Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / Chasing Comets and Conquering Light Pollution

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Chasing Comets and Conquering Light Pollution · Star Trails: From Backyard Astronomy to Cosmic Wonder

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Howdy Stargazers, and welcome to this episode of Star Trails.
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I'm Drew, and I'll be your guide to the night sky for the week starting October 20th to
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the 26th.
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This week brings meteor showers, conjunctions, some classic deep sky objects, and of course,
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a comet that has everyone talking.
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We'll complete a celestial family drama that played out in Greek mythology, and later in
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the episode we'll talk about the scourge of stargazers, light pollution, and what we can
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do about it.
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So grab a comfortable spot under the night sky, and let's get started.
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Comet C 2023 A3, also known as Shushin Shin Atlas, is currently one of the most exciting
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celestial objects in the sky.
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It reached its closest approach to Earth on October 12th, and will remain visible in the
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evening skies throughout this month.
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Look for it around twilight, shortly after the sun sets, and make sure you have an unobstructed
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view of the western horizon.
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The comet is steadily climbing higher each night, making it easier to observe as the
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days progress.
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By October 26th, it will be about 38 degrees above the horizon.
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That's about the height of four fists held at arm's length to the sky.
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And it sets roughly four and a half hours after sunset.
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During this period, the comet's tail is expected to become more prominent, stretching dramatically
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as it moves further from the sun.
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If you're in a location with dark skies far from city lights, you may even spot some
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detailed features of the tail.
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While binoculars or a small telescope will enhance your view, it may also be visible
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to the naked eye in optimal conditions.
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This period may be the best chance to observe this comet, as it won't return for tens of
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thousands of years.
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The moon will be rising later in the evening this week, which may prove useful for comet
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spotting.
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I went out and photographed comet A3 a few days ago, and I can confirm it's a spectacular
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object, visible even in the light of the full supermoon.
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With averted vision, I was barely able to make it out, but it jumped out of the sky
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in my 11x70 binoculars.
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I was able to photograph it using an iPhone in night shot mode, and it looked great at
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200mm when photographed with a full-frame, mirrorless camera.
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It took me two tries to spot A3.
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My first effort went horribly awry as I attempted to locate it against the bright backdrop of
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metropolitan light pollution near my home.
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But since we've had consecutive clear nights lately, I decided to try spotting it the next
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evening, but this time I drove about an hour into one of the most desolate counties in
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my state, to a location where I've had good success shooting the Milky Way in the past.
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Lens still weren't great.
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I was fighting against both the brilliance of the full supermoon and time.
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The comet was low in the sky.
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I estimated it was about 10 degrees above the horizon by the time I arrived, so it wasn't
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going to hang around long for photos.
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I put my camera on a tripod and found an old barn to place in the foreground for some wide
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shots.
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Then I switched to a 200mm lens for a closer view, and before I left, I placed my iPhone
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on a tripod to see how those would turn out.
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I discovered that if you're in a reasonably dark area, a steadily held smartphone using
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a night shot or astronomy mode can easily capture this comet.
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Although I did manage to eke out a few images, I won't be entering these into a competition
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or even sharing them on social media.
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I plan to make another effort in the coming days, provided we have clear skies, and I
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encourage anyone listening to go out and see this comet now before it's too late.
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The last time I saw a comet this spectacular was Haley's Comet in 1985 when I was just
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10 years old.
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A3 is really that good, so go get your eyes on it if you can.
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And not to be captain obvious here, but the darker the skies, the better your view will
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be, and that goes for every object in the night sky.
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In the second half of the show, I'll tell you how you can find the darkest skies in
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your neck of the woods.
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But first, let's find out what else is happening in the sky this week.
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The last quarter moon is on October 24th, so you'll see half of it illuminated, rising
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late at night and setting in the early afternoon.
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Before that, on October 20th and 21st, keep an eye out for a nice conjunction of the moon
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and Jupiter.
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As the second brightest planet in the sky, Jupiter will shine brightly next to the moon
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all night long.
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By the end of the week, on October 26th, the moon will also be hanging out with Regulus,
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the red heart of the constellation Leo.
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This early morning pairing will be a great way to start your day just before dawn.
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Jupiter will be visible all night long, hanging out in Taurus.
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As I mentioned, you'll see it in conjunction with the moon on the 20th and the 21st, but
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it will be shining brightly throughout the week.
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Saturn is situated in the constellation Aquarius and is a perfect target for telescope viewers,
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especially with its rings becoming more edge-on as we head into 2025.
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You'll spot Mars rising in Gemini later at night, around midnight by week's end.
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On the night of October 23rd, it will also pass close to the moon, another conjunction
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worth checking out.
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Meanwhile, Venus, our bright evening star, will be glowing low in the southwestern sky,
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especially around October 24th when it appears next to the bright red star Antares in Scorpius.
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Don't forget the Orionid meteor shower, peaking tonight and into the morning.
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These meteors come from Haley's Comet and shoot across the sky at 41 miles per second.
