This weekend we move on to the constellation Hercules The Strongman.
Hercules was half man and half god. His father was the great god, Jupiter. His mother was the beautiful mortal Alcmene. In an act that would make Oedipus and Freud proud, Jupiter disguised himself as his father and slept with his mother! Hercules strength arrived early and even as a child many were amazed at his abilities.
This constellation sits between Corona Borealis to the west and Lyra to the east. Find Hercules from the familiar, distinctive "U" shape of Corona Borealis. From there, it's just a couple of degrees to the east. Once there, the constellation of Hercules is made up of many reasonably bright stars.
Hercules contains a few nice double and variable stars. First up is Alpha Herculis or Rasalgethi(mag2.78). This beautiful Red Giant Star has an greenish, magnitude 5.4 companion separated by 4.6". This is a beautiful object to go after. These should be a relatively easy split with good optics under steady skies. Next up is an optical double, Delta Herculis(mag3.14) composed of greenish and violet pair with a 22.3" separation. Finally, for a challenge, you might want to checkout Zeta Herculis(mag2.81). The separation of this pair varies from a mere 0.4" to about 1.6". This'll definitely push your scope and your skies to their limits.
Observing double stars can add a fun and easy component to typical observing sessions. For more information on observing double stars, checkout the Astronomical League's Double Star Observing List.
Ok, let's start things off with the granddaddy of all northern globular star clusters, the Great Cluster in Hercules , M13(mag5.8). This object is, without a doubt, one of the finest deep sky objects you'll ever come across. It is extremely accessible in amateur telescopes as it's easily found due to the closeness of a couple of bright stars, and also because it's around naked eye visibility. In larger apertures, this object will just about bring a tear to your eye - it is a stunning collection of jewels.
Utah Skies own Anthony Arrigo took the accompanying image in August of 2003 from Park City, Utah. The shot was a 10 minute unguided exposure at prime focus through a 10" f/4.5 reflector mounted on a Losmandy G-11
As you can see from the accompanying image, this M13 is dense with stars. Estimates on the number of member stars typically range from many hundreds of thousands to several million, and the latest research gives a distance to the glob' of about 23,000 light years. Assuming this distance, the cluster spans over 160 light years in diameter.
Charles Messier "discovered" this object in 1764 and described it as a "nebula containing no stars". His comment illustrates just how amazing his accomplishments were (an the darkness of his skies), being able to find all the objects that he did with a modest telescope of the 18th-century quality.
The accompanying image was taken by the 3.6 meter Canada France Hawaii Telescope located on the top of Hawaii's Mauna Kea.
Next we'll hit "The Other Messier Globular Cluster in Hercules", Globular Star Cluster M92(mag6.5) Were this beauty anywhere else in the sky it would be "the greatest glob in the northern hemisphere". Alas it sits in the shadows of its larger and brighter neighbor to the south. Regardless, this is another treasure easily accessible to amateurs.
Continuing along we come to another Globular Star Cluster, NGC6229(mag9.4), much smaller than M13 and M92. Nonetheless, it's an interesting object deserving at least a quick view.
Next up is Planetary Nebula NGC6210(mag9). Also known as the Turtle Nebula, this tiny object will require dark skies, aperture and magnification. Don't expect your views to match this stunning Hubble Space Telescope image.
Let's wrap things up with this weeks Utah Skies Challenge Object, Spiral Galaxy NGC6207(mag11.6). This object is pretty much a gimme. If you found M13 earlier, you probably glimpsed this in the process. This faint galaxy is about 1/3° northwest of M13.Good Luck!