Saturday, December 27, 2014
300,000 Hits; Wow!
I've been having a lot of problems with my Internet connectivity of late, hence the complete lack of anything for the past month and a half until a few days ago as more than a fleeting lock on a free wi-fi network is needed to do the research needed for most of my stuff here. Well, the web is back to cooperating and more stuff should be over the horizon come 2015 but, at the present, my little for-fun website had just eclipsed the 300,000 hit mark! Holy cow! Honestly, I never thought I'd be seeing anywhere near this number of hits so soon especially considering that I started this whole thing as just an online storage backup for my astrophotography. Well, just over 5 years (the first 2 accounted for only a few thousand hits) and over 300,000 hits later, all I can say “thank you!” to all of my readers. Hopefully, you've found my stuff at least a little useful as I have a lot more great stuff planned for the new year. Again, thank you and happy 2015, albeit a few days early!
Thursday, December 25, 2014
What Was the Star of Bethlehem?
It
is one of the most universally recognized images of all time but no
one knows exactly what it was. For 2000 years, the Star of Bethlehem
has captivated people the world over. Described in the Bible as the
star that led the 3 Magi to the infant Christ, little else is related
about the Star, leaving a lot of questions, and just as many possible
answers to its true identity assuming that the whole story of the
Star was not made up by the Biblical writers (the Star only appears
in the Gospel of Matthew).
One problem that must be confronted right before we can even start to narrow down the possible identities of the Star is this: no one knows exactly when Jesus was born. Our current calendar is based on the birth of Christ in that His birth separates the B.C./A.D. eras. However, it is clear that the dating is wrong as the Bible describes how the Holy Family fled to Egypt to avoid the wrath of King Herod, an well-documented historical figure who died in 4 B.C. Thus, 4 B.C. is the last possible year in which Jesus could have been born. It is now generally thought that Jesus was born anywhere between 8 and 4 B.C.
Now that our time frame has been narrowed down, we can start looking to the sky.
One problem that must be confronted right before we can even start to narrow down the possible identities of the Star is this: no one knows exactly when Jesus was born. Our current calendar is based on the birth of Christ in that His birth separates the B.C./A.D. eras. However, it is clear that the dating is wrong as the Bible describes how the Holy Family fled to Egypt to avoid the wrath of King Herod, an well-documented historical figure who died in 4 B.C. Thus, 4 B.C. is the last possible year in which Jesus could have been born. It is now generally thought that Jesus was born anywhere between 8 and 4 B.C.
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 to explain the Star 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 and, for that matter, a conjunction of 2
planets to about a degree of each other is nothing that unusual,
either. 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. Unfortunately, there are no records of
any Great Comets visible in the Middle East at that time. 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. Coincidentally, it is this astronomical focus of the Persians that can cause the traditional astronomical explanations for the Star to be discounted.
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 Christmas!
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. Coincidentally, it is this astronomical focus of the Persians that can cause the traditional astronomical explanations for the Star to be discounted.
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 Christmas!
Humble
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Wednesday, December 24, 2014
Tonight's Sky for December 24: Moon Meets Mars
New to astronomy? Want to see Mars but don't know where to look? Well, it's your lucky night as the Moon will be right next to the Red Planet.
To see the Moon and Mars, just go out after sunset and look low in the Southwest. The Moon is, of course, impossible to miss. As for that bright 'star' right next to Luna, well, that's actually Mars.
Friday, October 31, 2014
Happy Halloween 2014!
"Never mind me, I can bring you good luck . . . "
-Shadow the Cat
It's Halloween, which is not only filled with pop culture but also history and astronomy.
It's Halloween, which is not only filled with pop culture but also history and astronomy.
Pop
culture: well, wait for tonight and the scary kids and movies.
Astronomy:
October 31 is also a cross-quarter day, the mid way point of a season
in layman's terms. While inconsequential today, at the dawn of the
age of agriculture in about 5000BC, timekeeping was a matter of live
and death and any way of measuring time helped keep the latter at
bay. In addition to the seasons, the ancients would also mark the
mid-way days of any given season as important for this reason,
too.
History: with the ancients believing that the the night of October 31 was the time of the year when the barrier between the living and the dead was at its thinnest, it is also interesting to examine the ways the living have tried to contact the dead throughout the ages, especially when combined with the parallel advances in technology that resulted in spirit photography in the mid 1800s. While there are a few examples that cannot be conclusively refuted, some ghost photographs are so laughable it's hard to believe that, at one point, people actually thought they were real.
