Archive for the ‘Sun’ Category

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Observing Report: Total solar eclipse on August 21, 2017

August 28, 2017

My parents, Norma and John (seated), and me with London and Vicki (standing), with the projected eclipse.

Long Range Planning

Since the August, 2017, eclipse first came on my radar, my plan was to see it from somewhere on the Great Plains. I had two reasons for this. One, most of my family lives in Oklahoma, and it would be simpler for them to drive up to the eclipse path than to fly to somewhere more remote. Also, on the plains you can usually see weather coming from a long way out, and fronts move in predictable ways. I figured that if clouds did spring up on eclipse day, I’d have a better chance of driving to get around them on the plains than anywhere else.

Originally I’d been thinking Kansas or Missouri, both of which border Oklahoma and would have made short drives for my relatives. But a closer look at the eclipse map this spring dissuaded me. The eclipse would only barely clip the northeastern corner of Kansas, in the relatively densely populated area around Kansas City. The path of totality painted a broad stripe across Missouri, but mostly along a line connecting Kansas City and St. Louis. I figured that area would get hammered by visitors, and the cloud forecast wasn’t as favorable as it was for points west, either.

Map by Xavier Jubier/Eclipse2017.org

Nebraska, on the other hand, looked pretty good. My maternal grandparents used to live in Imperial, in the southwest corner, and they retired just a few miles down the road to Enders. Imperial would make a convenient rendezvous point, both for any family driving up from Oklahoma, and for me, Vicki, and London flying in from California.

In one sense Imperial was not convenient: it’s a long way from any major airport. Two hundred miles from Denver, and three hundred from Lincoln. But I like long drives in the country (really, I do!), and I was happy to trade some driving at either end of the trip if it would save me traffic in the middle.

I guess now is a good time to mention that I did not want to stay on the path of totality. I figured – correctly, as it turned out – that competition for rooms would be fierce, that at least some places would be gouging visitors, and that traffic would be a problem in at least some areas. Instead, I wanted to stay an hour or two off the path of totality, preferably somewhere out of the way, where crowds would not be a problem, but I’d still have a range of possible observing spots within easy driving range. Again, Imperial was a promising choice, and in early February, I called and reserved rooms for my parents and for Vicki, London, and me at the Balcony House Bed & Breakfast (which was outstanding, by the way – it’s worth going to southwestern Nebraska just to stay there).

By now, plans were firming up. I knew that the fall gross anatomy course at WesternU would be rolling by eclipse time, and Vicki and I would need to arrange things so we’d miss as few days of lab as possible (many thanks to our department chair for the time off!). But we also wanted some time in Imperial to unwind, and to visit places important to our family history. That meant leaving on Saturday, August 19, and coming back on Tuesday, August 22. The Balcony House didn’t have any rooms on Saturday night, and in fact, nobody else in Imperial did, either. So we decided to make Saturday an easy day and only drive as far as Holyoke, Colorado. Holyoke is another old family stomping ground – Grandpa and Grandma had lived there for several years, too, and it’s where my mom grew up.

Sun funnel testing in Claremont

The Sun Funnel Rides Again

Gear! I didn’t settle on exactly what I’d be rolling with until Thursday, August 17, just two days before we were to fly. My old Sun Funnel – veteran of the annular eclipse and Venus transit of 2012 and the partial eclipse of 2014 – was in storage in the garage. There was never really any question but what it would be going along; it’s just too darned useful for showing solar events to even small groups of people. I did have to decide which scope to use with it. We’d sold London’s AstroScan, but my flock of airline-portable scopes had grown in the meantime. Strong contenders included the GalileoScope, Tasco-Vixen 9VR, and SkyScanner 100. I set up and tested the 9VR and the SkyScanner, and I ended up going with the latter scope, for several reasons:

  1. It has the most aperture of any scope I was seriously considering.
  2. It’s at least somewhat collimatable.
  3. With its open design, I wasn’t worried about it overheating.
  4. It balanced the best with the Sun Funnel mounted.

