Sunday, December 27, 2009

The Star of Bethlehem Explained?


One of the greatest mysteries of the Bible and astronomy is the Star of Bethlehem, which guided the Magi on their journey to the baby Jesus. The description of the star in the Bible leaves a lot of questions, and just as many possible answers to its true identity.

One problem, by far the biggest, must be confronted right before we can even start to narrow down the possible identities of the star: no one knows exactly when Jesus was born. Our current calendar is based on the birth of Christ. Unfortunately, this is wrong. It is now thought that Christ was actually born in the span of 8 to 4 B.C. In the Bible, the Holy Family fled into Egypt to avoid the wrath of King Herod, who died in 4 B.C. Thus, that year is the last possible year in which Jesus could have been born.

Now that our time frame has been narrowed down, we can start looking to the sky. There are two schools of thought about the Star of Bethlehem: it was either astronomical or astrological.
Astronomical possibilities include supernova, planets, comets, and conjunctions. In the year 7 B.C., there was a conjunction of Jupiter and Saturn. However, this is very unlikely as the planets were about a degree (little finger at arm's length) apart. Unless the Magi had very poor eyesight, there is no way that two planets this far apart could be mistaken for a single object. Comets have been suggested, especially since they were often described as “hanging” in the sky. This is exactly as the Star was described in the Bible. A last possible interpretation is a supernova. A bright object was seen for about 70 days in 5 B.C. By Chinese and Korean astronomers. This may just be it, but there's a problem: the star was described as moving, which leads into the other school of thought: astrology.

People at this time were almost universal believers in astrology. A notable exception here were the Jews, who were forbidden to practice astrology at numerous spots in the Old Testament. As far as everyone else was concerned, heavenly bodies had special meaning.

One thing we know was that the Magi came from the East. Considering the geographical location of Judea, “East” almost certainly meant Persia. In Persian language, the word “magi” referred to Zoroastrian priests, who practiced medicine and magic (“magic” comes from “magi”), which could also include astrology, at which the Persians were very sophisticated.

One particular passage in Matthew can greatly narrow down possible candidates for the true Star of Bethlehem. According to the Gospel, “the star which they had seen in the East went before them till it came and stood over where the young Child was.” If this is to be believed, the Star was a planet. Over the course of months, a star's position will change as it rises about four minutes earlier each night. Stars don't stand still, but planets do.

Observe a planet over the course of a year, noting where it is in the constellations. For most of the time, it moves forward. However, there are times where it stops, reverses course, stops again, then continues forward. This apparent change in direction called retrograde motion is an optical illusion caused by the Earth passing the slower planet as both orbit the Sun. A comparison can be made to passing cars on the highway. As you pass, the slower car seems to travel backwards. The same is true of planets.

Besides retrograde motion, there is more. Planets and constellations had different significances. Jupiter was widely considered to be associated with kingship. The constellation of Aires the ram was often associated with Israel/Judea. Putting this information together with the knowledge that the Star of Bethlehem was almost certainly a planet allows one to start putting the puzzle together.

In 6 B.C., an astronomical/astrological event that fits the bill very nicely occurred. In that year, the planet Jupiter (planet of kingship) moved into the constellation of Aires (the constellation for Israel/Judea). Thus, this could be interpreted as a sign that a new king of Israel was born. To add even more weight to the hypothesis, Jupiter first appeared as a morning object in the East. At this time, the Sun was also in Aires (Jupiter was rising just ahead of the Sun). In astrology, any constellation is at its most influential when the Sun is in it. Also, it was believed at the time that planets were at their most powerful as they emerged in the East after a period of invisibility in the Sun's glare.

As it would have taken the Magi months to reach Bethlehem from Persia, this also explains the motion of the Star. As time progressed, the Magi could have observed Jupiter slow down and stop before going into retrograde motion. The stoppage could have coincided with the arrival of the Magi in Bethlehem after stopping in Jerusalem and being told of the prophecy predicting the Messiah's birth there.

This is by no means more than a hypothesis. The Star of Bethlehem will probably never be conclusively explained. Either way, merry belated Christmas if you celebrated on the 25th, or merry Christmas if you celebrate on January 7.