Oh, yes, black cats aren't bad luck, either. In fact, they're considered lucky in some cultures.
History: with the ancients believing that the the night of October 31 was the time of the year when the barrier between the living and the dead was at its thinnest, it is also interesting to examine the ways the living have tried to contact the dead throughout the ages, especially when combined with the parallel advances in technology that resulted in spirit photography in the mid 1800s. While there are a few examples that cannot be conclusively refuted, some ghost photographs are so laughable it's hard to believe that, at one point, people actually thought they were real.
Oh, yes, black cats aren't bad luck, either. In fact, they're considered lucky in some cultures.
Humble
Requests:
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Monday, October 27, 2014
10 Years Later: October 27, 2004 Total Lunar Eclipse
It
was 10 years ago today that I witnessed my first total lunar eclipse
and this is, so far, the only one I've managed to witness from start
to finish without any obscuring clouds blocking the show for part of
the time. Needless to say, this was quite an introduction.
It's weird how one can remember the most minute details of a memorable day (or night).
On October 27, 2004, I was in my senior year of high school and the night also coincided with a college planning event at my local community college. My parents and I went to this event (this was big for them, too) but there was more than my college education on my mind as I knew from my astronomy class in high school that there was going to be a total lunar eclipse that night that would result in the Moon turning a blood-red color.
Unfortunately, there was a problem: clouds.
In my astronomy class, I was directed toward this extremely cool website called the Clear Sky Clock, which has cloud (among other sky-related) forecasts for hundreds of locations across North America. For the night of October 27, 2004, things were looking decidedly iffy, as evidenced by the sky when stepping out of the college planning event, which consisted of a patchwork of clouds and clear sky.
Anyway, my parents took me to the Neilsen, the observatory operated by the Black River Astronomical Society (which I joined a few months after the eclipse) so I could get my extra credit in astronomy class.
Then, almost if on cue, the clouds broke for good just as the show began.
The best part about this whole night is that I have a tangible reminder: a series of pictures. In high school, I was also in the journalism/yearbook class, which allowed me access to these high-tech things called digital cameras. For October 27, I signed out a circa 2000 Sony Mavica, which used 3.5”' floppy discs (good for 6 pics each) for storage for some photo shoot (probably tennis). Needless to say, there was more on my mind than the yearbook photo shoot as I signed out the camera on the day that also coincided with the eclipse.
Taking a 'let's see what happens' attitude toward the eclipse, I brought the camera with me to the Neilsen with the intention of trying to shoot the eclipse.
Result: a series of pics I've yet to duplicate.
Just as the eclipse began, the clouds started to part for good, revealing the Moon in unobscured detail. At first, the lower left corner of the Moon began to disappear. In time, the shadow proceeded to 'eat' the rest of the Moon. Eventually, thanks to light scattering, the Moon turned blood red as totality had arrived.
Just about at midnight, totality ended and the Moon began to turn back to its normal color. At about this time, my parents (to whom I owe an enormous debt of gratitude for not only allowing, but encouraging my hobby) arrived to take me back home. After we got back, they let me stay up to watch the remaining partial phases of the eclipse, which featured the obscured Moon going back to normal for about the next hour or so.
End result: I didn't go to bed until past 2am on a school night but I got to see a total lunar eclipse from start to finish (and captured it on camera), which made being tired the next day at school well worth it.
Now, 10 years later, this still remains a feat I have yet to duplicate (darn clouds)!
It's weird how one can remember the most minute details of a memorable day (or night).
On October 27, 2004, I was in my senior year of high school and the night also coincided with a college planning event at my local community college. My parents and I went to this event (this was big for them, too) but there was more than my college education on my mind as I knew from my astronomy class in high school that there was going to be a total lunar eclipse that night that would result in the Moon turning a blood-red color.
Unfortunately, there was a problem: clouds.
In my astronomy class, I was directed toward this extremely cool website called the Clear Sky Clock, which has cloud (among other sky-related) forecasts for hundreds of locations across North America. For the night of October 27, 2004, things were looking decidedly iffy, as evidenced by the sky when stepping out of the college planning event, which consisted of a patchwork of clouds and clear sky.