For the flights, I put the SkyScanner in the padded bag that my Apex 127 came in, and packed t-shirts and socks around it. The Sun Funnel I broke down – I put the screen material in a folder between sheets of clean paper, and I stuffed more socks in the funnel itself. I also brought along four pairs of eclipse glasses, a piece of #14 welder’s glass (previously seen here), and 10×42 Bushnell binoculars to look for solar prominences during totality.

London with his grandparents in front of the Balcony House in Imperial, Nebraska

One more piece of gear came to me on the road. Sunday morning we woke up in Holyoke, Colorado, had lunch at The Skillet (which had excellent country cooking), and then popped across the street to the Family Dollar for a few odds and ends. I’d been thinking of making a little sun-finder, like the one David DeLano detailed in this post. My SkyScanner has a DIY wooden bracket that is square to the tube, so I just needed something round that I could use to project a spot of sunlight. I ended up going with a $1 empty condiment bottle, which I already blogged about here. When we rolled into Imperial that afternoon, I unpacked all of the gear and did a test run on the sidewalk in front of the Balcony House. Everything was ready – now we just needed clear skies.

Targeting on the Fly

My initial targets for possible eclipse observing spots were the towns of Tryon and Stapleton, Nebraska, both about a half an hour north of North Platte. I picked up a Nebraska road map and highlighted possible routes from Imperial to either Tryon or Stapleton, going either north to the path of totality and then east, or vice versa. Either town would have required about 2.5 hours of driving on a regular day, and I figured it would be smart to budget for eclipse traffic. The east-then-north route to Stapleton had the following problem: it went through North Platte, and if traffic was apocalyptically bad, we might get stuck on the edge of the path of totality, or even outside of it. The north-then-east route to Tryon would get us close to the centerline first, with fewer opportunities to get stuck off the path.

Ah, but then. A few days out, and the weather apps were predicting partial clouds and possibly even rainfall for west-central Nebraska. Right up until Monday morning, North Platte, Tryon, and Stapleton all looked they might get clouded out. So Sunday the five of us – Mom, Dad, Vicki, London, and me – had a council of war. To the level of detail possible in weather prediction, the area around North Platte looked lousy, but Scottsbluff, in far western Nebraska, was supposed to have sunny skies. Between North Platte and Scottsbluff, the weather looked progressively better to the west, and worse to the east. So we changed things up: instead of turning east to Tryon or Stapleton, we’d stay on Highway 61 north out of Ogallala and shoot up to Hyannis, then turn west on Highway 2 and go as far as we needed to find clear skies. This was basically the Tryon plan with the directions reversed: go straight north to the eclipse path first, then drive east or west along the path to a promising destination.

The Drive Up

I wish I had had the time and opportunity to take pictures during the drive up from Imperial. It was beautiful. We left Imperial right after dawn, and the rising sun turned the fields to gold. Within a few miles, we could see banks of fog lying in the low spots on the landscape. And then a few miles further, the fog was lying everywhere. We started driving through fogbanks that congealed into an unbroken blanket by the time we reached Ogallala. The weather apps were still projecting clear skies to the west and, well, unclear skies to the east, so we kept going.

The fog had cleared by the time we saw our first eclipse-watchers, at the fairgrounds in Arthur. There were hundreds of people in RVs, tents, cars, and trucks, looking worriedly up at a sky that was completely socked in with clouds. We kept going, and saw a few hundred more scattered along the side of the road as we approached the center line. About this point we hit what I can barely bring myself to describe as ‘traffic’. At its worst, we were the 9th and 10th vehicles in a convoy of 13, but the convoy was rolling along at a steady 62 or 63 miles per hour, which was fine and certainly not worth the risk of trying to pass someone on a two-lane road in the Nebraska sandhills. The hills themselves were liberally spangled with wild sunflowers. From a distance, they looked like they’d been dusted with pollen. Everywhere we went the landscape was green.

Alliance

From a purely eclipse-viewing perspective, I would have been happy with any of the towns on Highway 2 west of Hyannis. Sure, they were a few miles off of centerline, but the difference in the duration of totality would have been trivial. And I figured we’d miss the big crowds expected at Alliance. But this plan had one fatal flaw, which I did not anticipate: a complete absence of public restrooms west of Hyannis. If I’d been by myself, I might have just pulled over anywhere and, er, recharged the water table as needed, but that’s a less attractive option to a group that includes two women and two senior citizens. Actually, there may have been a public restroom in Lakeside, but we had no chance to find out, as there was a big train blocking the road into town when we came by. So we headed on into Alliance and braced for the worst.

