Summer and Fall are my two favorite seasons to observe. I like fall because the temperatures are mild, and you can see most of the good winter stuff, provided you observe late enough, also humidity is generally low and there are no bugs. Summer is great, because of good temperatures, the Summer Milky Way, and all of the excellent treasures of the summer sky. Once Summer starts, "Galaxy season" has now ended and "Globular season" has now begun!
One thing to keep in mind when observing, is that you will have a much better experience if you take it slow and spend time observing these objects, instead of racing through them to check them off. Especially with Showpiece objects, you can observe some of them 5o times and still see something new, or still find them amazing, so spend some time studying them and looking for detail. You'll find that your logs become much more interesting if you do.
Globular Clusters:
Many people claim that GC's are their favorite objects to observe. They are definitely beautiful, offering high contrast views, and responding well to a wide range of magnification. I've often heard people describe them as looking like a pile of diamonds, a very fitting description. During the month of June, Hercules is high in the sky. So it is only fitting to observe M13, the greatest of all the northern globulars. From dark skies this object should be naked eye, if your eyesight is decent. M13, was probably my first naked eye deep sky object, while on a ship in the atlantic ocean, traveling to bermuda. First find the Keystone, and focus on Eta Herculis. Then slew towards Zeta Herculis. I move the scope towards Zeta Herculis until Eta Herculis is in the edge of the field of view of my 9x50 finder scope. M13 is easily visible in a finder scope, so should be easy to locate at this point. Notice at low power how it has a bright core, and an outer haze, that begins to resolve into stars. By increasing the power, stars begin to resolve. The funny thing about M13, is that no matter how big of a scope you get, or how much power you use, there always seems to be more stars in the core, and they never resolve all the way. At about 100x you should notice the outer haze begin to look like spider legs of sort. Also at higher powers, the core appears to look like a peace sign, because of less concentrated areas in the core. If you've found M13, make sure to read the section on galaxies as well, for a surprise!! While in Hercules, you might as well observe M92 as well, to see a smaller example of a showpiece globular. To locate it, imagine a triangle, between Pi Herculis and Iota Herculis, with M92 being half way between the two, forming the top of the triangle, or bottom if you're viewing late at night or in the fall. One neat thing about M92, is that I have recorded that the core appears to be slightly off center with the outer haze of stars when viewed at 150x. Try it and see for yourself.
Now, there is also a third, more challenging globular cluster in Hercules, NGC 6229. Right between 52 herculis and 42 herculis. This globular is much more compact than the other two, however in my 10 inch on June 21'st 2009, I recorded it as being remarkably brighter than I expected, with a small compact bright core that begins to resolve at around 150x. For another globular cluster that is a challenge, but easy to locate. Turn your scope to Antares, in Scorpius, preferably in late June, or even later in the summer. Most people have observed the nearby globular, M4. However there is much dimmer, and fainter globular between M4 and Antares, and 57x it will fit in the same 68 degree field as Antares. This globular is NGC 6144. It may require averted vision at first however after repeated observations, I've found I can observe it directly. It is a small-intermediate sized cluster, appearing as a fair mist at 60x. It can sometimes be a challenge for a 10 inch scope, and in scopes smaller than 8 inches it will probably be very difficult. The fact that the glare from Antares often interferes with noticing this cluster initially, only adds to the challenge.
Antares is the bright star, M4 is the larger globular, NGC 6144 is in between the two
Galaxies:
Summer is not known for galaxies, and with Virgo setting, many bright galaxies are now unobservable, and the galaxies that are treasures in the fall have not yet begun to rise. If you managed to observe M13 you are in luck because if you observe M13 with about 60x, and at least a 68 degree field, you may be able to spot NGC 6207, a small galaxy, that appears faint in smaller scopes, but is still detectable. Most people don't notice this galaxy, because of any combination of skies too bright, not enough aperture, or they are simply too attached to the views of M13 to notice a nearby galaxy. In fact I never observed this galaxy until July 2008. This spiral galaxy is also an Arp Peculiar Galaxy, and I find that the best views come at about 100x. See if you can observe its asymmetrical appearance. Another challenging galaxy in hercules is NGC 6181, just off of Kornephoros, in Hercules. 5th magnitude star HR 6152 is in the same field as this galaxy. In a 10 inch scope this galaxy is fairly faint, however the core is relatively bright, and the galaxy is noticeably elongated, from the spiral structure. My first encounter with this galaxy was June 21st 2009.
NGC 6181
Planetary Nebulae:
One of the most magnificent objects visible in the summer is the Ring Nebula, M57. to Locate this object, look between Sheliak and Sulafat. It's not much for color, compared to other smaller PN's but the contrast is excellent, and the ring structure is obvious. I prefer to use about 150x. Look to see if you notice that one side of the ring droops down more than the other, and that the structure is elongated, and not a circular object. If you are using large sized aperture and the seeing is excellent, use high mag and see if the 15th magnitude central star is visible. if you can see it, you've accomplished something that can be quite difficult! I've seen the central star once in an 18 inch dob, and once in a 25 inch dob. Many observers say that M57 is their most viewed object, myself included.
Returning to Hercules, we have NGC 6210, the Turtle nebula. This nebula lies about halfway between Kornephoros and 51 Herculis. Using about 85x or so you should be able to notice a star that appears green/blue and is slightly dim in comparison with its size, or does not focus in the same way as the other stars in the field. This is a dead give away. To me, this is the greenest appearing planetary, however people often argue over whether it appears green or blue. It just depends on the individuals eyes. Up the power to around 200x and you will notice the structure. It has a 12th magnitude central star, which I have never seen. around 400x in a larger scope really makes this object amazing. The other layer of nebulosity begins to show. It's strange elongated "leg" like structures are the reason it is nicknamed the Turtle Nebula.
NGC 6210
Open Clusters:
A good open cluster is IC 4756, in Serpens Cauda. If you have dark skies, look off of Theta Serpens, and you may see this cluster nearby naked eye! This cluster is fairly large and dispersed, I estimate about 80 or so visible stars. Open cluster NGC 6633 is also nearby.
Another naked eye open cluster is IC 4665, off of Beta Ophiuchus. The stars in this are very bright, and I've always interpreted them to make a trident shape.
Multiple Star Systems:
In Lyra, locate Vega, below it is the double-double, also known as Epsilon Lyrae, which splits into two stars easily, I can even split this naked eye. However put a wide field 200x eyepiece on it, and notice how both stars also split into very tight doubles!!
Also, be sure to try Alkalurops or Mu Bootis, an easily split double star, that 200x will show as a triple star. While in Bootes, be sure to observe Izar as well, which splits around 150x and will show a bright orange star accompanied by a smaller bluish-white star.
That's a good list of objects for a night out this month. I have not included any emission nebula, I'll be saving those for later months, so expect to see a lot more of them in the July and August editions.
Enjoy the list and clear skies to all!
