Archive for the ‘solar observing’ Category

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Hideously belated observing report: Mercury transit on November 11, 2019

August 22, 2020

Not a ton to say about this other than that we saw it. London was home from school for Veteran’s Day. It was sunny, warm, and bright, and neither of us fancied spending a ton of time standing in the sun, so we limited ourselves to a few quick peeks rather than continuous observation.

About the only notable thing about the transit was our observing rig, which is probably the redneckest job I ever threw together. Most of my good gear was packed away at the back of the garage and I didn’t fancy digging it out, so I taped a pair of cardboard eclipse glasses over the front of the SkyScanner 100 to create a subaperture mask, taped some spare cardboard from a torn-up Amazon box over that to block all the filter-less areas, and set the whole rig on our green-waste bin. It was decidedly low-tech, but not as sketchy as it sounds–I taped everything very securely to the tube so none of it could fall off, because the risk of direct, unfiltered sunlight through a scope is nothing to joke about. Then London and I took turns shading each other’s faces so we wouldn’t be squinting against the sun while we observed.

I didn’t take any pictures, we just watched the crisp little BB of Mercury drift across the face of the sun. The “lenses” of the solar glasses are about an inch in diameter, so basically we turned the 100mm f/4 system into a 25mm f/16 system, and a light cone that long is pretty forgiving. Which reminds me, I’ve just been reading about people experiencing a pseudo-3D “marble” effect when viewing the moon through telescopes of 40mm aperture or less. I should make a 40mm aperture mask for my C80ED and see if I get that effect.

Anyway, thus ended the transits of the twenty-teens. I was fortunate to catch them all: the Venus transit on June 5, 2012 (observing report), one Mercury transit on May 9, 2016 (observing report), and this second Mercury transit on November 11, 2019. The next Mercury transits won’t be until the 2030s: November 13, 2032 (I’ll be 57), and November 7, 2039 (64). Then 2049 and 2052, 2062 and 2065, and 2078. I’ll be 103 if I make it to that last one. The next Venus transit won’t be until 2117, 142 years after my birth, so barring some kind of technological miracle I don’t reckon I’ll be seeing another. It was a privilege to see the one that I did.

Now transit season is over for a bit over a decade, so we’ll have to find other things to keep busy with. Fortunately the sky has much to offer. Stay tuned.

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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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Safely (and cheaply) observe the eclipse

August 17, 2017

A quick note for all eclipse observers, but especially those who haven’t been able to find eclipse glasses: here’s the #1 best eclipse activity for kids, and not bad for adults, either. Each person needs a stack of index cards and a push-pin or thumbtack. They can pick out their names or make little drawings by punching holes in one index card, then use that to project little crescent suns on the other index card. Safe, foolproof, can easily eat up an hour or more. Everyone should do this, and take pictures and post them. Pics attached here are from the 2014 partial eclipse (observing report here).

I wrote up an observing guide (link) for people on the Western University of Health Sciences campuses in Lebanon, Oregon, and Pomona, California, but really this stuff applies for everyone on the path of totality (Lebanon) or off (Pomona). Except for the timings, and you can get local eclipse timings here. My more complete page on safely observing the sun is on the sidebar (link).

Good luck, and clear skies!

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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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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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See the transit of Venus in Claremont

June 5, 2012

If no clouds come to spoil the fun, I will be in downtown Claremont this afternoon (Tuesday, June 5) with a scope set up for free public viewing of the transit of Venus. The transit starts at 3:06 PM, PDT, and will still be in progress when the sun sets at 7:59. I plan to be there for all of it. If all goes well, from about 2:50 onward I will be in the public square in front of the theater, on the northeast corner of First Street and Indian Hill Boulevard. Whenever the sun gets low enough to go behind the theater, I’ll head up to the top of the parking garage across the street, to watch the sun set with Venus still crossing the solar disk. You, whoever you are, are welcome to join me.

If by some freak chance it is cloudy this afternoon, I’m going to throw my gear in the car and run up to Big Bear, which gets more sunny days than almost anywhere else in SoCal (that’s why the solar observatory is there). In which case, you’re still welcome to join me, if you can find me. Try the Discovery Center on the north shore, if it’s sunny…or the nearest pub if it’s not.

Fingers firmly crossed for clear, sunny skies!

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More low-cost solar observing

June 4, 2012

In preparation for the transit of Venus tomorrow, I did a little hacking and tinkering late this afternoon. Although the sun funnel worked well enough for watching the eclipse, as we’ll see below it is not perfect for photographing the sun in any detail. My full-aperture solar filter still hasn’t arrived, but I got to thinking about how to make a safe direct viewing setup.

I recently acquired a Celestron Travel Scope 70, a little 70mm (2.75 inch) f/5.7 achromatic refractor. Like a lot of small refractors, the dust cap for the objective lens has a smaller removable cap in the middle, in case you want to stop down the scope for more pleasant viewing of bright targets like the full moon. The diameter of the small hole in the middle of the big cap is 40mm, so with big cap on but the small cap off, the scope functions as a 40mm f/10.