Anyway, my parents took me to the Neilsen, the observatory operated by the Black River Astronomical Society (which I joined a few months after the eclipse) so I could get my extra credit in astronomy class.
Then, almost if on cue, the clouds broke for good just as the show began.
The best part about this whole night is that I have a tangible reminder: a series of pictures. In high school, I was also in the journalism/yearbook class, which allowed me access to these high-tech things called digital cameras. For October 27, I signed out a circa 2000 Sony Mavica, which used 3.5”' floppy discs (good for 6 pics each) for storage for some photo shoot (probably tennis). Needless to say, there was more on my mind than the yearbook photo shoot as I signed out the camera on the day that also coincided with the eclipse.
Taking a 'let's see what happens' attitude toward the eclipse, I brought the camera with me to the Neilsen with the intention of trying to shoot the eclipse.
Result: a series of pics I've yet to duplicate.
Just as the eclipse began, the clouds started to part for good, revealing the Moon in unobscured detail. At first, the lower left corner of the Moon began to disappear. In time, the shadow proceeded to 'eat' the rest of the Moon. Eventually, thanks to light scattering, the Moon turned blood red as totality had arrived.
Just about at midnight, totality ended and the Moon began to turn back to its normal color. At about this time, my parents (to whom I owe an enormous debt of gratitude for not only allowing, but encouraging my hobby) arrived to take me back home. After we got back, they let me stay up to watch the remaining partial phases of the eclipse, which featured the obscured Moon going back to normal for about the next hour or so.
End result: I didn't go to bed until past 2am on a school night but I got to see a total lunar eclipse from start to finish (and captured it on camera), which made being tired the next day at school well worth it.
Now, 10 years later, this still remains a feat I have yet to duplicate (darn clouds)!
Humble
Requests:
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Friday, October 24, 2014
Pictures: October 23, 2014 Partial Solar Eclipse
2 eclipses that I could actually watch in 1 month? Wow, that hardly ever happens in Northeast Ohio. Well, I got lucky. A mere 2 weeks after a total lunar eclipse, I got lucky enough to see a partial solar eclipse just by stepping outside my house and looking West. In fact, this is the first solar eclipse I have witnessed since the 1994 annular eclipse when I would have been in early grade school.
Yes,
while hardly a total variety (List: All
Solar Eclipses for the United States Until 2100), it was
nonetheless an interesting sight, featuring about a 20% obscurement
of the Sun. In practical terms, there was no noticeable dimming of
the Sun whatsoever (some passers-by looked at me pretty funny as I
was shooting the eclipse with a solar filter held over my D700/200
f4 AI Micro Nikkor combo).
Anyway, enjoy the pictures. For the record, the next visible solar eclipse for us in the States will be on August 21, 2017, during which a total eclipse will be visible in a narrow patch stretching from Oregon to Georgia.
Hint: put in your vacation requests now!
Anyway, enjoy the pictures. For the record, the next visible solar eclipse for us in the States will be on August 21, 2017, during which a total eclipse will be visible in a narrow patch stretching from Oregon to Georgia.
Hint: put in your vacation requests now!
Humble
Requests:
If you found this informative (or at least entertaining), help me pay my bills and check out my Examiner pages for space news, cleveland photography, national photography, and astronomy for more great stuff.
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For
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Sunday, October 12, 2014
In-Depth Review: Sigma 24-104 f4 DG OS HSM Art
Tech
Specs
Focal Length: 24-105mm
Dimensions: 4.3 x 3.5 in.
Weight: 31.2oz.
Maximum Aperture: f4
Minimum Aperture: f22
Diaphragm Blades: 9
Front Element: non-rotating, non-extending
Optical arrangement: 19 elements in 14 groups
Autofocus Mechanism: Sonic Drive
Closest Focus: 17.7 in
Maximum magnification: .22x
Filter Size: 82mm
Background
At Photokina 2012, third party photographic lens maker Sigma has reinvented its business model with a new Global Vision, whose focus is, among on other things, producing optics that can go toe-to-toe with the manufacturer products instead of serving as a poor man's alternative. To that end, Sigma has churned out a lot of drool-worthy gear in the past two years. However, there was a major hole in Sigma's revamped lineup: a fixed aperture standard zoom for full frame. Cue the lens we're reviewing here today: the Sigma 24-105 f4 DG OS HSM Art. With a long history of making fast to semi-fast fixed aperture zooms, Sigma has a lot of background in such optics and, with a new Global Vision, a stronger drive than ever to make class-leading products. So, does the 24-105 f4 OS Art deliver the goods? Well, read on to find out!