Tuesday, December 15, 2009

Vega setting, Vega rising

On the last post explaining what was going on in the sky in the month of December, I set a unique challenge: in this season of long nights, try and observe (or even better, photograph) the same star on the set and on the rise. It is possible now and will be possible even into February. Above are my efforts from three years ago with my old HP Photosmart 945, so get out and give it a try. Click on the top picture and that cross shaped constellation (pointing straight down) is Cygnus the swan.


Setting


Rising

Wednesday, December 2, 2009

December Skies: What's Up This Month

The months of December through February are the cloudiestof the year, averaging only about 30% of possible sun, and star light. Needless to say, clear nights in December should be cherished, especially considering the sights to be seen and the fact that December brings the longest nights of the year, which allows for some unique fun. Only at this time of year is it possible to observe something twice on the same night: once on the set in the evening and again on the rise in the morning. Vega and Deneb, two bright stars of the Summer Triangle, make great targets for this once a year opportunity. I've done it, you should, too. On to constellations, December allows for observation of the sky for three quarters of the year. Take a last look at the fall constellations as the sun sets, probe the winter constellations in the dead of night, and race the light to behold the spring constellations as dawn nears. There's way too much to be seen for going into detail here, so grab your sky atlas and some warm clothing to prepare for an all night observing session that will take you through the majority of the year. As two last planetary notes, keep an eye on Mars, it will nearly double in brightness by the end of the month. Want to see Neptune? Look near Jupiter. This is the way Galileo saw it 400 years ago.

December Visual Observing Highlights

Early December: Jupiter emerges due South at twilight, no better time for telescopic observation. Also be sure to catch Venus at dawn low, extremely low, on the Southeastern horizon.
December 1: The full moon splits the sky between the Pleiades and Hyades
December 5: The waning gibbeous moon, Pollux, and Castor line up.
December 6: The moon is within 5 degrees of the Beehive Cluster. Use binoculars.
December 7: Cosmic triangle: Regulus, moon, Mars. Grab the camera. Earliest sunset of the year.
December 13/14: Geminid Meteors peak. Keep an eye to the sky about a week either side of this date.
December 18: The moon meets Mercury low in the Southwest. Test your horizon.
December 21: Winter Solstice, the longest night of the year.
December 28: The waxing gibbeous moon scrapes the Pleiades
December 31: Blue moon (second full moon of a month)
All month: Morning planets: Mars in Leo and Saturn in Virgo

Thursday, November 26, 2009

Quick Review: Canon 85mm f1.8 USM

Specifications at a glance:

Focal Length: 85mm (110mm APS-H, 136mm APS-C)
Dimensions: 2.8 by 3 inches
Weight: 15 ounces
Maximum aperture: f1.8
Minimum aperture: f22
Diaphragm Blades: 8
Lens Elements: 9 elements, 7 groups
Front element: non-extending, non-rotating
Autofocus Mechanism: Ring USM
Closest focus: 2.8 feet
Maximum magnification: 0.13x life size
Filter: 58mm

For more on the ratings system, click here.

Background:
Released in 1992, Canon's 85mm f1.8 USM lens is one of the oldest in Canon's lineup. While it may be an oldie, it's definitely a goody. In any debate of canon's best non “L” lenses, this one is sure to be brought up. With its fast aperture, USM motor, and modest price tag, this lens was designed for low light, sports, and portrait shooters on a budget. Shooting indoor sports court side is exactly why I bought this lens almost a year ago. Unfortunately, it gave the dreaded “ERR 99” and refused to autofocus about half the time on my old 300D/Digital Rebel, despite working perfectly on my newer 30D. I sent it back, which, due to B&H Photo's generous policy, was no hassle at all. Below is a brief review of the lens though analyzing some of my old pictures.

Optics: 4
Optically, this lens is a mixed bag, especially wide open. Even at f1.8, the center is sharp. Unfortunately, as one moves out, the sharpness falls off dramatically. On my 1.6x crop EOS 30D, the sharpness falloff starts about ¾ way out from the center. On a full frame camera, things in the corners must be pretty mushy wide open. Stopping down will improve sharpness across the frame. At f2.8, the center moves from sharp to razor sharp and the sharpness falloff starts to extend out further to the side of the frame. Stopping down to f4 yields virtually no improvement in the center, but the outer parts of the image continue to improve a bit. Unfortunately, the corners will never catch up to the center no matter how much you stop down. Now this may seem bad, but is it really? No, definitely not. This lens is not designed as a landscape/architectural lens where corner to corner sharpness is a must. The 85mm f1.8 USM is a portrait/telephoto/low light optic where, chances are, the subject will be in the center of the frame, where sharpness is good to start with. Chances are that, if used in its intended purpose, the soft corners of the lens won't matter anyway.

