Archive
08/05/2014 – Ephemeris – The gibbous Moon and the Perseid meteors
Ephemeris for Tuesday, August 5th. The sun rises at 6:33. It’ll be up for 14 hours and 29 minutes, setting at 9:02. The moon, 2 days past first quarter, will set at 2:07 tomorrow morning.
As the moon moves around the Earth, its illuminated fraction gets greater since it’s now moving around to be opposite the sun in the sky which it will reach in 5 days, the full moon. Tonight the face of the moon we see is 71 percent illuminated by the sun. Anytime the moon is between 50 and 100 percent illuminated by the Sun we call a gibbous moon. The word gibbous means hump-backed, and lets face it, the Moon looks cooler when it’s a crescent. If you’re interested in the growing Perseid meteor shower and want to see it in dark skies, the hours of darkness will be restricted tonight to between moon set at 2:07 a.m. and the beginning of astronomical twilight at 4:32 a.m., though you can push it to 5 a.m. before the twilight becomes objectionable.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The gibbous Moon tonight (August 5, 2014). Created using Virtual Moon Atlas.
08/04/2014 – Ephemeris – The Moon’s remarkable crater Clavius
Ephemeris for Monday, August 4th. The sun rises at 6:32. It’ll be up for 14 hours and 31 minutes, setting at 9:03. The moon, 1 day past first quarter, will set at 1:20 tomorrow morning.
Let’s take a look at the Moon tonight. The south end of the moon is bright part, the lunar highlands, the oldest terrain on the Moon. A huge crater is visible that just came into sunlight. It is the crater Clavius. It’s visible in binoculars, but it is best seen in a telescope with enough magnification so the moon more than fills the field of view. Clavius has four small craters on its floor in a slight arc, in descending order of size. Clavius itself is 136 miles (225 km) in diameter. It has a flat floor, but it’s large enough to be convex following the curvature of the Moon, a fact that can be seen when Clavius is close to the terminator as it will be tonight. It is another one of my favorite lunar features.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon highlighting the craters Clavius and Tycho for 10 p.m. August 4, 2014. Created using Virtual Moon Atlas.
A note: For science fiction fans in the book and movie 2001 a Space Odyssey by Arthur C. Clarke the U.S. Moon Base was located in the crater Clavius, and the lunar monolith, designated TMA-1 (Tycho Magnetic Anomaly 1) in surveys, was located in the nearby crater Tycho.
Clavius as photographed by one of the Lunar Orbiter spacecraft in the 1960s. From Digital Lunar Orbital Photographic Atlas. Credit Jeff Gillis, Lunar and Planetary Institute.
08/01/2014 – Ephemeris – There’s a star party tonight
Ephemeris for Friday, August 1st. The sun rises at 6:28. It’ll be up for 14 hours and 38 minutes, setting at 9:07. The moon, 2 days before first quarter, will set at 11:35 this evening.
Tonight the Grand Traverse Astronomical Society will host a star party at Northwestern Michigan College’s Rogers Observatory from 9 to 11 p.m. If it’s clear the planets Mars and Saturn and the Moon will be the featured attractions. Saturn’s rings are always a fabulous sight. Try to see the circular gap in the rings called Cassini division. Cassini is also the namesake of the spacecraft that has spent 10 years orbiting the planet. The moon Titan can also be easily seen. It’s a world larger than Mercury, has an atmosphere denser than the Earth’s and has lakes of liquid methane and ethane at its poles. Our Moon is two-thirds the diameter of Titan, and essentially airless, which allows us to see its features easily.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Bob Moler's Ephemeris Blog 