Focal Length: 24-105mm
Dimensions: 4.3 x 3.5 in.
Weight: 31.2oz.
Maximum Aperture: f4
Minimum Aperture: f22
Diaphragm Blades: 9
Front Element: non-rotating, non-extending
Optical arrangement: 19 elements in 14 groups
Autofocus Mechanism: Sonic Drive
Closest Focus: 17.7 in
Maximum magnification: .22x
Filter Size: 82mm
Background
At Photokina 2012, third party photographic lens maker Sigma has reinvented its business model with a new Global Vision, whose focus is, among on other things, producing optics that can go toe-to-toe with the manufacturer products instead of serving as a poor man's alternative. To that end, Sigma has churned out a lot of drool-worthy gear in the past two years. However, there was a major hole in Sigma's revamped lineup: a fixed aperture standard zoom for full frame. Cue the lens we're reviewing here today: the Sigma 24-105 f4 DG OS HSM Art. With a long history of making fast to semi-fast fixed aperture zooms, Sigma has a lot of background in such optics and, with a new Global Vision, a stronger drive than ever to make class-leading products. So, does the 24-105 f4 OS Art deliver the goods? Well, read on to find out!
Build
Quality: 5/5
The
Sigma 24-105 f4 OS Art is built to the standards that were, even just
a few years ago, reserved for manufacturer optics. Constructed out of
Sigma's exclusive Thermally Stable Composite (TSC) material, which
feels a lot like metal but whose formula is a closely-held corporate
secret, the lens has a decidedly solid feel to it. In addition, the
lens is inner focusing, which means that there is no moving/rotating
of the front element when focusing, which is good for people who like
to use polarizing filters. As for the rings, both zoom and focus
rings are rubberized, highly textured, and come across as having that
'just right' balance between ease of movement and lack of slop. For
some people, the dual cam inner design may be of a concern but, at
least in-hand, there's no wobbling whatsoever. However, I cannot
vouch for this lens when shot in harsh conditions as it not marketed
as weather resistant.
Survivability
This lens is focused by a built-in motor and stabilized by electronic gyros which will die eventually. To protect your investment, buy factory new and register your warranty with Sigma, which will fix your lens for free should something go wrong during during the warranty period and for a cost out of warranty so long as parts are available.
See also: Weather Resistant Sigma Lenses
Survivability
This lens is focused by a built-in motor and stabilized by electronic gyros which will die eventually. To protect your investment, buy factory new and register your warranty with Sigma, which will fix your lens for free should something go wrong during during the warranty period and for a cost out of warranty so long as parts are available.
See also: Weather Resistant Sigma Lenses
AF Performance: 5/5
Focus on the Sigma 24-105 f4 OS Art is as fast, accurate, and silent thanks to Sigma's Hypersonic Motor (HSM) technology, which is the company's version of a ring type sonic-drive AF system. As for tracking, the lens had no problems with birds in flight (see samples) on the D700. As with all ring-type AF, the lens has full time manual override, which allows for instantly overriding the AF simply by turning the focus ring, no need to flip switches. In reality, the AF/MF switch is more of an AF/AF Disable switch.
At 105mm
Optics: 5/5
Sharpness (Note: on DX, consider the mid frame here to be the
corner)
By looking at all the test images, a pattern emerges: the
Sigma 24-105 f4 OS Art is as good as it will get right out of the
gate at f4 across the focal range and frame, which means that
stopping down will only increase depth of field as sharpness won't
noticeably improve. Needless to say, that's a very, very good thing.
For nit pickers, there is some slight softening in the corner of the
frame on a FF sensor when viewed at 100%. For the non-pixel peepers
out there, this will be impossible to notice in real life shooting
and presentation.
Stabilizer
Mechanism
The Optical Stabilization (OS) feature is different than everything reviewed here in that there is no absolute way to quantify how well it works since the amount of camera shake is determined, by and large, on the inherent steadiness of the photographer's hand and shooting technique. That said, I was easily getting steady pictures of ½ second long at 105mm. Additionally, the stabilizer is absolutely silent in operation
The Optical Stabilization (OS) feature is different than everything reviewed here in that there is no absolute way to quantify how well it works since the amount of camera shake is determined, by and large, on the inherent steadiness of the photographer's hand and shooting technique. That said, I was easily getting steady pictures of ½ second long at 105mm. Additionally, the stabilizer is absolutely silent in operation
Vignetting
There is some shading with the Sigma 24-105 f4 OS Art wide open at f4, with it being most pronounced at 24 and 105mm. A stop down, the shading decreases dramatically and disappears by f8. At middle focal lengths, vignetting disappears by f5.6.