Autofocus Performance: 5
Armed with Canon's USM motor, the 85 f1.8 USM is a speed demon. Autofocus is virtually instantaneous, accurate, and to boot, just about inaudible. Needless to say, use of this lens won't be causing any heads to turn (the slap of the shutter will, though). However, be warned! With a maximum aperture of f1.8, the field of view will be razor thin the closer you are to your subject, so focus carefully. So if your images are out of focus, it may be your fault, not the lens's. Example: you do a close up portrait and focus on the end of your subject's nose. The end of the nose will be sharp but the eyes may be slightly blurry. You must focus precisely with such a fast lens. Fortunately, in well lit situations, you can stop down to f2.8 or more to achieve greater depth of field and room for error with focus.

Build/Mechanics: 4
The 85mm f1.8 USM lens is solidly built, especially considering its price point. The mount it metal and the rest of the lens externals are high quality plastics. The lens has a very dense feel about it. Shake it and there's no rattling whatsoever. The lens is inner focusing, which means that the front element does not extend or rotate during autofocus as the lens racks from macro to infinity. The focus ring is rubberized, well textured, and gives a very comfortable feel to it. Because the lens has a USM motor, the focus ring does not turn during autofocus and autofocus can be overridden by simply turning the ring at any time without the need to flip any switches. In operation, on my lens, the focus ring seemed a little snug in movement. Still, snug is better for manual focusing than sloppy. The lens takes 58mm filters.

Value: 5
This lens packs a lot of performance into a cheap package. It was selling for around $300 when I bought it and, with all the price increases, is now knocking on the door of $400. Still, it's a great value, especially considering it has the USM motor. With its excellent optics, USM motor, and build, this is a pro quality lens at a consumer grade price. If you choose to buy, you're putting your money to good use as this lens will deliver the goods every time.

Conclusion: 4.5
As a short telephoto prime lens, the Canon 85mm f1.8 USM is not a general purpose optic, it is designed for low light and/or portrait shooting. When used to its intended purpose, the lens performs admirably. Images are sharp in the center (where the action should be), autofocus is top notch, and the build is good for a consumer grade lens. On top of all that, despite the ridiculous price increases, it is still a great value considering the competition. If you own a full frame or APS-H camera and want a lens to shoot indoor sports or portraits, just go out and buy one. APS-C croppers, the story might be different for you. If you're looking to do portraits, no problem, move or have your subject move. If your game is indoor sports, one of the Canon's 50mm primes may be the better choice if you're shooting court side, as the 85mm essentially becomes 136mm. Still, crop factor aside, the 85mm f1.8 USM is a lot of fun to use, as it literally opens up new worlds in the dark.

The Ratings System

As I continue to add lens reviews, this is the rating system I will be using for the gear I test.

1 (poor)-you've bought a piece of junk
2 (below average)
3 (average)-you get what you pay for
4 (good)
5 (excellent)- among the best out there

These are the four basic areas where I will be examining the lenses:

Optics (more or less in-depth depending on how long I have the lens)
Autofocus operation (speed, accuracy)
Build/Mechanics
Value

Monday, November 9, 2009

High Marks for Canon's New EOS 7D

Digital Photography Review (DPR), possibly the web's foremost camera review site, just completed an in-depth review of Canon's new EOS 7D. While the camera's many new features (new AF system, weather sealing, and new flash system) all looked great, the adition of an 18Mp sensor left a lot of people shaking their heads in disbelief.

When Canon launched its 15Mp EOS 50D in 2008, it was found to be noisier than the old 40D, released a year before. Much of the blame was put on the smaller pixels of the new camera. Aparrently, the pixel density vs. noise limit had been reached, especially considering how other manufacturers held their pixel counts steady since the 50D regression. A lot of people were hoping for a new Canon digital SLR in the 10-12Mp range. Instead, they got the 18Mp 7D. Needless to say, a lot of people expected the 7D to be even worse.

