Orion is proud to partner with BBC Sky at Night Magazine, the UK's biggest selling astronomy periodical, to bring you this article as part of an ongoing series to provide valuable content to our customers. Check back each month for exciting articles from renowned amateur astronomers, practical observing tutorials, and much more!
Pete Lawrence looks at how your images can help monitor the position of potentially hazardous objects crossing Earth's orbit.
Asteroids or minor planets are small Solar System bodies that are visible because they reflect sunlight. The larger members of this group have dimensions measured in hundreds of kilometers, but asteroids can be as small as 1m along their largest axis. Most asteroids are located in what's known as the main belt, a huge repository for such objects located between the orbits of Mars and Jupiter. In all but very rare circumstances, asteroids appear star-like through amateur scopes. Visually, they can be measured in terms of their brightness, position and occasional apparent interactions with other objects.
The sheer number of asteroids in orbit around the Sun means that occasionally we get to see one occult a distant star. Asteroid occultations provide an important way to determine the shape profile of these rocky bodies.
Accurate date and time recording is vital when observing asteroids, as it is this information which ultimately is used to refine the objects orbit and position.
Asteroids look just like stars when viewed through a telescope. It's only when their positions have been noted or photographed over an extended period — normally days — that their motion and true nature is revealed. Most asteroids appear to move slowly against the background stars but those that venture close to Earth may have enough apparent speed to appear to move in real time when viewed through a telescope or binoculars.
Bodies that have orbits bringing them close to Earth are known as near-Earth objects (NEOs) of which near-Earth asteroids (NEAs) are a subset. NEOs larger than 140m that cross Earth's orbit are classed as potentially hazardous objects (PHOs) and again, asteroids form a subset known as potentially hazardous asteroids (PHAs). To date, all known PHOs are PHAs.
Scientific asteroid images for astrometry and photometry need to record the body as a sharp dot without trailing. For slow-moving asteroids this may not be an issue, but fast movers require short exposures or setups that track the asteroid itself. This is especially useful for the high-cadence photometry necessary to determine the light curve, and hence spin-rate, of an asteroid.
For more general appeal, in outreach material for example, a fast-moving asteroid provides a convenient way to produce a trail that would otherwise take many extended exposures to capture. In this instance, a correctly polar aligned telescope tracking at the sidereal rate or, better still, autoguided on the stars, will produce a sharp star field with the asteroid as a light trail. A similar effect can be created by aligning shorter exposures on the stars, and stacking them with the brighter elements set to show through.
Many asteroids are within range of a basic telescope and DSLR setup. For scientifically calibrated work, CCD cameras, (preferably with specialist filters) are recommended. By using planetary imaging techniques, larger telescopes may even be able to capture larger asteroids as extended discs during favorable oppositions, rather than the usual star-like dot.
Use software to help you plot the exact position of small space rocks
Measuring the position of an asteroid is an important step in determining and refining its orbit. This is especially true for asteroids on eccentric orbits, which have the capacity to pass close to Earth. Smaller bodies returning to the inner Solar System may have been gravitationally perturbed, leading to changes in the previously established orbit, and these need to be monitored.
The astrometry of asteroids is similar to comet astrometry, with the exception that asteroids are somewhat easier to measure, appearing as singular dots of light without the complexity that accompanies the expansive head of a comet.
It is recommended that serious astrometric measurements follow the guidelines set out by the International Astronomical Union's Minor Planet Center (MPC), available online at www.minorplanetcenter.net/iau/info/Astrometry.html.
The basic workflow for the astrometric measurement of an asteroid is quite straightforward. First you need to obtain a set of images that include the object you intend to measure. Then you'll need some software assistance to measure the position accurately; the shareware Astrometrica is highly recommended.
Astrometrica allows you to 'blink' your images, which should reveal the asteroid moving against the static star field. The software will need to identify the star field in the images in order to determine the asteroid's position. You can help here by manually identifying the star field and supplying Astrometrica with the correct RA and dec. coordinates for the center of the imaging frame. Once entered, the program attempts to match the star field.