There is some shading with the Sigma 24-105 f4 OS Art wide open at f4, with it being most pronounced at 24 and 105mm. A stop down, the shading decreases dramatically and disappears by f8. At middle focal lengths, vignetting disappears by f5.6.
Distortion:
There is some distortion here, but nothing out of line as for what one can reasonably expect for such a lens.
There is some distortion here, but nothing out of line as for what one can reasonably expect for such a lens.
CA
Nil here.
Nil here.
Macro
While anything but a dedicated macro lens (.22x is its maximum magnification), the Sigma 24-105 f4 OS Art is still pretty good for capturing larger macro subjects, like flowers, especially with today's cameras and all of their megapixels, which allow for a lot of cropping. The above images are the full picture (albeit at a reduced resolution) with a 100% crop.
While anything but a dedicated macro lens (.22x is its maximum magnification), the Sigma 24-105 f4 OS Art is still pretty good for capturing larger macro subjects, like flowers, especially with today's cameras and all of their megapixels, which allow for a lot of cropping. The above images are the full picture (albeit at a reduced resolution) with a 100% crop.
Flare/Ghosting
This lens is remarkably resistant to flaring.
Astrophotography
Infinity focus is not exactly infinity here, which means that you will need to fiddle with focus on a bright star with live view at full magnification.
Infinity focus is not exactly infinity here, which means that you will need to fiddle with focus on a bright star with live view at full magnification.
Bokeh
With its 9-blade, rounded design, out of focus blur (bokeh) is buttery smooth.
With its 9-blade, rounded design, out of focus blur (bokeh) is buttery smooth.
Value:
5/5
Ah, here's the tough one as, at $900 new, the Sigma 24-105 f4 OS Art is not cheap by any means. On the other hand, when one looks at the manufacturer equivalents, this lens looks decidedly economical as the equivalents from Canon and Nikon, (Sony has no equivalent) both are a lot pricier. For both Canon and Nikon shooters, you get a dust seal at the mount on both of your camera makers' lenses (and an extra 15mm for Nikonians) but the question is this: do you plan to shoot in conditions that would warrant the rubber gasket at the mount that will add $250 and $400 to the price of the Sigma, respectively?
Ah, here's the tough one as, at $900 new, the Sigma 24-105 f4 OS Art is not cheap by any means. On the other hand, when one looks at the manufacturer equivalents, this lens looks decidedly economical as the equivalents from Canon and Nikon, (Sony has no equivalent) both are a lot pricier. For both Canon and Nikon shooters, you get a dust seal at the mount on both of your camera makers' lenses (and an extra 15mm for Nikonians) but the question is this: do you plan to shoot in conditions that would warrant the rubber gasket at the mount that will add $250 and $400 to the price of the Sigma, respectively?
Competition
To put it plainly, the standard zoom lens is the most crowded segment on the market for the simple reason that such lenses are just so doggone useful. The direct competitors in the mid aperture stable from the manufacturers already addressed, there are a lot of other alternatives, too. For starters, there are the 24-70 f2.8s that are, again, made by just about everyone (Sigma makes one, too). Obviously, these lenses trade about 30mm of reach for an extra stop of aperture. The extra brightness is often offset with the cost of losing the stabilization, which often results in a wash at the checkout. The exception here: Tamron, which makes a stabilized 24-70 f2.8. Current models aside, there are out of production lenses in this focal range in both f2.8 and f4 versions, some with and other without stabilization, on the used market. Again, there's a tradeoff for that lower price: questionable support from the manufacturer. Long story short, if your old lens breaks, there may not be any parts with which to fix it, which will essentially turn your lens into an expensive paperweight.
My advice: with an AF lens (especially when paying this much), it's safer to buy new and the main consideration should be the f2.8 vs. f4.