I don’t have any loose solar film to make a 70mm solar filter or even a 40mm solar filter. But I do have a stack of eclipse glasses, each of which has two 1×1.5 inch eye holes covered with solar film. So I cut one of the eclipse glasses in half, made a round 25mm aperture in a square piece of cardboard, and mounted the eclipse glasses ‘lens’ (solar film still surrounded by two sheets of thin cardboard) and the 25mm aperture stop on the back side of the big dust cap. I didn’t think to take any pictures of the inside of the dust cap to show how it all goes together, but hopefully the general idea is clear enough. With the big dust cap on and the small dust cap off, the scope admits a 25mm beam of fully solar-filtered light to the objective, turning the scope into a 25mm f/16 solar refractor. And because the solar filter is on the inside of the big dust cap and protected by the small dust cap (in front) and the second piece of cardboard with the 25mm aperture stop (behind), I can leave it in all the time. Take the big dust cap off, the scope functions normally. Take only the small one off, I’ve got a 1-inch solar scope.

Two other design decisions to note. First, the finder–and I use the term advisedly–that came with this scope is without doubt the worst finder I have ever seen on a commercial scope from a brand name manufacturer. It looks like a 5×20 straight-through magnifying finder. However, right behind the (single, plastic) objective lens is an aperture stop with only a 1-cm hole in the middle. So in fact it’s a 5×10 finder with a plastic singlet objective. The immense irony is that the scope doesn’t need a finder at all; throw in a 32mm Plossl and you get 12.5x and 4-degree true field of view, so the scope effectively functions as its own superfinder. So I unscrewed both ends of the finder and dumped out all the plastic optics, turning it into a hollow sight tube. Why is this important right now? Because it’s really dumb to leave a magnifying finder on a telescope being used for solar observing; it’s too easy to forget what you’re doing and accidentally looking through the unfiltered finder and cause serious eye damage or blindness. There’s a good reason that every commercial telescope comes with a “don’t point the scope at the sun, dummy” tag or sticker or both. This is not something to mess around with. If you’re going to observe the sun with a telescope, cultivate the same habits of awareness and deliberate action that you would use around loaded firearms and power saws.

Oh, the included 45-degree prism diagonal is also rubbish and the light tripod looks pretty dodgy. Today I used my standard small-scope setup–an AstroTech 90-degree dielectric star diagonal and a Universal Astronomics DwarfStar alt-az head on a Bogen/Manfrotto tripod–and I’ll doubtless do the same in the future.

The other design thing was the sun shield. At first I tried going without but look into a dark eyepiece to catch a filtered (= comparatively dim) view of the filtered sun while unfiltered sunlight was hitting the top of my head and my upper eyelid had me squinting and developing a minor headache almost immediately. The plastic dewshield on this scope pulls right off, so I got a handy piece of cardboard (part of the packaging of a picture frame), cut a hole just big enough to admit the front end of the scope without the dewshield, slid the cardboard sunshield on and used the plastic dew shield (and dust cap with solar filter) to hold it in place. I also cut a second, smaller hole to let light in to my sight tube sun finder.

If you do something similar, make sure that the sun shield can’t get blown off and take the solar filter with it. In my case, the dewshield slides on a long way and grips both the sun shield and telescope tube firmly; a strong enough breeze might upend the whole setup, but it couldn’t blow off just the shield and filter. Again, eye safety is paramount; don’t take any chances.

Okay, so how did it work in practice? Pretty darned well. I had already aligned the sight tube with the telescope, so all I had to do was rotate the sun shield a bit to make sure the second, smaller hole lined up with the sight tube. Then I could point the scope roughly at the sun and pan around until a perfectly round beam of sunlight (projected on my hand) emerged from the sight tube. That always put the sun in the field of view of a 25mm Plossl (16x, 3 degree true field of view). The view of the sun at the eyepiece was reasonably bright–for an astronomical object, not compared to the unfiltered sunlight streaming down all around–and razor-sharp. The sunspots with their umbrae (dark centers) and penumbrae (lighter borders) were striking, like they’d been etched on stained glass.

Happily, the filtered scope yielded nice, even light all over the surface of the sun, no matter where it roamed in the field of the view. My one beef with the sun funnel is that it can be hard to get really good photos because of the inherent granularity of the screen material. Inevitably some part of the projected sun is brighter than another, and if you manage to get the light perfectly centered, it can easily wipe out the sunspots. The best way I’ve found to avoid this flashlight-beam effect is to photograph the sun from a bit to the side, out of the direct path of the projected light (that’s how I got this very sharp photo), but then the sun is out of round–not ideal if you’re hoping to combine images into a composite or movie, or even get a nice, square-on shot of a circular sun.

For example, in the photo above the sunspots on the left are sharp enough–the big one even shows the umbra and penumbra clearly–but the dimmer two on the right are lost in the flashlight glow of the sun lighting up the screen material from behind. And in this view the sun is already way out of round.

