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Lets have a look at the diagram below. The Moon travels around the Earth (blue arrow), and half of the lunar surface always is lit by the Sun (the half that is facing the Sun), while the other half is dark. The lunar phases are caused by the relative positions of the Sun, Earth, and Moon. Because the Moon orbits the Earth, different portions of the Moon seem to be lit by the Sun.

The phases on the image below are numbered from 1 through 8. At the bottom of the image you can see which bright part of the Moon we see.


© Image by backyard-astro.com


1. New Moon (day 0)
The Moon is between the Sun and the Earth. Its dark side is facing the earth and we cannot see the Moon in the nighttime sky. Its bright side is facing the Sun. The new Moon rises in the east around sunrise, and sets in the west near sunset.

2. Waxing (growing bigger) crescent Moon (day 3)
The Moon looks like a crescent. In the Western evening sky, it can be found to the east of the Sun. Its bright "horns" always point away from the setting Sun. It sets a few hours after sunset.

3. First quarter (day 7)
After 7 days the Moon has travelled 1/4 of its way around the Earth since new Moon. We see 50% of the sunlit half of the Moon and 50% of the lunar disk is dark. It rises around noon and sets at midnight.

4. Waxing gibbous Moon (day 10/11)
After the first quarter we see more than half of the bright side of the Moon. The visible part of the sunlit side of the Moon grows every night until the Earth is between the Sun and the Moon and we reach full Moon)

5. Full Moon (day 14)
The Moon is now halfway in its orbit around Earth, and we can now see the entire bright side of the Moon. The full Moon rises at sunset and sets in the Morning at sunrise. It is visible all night.

Now the Moon starts with its second half of the orbit around earth. It proceeds like the first half but then in reverse.

6. Waning (growing smaller) gibbous Moon (day 18/19)
The visible bright part of the Moon grows smaller night after night.

7. Last quarter or third quarter (day 22)
Again we see 50% of the bright half of the Moon and 50% of the dark half of the Moon. It rises at midnight and sets at noon.

8. Waning crescent (day 26)
Only a small part of the sunlit half of the Moon is visible. The waning crescent rises in the morning sky, before the Sun rises. It's bright "horns" are always pointed towards the rising Sun.

After 29.5 days the Moon is new again (number 1 in the diagram) and the cycle starts all over again. The period of 29.5 days (29 days, 12 hours and 44 minutes) between two successive new Moons is called a synodic month or lunation.
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Image 1: Overview of a nearly full Moon


Overview
On the image above, an overview image of a nearly full Moon (which I shot in August 2004 with the TAL 100RS mounted on a photo-tripod!), the transparent yellow patch represents the area that you is shown on overview image 2 and 3. Image 1 his been severely processed, to emphasize the contrast between the Maria and the Terrae.

Maria and Terrae

Roughly, the lunar landscape can be divided in two types of surface, the dark areas known as Maria and the light areas known as Terrae. The Maria, or seas, are the grey smooth plains on the lunar surface. The Terrae, also known as highlands or uplands, are the bright and rugged areas of the Moon, full with craters, mountain-ridges and other interesting features. But why are they called Maria and Terrae?

In the year 1609, Galileo was the first person to look at the Moon with a telescope. Galileo concluded from his observations that the Moon's geography was not so different from our earth. He saw mountains, valleys and plains. Mistakenly he thought that the dark smooth areas he saw were oceans. That's why he called them Maria (Latin for seas). The brighter parts, a much more rugged terrain, were called Terrae (Latin for lands). In reality however, the Maria tend to be the lowland and the Terrae the highland.

Copernicus-Riphaeus area
Before we take a closer look at Copernicus, I would like to point out a few other interesting features that can be seen on the images 2/3. Lets start in the Southwest with Montes Riphaeus and Euclides (Rukl 40/41). Tonight this isolated mountain range was visible near the terminator. The formation immediately drew my attention because of its distinct form. Together with the southwestern rim of Euclides P it looked like a starfish with the crater Euclides at its centre. Euclides is a young, simple impact crater with a very sharp and well-defined rim. Its diameter is 12km. In stark contrast with this young crater is the old crater Euclides P, which lies to the north of Montes Riphaeus, on the shores of Mare Insularum. The crater almost completely vanished beneath dark Mare material. The tip of the arrow that points out Euclides P touches the southwestern rim of the crater.