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Be aware the moon will be quite bright during the peak, which means it may drown out some
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of the fainter meteors.
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Try to block the moon behind a tree or building and focus on the darker parts of the sky.
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Later in the week, the Leonis-Manorids meteor shower peaks on October 24th, but these are
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a bit quieter, with fewer meteors per hour.
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For deep sky enthusiasts, the Perseus double cluster will be well positioned in the northern
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sky on October 26th.
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This duo of open star clusters NGC 869 and NGC 884 are about 7,500 light-years away,
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and you can find them nestled between Perseus and Cassiopeia.
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Even with just binoculars, you'll be able to see this rich field of stars sparkling
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against the darkness of space.
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Also well placed this week is the Andromeda Galaxy, our nearest galactic neighbor.
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At about 2.5 million light-years away, it's the largest galaxy visible from Earth and
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can be spotted with the naked eye if you're in a dark area.
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You'll find it in the constellation Andromeda, rising higher in the sky as the night goes
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on.
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And for telescope users, the Triangulum Galaxy M33 is another great target.
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It's the third largest member of our local group of galaxies and offers a beautiful spiral
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structure for those with larger scopes.
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You'll find it in the small constellation Triangulum, which is located roughly between
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Andromeda and Aries.
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Lastly, don't miss the Pleiades, or Seven Sisters star cluster.
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This open cluster in Taurus is always a breathtaking sight, and it will be visible in the eastern
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sky.
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A prominent constellation that rises this time of year is Cepheus, the king.
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If he sounds familiar, it's because he's been a big player in some of the night sky
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lore we've discussed recently, particularly in the stories of Andromeda, Cassiopeia, Cetus,
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Pegasus, and Perseus.
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Right near the constellation's Cassiopeia and Draco, Cepheus is best seen in the northern
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sky during the fall and early winter months.
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It's easily identifiable by its house shape, a five-sided figure that somewhat resembles
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a child's drawing of a house with a peaked roof.
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The constellation contains several notable stars, including Alderaemon, the brightest
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star in Cepheus, and Delta Cephe, which has been critical in the study of variable stars.
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In fact, Delta Cephe is the prototype of Cephed variable stars, which astronomers use to measure
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distances to far off galaxies.
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Another highlight is the Garnet Star, a strikingly red supergiant that shines with a deep, ruddy
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hue.
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Cassiopeus also hosts IC 1396, an expansive star-forming region containing the Elephant's
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Troncnebula, a favorite among astrophotographers.
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According to Greek myths, Cepheus was the king of Ethiopia, and he was caught up in some
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celestial drama after his wife, Cassiopeia, boasted that she was more beautiful than the
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sea nymphs.
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Cassiopeus angered the sea god, Poseidon, who sent a sea monster, Cetus, to ravage their
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kingdom.
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To appease Poseidon, Cepheus and Cassiopeia sacrificed their daughter, Andromeda, by
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chaining her to a rock.
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But the hero, Perseus, swooped in riding Pegasus to save her just in the nick of time, and
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she ended up marrying him.
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The entire family is immortalized in the night sky as constellations, with Cepheus often depicted
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as a king on his throne or holding a royal scepter.
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If you like fast cars, you've at some point probably heard the expression, there's no
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replacement for displacement, meaning that you can bolt on a turbo or a supercharger in
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various go-fast parts that boost an engine's power, but at the end of the day, the greatest
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performance will come with more displacement, in other words, a bigger engine.
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In astronomy, and especially astrophotography, there are tricks to pull dim objects from
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light-polluted skies, such as techniques involving filters, exposure stacking, certain types
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of cameras and computer processing.
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But everything gets a lot easier to deal with, and viewing is much more enjoyable if you
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can simply relocate to darker skies.
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Today we'll talk about the Bordle Scale, which measures the brightness of the night sky based
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on light pollution, and will get into practical ways you can still enjoy the stars even if
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you live in a brightly lit area.
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This light pollution scale was developed by astronomer John E. Bordle in 2001.
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The scale ranges from 1 to 9, with 1 being the darkest, most pristine sky you could ever
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imagine, and 9 being a sky flooded with artificial light, such as in the middle of a large city.
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If you've looked at any astrophotography online recently, you'll often see the photographer
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mentions the Bordle rating of the area where the photo was taken.
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Knowing your rating can give you a great sense of what you'll be able to see from your location
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or capture with your astrophotography rig.
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Let's break down a few key levels of the Bordle Scale.
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Bordle 9 is the worst of the worst.
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Think of downtown in a major city like New York or Tokyo.
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Here, you might only be able to see a handful of the brightest stars.
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Forget about spotting the Milky Way or planets other than Venus or Jupiter, and you can't
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see any deep sky objects.
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Bordle 7 and 8 are suburban skies.
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You'll see more stars than in the city, but the Milky Way is still a no-show.
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You'll be able to spot a few planets and the brighter constellations like Orion in winter
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or Scorpius in summer.
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I live in a transitional zone between Bordle 7 and 8, just a few miles outside a metropolitan
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area.