Conclusion: 5/5
There's no doubt about it: the Sigma 24-105 OS Art is quite a lens. Sturdy build, excellent mechanics, great optics, and all at a bargain price when compared to manufacturer alternatives combine to make this lens a very attractive buy. In the end, the main consideration when buying a standard zoom comes down to this: a shorter f2.8 or a longer f4 with a stabilizer. If you decide to go with the f4 optic, there's no reason not to buy the Sigma 24-105 f4 OS Art as it really does represent a package that can cover 95% of the photographic applications of the people reading this review. Needless to say, I can't wait to see what Sigma has over the proverbial horizon!
Samples:
There's no doubt about it: the Sigma 24-105 OS Art is quite a lens. Sturdy build, excellent mechanics, great optics, and all at a bargain price when compared to manufacturer alternatives combine to make this lens a very attractive buy. In the end, the main consideration when buying a standard zoom comes down to this: a shorter f2.8 or a longer f4 with a stabilizer. If you decide to go with the f4 optic, there's no reason not to buy the Sigma 24-105 f4 OS Art as it really does represent a package that can cover 95% of the photographic applications of the people reading this review. Needless to say, I can't wait to see what Sigma has over the proverbial horizon!
Samples:
Sigma Fan? Check Out These ReviewsSigma 35 f1.4 DG HSM Art
Sigma 100-300 f4 DG HSM Apo
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Wednesday, October 8, 2014
Pictures: October 8, 2014 Total Lunar Eclipse
Well, it's come and gone, the total lunar eclipse of October 8, 2014. Luckily for me, I was able to catch this eclipse in 'full' from my location (full is quoted because the Moon set at totality). Still though, this was the first eclipse not clouded out in Northern Ohio since August, 2007 event (which also set in totality).
While nowhere near as good as the October, 2004 event (has it been 10 years? I'm starting to feel old now!) thanks to the fact that this eclipse was visible from start to finish and was at totality around midnight with the Moon high in the sky, it was still nice to see an eclipse without having to peer through clouds.
So, here you go, the total lunar eclipse of October 8, 2014 . . .
So, here you go, the total lunar eclipse of October 8, 2014 . . .
Humble
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Sunday, October 5, 2014
Ebola, ISIS, and the Blood Moon Prophecy: Be Very, Very Afraid!
In a couple of nights, a total lunar eclipse will be visible for North America, the second of the so-called 'tetrad' of a cycle of 4 consecutive total lunar eclipses (which is somewhat of a rarity). As many astronomers plan to look up at the sky, prophets of doom are busy predicting the End Times, citing the Moon as a harbinger of death or, at the very least, some upcoming major change.
Reading the news headlines of today, it is not hard to deny that major world-shaping events are taking place in dramatic fashion.
First
up: the Ebola outbreak continues unchecked in West Africa and as our
oblivious government continues to allow people into our country from
this disease-infested region, it is really no surprise that Ebola
patients are starting to show up on American soil. Oh yes just go
about your lives as normals, there's no
danger of bio-terorism. Yeah, right.
Second, the terrorist group ISIS (also known as ISIL ans IS) has just beheaded another hostage in a gruesome video posted online and is again threatening to do the same to yet another captive, this one a retired Army Ranger. The fact that this group that some see as more evil than the Nazis (the Nazis at least realized what they were doing was evil and tried to hide it from the world) continues to run amok is making a lot of people nervous as we continue to debate whether or not we should put more American boots on the ground.
These two headlining stories aside, the usual tales of violence, mayhem, and immorality also continue to fill our local newspaper headlines, begging the feeling that our society is coming apart at the seams.
However, one thing is not to blame for all of this chaos: the Moon.
Starting in 2008, pastor Mark Biltz began teaching that the Second Coming was near. How does he know that? According to Biltz, he has discovered astronomical patterns (which he refuses to reveal) that led him to believe that the next tetrad of eclipses would coincide with the end times. Using technology such as his website and Youtube to spread his message, Biltz quickly built a cult-like following with modern-day doomsday believers, a following that has grown into all-out hype now that the tetrad in in process.
Cue our next prophet of doom.
Writing in his 2013 book Four Blood Moons: Something is About to Change, John Hagee notes that the last three tetrads corresponding to the Jewish feasts of Passover and Sukkot (as this current one does) correspond to pivotal events in the history of the Jewish people: the expulsion of the Jews from Spain (1492-3), the founding of modern Israel (1949-50), and the Six Day war (1967-68). As a result, thanks to the “rarity” of tetrads and their past correspondences with important events in the history of the Jews, Hagee predicts that something big is just over the course of the horizon that could mark a dramatic shift in the fortunes of the Jewish people, and, thanks to the global society we now live in, the world as a whole.