If it doesn't quite get things right, you can adjust the alignment manually. Astrometrica's star template can be adjusted for scale with a focal length used setting, for rotation with a position angle setting and positionally with an onscreen arrow key pad. Once the alignment has been set, clicking on the object will generate an MPC compatible log file of positional data which can then be submitted according to the submission guidelines.
Accurately plotting of the brightness and shape of distant asteroids is a team effort
Occasionally an asteroid will pass in front of a star, dimming the star's light as it goes. There are numerous programs available to predict such events as well as websites, such as Euraster, which presents results without you having to having to calculate them yourself.
A typical asteroid occultation path will be a narrow track and may require you to travel to a specific location in order to view and record the event. This adds additional complexity in that it requires the use of a portable observing and recording setup and a means to accurately calculate your location and altitude. The modern way to do this is with some form of GPS recorder.
One of the hardest parts of observing asteroid occultations is to locate the star that is going to be occulted. This can be done using a Go-To system, but you often need to use very accurate star charts to augment the process, especially when the star to be occulted is very faint.
A common way to record asteroid occultations is with a low light video camera. The resulting video, normally recorded in the AVI format, can then be analyzed by specialist programs such as LiMovie or Tangra, which are both available for free.
A successful occultation should produce a light graph for the star that shows it dim as the asteroid passes in front of it and brighten as the asteroid moves out of the way. Accurate timing of the star's dimming will produce a line profile across the asteroid. Interesting though this is, such profiles really become useful when multiple observers record and communicate these events. With multiple profiles recorded, it's then possible to produce a more complete profile of the asteroid.
Obviously for this to be of any worth, a highly accurate time signal needs to be used. A device such as the International Occultation Timing Association's video time inserter (IOTA-VTI; https://occultations.org) is an ideal way to do this as it has the capability to insert coordinated Universal Time (UTC) on every frame of a recorded video signal.
ABOUT THE WRITER
Pete Lawrence is an expert astronomer and astrophotographer who holds a particular interest in digital imaging.
Copyright © Immediate Media. All rights reserved. No part of this article may be reproduced or transmitted in any form or by any means, electronic or mechanical without permission from the publisher.
Orion is proud to partner with BBC Sky at Night Magazine, the UK's biggest selling astronomy periodical, to bring you this article as part of an ongoing series to provide valuable content to our customers. Check back each month for exciting articles from renowned amateur astronomers, practical observing tutorials, and much more!
Astro imager Will Gater explores the photo opportunities presented by the myriad spacecraft that can be seen speeding overhead through the night.
Nightscape images that contain glinting Iridium flares or space stations have been a staple of astro-imaging for decades. For beginners, they're great targets to practice your skills on, and it's possible to get really striking images with a basic setup consisting of nothing more than a DSLR and tripod. If you have a bit more experience, don't dismiss shooting a satellite or space station; even advanced photographers can find fresh challenges in experimenting with the framing and foreground of such photos, and in finessing the quality of the final shot. Done well, these pictures can really spark the imagination in ways that other types of astro-images might not.
The timing, brightness and location on the sky of any potential Iridium flares is dependant on your location, so — just as with ISS and other bright-satellite passes — in order to find out when and where one will be visible from your site you'll need to consult a website like Heavens Above (www.heavens-above.com). Once you have this information you can set about planning your shot.
The free planetarium software Stellarium (www.stellarium.org) is particularly useful for this as you can use its plugins to overlay a rectangle showing the size of your camera's field of view on the sky. By cross-referencing the Stellarium view with the information and star chart from Heavens Above, you can identify the path and position of whichever satellite you're aiming to catch and try out different compositions. Stellarium can show the track of the ISS on the sky, and the paid app SkySafari Plus can also perform the same task.
Shooting a series of consecutive 10- to 20- second exposures at a mid-range ISO with a DSLR, kit lens and static tripod will pick up most bright satellite passes. With Iridium flares, aim to start capturing images about 90 seconds prior to the predicted flare time and end the series about the same amount of time after the flare reaches its brightest; this way you'll capture a pleasing trail that slowly builds in brightness, peaks, then fades away. You can then bring the series of images you've captured into processing or stacking software and combine them, so that the short trail in each photo joins the others to form a longer one.
