Salutations celestial sight seers!
I'm David Fuller, welcome to Eyes on the Sky; what's up this week?
This will be a seriously fun week to watch the Moon.
On June 10-th, our natural satellite is two days past new, so a very slim crescent hangs
low in the sky not long after sunset.
And because the Moon travels near the ecliptic, the same line in the sky where the Sun travels,
close to where the planets do, it happens to be passing by the line-of-sight view of
Mercury and Venus that evening.
Despite being brighter at around magnitude negative seven, Venus may be easier to spy
first, as it's negative four magnitude point in the sky is difficult to miss.
Both should start appearing around 30 minutes past sunset, and once you spot Venus, just
look eight degrees away in this direction for the slim Moon phase.
Be sure to train a telescope at it too, as the craters Berosus and Hahn, which you can
see deeply shadowed here, are visible this evening (June 10).
You'll need to look quickly too, as the setting Moon will be dropping lower in the sky, forcing
you to view through more atmosphere, which may mar your view.
If you look a day later (June 11), those two craters are still visible, but not nearly
as well-shadowed.
They are easy to spot though, just north of the large Mare Crisium, the dark-floored,
lava-filled region located here.
At 74 kilometers across, Berosus is decent sized, and has a flooded plain that filled
with lava billions of years ago.
It is named after a Babylonian priest from around 270 BC, who noted the locked rotation
of the Moon.
The libration of the Moon is such that we can see the most northern limb edge on the
13-th.
You really are peeking around the edge here; look on the northern side, starting at the
pair of craters Atlas and Hercules.
Moving out towards the limb is Endymion, and practically on the limb -- but just inside
it this week! - is the difficult-to-see most any other time Mare Humboltianum.
This feature is over 35,000 kilometers square in area, which is larger than the country
of Belgium.
Lunar X coming up next!!
Dark Sky Fact: Replace typical incandescent post lamp bulbs with silvered ones.
Look at the substantial improvement from this one simple change.
More info and Eyes on the Sky dot com.
By the weekend, the Moon is nearing First Quarter phase, and for the Americas and Europe,
it is ideally place for viewing the Lunar X and Lunar V features.
For North America, the timing of the Lunar X is not terribly ideal, as it occurs during
daylight hours.
But as you can see from this video I took last year, it is possible to see the "X" during
daytime.
So starting at 1900 hours Universal Time on the 15-th, which is 3 PM Eastern / 12 PM Pacific
time, the "X" begins to appear along the terminator.
That is the line separating the lighted portion from the unlit area of the Moon facing us.
An hour later, the X has increased in size and brightness, but the best view is probably
an hour and a half after that, at 2130 hours Universal, 5:30 Eastern and 2:30 Pacific.
If you look about a quarter of the diameter of the Moon north along the terminator, you
can also spot the Lunar "V" around the same time or maybe just a little bit later, a feature
visible near the crater Ukert and Mare Vaporum.
The Lunar X only lasts about 4 or 5 hours, so be sure to look at the appointed times.
Observing tip: No neutral density filter yet?
No problem!
Reduce the Moon's comparative brilliance at the eyepiece by setting up NEAR some outdoor
lighting, which will keep your eyes from dark-adapting and avoiding them hurting while lunar observing.
Along The Ecliptic: Venus and Mercurty are still playing tag near the horizon in the
evening, while Saturn sits at nearly due south as darkness falls -- catch all three this
week if your skies cooperate.
That's all for this week.
Keep your eyes on the sky and your outdoor lights aimed down, so we can all see, what's
up.
I'm David Fuller, wishing you clear and dark skies.