Now for facts.
For starters, Tetrads are not all that rare as there have been 62 of them in the past 2,000 years. That equates to a tetrad about every 30 years, meaning that, on average, a person will see two of them in a lifetime. As for tetrads that have eclipses falling on Passover and Sukkot, those are rarer, with only 8 of the 62 falling on such dates. Still, with about 1/8th (12%) of tetrads having eclipses falling on these two holidays, the whole tetrad-Passover-Sukkot alignment doesn't look all that rare anymore, after all, does it?
As for the other tetrads falling on these two holidays, they took place in the following years: 162-3, 795-6, 842-3, and 860-1.
Now, even with the tetrads not being all that rare in themselves, isn't it still an oddity that they happen to fall on these important Jewish holidays? Well yes, that is until you learn that the ancient Jewish calendar (still used for determining the dates of religious holidays) is a Moon-based calendar! Gee, Full Moons (the only time a lunar eclipse can occur) on dates of major holidays now have a perfectly rational explanation.
Now, as for the implication that a series of 4 consecutive total eclipses leads to pivotal events in the history of the Jewish people, this is an extreme example of the logical fallacy post hoc ergo propter hoc (“after this, therefore because of this” in Latin), which is basically false causal reasoning, an argument based on the assumption that two completely different events are related to one another in that Event A causes Event B. Example: you see a black cat (Event A) on your way to work and have a bad day at work (Event B), so you assume that the black cat caused you to have a bad day at work. Pretty stupid, huh? Well, not according to the millions of people who pushed Blood Moons into the bestseller category on Amazon, where it has remained in the top 150 titles essentially since its release.
In reality, there is only a single way that the Moon has any measurable impact of events here on Earth: its gravity. Want to see proof of this? Look no further than the famous Bay of Fundy and its tides. Gravity aside, the Moon does nothing for us here on Earth, except scare the gullible, apparently.
Hagee's false causal reasoning exposed for what it is, how about Biltz and his interpretation of the Bible?
For fundamentalist Christians, the Bible is literal truth, case closed. However, even for the most devout Bible thumper out there, there's no denying that the holy book can be very vague at times. Let's take a look at the verses Joel 2:30-31, which state that (30) And I will show wonders in the heavens and on the earth, blood and fire and columns of smoke. (31) The sun shall be turned to darkness, and the moon to blood, before the great and awesome day of the Lord comes.” This is the passage that Biltz uses as the basis for his Doomsday prediction.
Okay, there is no doubt that, if one applies natural events to this “prophecy,” the events spoken of here can only be a solar and lunar eclipse. Problem: eclipses occur in cycles thanks to celestial geometry. Result: a lunar eclipse at Full Moon is often followed by a solar eclipse at New Moon, roughly 2 weeks later. Bottom line: eclipses often follow each other, though having the perfect alignment for a pair of total eclipses is rarer, it's nothing that unusual. Doing a little math with the roughly 6-month eclipse seasons, that's roughly 4,000 such cycles in the last 2,000 years, which means that such a succession of events is nothing unusual at all.
In the end, what do we have? Well, how about two prophets of doom with theories filled with more holes than a block of Swiss Cheese.
Case closed.
Yes, when it comes to Ebola and ISIS, we have reasons to be afraid, but those reasons have absolutely nothing to do with the Moon.
Second, the terrorist group ISIS (also known as ISIL ans IS) has just beheaded another hostage in a gruesome video posted online and is again threatening to do the same to yet another captive, this one a retired Army Ranger. The fact that this group that some see as more evil than the Nazis (the Nazis at least realized what they were doing was evil and tried to hide it from the world) continues to run amok is making a lot of people nervous as we continue to debate whether or not we should put more American boots on the ground.
These two headlining stories aside, the usual tales of violence, mayhem, and immorality also continue to fill our local newspaper headlines, begging the feeling that our society is coming apart at the seams.
However, one thing is not to blame for all of this chaos: the Moon.
Starting in 2008, pastor Mark Biltz began teaching that the Second Coming was near. How does he know that? According to Biltz, he has discovered astronomical patterns (which he refuses to reveal) that led him to believe that the next tetrad of eclipses would coincide with the end times. Using technology such as his website and Youtube to spread his message, Biltz quickly built a cult-like following with modern-day doomsday believers, a following that has grown into all-out hype now that the tetrad in in process.
