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  • Deep Sky Astronomy April 2017 Northern Hemisphere

    Here we are in April now, and I am sure at least some of you are fighting with clouds and rain. But for those fortunate enough to have clear skies galaxies abound. This month for our northern targets we shall visit the front leg of the great bear for one of my favorite non-Messier galaxies. Then scratch the shoulders of our celestial lion for a galactic duo (or is that a trio?). Four our southern friends we will visit the profusely rich constellation of Centaurus for three bright galaxies that are sure to please. So let’s take a look at what is in the Deep Sky This Month…..

    Northern Celestial Hemisphere:

    NGC 2841 (Ursa Major):

    Spiral Galaxy, mag=9.5, size=8.1’x3.5’, SBr=12.9 mag/arcmin2

    The riches of Ursa Major cannot be overstated as it contains a profusion of galaxies that are worthy targets for the backyard astronomer. NGC 2841 is one of the brightest within this expansive constellation and one of my favorite non-Messier galaxies. Situated along its front leg, less than 2° southwest of mag 3.2 Theta Ursae Majoris, it is brighter than both M108 and M109, with a higher surface brightness as well. Visually it will appear as an elongated ellipse of light with a noticeably bright core area.

    I have observed this fine galaxy with instruments ranging from 15x70 binoculars to 12 inches. With the binoculars at a semi-dark location it was easy to spot its fairly bright spindle shape. With a 5 inch refractor under my moderately light polluted backyard, even at a lower elevation it was easily seen, though its lower position in the sky muted its appearance due to atmospheric extinction. Using the 12 inch at the same location but with the galaxy at a much higher elevation and at a time of excellent transparency, it was large and quite bright visually. The core region itself was intense and had an oval appearance itself. Its major axis is oriented southeast to northwest, where an 11th magnitude star is pinned to its tip. The overall appearance was mottled with variations of light and dark across its dusty disk. Be sure to look for a drop-off in brightness along its northeastern side due to the presence of obscuring dust..

    Though it doesn’t lie in particularly rich stellar field, because it is close to Theta UMa, it is still not difficult to locate. Starting at Theta, you will notice just to its northeast is the mag 4.5 star 26 UMa. Looking at the chart below, plotted to stellar magnitude 13.0, if you follow a line from 26 UMa through Theta and onward for about 1.5° you will spot a north-south curved line of stars dominated by a 6th and 7th mag pair in its middle. Turing northwest from this pair you will spot two stars lined up toward the northwest, the first one is of 9th mag and the one beyond it of 8th. If you haven’t already noticed the presence of the galaxy in the field, it is just southwest of this 8th mag star. You will also see these two stars point to another couple of stars (6th & 7th mag) further to the northwest and perpendicular to their line. One can also follow a line from 26 UMa to the WSW through a 6th mag star an onward to arrive at the pair of stars to the northwest as well. Therefore, one can in a way triangulate the position of NGC 2841 by using these two paths as seen in a lower magnification wide field view.


    NGC 3226 and NGC 3227 (Leo)

    (N3226) Elliptical Galaxy, mag=11.7, size=3.2’x2.8’, SBr=13.8 mag/arcmin2

    (N3227) Barred Spiral Galaxy, mag=10.9, size=5.4’x3.6’, SBr=13.9 mag/arcmin2

    (N3222) Lenticular Galaxy, mag=13.2, size=1.3’x1.1’, SBr=13.2 mag/arcmin2

    The king of the beasts rides high in our sky during the springtime, as if heralding the coming parade of galaxies. Our highness not wishing to be outdone by the other nearby constellations has its own ample supply of the distant star islands. To find the jewels we are highlighting this month, one needs to simply aim their scope at the bright and beautiful double star Gamma Leonis (Algieba). This pair is composed of a reddish-orange primary at magnitude 2.3 contrasting nicely with its mag 3.5 yellowish companion. Separated by 4.4”, obtaining precise magnitude measurements for the pair has proven difficult because the light of the other interferes with the other. Less than 1° east of this nice pair we can find an interacting pair of galaxies also known as Arp 94, from Dr. Halton Arp’s Atlas of Peculiar Galaxies.

    Observing the duo from my moderately light polluted backyard with a 10 inch dob I found them a pair of subtle glows with very apparent core brightness present at 69x. Increasing magnification the core of NGC 3227 seemed brighter than that of its companion. It was also evident that NGC 3227 was more elongated. Under the same conditions with the 17.5 inch dob, they were both bright and large patches of light with intensely bright cores, again with NGC 3227 being slightly more elongated. During this observing session with the 17.5 inch I also noted the presence of a third galaxy, NGC 3222 just a few arc minutes west of the pair in the direction of Algieba as a dim rounded glow. Using the 10 inch at our dark site, the improvement over the same scope at home was obvious as the primary pair were quite bright with strong stellar cores. Their halos were extended and almost touching at lower magnification, but they separated a bit as power was increased. The bonus galaxy here, NGC 3222 was seen in the 10 inch at this location similarly to what the 17.5 inch displayed at home. It was a dim small round glow, easily seen, though not strongly present as compared to the main pair just to its east.

    As indicated above, finding these two is a simple process of aiming your scope at Algieba and then nudging east. Placing the double Algieba in the western side of the field of view will place trio within a reasonably wide field of view as the primary pair are just 49’ to the east. The chart below is plotted to stellar magnitude 13.0.


    (concluded in southern section)
    kingclinton likes this.
    This article was originally published in blog: Deep Sky This Month - April 2017 (Northern) started by KT4HX
    Comments 1 Comment
    1. admin's Avatar
      admin -
      Great article for night sky observing this month, thanks!
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