Since most satellites zip across the sky, capturing a series of photos from a static tripod will result in gaps in the final 'combined' satellite trail due to the short delay between exposures. To get around this you can mount your camera on a tracking mount and take one, much longer, single exposure. This requires balancing the exposure length — which will need to be several minutes — with the lens aperture, ISO setting and sky brightness, but can produce attractive unbroken satellite trails against rich, starry skies. Remember, if you do this any foreground will be slightly blurred.
One of the most exciting areas of satellite astrophotography to develop in recent years is imaging the International Space Station passing in front of the Sun or Moon. Imaging these 'transits' requires extensive planning, but the resulting pictures are extraordinary. A typical transit might last seconds, — sometimes much less — and will only be visible from within a narrow strip of Earth's surface. To find out when an ISS transit is visible near your location you can use the excellent ISS Transit Finder (transit-finder.com). If you intend to image a solar transit, where the space station is silhouetted against the disc of the Sun, you'll need to use a certified solar filter for your telescope and be sureto remove any finderscopes. Here are the key steps required to capture this thrilling phenomenon with a scope and DSLR camera.
Step 1: Plan
Find out when a transit will be visible nearby using the ISS Transit Finder website. You may have to travel to be in a position to capture the event. Use planetarium software to check where in the sky the Sun or Moon will be.
Step 2: Setup
Next set up your scope and have it track at the solar or lunar rate (depending on your target). If you're imaging the ISS transiting the Sun, fit a specialist, certified solar filter and remove any finder scopes.
Step 3: Focus and exposure
Focus the view — use the terminator if viewing the Moon, or sunspot or the solar limb if viewing the Sun. Whether you capture stills or video, make sure that the exposure length is very short so that the ISS does not blur.
Step 4: Capture video or a rapid burst of stills
Start capturing video or a burst of stills as the moment of the transit approaches; that way if there is a slight error in your timing you'll still get the shot. For a DSLR video use the highest frame rate that the camera allows.
Step 5: Review, extract and process
Review and process the frames from our video or still images that show the ISS. Software such as PIPP (https://sites.google.com/site/astropipp) can extract still frames from videos. Then process and enhance the images.
If, like us, you remember fondly the days of NASA's Space Shuttle, you may well recall that on occasions the spacecraft and its — just-detached — external fuel tank would be visible passing over the UK shortly after launch. There was nothing quite like watching the rocket roar off the pad live on NASA TV then seeing the very same shuttle and orange fuel tank — both appearing as points of light; the orbiter appearing white, the fuel tank a subtle ochre tint — silently glide overhead. Though the Space Shuttle is no longer flying, there's still occasionally a chance to catch a similar spectacle thanks to one of the new generation of ISS-servicing spacecraft: SpaceX's Dragon capsule.
Whether you'll be able to see the capsule on its way to the ISS just after lift off depends on the conditions of its launch. For the capsule to be visible, it needs to be dark or deep twilight in the UK, but the Dragon itself has to be in sunlight as it flies over. Helpfully, the CalSky website (www.calsky.com) publishes visibility predictions for some of the Dragon spacecraft around the time of scheduled launches to the ISS; you simply input your location details and it will tell you if the Dragon will make any visible passes. The pass you want to look out for — if it's listed — is the one that's about 20 minutes after the expected launch time, as that'll be the Dragon making its first flyover after departing the Florida coast. It's worth keeping an eye on either the NASA TV or SpaceX online video stream that usually accompanies the launch too, as it'll let you know if the lift off gets scrubbed.
One of the things that's so exciting about catching the ISS-bound Dragon just after lift off is that, from here in the UK, it's not just the capsule you get to see. Dragon is propelled into orbit by a SpaceX Falcon 9 rocket, and the separated upper stage of that rocket is visible next to the capsule as it passes over.
Not only that, but Dragon itself jettisons two solar-panel covers after lift-off and these appear either side of the spacecraft as two points of light which repeatedly brighten and fade during the pass as they tumble away. It's a truly electrifying sight and one that can be captured easily using a DSLR, static tripod and 50-100mm lens, and the same basic technique described in 'Nightscapes with a sparkle'. We've even been able to film Dragon firing one of its thrusters during a pass, using a DSLR and a telephoto lens.