However, what DPR found was a bit of a surprise. The 7D was not only easily better than the 50D at high ISO, but it even looks better than its chief competitior, the Nikon D300s. The image quality plus the dramatically improved features will undoubtedly give Canon shooters something to cheer about.

For more information on the 7D


Thursday, November 5, 2009

Rejoice! Standard Time returns!

Daylight Savings Time is gone and Standard Time (is it standard, it only lasts for just over 4 months) returns, which means good news for astronomers/astrophotographers.

The calendar says November, but the sky still says August, at dusk at least. With the advent of Standard Time returning, we will be treated to one last, brief peek at the summer constellations. So go out just as it gets dark to see the Teapot diving in the Southwestern sky. If you live in a dark area, you can still see the Milky Way, looking like steam, coming out of the Teapot's spout and rising up into Aquila and then through Cygnus. If the visual sight was not enough, a telescope at low power will reveal a swath of nebulae and star clusters, both open and globular, among the starry arch that is the Milky Way. Overhead and to the West, Hercules (two wonderful globulars) and Bootes (globular and double stars highlighted by Izar, which looks green and gold) are still visible. Since the summer constellations are still visible, all we need now is the warm weather!

And by the way, here's a re-edited M25.

Tuesday, November 3, 2009

New Stuff: September 2009 Astrophotos

Some good wide angle shots and three all new deep sky stunners.

Eagle Nebula reshoot. 1.5 hours total exposure, more than double last month's, to which I added more frames and stacked again. The difference in detail is clear.

The M103 open cluster.


The Little Dumbbell Nebula.


Full Moon setting over foggy field just before dawn.


Old Moon through the ED80.


Old Moon and Venus at Dawn.


Waning Crescent and Venus early in the morning.


Overexposed Moon ands Jupiter rising.















Thursday, October 22, 2009

New Stuff: August 2009 Astrophotos

August was a great month if going by the numbers. Below is a great gallery with some of everything from wide angle to prime focus in a telescope, plus one where I decided to get creative. Enjoy.

Foggy night with overexposed Moon

M2 globular cluster

Pleiades and Hyades-Star Wars style!


Eagle Nebula (M16), better one coming in Sept. gallery!


M56 globular cluster


Double star Alberio at prime focus in ED80


Gemini and Venus just before dawn


Orion rising just before dawn


Jupiter and moons at prime focus in Orion ED80.

Wide angle star clusters: Pleiades (top) Hyades (bottom).


Orange Moon rising (2 exposures stacked)


The same orange moon rising through Orion ED80


Venus and Moon through clouds


Crescent with sunset and clouds

Wednesday, October 21, 2009

New Stuff; July 2009 Astrophotos


M25 open cluster


The Butterfly Cluster (M7).







Conjunction of clusters and planets.









Jupiter due South at dawn.











The Ring Nebula (M57).













The Whirlpool Galaxy (M51). Not the greatest image in the world, but you get the picture.







Tuesday, October 13, 2009

Old Stuff: Winter 2009 Astrophoto Gallery

Not much for Winter 2008-2009. Cloudy winters in NE Ohio can be a real bummer for astronomers/astrophotographers.

M37 open cluster in Auriga

M35 open cluster in Gemini

January Crescent (yes, this is exciting stuff for Winter in NE Ohio)



Conjunction of (left to right): Venus, Moon, Mercury, Jupiter




Wednesday, October 7, 2009

Old Stuff: October 2008 Astrophoto Gallery

The Great Orion Nebula (M42) and the Running Man Nebula

The Pleiades Star Cluster (M45)



Venus (bottom) and Jupiter (top)









The Flame and Horsehead Nebulae

Sunday, October 4, 2009

Old Stuff: September 2008 Astrophoto Gallery

The Great Hercules Cluster (M13)

The Trifid Nebula (M20) and the M21 Open Cluster



M17 (Swan/Omega Nebula)






Saturday, October 3, 2009

Old Stuff: August 2008 Astrophoto Gallery

Lagoon Nebula (M8) re-shoot

The Perseus Double Cluster



The Great Andromeda Galaxy (M31) with Satellites


Friday, October 2, 2009

Old Stuff: July 2008 Astrophotography Gallery

M31 (Great Andromeda Galaxy) with satellite galaxies

M22 Globular Cluster



M15 Globular Cluster



M8 (The Lagoon Nebula)