Also note that this image is flipped horizontally compared with the image from the refractor. In fact, this image is correctly oriented. Normally Newtonian reflectors show things rotated by 180 degrees, but projecting the image on the screen undoes that and gets everything back to normal. The solar filter on the refractor just cuts down the intensity of the light, it does nothing to reorient the image, so the image at the eyepiece is right side up but, because of the 90-degree mirror, flipped left-to-right.

I didn’t go to all of this trouble just for the transit of Venus. I mean, I happily would have, had the transit been the only game in town. But it’s not–the Astronomical League has a Sunspotters observing program, and now that I have the gear for solar observing, I might as well start logging. I’ll keep you posted on that.

Now, I should point out that the flashlight-beam effect washing out the sunspots in the sun funnel is mostly a photographic concern. For visual appreciation, even solo, I think the sun funnel still wins. A 4-inch image scale and the ability to put your head and eyes wherever you want–and even wear polarized sunglasses to observe–can’t be beat. But for photography, I prefer the filtered direct view–even in a one-inch scope.

Fortunately I’ll be rolling with both tomorrow. Now if the weather just cooperates…

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Observing report: the 2012 annular eclipse

May 21, 2012

Today rocked. It would have rocked a lot less if things had gone the way I wanted them to. I put off ordering a solar filter for my telescope until last week, and of course everyone was sold out and even the manufacturers were backordered. One is on its way to me, hopefully, but it didn’t arrive in time for our eclipse trip, so I fell back on the sun funnel I built a couple of months ago, and my son’s Astroscan. This turned out to be the perfect combo. In the photo above I was testing the sun funnel in the hotel room, after our long drive from SoCal to Page, Arizona (spread out over 2.5 days, so very civilized and enjoyable, but still a lot of miles).

For the eclipse we set up on the lawn of the Courtyard Inn here in Page. Here’s first contact, when the moon first starts crossing the solar disk. Click for the big version and look at the sunspots–this is the sharpest sunspot photo I got all day.

In addition to the sun funnel I brought a piece of #14 welder’s glass for naked-eye viewing. The eclipse glasses London is wearing were supplied by the hotel when we checked in–I thought that was an awesome thing for them to do, and I told them so.

The middle group of sunspots is getting devoured by the moon.

Almost to second contact, when the trailing limb of the moon crosses the edge of the sun. I like the meta-ness of this photo of a photo-in-progress via a projected image of a projected image.

Just after second contact–we have annularity!

Annularity. This was incredible. I would write more about it, but words fail me.

And here’s why it’s a good thing that my solar filter didn’t arrive on time. If it had, I would have brought my 5″ Mak and left the sun funnel at home. And when the tour bus pulled up 50 feet away and disgorged all these people 5 minutes before totality, they would have missed the eclipse. Thanks to the sun funnel, we had a nearly constant stream of visitors coming by during the first half of the eclipse, and we made some new friends. There’s no way all those folks would have had time to see the eclipse at the eyepiece if I’d been rolling with a solar filter. So from here on out, I’m a sun funnel man. Oh, I will probably also set up a filtered telescope nearby for observing at the eyepiece, but the sun funnel is a key piece of gear, and I don’t intend to voluntarily be without it for future solar events (like the transit of Venus coming up in two weeks).

Third contact–the leading edge of the moon hits the far edge of the sun. See the little points of light between the ‘horns’ of the moon sun? Those are Bailly’s beads, the last rays of sunlight shining through valleys on the limb of the moon. They’re visible at second contact, too, I just failed to capture them in pixels.

I was afraid that the second half of the eclipse would be boring–like the first half run in reverse. It turned out to be a blast. Precisely because we’d all seen it all before (or thought we had–keep reading), we felt free to goof around a bit. Here I removed the sun funnel and put in a regular eyepiece to project the eclipse on my t-shirt. This is a hairy operation–you don’t want to be the projectee and the one pointing the scope at the sun, or you’ll be tempted to glance down into–what? Oh, that’s right, the blindingly intense beam of concentrated sunlight shining out of the telescope. Fortunately I had the presence of mind not to do that, but after this shot, we didn’t let anyone get on the eyepiece side of the scope without eclipse glasses on. This led to some modest hilarity of trying to guide the effectively blind subject to kneel just so beside the scope.

More second-half fun: the sun goes behind an antenna on the next ridge over, maybe a mile away. I suppose a purist might not want anything man-made screwing up the eclipse, but we all thought this was super-cool.

People farther west got to see the entire eclipse, but here the eclipse was still in progress when the sun started to set. Again, some folks might have been bummed but we thought it was crazy-cool to see the sun blocked by both the moon and the Earth. Check out the electrical towers on the distant horizon, much farther away than the antenna in the previous pic. All three sunspot groups are still visible, too.

Moonset at sunset. I don’t even know what you call this…third-and-a-half contact, maybe? Whatever the actual name, we all thought it was the highlight of the second half of the eclipse.

The last sip of sunlight. Good times.

Stay tuned, we’ll do it all over again in a fortnight, only with a much smaller (in apparent size, anyway) object blocking the sun. There’s still time to build a sun funnel and scare up a cheap scope if you’re so inclined. Clear skies!