Images 2 and 3, Copernicus and Montes Riphaeus area (click to enlarge)


To the northeast of Euclides P lies the Apollo 12 landing area. To the East of the Montes Riphaeus, in the hills north of Fra Mauro (Rukl 42) you can see the Apollo 14 landing place. Between Reinhold and Copernicus (Rukl 31) lies the double-crater Fauth and Fauth A. Together they are shaped like a keyhole. On the Apollo 12 image (image 5) you can see Fauth-Fauth A in close up, lying before Copernicus.

Copernicus
My favorite crater on image 2/3 is Copernicus, a young crater from the Copernican period (somewhere between the present and 1.1 billion years ago). Copernicus is a typical Tycho-style large complex crater. It has a diameter of 93 km and a depth of 3750 meters. The crater rim rises to a height of 1100 meters above the surrounding terrain. The 54 km wide floor looks more or less flat with a group of central peaks. The walls are terraced, which you can see only vaguely on image 2/3, but if you have a closer look at the Apollo image (image 5) the broad terraces are very obvious.

A blanket of ejecta surrounds Copernicus, which is typical for a complex crater of this size. Near full Moon you can see the extensive crater ray system that surrounds Copernicus (see image 4 below, image taken with TAL 100RS). The Copernicus rays are very bright. This is caused by the fact that during the impact that formed Copernicus, pieces of bright highland material were excavated and launched into all directions. The bright material landed on top of the darker Mare lava, producing a beautiful contrast.



Image 4 (left), Copernicus crater rays (click to enlarge), Image 5 (right), Copernicus (click to enlarge) Image credit: NASA


Copernicus is definitely my favorite complex crater. Next time I will try to get some high-resolution images of the crater itself and its immediate surroundings. « Collapse

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M 42 and M 43
I took of with the Orion nebula (M42). What struck me was the fact that this nebula was easier to detect and better “visible” in my 85mm Zeiss at the lowest possible magnification (16x with the Televue Plossl), than it was in any other instrument I have been using. I checked Roger N. Clark’s book, Visual Astronomy of the Deepsky, and found out that the ODM (Optimum Detection Magnification) for this nebula is about 14x when using a 4-inch instrument under dark skies. My TAL 200K is an 8-inch and M 42’s ODM for this instrument is 27x. The lowest possible magnification on my 8-inch is 62.5x and on the Zeiss I get 16x with the same eyepiece, a 32mm Televue Plossl. In other words, the 3.3-inch Zeiss comes much closer to the ODM than the 8-inch TAL. I don’t know for sure, but maybe that’s why M 42 is best in the Zeiss. M 43 was also visible in the Zeiss using just a little averted vision. In the 8-inch 200K M 43 was not more apparent then in the 3.3- inch Zeiss.

Anyway, after studying M 42 and M43 in the 85mm Zeiss, I switched to the TAL 200K for some medium to high power views of the Trapezium. I was lucky tonight! Despite the mediocre seeing conditions, for the first time ever I immediately detected the 5th Trapezium star (at 166x with the 12mm Lanthanum), the so-called E-component, from my own light polluted backyard. I have already seen the E and F component two years ago from a dark sky site, but never from my own backyard. The central area of the Orion Nebula normally takes very high magnifications well, but tonight 222x (7mm Vixen Lanthanum) was the maximum for the Trapezium area. Higher magnifications only blurred the view.

Eskimo Nebula (NGC 2392)
The Eskimo nebula, the brightest planetary in the winter night sky, looked awesome tonight. At the lowest magnification (62.5x) it was clearly visible as a fuzzy ball of light with averted vision. With direct vision the nebula disappeared, but the 10th magnitude central star popped into view, exactly the same effect as with the Blinking Planetary (NGC 6826) in Cygnus. At 400x (this nebula did allowed high magnification tonight!) it was clearly visible that the nebula consists of a brighter inner circle and a slightly darker and fuzzier outer circle of nebulosity. This is a very rewarding object to observe. I tried all filters and magnifications available. I noticed that the OIII filter has its limitations on my 8-inch with high magnifications. Above 166x (12mm eyepiece) the OIII makes the view to dark. I can observe much more detail at high magnifications without the OIII. At 200x I found the overall image I got at its best. I did not detect the dark ring that separates the brighter inner part from the somewhat dimmer outer ring. I have not detected “the eyes” of the Eskimo.

