How to estimate Danjon Scale of Brightness

Lunar eclipses get their colorful red-orange hues from sunlight that is filtered and bent by the Earth's atmosphere around into its shadow. This is the light of all the world's sunrises and sunsets ringing the globe at the time. Bright and colorful eclipses occur when our planet’s upper atmosphere is most transparent. Major volcanic eruptions spew dust and aerosols into the stratosphere, resulting in darker lunar eclipses.
The Moon's brightness varies greatly from eclipse to eclipse, which would tell a lot about the state of the Earth's upper atmosphere if only we understood it better. To help in compiling statistics of this kind, many observers rank each eclipse they see on the five-point Danjon Scale.

Danjon Scale of Brightness

0 Very dark eclipse, Moon almost invisible, especially at midtotality.


1 Dark eclipse, gray or brownish coloration; details distinguishable only with difficulty.


2 Deep red or rust-colored eclipse, with a very dark central part in the umbra and the outer rim of the umbra relatively bright.


3 Brick-red eclipse, usually with a bright or yellow rim to the umbra.


4 Very bright copper-red or orange eclipse,with a bluish, very bright umbral rim.



An even simpler technique was advocated 80 years ago by Harvard astronomer Willard Fisher, who graded mid-totality into three classes depending on the equipment needed to see details on the Moon's surface: (1) the naked eye, (2) a 50-millimeter finderscope or binoculars at 7x, or (3) a 150-mm (6-inch) telescope at about 20x. Fisher reasoned that the Moon's surface brightness is unaltered by the aperture, but the visibility of low-contrast features like lunar maria depends greatly on the image scale. The darker the eclipse, the greater the aperture (and power) needed.

Still another useful gauge is the Moon's stellar magnitude at mideclipse. People who wear thick eyeglasses can simply take them off, turning the Moon and bright stars or planets into blobs of about equal size for easier comparison. Looking through the wrong end of binoculars also works.


courtesy sky and telescope

Useful Projects for a Lunar Eclipse

Amateur astronomers often plan how they'll take photographs, image sequences, or even time-lapse videos of a lunar eclipse. But don't overlook the scientifically useful projects that are just begging to be carried out. You don't need anything but clear skies and some very simple equipment.


Color


Total lunar eclipses come in a great variety of brightnesses and hues. In February 1860, Irish amateur Mary Ward likened the Moon to "a red-hot penny" in the sky. But the famously dark eclipse of December 1963 was so dim that some skywatchers could not find the Moon when they stepped outdoors near mid-totality!


To help in comparing reports from various observers, even years and cultures apart, French astronomer André Danjon devised a five-point scale that is still used today. To learn how to give this eclipse a Danjon L rating, read the article about it in this blog.


Brightness


For many years Brazilian astronomer Helio C. Vital has led a very active group of observers in monitoring the brightness of the eclipsed Moon, not only as it moves across the shadow but also from one eclipse to the next. For example, he's found that a total eclipse is fairly bright if it takes place when Earth's atmosphere is nearly free of aerosols. But within a few years after a major volcanic eruption, eclipses are often much darker. Some darkening was even detected after the October 6, 2006, eruption of Mount Rabaul in Papua New Guinea.


So how do you make an estimate? If you wear thick glasses you can try taking them off so the Moon and bright planets or stars look like equal-size blobs. Looking through the wrong end of binoculars also helps. 


Size of the Umbra


Timings of celestial events offered early mariners a way to find their longitude far from home. This method was used by Christopher Columbus, who timed the start and end of a lunar eclipse in 1504 during his fourth trip to the New World. When astronomers tried to refine this method, however, they quickly found that the dark center of the Earth's shadow, called the umbra, was larger than pure geometry indicated by about 2%, because our atmospheric sheath adds to Earth's effective diameter. 


To time when the Moon's edge enters or leaves the shadow is often iffy. Instead, it's more accurate to time when individual spots and craters cross the shadow's edge. For example, from 697 crater timings sent in by Sky & Telescope readers, I derived an enlargement of 2.1% for the July 1982 eclipse. But for a similar event only six months later, 298 timings gave 1.7% enlargement. In each case the probable error was less than 0.1%. So the enlargement definitely varies slightly from eclipse to eclipse, for reasons not yet understood.


The Moon photo above has prominent features labeled on it, and you can click here for our predictions of their entrance and exit times in the umbra. Before making your timings, set a watch to accurate radio time signals. Write down the time (to the nearest 5 seconds) when the edge of the umbra crosses the center of the crater or other feature. It's as simple as that! (The shadow edge is a little fuzzy, so try to judge the point where light is falling off most rapidly and adopt that for your timings. Use a 2.4-inch or larger scope.)


If you carry out any of these simple projects at the next eclipse of the Moon, please e-mail the results to us for later analysis.


But no matter what you do, set aside a little time to sit back and enjoy the eclipse, too!


courtesy - sky and telescope

 Total eclipse of the MOON, June 15, 2011 A.D.; Wednesday

The eclipse will be visible in INDIA

 Area of visibility: The eclipse will be visible in the region covering South America, Africa, Europe, the Middle East, Asia, Australia, Antarctica and Atlantic, India and southwestern Pacific Ocean.

The places from where the beginning of the umbral phase is visible at the time of moonset are some regions of South Pacific Ocean, Fiji, some region of North Pacific Ocean and parts of north-eastern Russia.

The places from where the ending of umbral phase is visible at the time of moonrise are some regions of South Pacific Ocean, parts of western Chile, Bolivia, parts of North West Brazil, some region of North Atlantic Ocean.

CIRCUMSTANCES OF THE ECLIPSE

	Indian Standard Time
Moon enters penumbra Moon enters umbra Moon enters totality Middle of the eclipse # Moon leaves totality Moon leaves umbra Moon leaves penumbra	15d 22h 53.1m 15d 23h 52.6m 16d 00h 52.1m 16d 01h 42.6m 16d 02h 33.0m 16d 03h 32.6m 16d 04h 32.2m

* Magnitude of the eclipse = 1.705

Occultation prediction for DELHI India for January 2011

Occultation prediction for DELHI India

Visible with moderate telescope of 6" (15cm) dia.

    day  Time   P   Star  Sp  Mag  Mag    % Elon Sun  Moon   CA   PA  VA

  m  d  h  m  s      No  D     v    r V  ill     Alt Alt Az   o    o   o

Jan 14 14 57 35 D     435 F5  5.8  5.6S  70+ 114     78 234  88N  73  24

47 Arietis

Jan 15 17 54 59 D     584cB9  6.1  6.0v  80+ 127     53 272  68N  58 345

Jan 16 19 23 45 D     742SG8  5.8  5.2   88+ 139     46 276  75S 100  27

Jan 17 22 27 19 D     916SG7  4.3        95+ 153     19 287  65N  65 358

Jan 18 15  0 19 D    1047SA2  5.3  5.3   98+ 164     51  90  38S 144 215

Jan 20 21 38 28 R    1344 K5  6.5  5.7   99- 166     61 244  78S 290 236

Jan 22 17 32 45 R    1566cK4  6.3  5.6   88- 140     28 103  78S 286 345

Jan 22 22  6 48 m    1582wA3  6.4  6.3   87- 138     62 196   9S 217 203

Jan 23  0 41 27 R    1587DF2  5.9        87- 137     38 246  89S 298 245