Our setup at the Western Nebraska Community College shindig. The forest of telephone poles in the background is where line repair people train.

The worst turned out to be not that bad, actually. We drove past a big group assembled on a grassy field on the east edge of town, and on to the first gas station that looked like it might have restrooms. By the time we’d all had a biology break, it was almost time for the eclipse to start. We decided to head back out to the east edge of town and see if the group on the grass still had some parking spots. This turned out to be an excellent choice. The parking was organized by the Western Nebraska Community College, which had free porta-potties and eclipse gear for sale. We ended up next to a family from Denver that we had met in line at the gas station. They all had eclipse glasses but no other optics, so I set up the Sun Funnel so they could watch with us, and they returned the favor by taking pictures of our party.

The Eclipse

As soon as we had the cars parked, I was busy setting up the Sun Funnel, while everyone else got folding chairs set up and got their eclipse glasses on. I got the photo above, my first shot of the eclipse, at 10:45 AM.

There was a wind out of the north that kept threatening to snatch our hats away, and it was flirting with blowing the scope over. I can’t remember ever setting up the Manfrotto tripod for low use, with the legs spread almost straight sideways, but I remembered from the documentation that doing so was possible. That fixed the stability issues with the scope, and from that point on, all we had to do was re-aim it every few minutes (I’d already made this switch in the family shot above – that shot is out of order in terms of eclipse phases). As I mentioned in a previous post, not only was the dollar store mustard bottle sun finder cheap and effective, but I could see the projected dot through the translucent walls of the bottle so I didn’t have to get my head behind or underneath it to aim the scope – handy when the sun was almost directly overhead.

A labeled shot from the end of the eclipse, when all six of the big sunspots were visible, with the Earth added for scale. All of the other crud on the image is dirt and bits of grass – that’s what happens when gear is left out in the wind in a grassy field for three hours.

There were half a dozen nice sunspots, and it was fun to watch the moon overtake them. A lot of the people who stopped by to look at the sun funnel weren’t familiar with sunspots, so I gave them the quick spiel: giant magnetic storms on the sun, with the biggest that we could see then being about the same size as planet Earth.

About halfway between first contact and totality, the north wind started pushing clouds across the sky, which you can see in the above video. This added some definite suspense to the proceedings, especially when, about 5 minutes before the start of totality, a huge “dreadnought class” cloud came over. I think everyone on the field was on pins and needles – we could still see the sun, as the next photo demonstrates, but it wasn’t what you’d call a great view.

Fortunately the cloud moved out of the way right at the start of totality. And I mean precisely then. Below is a shot from just a couple of seconds before, with the diamond ring effect haloed by the tail-end wisps of cloud. Those wisps moved out just as the moon covered the last light of the sun, and our view of totality was perfectly clear.

That photo above is my best eclipse shot. Vicki has a DSLR but I didn’t take it along. I did waste a few seconds, but only a few, trying to get a couple of HDR shots with my iPhone, but they didn’t really come out. I had read plenty of horror stories of people who basically missed their first eclipse messing around with cameras, so I resolved long ago that if I was lucky enough to have clear skies for totality, I’d try to spend them looking, not shooting.

For the most part, the partial phases of the eclipse were familiar to me from the 2012 and 2014 eclipses. Totality was a whole ‘nuther beast. This was my first total eclipse, and even though I had read a lot of eyewitness reports and seen some videos of other total eclipses, several things surprised me:

  1. Neither of my previous eclipses had been close enough to total to produce the weirdly sharp shadows that you get on either side of totality, when the thin crescent sun acts more like a point source than a bright extended object. So I’d never seen that effect before, and neither had anyone that I was with. We had fun marveling at our shadows, but I didn’t think to get any pictures or video of them. You can see the sharp shadows starting at 1:25 in this video.
  2. It got a lot darker a lot earlier than I expected. This was especially true in the last 10 minutes before totality. It was extremely weird – before the dreadnought cloud moved in, we were all aware of standing in direct sunlight, just not much of it. It wasn’t like diffuse sunlight coming through clouds, and it wasn’t like sunset light, either. I’ve never seen anything else quite like it – which I guess is part of the reason people chase eclipses, to see things you can’t see any other way.
  3. The inner corona was a lot brighter than I expected. I couldn’t really see any of the outer corona, just a thin bright ring around the moon. It was bright white. The contrast between the blazing white of the corona and the absolute blackness of the moon made the latter even more unearthly. In Seeing in the Dark, Timothy Ferris described the moon during totality as an “awful black ball” and I can now vouch for the accuracy of that description. It doesn’t look right.
  4. Even at the midpoint of totality, the sky was brighter than I had thought it would be, and the ground was darker. We all did look up, and saw Venus, Mars, Mercury, and Regulus, but I didn’t see any other stars; the stars didn’t ‘come out’ as I had expected. In contrast, right where we were, looking around at family members and other eclipse chasers, it was dark, like being outside half an hour after sunset. And the 360-degree twilight lit the horizon all the way around in shades of orange, salmon, pink, and violet. In general, the terrestrial effects of the eclipse were more pronounced and arresting that what was going on in the sky – with the undeniable exception of that awful black ball.
  5. I assume that the atmospheric effects on either side of totality are symmetrical – that the weird light I mentioned above in point 2 extends just as far after totality as before, and that the 360-degree twilight extends just as far before totality as after. But that’s not how I perceived them. I noticed the oddly thin light before totality, and after totality had ended I was surprised at how long the sunset effect persisted. The above photo is from a minute and a half after the end of totality, looking north-northeast, about 90 degrees off the path of the shadow, and the twilight effect is still visible in the distance.

After Totality

Totality was a rush. In the aftermath we sat around talking happily about how amazing it had been, and watching on the sun funnel as the moon gradually uncovered the sun. London and I made pinhole projections – his is above, mine below.

We also wandered around until we found a cottonwood that was projecting crescent suns on the street. Here’s a photo:

And a video – this worked out better than expected, because the wind was blowing the leaves and branches around and making the crescent suns flicker, like sunlight glinting off moving water. Shame I didn’t think to turn the phone sideways, but I’d just had my mind blown, so I’m giving myself a pass.

All too soon it was winding down. The telescope and sun funnel had been the first things set up when we rolled in, and they were the last things put away when we left. Here’s my last shot, from 1:16 PM:

Ironically, after all the gloomy predictions, traffic was worse getting away from the eclipse than it had been getting to it. I’d hoped that maybe we could head south out of Alliance and fast-track it back to Ogallala on Highway 26, but that way was jammed up. So we went back the way we came. On the drive home we were the 5th and 6th vehicles in a train of 17, and we had to settle for a bit under 60 mph, but we still made it back in good time. There was another train blocking the access into Lakeside, so I still don’t know if the town has a public restroom.

The trip had one neat little coda. On the flight home, London had the window seat, and he spotted the young crescent moon, back in the evening sky after its big adventure. I passed him my phone, and he got some great shots. Here’s the best:

What now?

There will be other solar eclipses between now and the next “Great American Eclipse” of 2024, but most of them will happen in other parts of the world, and the chances that I’ll have the opportunity to go see them are slim. Here are the upcoming eclipses and transits that I am hoping to observe in the next decade – as always, assuming the skies cooperate:

  • January 31, 2018 – total lunar eclipse
  • January 21, 2019 – total lunar eclipse
  • November 11, 2019 – transit of Mercury
  • May 26, 2021 – total lunar eclipse
  • May 16, 2022 – total lunar eclipse
  • November 8, 2022 – total lunar eclipse
  • October 14, 2023 – annular solar eclipse
  • April 8, 2024 – total solar eclipse
  • March 14, 2025 – total lunar eclipse
  • March 3, 2026 – total lunar eclipse

That’s a pretty good lineup, I think. For more details on all of these events, see MrEclipse.com.