Ordinarily, high frame rate cameras are used to create detailed images of targets like the lunar surface and planets. But it's also possible to use them to capture high-resolution shots of the ISS showing its modules and solar arrays.
The primary challenge with this type of imaging is tracking the rapidly-moving ISS, since most high frame rate camera and telescope combinations will provide a small field of view that is tricky to keep centred on the station.
Tracking is typically done manually with the help of an accurately aligned finderscope and the mount's handset set at the highest possible slew rate or, in some cases, carefully manoeuvring the telescope by hand. Essentially you start your computer recording a video from the camera and hope that at some point during the pass your guidance causes the ISS to race through the frame.
Focusing can be done in advance on a bright star — or even better, the Moon — while the correct exposure length will depend on the setup you're using; crucially it'll need to be short enough to stop the ISS from blurring and this may mean that you have to greatly increase the camera's gain to compensate.
The reason it's possible to see the ISS against the starry sky is that, at the altitude of its orbit, it's still illuminated by the Sun. Sometimes, however, the ISS will disappear into the darkness of Earth's shadow. Just before it does that you can see and image one of the most beautiful satellite phenomena of all: the ISS experiencing 'orbital sunset'.
As the station slips into the shadow, the Sun sinks below the Earth's limb as seen from the ISS in orbit. In the last moments leading up to that 'sunset' the whole structure is bathed in a deep-orange light. And because that light is the same sunlight that illuminates the station as it passes over us, from the ground the ISS turns from a brilliant white to a deep orange-red, before disappearing.
This effect can be seen clearly in binoculars from suburban sites, but is a particularly rewarding target for imagers and naked-eye observers under darker skies. The passes in which the ISS moves into Earth's shadow are clear in the night-sky charts that accompany each ISS pass prediction on Heavens Above (www.heavens-above.com); they're the ones where the pass seems to abruptly 'stop' amongst the stars. Point your camera in the direction of that end point and — with a long exposure of a minute or so using a DSLR on a tracking mount — you should pick up the gradual fade to orange in the ISS's trail.
Iridium 'flares' appear as a brief and slow-moving point of light that brightens rapidly and fades just as fast. They are produced when the antennas of any of the numerous of Iridium communications satellites catch the Sun's light and reflect it back to Earth. In January, the first in a new fleet of Iridium satellites was launched. The antennas of these new satellites aren't as reflective, so the days of Iridium flares could be numbered.
ABOUT THE WRITER
Will Gater is an astronomy journalist, author and presenter. Follow him on Twitter at @willgater or visit willgater.com
Copyright © Immediate Media. All rights reserved. No part of this article may be reproduced or transmitted in any form or by any means, electronic or mechanical without permission from the publisher.
Orion is proud to partner with BBC Sky at Night Magazine, the UK's biggest selling astronomy periodical, to bring you this article as part of an ongoing series to provide valuable content to our customers. Check back each month for exciting articles from renowned amateur astronomers, practical observing tutorials, and much more!
Astronomer Will Gater reveals the best way to observe and image transient and evolving celestial phenomena, and how you can help scientists in the process.
For most of us our interest in astronomy is, and hopefully will continue to be, a lifelong passion. In 10, 20, even 30 years from now we'll look up to the night sky and in the stars, galaxies and nebulae that fill our view we'll see old friends, unchanged over all that time. The truth is, of course, that the stars and galaxies we see are moving through space, and nebulae are evolving — they're just changes that are unfolding on an extraordinarily long cosmic timescale.
But that's not to say that we humans can't perceive any alteration or movement in the night sky. Quite the opposite. One could argue that the heart of amateur astronomy — and indeed one of the key elements of astronomy as a field of scientific study — is a rich and deep tradition of observing the changing night sky, from the appearance of comets to the monitoring of variable stars and the searches for supernovae in distant galaxies.
In the following pages we're going to explore some other transient and evolving celestial phenomena that you can observe and photograph with relatively simple equipment — the kind of kit that many amateurs have access to — so that you can see for yourself that the sky, and indeed the cosmos all around us, really is in motion.
