Steve’s Virtual Planet

Naked Eye Lunar Observing Pt 2

In this post, we’ll continue the discussion of naked eye targets on our Moon. In the first post, we looked at some of the larger mare that present themselves during the week from new moon to 1st quarter. Let’s “follow the terminator” and look for some more challenging objects to be found during the week up to 1st Qtr. We’ll use some of the so called “Pickering Dozen” to add to the hunt. I’ll call them “P12″ for short.

When the moon is illuminated “half way” on the right side, there are fewer of the prominent craters that appear later on. However, if you have located Mare Serenitatis and Mare Tranquillitatis, you can use these to find some more challenging mountains and regions on their edges. Between these two large features is a thinning kind of peninsula known as the Plinius Region, named for the crater in its vicinity, Plinius. You should be able to make out this feature to the left of the field at the juncture of both of these large features.

Another of the P12 is immediately to the left. Mare Vaporum, The Sea of Vapors. At first quarter, this feature will be just to the right of the terminator just above the equator. It’s a smaller mare that looks a bit like an extension of Serenitatis to the south west.  That will be our reference point next time when we hike the Apennine Mountains!

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Naked Eye Lunar Observing Pt 1

This is the first of (hopefully) several posts that discuss naked eye targets on our Moon. Instead of a map or a geographical approach, I’ll “follow the terminator”, the shadow line that progresses across the moon’s surface as the phases advance.

For some easy targets, why not start with the Lunar Mare (maria is singular), those dark and typically large areas on the lunar surface. Before the time of Galileo, most people thought these dark areas were “seas”, hence the name. Now we know they are large flat (dry) plains of fairly smooth basalt that formed 3-4 billion years ago from early volcanic activity.

It’s best to get a small moon map in front of you so you can get oriented. The are downloadable ones like this one from S&T with a printable map on page 10 or this image with different sizes for different screens.

With map in front of you, work from the right back towards the left. This is the way the moon will be revealed as the phases progress from New Moon to Full Moon. It is also the first half of the moon’s full cycle that is visible in the evening. The first obvious object you can see even within the first week is Mare Crisium. As the nights pass, you will then see more of the Mare (The Sea of) - Fecunditatis (fertitility), Tranquillitatis (tranquility), Serenitatis (serenity). By the time of the First Quarter, you will be able to see all of those features.

In the next post, we’ll look for some more challenging objects to be found during the week up to 1st Qtr.

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How long is a month?

If you check deeper into the meaning of “month”, you quickly find Earth’s moon right at the center of the explanation. It turns out that the ancient Babylonians pretty much started this examination in the years around 500BC. These early mathematicians and astronomers took extra care in watching and noting the movement of the moon. They came up with several methods and terms to show how the moon tracked around the Earth and how long it took.

There are different ways to describe Earth’s orbit and the orbit of the moon around our planet. Its related to the geometry and timing of those orbits. The method for describing the complete cycle of the moon phases is known as the synodic month. This is the view of the moon from Earth’s perspective and is relative to our point of view. The other method has a more general and wider viewpoint and it is known as the siderial month.

In order to get a better feel for these two concepts, it’s handy to have some kind of diagram or, even better, an animation to show the Moon phases as it orbits the Earth. If you can get your mind around the geometry from your perspective and the solar system perspective (as in the animation), it’s easier to see how “the month” is defined in both of the methods above.

Ultimately, we are talking about lunar calendar systems and there are actually quite a few. The ancient astronomers weren’t just moon gazing but trying to understand what they were looking at. Their persistence lead to what is now a very refined but kind of crazy way of showing what month it is. After all, we want everyone to know our Birthday in time or maybe we just want to take a month off!

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Autumn targets sans planets

These last couple of months have seen the gradual westward track of Saturn. It’s way too early in the year for observing Jupiter. Uranus and Neptune are up later but they aren’t easy to get in a small scope. The evenings are getting dark a little sooner now, so, why not work on finding other nice objects to look at.

Well, check the Messier catalog first. A few choices there. Maybe a planetary nebula or two. Check. Galaxies? Yep. How ’bout stars with color. Yep. Several of those to enjoy. Of course, there’s always the standby - double stars! You never run out of them. The links below will take you to Wikipedia for more details. So, here goes.

First, the Messier objects - M57, the Ring Nebula still one of the best planetary nebula; M11, The Wild Duck (open) Cluster in Aquila, a good wide angle object for binoculars or low power scopes; M45, The Pleiades, another great open cluster, is up later in the evening. For galaxies, there is of course M31, The Andromeda Galaxy. And if you look lots of stars in one view, you can’t go wrong with two of the best globular clusters - M13 in Hercules and M15 in Pegasus.

Two other planetary nebula are in the NGC Catalog and high overhead - The Blinking Planetary (NGC6826) in Cygnus and The Blue Snowball (NGC7662) in Andromeda. Both are slightly brighter than M57, but they benefit from averted vision. So look off to the side slightly in your field of view to get a better view.

For colorful objects, you’ll be seeing red! There’s Herschel’s Garnet Star in Cepheus, a very nice red super giant star; there’s also Antares in Scorpius, and also Arcturus in Bootes, both a very noticeable orange.

Finally, for doubles, there’s Albireo, in Cygnus and Kappa Her in Hercules. Enjoy!!!

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The Lunar 100

If you are on a mission to discover our Moon and your looking for a detailed observing guide, one of the best ones to start with is Charles Woods, Lunar 100. For a number of years now, Charles has written a frequent column about the moon in Sky and Telescope magazine. He came up with this list of 100 favorite objects and published them in 2004. It’s a great reference and the resources below will get you started.

