By James Maynard
Neptune, one of the most challenging objects
to find for amateur astronomers (Pluto is impossible except with large telescopes),
is also one of the most rewarding objects to finally get to see through
the eyepiece of a telescope, or in dark skies, even a pair of binoculars.
This week, I shall try to lay out a ground plan (or sky plan depending on
the way you think about It) to find this elusive, methane rich world.
The summer will be offering us three of the four Jovian planets, all in
the same region of the,sky. Jupiter, Uranus. and Neptune will be entering
our night skies one by one. with Neptune being the first to appear. Saturn
is the only one of the Jovian (literally, "Jupiter like") worlds
not to grace Earth's evening skies until late this summer.
In order to most easily find Neptune, we
will guide off of three easy to find stars, and measure our way to Neptune
from there. The three stars are among the easiest to find in the early summer
sky; they are Deneb, Vega, and Altair- These stars form a bright triangle
in the east southeast sky at 10 pm this time of year. Look for them as a
triangle which is pointing down, with the bottom star being 
Altair.
At the top on the eastern side, 43-degrees above the horizon, is the magnitude
1.3 star Deneb, near the stars Sadr and Epsilon-Cygnus, which are each about
two and a half times dimmer than Deneb. Epsilon-Cygnus, Sadr, and Deneb
seem to make their own little triangle In the interplay between the stars.
At the western part of the top of the triangle is one of the brightest stars
in the sky, Vega. Vega shines at magnitude 0.1, making it easily identifiable.
Look for it nearly two thirds of the way up above the east southeast horizon.
In a side note, in another 12,000 years, Vega will be the north star due
to the wobbling of the Earth's axis, known as precession.
Later in the year, a movie titled "Contact" will be released,
based on Carl Sagan's novel of the same name, and starring Jodie Foster.
This movie is about the first alien transmission received on Earth, and
in the movie, Vega is the star from which the signal came.
The top of the triangle is about 23-degrees across, from Deneb to Vega, and from Vega down to Altair is another 34-degrees. If you so chose, you could go back to to Deneb in a 36-degrees jump. From Altair go in a straight line following the direction which the arrow is pointing another 29-degrees. There lies Neptune. As we've said in previous articles, a clenched fist held at arms length is about 10-degrees side to side. Neptune can be found 8 degrees above the horizon at 10 pm this week.
In 1612, Galileo saw Neptune and did not recognize it for the planet which it is. It is probably a good thing, after all, he was in enough trouble as it was. Galileo's instruments were crude and primitive, with colored rings surrounding the images, and yet he was able to see the most distant large planet in our solar system. In order to give yourself the best chance for seeing this elusive azure world, bring yourself and a pair of binoculars or a telescope to a dark spot, with a low horizon the the southeast. Although it is only 2.3 arc minutes (about 1/25-degrees across), it will resolve itself into a disk when seen through a telescope. If you are using a telescope, use a low power eyepiece, which will make the search easier (and after all, you can't see any detail on Neptune except with the world's largest telescopes. It's just a matter of seeing something not known as a planet until 1846!). Also, watch for the telltale sky blue color of Neptune.
Neptune
is lodged between the small, dim globular cluster M75 to the south, and
the dim galaxy Bernard's galaxy to the northwest.
Later in the month, keep your ears and eyes open for news of the meteor shower known as the Southern Delta Aquarids, peaking on the night of July 24th.
Clear skies, and good viewing.
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