Cue our next prophet of doom.
Writing in his 2013 book Four Blood Moons: Something is About to Change, John Hagee notes that the last three tetrads corresponding to the Jewish feasts of Passover and Sukkot (as this current one does) correspond to pivotal events in the history of the Jewish people: the expulsion of the Jews from Spain (1492-3), the founding of modern Israel (1949-50), and the Six Day war (1967-68). As a result, thanks to the “rarity” of tetrads and their past correspondences with important events in the history of the Jews, Hagee predicts that something big is just over the course of the horizon that could mark a dramatic shift in the fortunes of the Jewish people, and, thanks to the global society we now live in, the world as a whole.
Now for facts.
For starters, Tetrads are not all that rare as there have been 62 of them in the past 2,000 years. That equates to a tetrad about every 30 years, meaning that, on average, a person will see two of them in a lifetime. As for tetrads that have eclipses falling on Passover and Sukkot, those are rarer, with only 8 of the 62 falling on such dates. Still, with about 1/8th (12%) of tetrads having eclipses falling on these two holidays, the whole tetrad-Passover-Sukkot alignment doesn't look all that rare anymore, after all, does it?
As for the other tetrads falling on these two holidays, they took place in the following years: 162-3, 795-6, 842-3, and 860-1.
Now, even with the tetrads not being all that rare in themselves, isn't it still an oddity that they happen to fall on these important Jewish holidays? Well yes, that is until you learn that the ancient Jewish calendar (still used for determining the dates of religious holidays) is a Moon-based calendar! Gee, Full Moons (the only time a lunar eclipse can occur) on dates of major holidays now have a perfectly rational explanation.
Now, as for the implication that a series of 4 consecutive total eclipses leads to pivotal events in the history of the Jewish people, this is an extreme example of the logical fallacy post hoc ergo propter hoc (“after this, therefore because of this” in Latin), which is basically false causal reasoning, an argument based on the assumption that two completely different events are related to one another in that Event A causes Event B. Example: you see a black cat (Event A) on your way to work and have a bad day at work (Event B), so you assume that the black cat caused you to have a bad day at work. Pretty stupid, huh? Well, not according to the millions of people who pushed Blood Moons into the bestseller category on Amazon, where it has remained in the top 150 titles essentially since its release.
In reality, there is only a single way that the Moon has any measurable impact of events here on Earth: its gravity. Want to see proof of this? Look no further than the famous Bay of Fundy and its tides. Gravity aside, the Moon does nothing for us here on Earth, except scare the gullible, apparently.
Hagee's false causal reasoning exposed for what it is, how about Biltz and his interpretation of the Bible?
For fundamentalist Christians, the Bible is literal truth, case closed. However, even for the most devout Bible thumper out there, there's no denying that the holy book can be very vague at times. Let's take a look at the verses Joel 2:30-31, which state that (30) And I will show wonders in the heavens and on the earth, blood and fire and columns of smoke. (31) The sun shall be turned to darkness, and the moon to blood, before the great and awesome day of the Lord comes.” This is the passage that Biltz uses as the basis for his Doomsday prediction.
Okay, there is no doubt that, if one applies natural events to this “prophecy,” the events spoken of here can only be a solar and lunar eclipse. Problem: eclipses occur in cycles thanks to celestial geometry. Result: a lunar eclipse at Full Moon is often followed by a solar eclipse at New Moon, roughly 2 weeks later. Bottom line: eclipses often follow each other, though having the perfect alignment for a pair of total eclipses is rarer, it's nothing that unusual. Doing a little math with the roughly 6-month eclipse seasons, that's roughly 4,000 such cycles in the last 2,000 years, which means that such a succession of events is nothing unusual at all.
In the end, what do we have? Well, how about two prophets of doom with theories filled with more holes than a block of Swiss Cheese.
Case closed.
Yes, when it comes to Ebola and ISIS, we have reasons to be afraid, but those reasons have absolutely nothing to do with the Moon.
Humble
Requests:
If you found this informative (or at least entertaining), help me pay my bills and check out my Examiner pages for space news, cleveland photography, national photography, and astronomy for more great stuff.
If
you think this was cool, why not tell a friend?
For
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follow
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