NGC 2903, M65 and M66
Later that night I decided to have a go at some galaxies in Leo, NGC 2903, M65 and M66. These three more or less bright galaxies in Leo stayed almost completely “invisible” tonight. I could detect the brighter core of NGC 2903, but that was all there was to see. M 65 / M 66 stayed invisible. Not a good night for galaxies, even not for the few brighter ones I sometimes can observe from my backyard.

Saturn and M 44
As time went by, the seeing became worse and worse. Around 23.00 hours UT I aimed the 200K on Saturn. High magnifications proved to be completely useless. It only blurred the view of Saturn. I decided to have a look through the 85mm Zeiss, and at 30x the view was simply wonderful! Saturn and M 44 filled the field of view almost completely. M 44 is a real object for binoculars and rich field telescopes. When it teams up with one of the planets, it always looks spectacular! This was the highlight for me tonight. The stars looked just like sparkling diamonds, and together with the bright Saturn the overall view was simply awesome.



Image from Skytools 2 by CapellaSoft (click to enlargr)


Castor, Iota Cancri, Alcor and Mizar, Sirius and Polaris
I ended my observing session with a few beautiful (double) stars. Castor at 133x showed only the AB pair as two bright white stars. At the time I was observing Castor I didn’t know that there is a C component, a magnitude 8.8 red dwarf, about 73” from the A component. I will try to observe this faint companion next time.

Iota-1 Cancri is one of my favorite doubles. Even in the 85mm Zeiss at 60 to 70x the two components are visible as a golden a blue pair, almost as beautiful and striking as Albireo. This double should be on everyone’s observing list, just like Alcor and Mizar. This naked eye-duo looks great through almost every instrument. I simply enjoyed the view through the small refractor for a few minutes, before I pointed the Zeiss at Sirius, the brightest star around. Now I could see the quality of this small instrument. Sirius looked just like a bright white star. No colors visible around the edges and no Fringe Killer needed!

Last but not least was Polaris. Believe it or not, after all these years, this was the first time I looked at Polaris with my telescope, and I found this double surprisingly easy to see. Polaris has two components A and B. A is a magnitude 2.0 yellowish star and the much fainter B (magnitude 8.2) can be found at a position angle of 218 degrees and at a distance of 18.4”.

At 00.30hrs UT I decided it was time to pack up, after four and a half hours of freezing cold. Around 2 o’clock AM local time I sat indoors, warmed by the heater, enjoying a glass of malt whiskey (no ice) and dreaming about the beautiful objects I had seen tonight. These are the nights that keep me in this wonderful hobby……..




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There were three craters visible with well-defined central peak(s), Tycho, Longomontanus and Moretus. Moretus also showed its terraced walls tonight, a very pretty sight. On the floor of Gruemberger, there was a feature that casted a needle-shaped shadow, but I don’t know if Gruemberger really has a kind of central peak. The floor of Gruemberger looked very rough, not smooth, like the floor of Longomontanus. Maginus looked like a good example of an older crater with degraded walls, while Tycho is the complete opposite, a very young crater with an extensive ray-system (that is best observed around full Moon).

I roamed through this wonderful area for more than two hours, and at the end of my observing session I shot a few images. I’m really proud of the image below, which is the sharpest single-shot image I ever managed to get of this particular interesting region. I used the 8-ich TAL 200K, the Nikon Coolpix 4500 and a 20mm Vixen Lanthanum eyepiece (equipped with a Baader IR block-filter). I also used a 2x Xtend-a-View pro from EagleEye OpticZoom. This little gadget made focusing the coolpix a lot easier.

Anyway, both images below are identical, but the image on the left is simply the image as it is and on the image on the right I added the names for the most prominent (and some not so prominent) features in the Longomontanus-Clavius-Moretus region. Click on the images to enlarge. Enjoy!





The image is a single shot image (not stacked) taken on January 9th 2006, 21.06 UT. Shutter time was 1/30s, f=5.1, 4x optical zoom, iso 100. The image was processed (unsharp masking, resize, levels, de-noised on several different levels).