The revised Sky and Telescope reference article is on this page, but there is also a Lunar 100 page on Wikipedia. The table in the second link is easier to work with and has many of the objects hyperlinked for further study. However, the S&T article has the Rukl chart reference number for most of the objects. Antonin Rukl’s Atlas of the Moon is one of the definitive books with all hand drawn maps that are indexed.  There is a useful wiki reference on the web if you can’t find his book. For a printed hold-in-your-hand quide, Shop at Sky has a nice laminated reference on a card. I’ll have more on the Rukl Atlas in a future post.

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Summer Geometry

The night sky is peppered with all kinds of star patterns that have fascinated human kind for untold centuries. These patterns were thought to be gods and creatures of all kinds, kindly (mostly) looking over our affairs here on Earth. For the grander groups of stars, we save the name constellation. But sometimes smaller groups appear that have an even grander attraction. We call these patterns either within (or without) their constellations asterisms.

One of the most recognizable asterisms in the sky is the Summer Triangle. Unlike many other asterisms that are confined to one constellation, with the Summer Triangle, you get three for the price of one! The key stars in The Triangle are as follows: Vega in the constellation Lyra (The Lyre), Deneb in Cygnus (The Swan) and Altair in Aquila (The Eagle). Vega is the brightest of the three and easy to find through the summer into early Fall. Once you get to know how the Triangle is placed in the sky, you can also use it as a guide to other constellations and stars.

Follow the links above to the different objects. You’ll find that the three constellations have long been associated with birds of some kind, no matter what culture is gazing up. If you’re keen to investigate the mythology, check your local library for Richard Hinckley Allen’s “Star Names: Their Lore and Meaning”. It’s one of the great modern resources for ancient astronomy.

Revel in the magic of the Three Mythical Birds of Summer!

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Jupiter’s Christmas Return

It’s now well after the Autumn Equinox and the finish of daylight savings time. Shorter days are now the rule, sunsets coming earlier paving the way for evening viewing and just in time for the return of Jupiter in the mid evening skies. So the shift grants even more time for catching the king of planets.

As we approach mid November, the giant planet will be about 4.5 AU from Earth, about 418 million miles away. The apparent magnitude is now about - 2.08 and will be increasing towards -2.15 by month’s end.

Now would be a good time to begin this season’s Jupiter viewing, coming off of the eastern horizon at 9:15PM. By late November, Jupiter will be rising much earlier and easier to catch in the evening hours.

Jupiter will be with us in the evening sky through the end of May. Plenty of time to explore the moons and features of our largest planet.

More on Jupiter in the coming weeks as the King of the Solar System brings another great season of Big Planet views. Stay tuned!

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S.V.P. Star News - How far are they?

Recently, I found this article on the history of measuring distances to the stars. Accurately measuring the distances to closeby stars allows astronomers to further calibrate their models of stars. This branch of astronomy is known as astrometry.

In august of this year, this topic got a bit more interesting with a new finding of the distance to the Pleiades Cluster. I’ve also written on the general topic of the cosmic distance scale. Not only do scientists benefit from better data in general, they can more accurately judge distances of far off objects based on their measured, or apparent magnitude.

When we look at the sky, we witness the star’s light as apparent magnitude. But we can still appreciate the object itself by consulting the data that has been compiled and calculated. Space is vast and almost beyond our comprehension. These scales give us a sense of our place in the cosmos .. and our size!

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M6 - The Cosmic Distance Scale

What do you get when you put a bunch of bright young stars together in a prominent place? No, it’s not a Hollywood casting party, it’s an open cluster! In fact, you could end up with as many as a thousand stars in one bunch. It’s “Bigger than the Oscars”!!! But we’re talking about open clusters here, not film stars.

There are quite a few open clusters in our galaxy, the Milky Way, over a thousand actually. They are usually relatively close to Earth in the so called galactic plane and thus a little easier to study. They are key elements in our understanding of stellar evolution and astronomers can use them to get a better grasp of the size of our galaxy and the universe in general.

This way of measuring how big things really are out there is known as the Cosmic Distance Scale. In order to make such measurements, we need a reference, a cosmic yard stick. And that’s where Open Clusters come in. One such cluster is The Butterfly Cluster, also known as Messier 6 (M6 is the catalog number). It’s in the constellation Scorpius.

The web site Astronomy Picture of the Day (APOD) recently had a page on M6 and the topic of how it’s used to measure this scale. Check out the link for the Great Shapley-Curtis debate over the “Scale of the Universe”. It’s guaranteed to make you feel .. well .. small!

Enjoy the party .. and .. Clear skies!

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International Moon

Recently, there were a number of news items on the web about the International Observe the Moon Night, the InOMN. This organization us a combined effort from the NASA Night Sky Network, Astronomical Society of the Pacific and other groups to promote the observation of our closest cosmic neighbor, The Moon!

They have one whole night dedicated to our Sister in space and it’s received some great coverage in the astro press as in this S&T Moonwatching story. But even though this has been organized as a once-a-year event, there are great resources listed in this article for moon watching all year long.

Also on the S&T site is this useful reference called A Month of Moonwatching. There are many great guides for lunar observing and a few get very detailed about watching the moon night by night. It can be quite involved but this article breaks it down to baby steps. It’s a great way to get introduced to the “art” of moon gazing!

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