster within

Event Date: March 4th

Time: 4:34(.06) AM

Brief

  Let's continue with our viewing of faint Libra, which I featured more in depth yesterday, besides only its brightest stars.  The Scales are seen looking away from the plane of the Milky Way, which we see pass to its east between Scorpious and Sagittarius.  This is more noticeable when high enough and when Libra is far enough past transit.  As a result of looking this many degrees from the galactic equator, therefore its spectrum, there is very little deep sky that is easily visible even through a telescope.  There are other galaxies to view nearby, seen in and near Virgo and Leo, instead of Libra, making the weighing scales' part of the sky somewhat ignored.  However, there is one very attractive celestial body to see within Libra's boundaries: Saturn!  Albeit only for 2+ years, it will help give the constellation a little more attention, perhaps.  Besides that, the only labeled deep-sky that gets easy binocular and telescope attention is a globular star cluster: NGC 5897.  In the second image, the 10th magnitude cluster is magnified, yet requires enough magnification and light gathering power through a telescope to see.  Although a near-3rd quarter Moon is nearby, it is far enough away from the labeled deep-sky to not interfere much if skies are free from any clouds and/or high humidity.

Detailed

The field for the cluster is 15 arc-minutes, which is a magnification of about 200x.  The cluster seems more compact at magnifications about half of this.  It is what I call a "loose globular, since when compared to others such as M3 and M13, the center is very definite and there is a rapid spreading of the stars once we look far enough from the center.  In the case of NCG 5897, there is no definite core.  At magnitude 8.5, this cluster is dimmer than 7th magnitude M3 and 13, partly for being much further away at 41,000 light years.  More info and images of the cluster can be found at this link http://spider.seds.org/spider/MWGC/n5897.html  As seen from the images there, it is an excellent target to photograph using long exposure.  Once the Moon is further out of the way, give that a try if you have the equipment for it.  Whether a powerful telescope or a small less-powerful one, the cluster is a fun one to find, being a bit challenging to do so.  With Saturn not far and being brighter than any of the constellations stars, imagine a line starting there extending through one of yesterday's mentioned stars: Zubenelgenubi.  The general direction of this line if straight, takes us to the cluster.  When Saturn moves in retrograde next season and early summer, that line starting with it and ending with the cluster ends up being more straight.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.