In sum, the eclipse was awesome, in every sense of the word. I get now why people become eclipse chasers. I’m not quite to the point where I can afford to go jetting around the world to catch every single one, but I will make it to every future eclipse that I can. If you ever get a chance to stand in the path of totality, go.

UPDATE 29 August: Mike’s comment below about Cthulhu reminded me that I needed to post another picture. After I put the diamond ring photo on Facebook, my friend Jarrod posted this modified version, which I can’t unsee. Cower before Ecl, the Dragon of Totality:

Eclipse dragon

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Dollar store mustard bottle sun finder

August 20, 2017

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Probably self-explanatory from the picture, but just in case: tape it to the scope, parallel to the tube, and when the spot of light coming through the nozzle is centered on the bottom of the bottle, you’re on target. Some nice sunspots today.

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Update August 23 – Another nice thing I discovered at the eclipse: because the condiment bottle is translucent (at least this model), you don’t have to get behind it to see if it’s working. Peering through the side of the bottle is good enough. Handy when the sun is high in the sky.

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Observing report: the transit of Mercury from western Colorado

May 19, 2016

Mercury transit 9 May 2016 - telescope setup

I was in Utah from May 4 to May 15, chasing dinosaurs with Mike Taylor, a colleague of mine from England. I took a telescope along in hopes of getting some dark-sky time, and to hopefully catch the transit of Mercury on May 9.

Things did not look promising at dawn on the 9th. I was in Fruita, Colorado, and when I got out of bed, the sky was completely overcast. Mike and I decided to head out west of town to visit Rabbit Valley, where a nearly complete skeleton of the long-necked dinosaur Camarasaurus is visible in a hard sandstone ledge. (Why is no-one excavating this dinosaur? Because we already have many nice specimens of Camarasaurus, and the sandstone around this one is like concrete. It would be a mountain of work for very little payoff.)

We spent about two hours measuring and photographing the skeleton, and as we did so, the clouds started to break up a bit. By the time we got back to Fruita, a little after 11:00 AM, the sky was clear except for a few scattered wisps of cloud. I set up my telescope in front of the Dinosaur Journey museum and started watching and photographing the transit.

Mercury transit 9 May 2016 - Mercury crossing the sun

I was using the same setup as in the last post: my Celestron C80ED refractor, a Celestron 8-24mm zoom eyepiece, and a GoSky full aperture solar film filter. For photography, I used a Nikon Coolpix 4500 for still photos and my iPhone 5c for video.

I caught about the last hour of the transit, and I got to share the view with about a dozen museum staff and passersby. A few light clouds drifted through the field of view, which looked pretty cool and didn’t obscure the view at all.

At 12:42 Mercury finished exiting the disk of the sun. The next Mercury transit will be in 2019 – I hope I’m as lucky then as I was this time.

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Getting ready for Mercury

April 18, 2016

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The planet Mercury will transit the sun on the morning of Monday, May 9. Mercury transits are not as rare as the more famous transits of Venus, but they still only come around once or twice a decade on average. The last Mercury transits before this one were in 2003 and 2006, and the next two after this year will be in 2019 and 2032. From southern California, the transit will already be underway when the sun rises at 5:57 AM, maximum transit (the point when Mercury is the furthest inside the sun’s disk as seen from Earth) will be at 7:58, and Mercury will exit the sun’s disk between 11:39 and 11:42 AM (all times in PDT).

For the transit of Venus in 2012, I used a simple homemade device called a “sun funnel” attached to a small reflecting telescope to project an image of the sun. You can read more about that here and here. The sun funnel worked well enough – I also used it for the annular eclipse in 2012 and the partial eclipse in 2014 – but the screen material degrades the resolution somewhat. Mercury is a lot smaller than Venus, and much closer to the sun, and both of those factors make it appear much smaller than Venus during a transit.