While the planets might be the quintessential 'wandering stars', drifting against the night sky's sparkling backdrop over weeks and months, there are other objects within the Solar System whose movement across the heavens is far more dramatic — so much so that their motion against the stars can be discerned over hours and minutes, rather than many days. Near-Earth asteroids are small, typically irregularly shaped bodies, whose orbits bring them relatively close to our planet at times. If a near-Earth asteroid is big and bright enough it can be a thrilling object to catch sight of in a telescope eyepiece, or capture on camera, as it makes a close approach. ESA maintains a database at http://neo.ssa.esa.int/web/guest/close-approaches that you can examine to see when any large, relatively, bright objects are next passing by — and of course the BBC Sky at Night magazine Sky Guide will usually contain news of upcoming notable near-Earth asteroid passes.
Watching a near-Earth asteroid slowly wander across a star field at the eyepiece can be tremendously exciting, but it's the sort of target that really requires a medium- to large-aperture instrument to be seen well. On the other hand, even a modest astrophotography setup can capture brighter near-Earth asteroids — here we explore how.
Step 1 — Equipment Small refractors or Newtonians combined with a CCD camera or DSLR are well-suited to imaging bright near-Earth asteroids; we've even had success using just a DSLR and a 135mm telephoto lens. You'll also need a mount that can track the sky accurately for a few minutes at least.
Step 2 — Track and focus Set up your imaging kit. If you're using an equatorial mount get the polar alignment (and thus the mount's tracking) as accurate as you can, as this will help both image quality and processing later on. Next, focus on a bright star — ideally with the help of a Bahtinov mask.
Step 3 — Locate and image capture Use Stellarium (stellarium.org) and its Solar System Editor plug-in to find a near-Earth asteroid's location. Slew to the coordinates, take brief test exposures, then cross-reference the star field with Stellarium. When you've confirmed the near-Earth asteroid is in frame, check it's not moving out of shot. Capture a series of exposures.
Step 4 — Stack or animate You should now have a set of images (typically taken over several tens of minutes) that shows the near-Earth asteroid moving between frames. You can now process and stack these together with your chosen image processing software to show the asteroid's path, or collect and save the frames as an animated GIF.
As astronomers we're familiar with the Moon's phases, caused by its movement around the Earth and the changes in illumination that come from the varying geometry of the Earth, Moon and Sun relative to one another. Prior to full Moon, the boundary demarcating night and day on the lunar globe, and the line that gives the phase its 'shape' — called the terminator — is the swathe of terrain where the Sun is rising over the lunar landscape. At this point in the lunar cycle the phase is waxing (growing), as the terminator travels across the disc. After full Moon the terminator moves westwards from the eastern limb once again, but is now where the Sun is setting, with the phase waning (shrinking).
This night-by-night movement of the terminator, and consequently the daily change in the lunar phase, is large and easily visible to the naked eye. But you can also observe and image subtle variations in the Moon's phase over the course of just one night. Watching the Sun rise or set over a chain of mountains or a large crater rim is a captivating observing experience; it is quite something to see the lighting change, and shadows lengthen or shorten. It's evidence of the Moon's orbital motion, happening right in front of your eyes.
The UK winter months, when the Moon is high for hours in a dark sky, are an ideal time to attempt the observation. Our favourite targets to see this phenomenon on are the large craters Copernicus and Plato — the latter especially, for the shadows from its rim that creep across its smooth floor — the lunar Alps and the Sinus Iridum.
A high frame rate camera and a modest amateur telescope can capture the changes easily. If you are able record an AVI video every 20-30 minutes or so for several hours, you can create dramatic animations of the changing illumination. This requires each processed image produced from the raw AVI videos to be brought into software — such as Photoshop or GIMP — as a separate layer. Multiple layers within a single picture can then be saved as an animated GIF file.
Taking pictures or making observations of some of the phenomena we've covered in this article can be an exciting experience in itself, but it's also possible that your records could help professional astronomers with their research. For example, if asteroid imaging is your thing, the scientists working on the OSIRIS-REx mission — which will return samples from the surface of the asteroid 101955 Bennu in 2023 — run a project called Target Asteroids! (https://www.asteroidmission.org/get-involved/target-asteroids) It uses data captured by amateurs to help learn more about certain asteroids. Alternatively, if you've been lucky enough to capture a picture or timelapse of the Northern Lights on holiday, the Aurorasaurus citizen-science project (http://aurorasaurus.org) is collecting images of a poorly-understood auroral phenomenon dubbed, rather unusually, 'Steve' — if your snaps show the unusual filamentary feature they could be useful to researchers.