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The Moon
We started with the Moon. The view through the TAL 250K and bino-viewer was simply stunning. The first thing that caught our attention was the alpine valley area. The view of the Alps and especially the shadows they casted, were awesome. They looked like a row of teeth on the lunar surface. Then there was in the same field of view the extremely long, triangular shadow of Mons Piton. To the north-northwest of Piton, the tops of Mons Pico and the mountain just to the south where lit by the Sun while the base and Mare floor where still in the shadows. Just right in front of the Alps some of the Mare ridges where visible.

To the south of the Alps, a part of the northeastern part of the Apennines was already visible, and with the bino-viewer it was as if we observed the mountain chain in 3-D. To the south-southeast of the Apennines, on the edge of Mare Vaporum, was a large rectangular area visible. It looked just like a big landslide to us. With the bino-viewer, Rima Hyginus with the crater in the middle, was again a wonderful sight. To the west of Hyginus, part of the Rimae Triesnecker complex was visible.

On the southern hemisphere, the most interesting feature was the group a group of four craters, Ptolemaeus with to its east Albategnius and to its south Alphonsus and Arzachel. On the floor of Alphonsus, a dark patch could be seen on the western rim of the crater floor. This is probably the result of some volcanic outfall.

We observed the Moon for quite some time, and we concluded that with the bino-viewer the views are simply the best. You see much more detail than with one eye, and observing is not tiring at all. You can observe using both eyes for hours on end. What also surprised us was that you could see Rima Hyginus with the 85mm Zeiss Diascope, with the zoom-eyepiece at maximum zoom (60x). The quality of this small birding-scope is very good.



Image shot with the Coolpix 4500, Zeiss Diascope and Zeiss zoom
eyepiece a few hours before the actual observing session


Saturn
We only had a short look at Saturn. The seeing was deteriorating quickly (a lot of moisture in the air), and high magnifications were useless. However, the Cassini division was very clear, and we could also see a dark band across the surface of Saturn. We are still discussing about this dark band, was it the shadow of the rings, or a dark zone in the clouds of Saturn?

Deepsky
We started with M 35 in Gemini. This large open cluster looked best in the 8-inch Vixen, because of the wide field of view (f/4 800mm) that you get with this instrument. From there we went to Orion. M 42 was unbelievable in the bino-viewer. Of course you can only see a small part of this nebula in the TAL 250K, using the bino-viewer, but the views were great, even without the nebula filters. The area around the trapezium is one big complex of nebulosity, which you can observe again and again, and you always will see new details. We did not detect the E or F component of the trapezium group (theta Orionis). With the Zeiss Diascope at 60x, the Orion Nebula looked like a big bird flying through the skies with its wings spread. It was amazing to see how far out both nebulous wings spread out from the centre. Again a very pretty sight. M 43 was also visible in the 85mm refractor, using a little averted vision.

We also looked for the running man (dark area between NGC 1973, 1975 and 1977) but we did not detect any nebulosity in the area. The same goes for the Horsehead nebula (IC434) and M 78. They also stayed invisible, even with the nebula filters we used.

Next on the list was M 44 (Praesepe) in Cancer. This is really a wide open cluster, and it fitted niceley in the 8-inch f/4 Vixen and the 85mm Zeiss. The best view however was with the 15x80 binoculars. Saturn and M 44 nearly fitted into the same field of view! From M 44 we moved to Gemini again. This time for a planetary nebula, the Eskimo Nebula (NGC 2392). It was very easy to spot at higher magnification (fuzzy appearence), but at low powers it just looked like a star. With the bino-viewer and the two Zeiss eyepieces, you could see a grayish, equally bright centre and a fuzzy outer ring around it (probably the Eskimo’s fur-lined hood). We did not see “the eskimos eyes” which you see on the many photographs. From there we hopped south into Monoceros to have a look at the “Christmas Tree”, NGC 2264. It didn’t fit into the TAL’s field of view but with the 8-ich Vixen, it looked just fine, a small Christmas tree. We also looked for Hubble’s variable nebula, but it was “invisible”. Hubble’s variable nebula (NGC 2261) is very intriguing object. Sometimes you simply just see it, and sometimes it is completely invisible.

Finally, we observed a few double stars with the Zeiss. Cor Caroli and Alcor/Mizar are still two of my favorites after all these years. The Zeiss shows them really well, esthetically a beautiful sight. Around three o clock we packed up after six hours of observing. After two months of cloudy nights, last night was a real treat! « Collapse