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I want maximum resolution for observing and photographing the upcoming transit, so I finally sprung for a full-aperture solar film filter for my 80mm telescope, which you can see set up at the top of this post. I got it out the other day for a test drive and got some decent photos of the current large sunspot AR2529, shown above. I’m pretty happy with the results – now if we can just get clear skies on the morning of May 9. If you’re curious, the filter I got is the GoSky Optics full-aperture filter with Baader solar film. There are several sizes available to fit all kinds of telescopes, and the filter attaches securely to your telescope tube or dewshield with three nylon-tipped screws. I got the filter for telescopes 81-113mm in diameter (outside tube or dewshield diameter, not optical diameter!), which is currently a little under $50 on Amazon.

This is my second GoSky product, after the universal cell phone adapter I picked up last fall, and I’ve been impressed with the solid construction and good fit-and-finish of both products. Some of the weird large-scale blotchiness in sun photos is probably either distortion from the iPhone’s tiny field lens, or gunk on the surface, and the uneven margin of the solar disc is from atmospheric turbulence. But I think the graininess across the surface of the sun is actual solar granulation. I couldn’t see it on the iPhone – not enough image scale. If I had, I’d have thrown in a shorter focal length eyepiece and tried some higher-magnification shots. They might not have turned out well even if I had taken them – the seeing was pretty awful – but it would have been worth a shot. Something to try next time.

The diameter of the sun is 109 times that of Earth. Here's how Earth would compare to the current large sunspot if they were side-by-side.

The diameter of the sun is 109 times that of Earth. Here’s how Earth would compare to the current large sunspot if they were side-by-side.

Unfortunately, I won’t be here in California to share the transit with my local friends and fellow observers. I’ll be in Utah chasing dinosaurs from May 4 to May 14, so I’ll have to catch the transit from there. I’m driving up and bringing my 80mm scope to take advantage of dark Utah skies in the evenings. If you want to plan your own transit observation, or just want to investigate how the transit will appear from various points on Earth’s surface, this interactive map is excellent. And if you need safe, inexpensive ways to observe the sun, check out my page on safe solar observing. Clear skies!

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A tour of Big Bear Solar Observatory

October 13, 2015

BBSO from up high

The gleaming white domes of the Big Bear Solar Observatory sit at the end of a causeway that projects from the north shore of Big Bear Lake – they draw the eye from almost any point in Big Bear Valley. And as I mentioned in my last post, the Pomona Valley Amateur Astronomers got to visit the BBSO on Friday, October 9.

BBSO causeway

We were greeted at the gate by Claude Plymate, Chief Observer and Telescope Engineer at BBSO, and Teresa Bippert-Plymate, who is not only a professional solar astronomer but also the president of the Big Bear Valley Astronomical Society. As pros who are also enthusiastic amateur observers, Claude and Teresa did a great job of pitching the tour with just the right balance of necessary background, technical detail, and the hands-on practicality of managing big scopes and the complicated hardware and software necessary to run them.

BBSO GONG scope

The first thing you come to on the causeway is a big white storage container with a coelostat (sun-tracking mirror) – this is one of the six Global Oscillations Network Group (GONG) installations spaced roughly equally around the world. The GONG telescopes track the sun around the clock for helioseismology research, mapping the acoustic pressure waves that propagate around and through the sun.

PVAA group outside BBSO domes

The smaller dome just short of the end of the causeway holds two telescopes on a common mount. One is a 10cm full-disc hydrogen-alpha solar telescope, the other is a second smallish refractor for Project Earthshine, which tracks the Earth’s albedo by measuring the intensity of the earthshine that falls on the moon’s unlit side.

London with BBSO New Solar Telescope

The observatory’s ‘big gun’ is the 1.6-meter New Solar Telescope, an off-axis Gregorian. One-point-six meters is 63 inches, which means this scope has a slightly larger aperture than the famous 60-inch reflector on Mount Wilson (which I’ve been fortunate to visit – see here and here). Here’s the light path of the NST (an unmodified version of this image is at the bottom of the post):

BBSO New Solar Telescope light path

And here’s a view on the right side of the scope showing the mask that rejects the light from most of the sun (which bounces onto the back wall of the dome, landing at about the same intensity as natural sunlight). The mask has a small hole which allows light from a small part of the sun to pass through to the chain of lenses and mirrors that bounce the beam to the research instruments on the next floor down.