And of course many national astronomical societies and organisations gather reports and observations of transient and changing astronomical phenomenon sometimes for publication and analysis in their journals.
So whether it's through a citizen-science project or a more traditional endeavour, like meteor counting, planetary imaging or variable star observing, there are many ways that we amateurs can make a meaningful contribution.
We needn't look lightyears out into space to find evidence of the dynamic and ever-changing nature of the cosmos we live in. In fact you'll find it on our celestial doorstep in the form of our star, the Sun. This seething ball of plasma is constantly changing. Its churning 'surface' — the photosphere — is occasionally pockmarked by dark, transitory, blemishes known as sunspots, while above huge tendrils of plasma, called prominences, rise and waver as they are corralled by the star's magnetic fields.
To observe these features safely however you'll need specialist equipment. To study the photosphere, for example, a telescope needs to be fitted with a certified solar filter and any finder scopes should be removed too. With careful and correct use and installation — conforming to the manufacturer's instructions — certified solar filters can provide superb views of evolving sunspots and large sunspot groups.
There are also specialist dedicated solar telescopes available which, as well as filtering the Sun's light so it is safe to view, show only certain specific wavelengths of the Sun's radiation. One type of dedicated solar telescopes shows what's known as the 'hydrogen-alpha' band in the Sun's spectrum. These solar scopes reveal a layer in the Sun's atmosphere known as the chromosphere and in doing so open a window onto one of the most dynamic regions of our star.
While an ordinary certified solar filter will show the solar photosphere as a smooth whitish or yellowish disc, perhaps marked by sunspots or speckled bright patches known as faculae, a hydrogen-alpha solar telescope will show the Sun's chromosphere as a bright, scarlet-red globe shrouded in a mass of plasma 'fibres'.
A hydrogen-alpha solar telescope will also often reveal the prominences leaping off the limb of the Sun, and these can change in literally a matter of minutes, meaning they are a wonderful target for high-resolution imaging where spectacular animations can be made of their evolution. Sketching can be a great way to record the changes in these features too.
The powerful magnetic fields associated with sunspots also have an effect in the chromosphere. There they manifest themselves as bright 'active regions' where loops of plasma twist and turn around the dark sunspots. Like prominences these too can change and evolve over short periods. Sometimes they may even exhibit very bright, fleeting, beads or filaments of light. These are thrilling events for solar observers and imagers, and are known as solar flares.
One of the most obvious signs that we live on a rock spinning in space is the motion of the stars across the sky during the course of a night. This movement is a result of Earth rotating on its axis, and you don't need a hugely advanced setup to capture it on camera; a DSLR, wide kit lens and static tripod are ideal for tackling a classic star trail shot. Leave the shutter open for 30-60 seconds and the rotation of the Earth will blur the stars into short arcs. If you want to take things a step further, try creating a timelapse of the sky — and perhaps the Milky Way too — moving. You can use the same kit as for a star trail shot, but you'll need to approach the way you capture the images in a slightly different way. For timelapses you don't actually want the stars to trail. What you need are for them to be points of light so that when you come to animate the shots it looks almost as if the sky is a static picture that's drifting over a landscape. This may mean that you have to keep the exposure length short, increase the ISO and open your lens's aperture right up to compensate. When you've found the right settings, set the camera taking exposures continuously, say for 30 minutes for a short timelapse. You'll typically capture hundreds of photos doing this, so make sure your camera's memory card and your computer are up to the task! The images can then be processed as a group in image processing software and then imported into a video editor to be animated into a smooth video. There are numerous ways of achieving the latter — for example in iMovie you'd do it by setting the 'duration' of each still image to 0.1 seconds. This technique can also be used to make timelapses of other dynamic astronomical phenomena, such as aurorae and noctilucent clouds.