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But still, with binoculars, I can spot star clusters and some major nebula, such as the
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Great Nebula in Orion.
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Bordle 4, 5, and 6 are rural skies, with varying degrees of light pollution.
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In 5 or 6, you can start to see the Milky Way on a clear night, but it's faint.
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As you move toward Bordle 4, the Milky Way gets clearer, and you might spot some of the
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brighter nebula and the Andromeda Galaxy.
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When I went out to photograph Comet A3 a few days ago, my location was in a Bordle 4 zone.
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My local astronomy club's observation site is also located in Bordle 4.
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Bordle 2 and 3 zones are considered truly dark skies.
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You can see the Milky Way shining brightly, and if you have a telescope, you can start
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tracking down faint galaxies.
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Bordle 1 is the dream.
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A truly dark sky where the Milky Way is so bright, it casts a shadow.
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You can see thousands of stars, all the constellations, the zodiacal light, and even faint details
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of nebula without any equipment.
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It's the kind of sky you can find in remote deserts, high mountains, or far out at sea.
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I live in a southeastern state where Bordle 4 is common in between small cities and a few
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metropolitan areas.
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In my experience, I typically need to drive about 30 miles away from my home location
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to get truly dark skies.
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In my state, we have a handful of small areas that are Bordle 3 or even 2.
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So how can you determine what zone you're in and where some darker skies are?
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My favorite resource is, of course, a website.
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Visit lightpollutionmap.info and click anywhere on the map to get detailed information on
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the sky brightness at that point.
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Zooming out will give you an idea of where light pollution hotspots are, and I'll include
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a link in the show notes.
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If you're stuck in a Bordle 7 or 8 zone, there are ways to enhance your stargazing.
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First up is reducing local light interference.
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It sounds simple, but blocking out nearby street lights or house lights can make a big
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difference.
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These nearby light sources wreak havoc on your night vision.
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And a spot where they aren't shining in your eyes.
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Even moving just a few blocks away from bright street lights or heading out to a park or
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field can make a difference.
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If you can, seek out higher ground, hills or rooftops where there's less light reflecting
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off nearby surfaces.
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Filters are another tool in your kit.
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Light pollution filters like a UHC that's ultra high contrast or a CLS, City Light Suppression
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Filter, can help cut through some of the artificial light by blocking certain wavelengths, such
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as those emitted by street lights.
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These filters really improve the visibility of faint objects like nebula, star clusters
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and galaxies, even in moderately light polluted areas.
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Astrophotographers who live in areas with a lot of light pollution have devised some smart
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techniques to deal with pollution.
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As with visual observation, a broadband light pollution filter can be especially useful.
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These selectively block the most common types of artificial light, like sodium vapor and
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certain LED lights, which are the main culprits in city and suburban lighting.
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You can also use narrowband filters, which only let through very specific wavelengths
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of light.
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These are useful for photographing nebula as they enhance the light emitted by ionized
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gases while filtering out other types of light.
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Another strategy for astrophotography is using a monochrome camera with narrowband filters.
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Monochrome cameras, as the name suggests, don't capture color the same way a regular
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DSLR might.
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They essentially shoot black and white images, so you have to use red, green and blue filters
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to create the layers for an RGB image.
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There are other useful filters for monochrome cameras too.
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By capturing different wavelengths separately, usually hydrogen alpha, oxygen 3, and sulfur
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2, you can build up a detailed high contrast image even in areas with significant light
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pollution.
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After capturing each filter's data, you can stack the images in image processing software.
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This technique is a favorite among astrophotographers who shoot in urban areas because it allows
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you to essentially exclude the wavelengths you don't want to capture, such as those of
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light pollution.
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Regardless of the camera used, image stacking is an essential technique for almost all astrophotography
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nowadays.
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By taking multiple long exposure shots and then using software to combine them, you can
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increase the signal to noise ratio in your final image.
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This helps to bring out faint celestial objects while minimizing the impact of light pollution.
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Programs like Deep Sky Stacker or Pixensight are popular for this technique, and the results
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can be stunning even from a city.
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Light pollution doesn't just affect our ability to see the stars, it's also impacting
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wildlife.
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Artificial lights confuse animals that rely on natural light cues for navigation, migration,
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and reproduction.
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Birds, sea turtles, even fireflies can suffer from the excess light that we throw into the
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sky.
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So reducing light pollution isn't just about us as stargazers, it's about keeping nature
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in balance too.
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Some communities are adopting dark sky initiatives.
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These efforts work to replace traditional street lights with shielded, downward-facing
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lights, which reduce unnecessary outdoor lighting and promote even more efficient lighting
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designs.
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It's a win for the environment, energy use, and of course for stargazing.
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That's it for today's episode of Star Trails.
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If you found this episode informative or entertaining, please share it with a friend.
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The easiest way to do that is by visiting our website, startrails.show, where you can
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find all of our episodes, including transcripts, night sky maps, and more.
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Until next time, keep looking up and exploring the night sky.
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Clear skies, everyone!