BBSO New Solar Telescope right side optics

It took me a while to wrap my head around how this works. If the mask rejects most of the sun’s light, doesn’t that mean that most of the telescope’s 1.6-meter aperture is wasted? The answer is no – the mask functions as a field stop, not an aperture stop. If I put a mask across the front of my 10″ Dob and let only a 4″ beam of light through, that’s an aperture stop – it effectively turns a 10″ f/4.7 obstructed system into a 4″ f/12 unobstructed system (which may be desirable for sharp planetary and lunar views, where light-gathering is not so important). But imagine I left the front of the scope uncovered and instead masked down the field stop at the bottom of one of my eyepieces, so that I could only see a tiny hole in the center. If I put the scope on Jupiter, I’d see Jupiter in the center of the field but nothing else – I’d be getting the full benefit of the 10″ mirror’s light-gathering and resolution on Jupiter, but rejecting the light from the surrounding starfield, which would reflect off the mask at the bottom of the eyepiece. That’s more or less what happens with the New Solar Telescope, only “the rest of the field” is the rest of the sun, and the small area that the scope focuses on is not a planet but a small patch of the sun’s surface. But that patch can be imaged with the full benefit of the 1.6-meter primary mirror’s angular resolution.

BBSO burnt light shield

Now, a 1.6-meter mirror focusing the light from the full disc of the sun onto an area about 3cm across is a hell of a lot of energy. That beam could fry electronics, melt metal, and start fires if it got off-course. There are multiple redundant systems to prevent that from happening – the dome can close, the primary mirror has a cover that can activate quickly, and if all else fails a 1/16″ steel plate slides into position in front of the field stop. A few years ago – before Claude’s tenure as Chief Observer! – there were not so many safeguards in place. The software that allows the telescope to track the sun briefly got confused by some passing clouds, and the scope stopped tracking properly. That allowed the concentrated beam of sunlight to slide off-target. The steel plate did its job and slid into place, and the scope melted two holes in it in the space of about 30 seconds. The folks at the observatory keep the melted metal plate as a visible reminder that they are in a very real sense playing with fire.

BBSO sunspot image

This sunspot is a bit larger than our planet.

Our last stop on the tour was the telescope control room, where another professional astronomer was driving the scope and taking data. There was a minor mechanical hiccup at one point and Claude had to swing into action, running back and forth from the control room to the instrument room to get everything back on track. It was amazing to see live images coming in in real time. I’ve been fortunate to tour a lot of observatories but never while they were working. At one point Claude and the other astronomer put the scope on a sunspot group which was just swimming in atmospheric distortion. Once the computer had enough data to engage the adaptive optics, they switched on the AO and the view instantly settled down to nearly rock-solid, like it was painted on the monitor.

BBSO New Solar Telescope

The NST is currently the largest, best-equipped solar telescope in the history of humankind, and it is producing the sharpest images of the sun ever taken. BBSO joins Mount Wilson and Palomar in continuing the long, proud history of world-class astronomy in southern California. And it’s 65 miles from my house. Many thanks to Claude and Teresa for being such gracious hosts and letting us see their beautiful machines in action.

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Observing Report: Partial solar eclipse on Oct. 23, 2014

October 27, 2014

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Last Thursday afternoon I went to London’s school to show the eclipse to the students. I was rolling with the Astroscan-plus-Sun-Funnel combo, veteran of the 2012 annular eclipse and transit of Venus, and the GalileoScope that David DeLano built for me, now sporting a Baader solar film filter from AstroMediaShop.co.uk.

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The eclipse started here at 2:11 PM, Pacific Daylight Time.

2014-10-23 eclipse in filtered scope

I’m still struggling to get good digiscoping photos with the iPhone. This one, shot through the filtered GalileoScope, is the least wretched of the lot. The immense sunspot group is AR 2192, the largest seen in 24 years. At nearly the size of Jupiter, It was easily naked-eye visible with eclipse glasses. There’s a nice video of it from before the eclipse at APOD.

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Oh, I also passed out a lot of eclipse glasses. The best deal I have found on them is this pack of 30 for $33 from Amazon. Of that 30-pack, two got mailed off to relatives (along with our entire previous stash of eight), London and I each brought home a pair (London promptly disassembled his to see how they were put together–that’s my boy!), and the other 26 went home with other excited kids.