A particularly fine chance to watch the motion of the heavens is on offer in the UK this month when, in the early hours of the morning on 6 November, the gibbous Moon will occult (slip in front of) the bright star Aldebaran in Taurus. As the Moon journeys across the background stars of Taurus, Aldebaran will disappear behind the brightly lit western limb of the Moon, emerging 40-60 minutes later from behind the unlit eastern limb. Occultations are great events for video astronomy, so if you have a digital camera that can shoot video try capturing Aldebaran suddenly popping into view as it reappears from behind the Moon. The exact moment of Aldebaran's reappearance (and disappearance) will depend on where in the UK you're observing from, so consult a planetarium programme, such as Stellarium (http://www.stellarium.org), for location-specific times.
ABOUT THE WRITER
Will Gater is an astronomy journalist, author and presenter. Follow him on Twitter at @willgater or visit willgater.com
Copyright © Immediate Media. All rights reserved. No part of this article may be reproduced or transmitted in any form or by any means, electronic or mechanical without permission from the publisher.
Orion is proud to partner with BBC Sky at Night Magazine, the UK's biggest selling astronomy periodical, to bring you this article as part of an ongoing series to provide valuable content to our customers. Check back each month for exciting articles from renowned amateur astronomers, practical observing tutorials, and much more!
This summer, Elizabeth Pearson travelled across the US to hunt down the total eclipse of the Sun on 21 August 2017.
In 1999, a total eclipse of the Sun passed over Cornwall. And I missed it. Ever since, I have wanted to see totality, and so when I heard that the Moon's shadow would be passing coast to coast over the US mainland on August 21st 2017, I knew I had to be there. I decided to take a road trip that would end up taking me almost 3,000km across the country as I attempted to chase down the lunar shadow.
My journey started in Salt Lake City, Utah, where I picked up the hire car that would prove to be my faithful steed for the week. My first stop was Salt Lake City's Clark Planetarium, where I found queues out the door. The crowds had been brought in by an email from a major online retailer recalling eclipse glasses, sparking a panic.
"A lot of people who thought they had glasses just got emails saying their glasses cannot be trusted, and have come to the Clark Planetarium because we have the real ones. We never thought we'd be the only supplier in town. We have a supply for today, we may even have a supply for tomorrow, but then who knows," says Seth Jarvis, the director of the Clark Planetarium.
Like most of the nation, Salt Lake City would only see a partial eclipse, making appropriate eyewear crucial. But for me, the 91 per cent it would see wasn't enough. I wanted totality. It was time to start chasing that shadow.
As I drove from Utah into Wyoming, I began to see signs that I was heading into totality country. On the highways there were notices banning heavy vehicles on August 20-22 to keep traffic moving, while in towns handwritten signs offered eclipse parking. Every business, it seemed, had special 'Totality Deals'.
Eventually I made it to Casper, Wyoming, the largest town on the eclipse's central line and host to the Astronomical League's annual AstroCon convention — which happened to coincide with my visit. The event had drawn people from all over the world, keen to see the eclipse.
"Once you've seen totality, you've just got to see it again," says Sue Baldwin, an eclipse chaser from Auckland, New Zealand. "The first time I saw it I bawled my eyes out for 30 seconds, and actually had to hit myself so I could look at the totality. It's just that emotional, there is no comparison."
With so many eclipse enthusiasts together under one roof I couldn't help picking up on their excitement. And it only grew when I drove on to my next pit stop of Alliance, Nebraska. "They're saying that there are going to be 20,000 people in town altogether," says Jessica Hare, the acting manager for local monument 'Carhenge', a replica of Stonehenge made from scrap cars and the reason this remote location is so busy when I arrive.
"For the most part people in town are excited. There's a reason we live here, though: we're not into big crowds," Hare continues. "But it's a change of pace for a few days and then we've got something to talk about for 60 years."
With only two days to go, people were already arriving and setting up camp. But amongst the bustle, an air of disquiet was beginning to form. People were checking the weather and all was not well. On August 21st, clouds were forecast across the eastern side of the US. Combined with the eclipse glasses scare, it looked like huge numbers of people might not get to witness the great event.