Incidentally, my favorite view of the eclipse was through the glasses, with no magnification. There is something awesome and terrible about watching another world come between you and sun, even partly.

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I wanted to do an activity with the kids so I brought a pack of index cards and had them make pinhole projectors. That succeeded beyond my wildest dreams. The kids were completely occupied for a solid 20 minutes, and we could do the projections indoors and save our UV exposure for the scopes (which I brought inside, of course–you don’t leave a solar scope set up and unattended).

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London’s school is Oakmont Elementary and ‘BLAST’ stands for Best Learning After School Time.

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We also looked at pinhole projections of the eclipse cast by trees.

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Just a bit after max eclipse, which was at 3:30.

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The last of the wine, at 4:40. Unless I get really rich in the next couple of years, rich enough to go on eclipse cruises, my next solar eclipse will be in August of 2017. A total solar eclipse will cut a path from the Pacific Northwest to the Southeast US. My tentative plan right now is to fly to Oklahoma, see the relatives, and then drive up to northern Kansas for the event. Kansas in August should be hot and sunny, and on the Great Plains you can usually see bad weather coming hundreds of miles off, which will let us adjust our targeting on the fly.

Eclipse story in Claremont Courier

A guy from the Claremont Courier came out to interview me and some teachers, parents, and kids. Thanks to the paper’s paywall, I haven’t seen any more of the story than this web preview, which at least features two of London’s best friends. If anyone out there has a hardcopy they’d be willing to scan or pass along, I’d be very grateful. Update Oct. 31: Whoops! The story wasn’t paywalled; it was unavailable because it wasn’t done. Here’s the full story, and here’s a post with a couple more eclipse shots.

All in all, I think about 90 people got to see the eclipse through my scopes. The kids were mesmerized–so were the adults, actually–and I was very, very happy. Can’t wait until the next one!

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Observing Report: a semi-cloudy night at Joshua Tree

October 8, 2012

My scope at Joshua Tree Saturday night. Clockwise around the scope are the bright star Capella just in front, the constellation Perseus (12:00), the Pleiades (2:00), the Hyades (V-shaped arrow of stars directly oppose Capella), and Jupiter (4:00). Photo by Kevin Zhao.

Saturday evening I was at Joshua Tree. My summer anatomy students invited London and me along to the Indian Cove campground. I didn’t have room in the car for the big gun so I took my 5” Mak, which is what it’s for—times when I need a decent amount of aperture in a small package. That was no loss: the sky was striped with high, thin clouds all night and never really cleared out. We got decent views of a few things, but the 10” would have been wasted. We used the Mak to look at the Double Cluster and Jupiter. In moments of steady seeing there were quite a few cloud belts showing, and all four Galilean moons were lined up on one side of the planet, which was pretty cool. London brought along his AstroScan and we used it to look at extended objects like the Pleiades and the Andromeda galaxy.

iPhone panorama by Chad Claus. Click for the big version!

The clouds might have made for lousy telescopic views but they made for gorgeous naked-eye skywatching. At sunset the whole sky was striped with light from one horizon to the other.

Here’s another view, actually taken by me for a change. This is the unprocessed raw image, direct from my Coolpix 4500.

Moon halo photo by Kevin Zhao. Jupiter is inside the ring at 1:00, and the Pleiades are outside at about the same angle.

When the moon rose around 11:30, it was surrounded by a ring of faint light. I thought it was a moonbow, but that’s something different. The ring we saw around the moon is called a 22-degree halo and apparently has no other or more poetic name. That’s a shame. In the early morning, when the moon had gotten well above the horizon, it was surrounded by a complete circular halo with radiating clouds on either side. That was worth the clouds. I’ve been under wonderfully clear desert skies many times, but I’ve never seen a moon halo quite like that. For once, I think the clouds were worth it.

Update: There wasn’t just a moon halo, there was also a sun halo Saturday afternoon. Agnes Kwon captured it in pixels. Witness:

Many thanks to Agnes, Chad, and Kevin for letting me illustrate my post with their awesome photos!