By the time I reached Sutherland in central Nebraska, where I had planned on watching the eclipse, the forecast had grown even worse. The nearest place with completely clear skies forecast was almost 400km back the way I had just come, along roads already gridlocked with traffic. Did I stay and risk being clouded out, or go and risk getting stuck on the highway?
I had come too far to end up staring at clouds. Time to chase those clear skies. Wanting to avoid the most horrific traffic, I picked a town just off the centerline and at 4am on 21 August, I was back in the car.
As I set off, the fog was so thick that at times I could barely see 30m ahead of me. But I was determined to beat the clouds and fought on until four hours later I reached my final destination — an old airfield in Mitchell, Nebraska. A few hundred people had already arrived, most of whom had also undertaken long treks, and were ready to see their first eclipse when it started at 10:25am.
When the hour came, we donned our (certified) eclipse glasses to watch as the Sun was slowly eroded away by the Moon. As the spectacle unfolded, the dwindling sunlight made its effect felt. The air, which should have been uncomfortably hot by now, felt more like a breezy afternoon.
With around 20 minutes to go, I reached to take my sunglasses off before realising I wasn't wearing them. The light was fading and taking the colour out of the world with it, like an old photograph that's been left in the Sun.
At 11:46am, with one minute left, the Sun was down to the merest sliver. I turned to the west to watch as a wall of darkness seemed to advance across the sky.
Turning back, I watched as a sudden explosion of diamond light came from the Sun as the last of its rays were covered, accompanied by a huge cheer from the crowd.
Where once the Sun had been, there was now a hole of utter blackness. A crown of light danced around it and I could almost see the fine tendrils swaying with the breeze. It seemed huge, stretching over a much larger area of sky than I'd expected. Around me, the sky was in twilight with pink trimming every horizon, as if the Sun had just set in all directions together.
The crowd was quiet now. After all the excitement and panic, I felt a sense of quiet calm. I was under the shadow of the Moon, watching plasma arcing a million kilometres out of the Sun. It was humbling, a reminder of our small place in the grand Universe.
All too soon, I could tell totality was reaching its end. The perfect circle of blackness was beginning to look lopsided. One minute, 53 seconds after the first, there was a second burst of light as the shadow passed, sweeping across the nation and taking the spectacle to the millions who waited farther east. As others rushed home, I stayed to watch as the Sun returned, taking a moment to appreciate what I had just witnessed.
Later that evening, back in Sutherland (where the weather had been perfect, of course), I headed out to look at the Milky Way, knowing our Galaxy is only one of billions that all move together in the ballet of the Universe. I've devoted my life to studying that dance, but I have never grasped its majesty like I did in that one minute and 53 seconds.
Once you've seen totality, you really do have to see it again. On April 8th, 2024, another eclipse will sweep across the US and I plan on being under the Moon's shadow once more. Maybe I'll see you there.
Sandhills, NE
The rural state of Nebraska is home to some of the darkest accessible skies in the world, making it a dream destination for deep-sky imagers.
https://visitnebraska.com/stories/visit-the-sandhills
Strategic Air and Space Museum, Omaha, NE
The museum is home to several space artefacts and a tribute to Nebraskan astronaut Clay C Anderson, as well as dozens of aircraft.
http://sacmuseum.org
Clark Planetarium, Salt Lake City, UT
As well as shows in the dome, the Clark Planetarium houses a space museum with interactive exhibits to enthuse little astronomers.
https://slco.org/clark-planetarium
Yellowstone National Park, WY
Spend the days exploring the world-class park and the nights taking in the dark skies. An astronomy program runs in summer.
www.nps.gov/yell/index.htm
Carhenge, Alliance, NE
This huge replica of Stonehenge made from cars was built in 1987 as a tribute to the artist's father, and has proved to be a popular road trip stop ever since.
http://carhenge.com
Craters of the Moon, ID
Follow in the footsteps of the Apollo 14 crew, who underwent geology training in this volcanic landscape prior to their trip to the Moon.
www.nps.gov/crmo/index.htm
ABOUT THE WRITER
Dr Elizabeth Pearson is BBC Sky at Night Magazine's news editor. She gained her PhD in extragalactic astronomy at Cardiff University.
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