The KBO is a small chunk of ice named 2014 MU69, at a distance of around 44 AU. We know where to find it in the sky, but we don't know its orbit precisely enough to target the spacecraft's cameras as we fly past it. Taking more images -- even with Hubble or large ground-based telescopes -- won't do the job. But hope is not lost: there are several stellar occultations, where MU69 will pass in front of a distant star, that can be used to help measure the KBO's position and size. If you set up a telescope at the right place, and observe the right star at the right time, you'll see it briefly blink out. If you do this from even a couple of different places along the shadow path, you can get a good idea of the size and position of the body.
This is relatively common thing to do for a 'large' body like Pluto. MU69 is comparably tiny -- some 10,000 times fainter -- and this makes observing an occultation a real challenge. But, New Horizons has just one chance to fly past it, so in prep for the encounter, the mission and NASA decided to invest substantial effort into a large campaign to observe three occultations with MU69 during the summer of 2017.
I was lucky enough to be invited to join about 25 others in heading to South Africa to observe the occultation on the morning of June 3, 2017 (the first of three occultations). We brought 5000 pounds of telescopes with us, primarily a dozen 16-inch motorized Dobsonians, fitted with low-noise detectors. Our plan was to fly to Cape Town, get up to speed on the equipment, and then spread apart across the occultation path, in order to observe the event on the morning of the 3rd. Another group of 25 headed to Argentina to see the same event, essentially a backup in case of bad weather at one site.
Although I've analyzed a lot of occultation data from from the ground and New Horizons, this was my first* occultation-chasing trip. This trip had a combination of professional astronomers (students, postdocs, faculty, etc.) and some very advanced amateurs, and we all learned from each other. It's an amazing world where we get to do these sorts of projects while traipsing past sage brush and springbok, and see the effects several years later in our new knowledge of the Kuiper belt.
As of early July, the data taken in June were still being analyzed. This particular occultation is a lot more complex than a Pluto occultation: smaller target, many more chords, and low SNR. [Update: Check out the NASA press release on the occultation results!]
Many thanks to the organizers for bringing me on board, and for everyone else for putting up with me sticking a camera in their face!
* I attempted to observe a Pluto occultation from Sutherland with Amanda Sickafoose, but we were blizzarded out and were eating lamb shank in town by the time of the event. And, Trina Ruhland reminded me that I observed an asteroid occultation with her and her dad -- my thesis advisor, John Bally -- at their rooftop observatory in Colorado.
A few other pages worth reading:
![]() | Ted and Paul are amateurs frrom Phoenix. They're both really experienced observers, who've spent a lot more time using telescopes like these in the field than many of us. |
![]() | Eliot Young, Michaael Person, and Anicia Arredondo. |
![]() | Michael Person and Anicia Arredondo. |
![]() | Con Tsang and RJ Smith load that optical tube assembly (OTA) into the base. |
![]() | Alex Rolfsmeier searches for a target. |
![]() | Ted Blank and a row of bakkies. |
![]() | Looking at that mirror cell. |
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![]() | Bridget Anderson and John Wilson get their hardware ready. They are from UVA and brought their own three large telescopes (two 14" Celestrons, and a 24"), so they've got their own boxes to unpack. |
![]() | Sam, Jef, Eliot, and Alex confer. |
![]() | Eliot is convinced he will eventually find Jupiter. |
![]() | Anne Verbiscer is our leader! |
![]() | Ted Blank and Con Stang. |
![]() | Anne Verbiscer is our leader! |
![]() | RJ Smith, Paul Maley, Eliot Young, and Simon Porter all love Pluto, even though only Simon is vocal about it today. |
![]() | Anne head down the street to set up! |
![]() | Paul and Ted cover up their vehicle to protect its juicy contents. |
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![]() | "Hey guys... can you come over here?" |
![]() | Well, here's something you never want to see... the primary mirror has somehow come off entirely! The scrapes on the side of the tube show that it's been bouncing around for some time. |
![]() | Simon gets down to assess the situation, and unscrew the mirror cell. |
![]() | Oh no... |
![]() | Amir photographs the broken connection, while Trina inspects the beautiful scenery behind her. |
![]() | The mirror is apparently glued into place, using a silicone adhesive. It had just a single point of attachment. |
![]() | Trina packs up the rest of that telescope. They won't be needing it tonight... |
![]() | We're really lucky to get a visit by Martin Lyons, a telescope builder with one of the local clubs (the Cederberg Astronomical Observatory. We talk about mirror gluing with him. |
![]() | Jeff has bought some strong adhesive, and is getting ready to glue it. |
![]() | Glueing that mirror back on... |
![]() | It's very sticky adhesive -- that sort of amount will take hours to rub off of one's hands (as I found out from experience). |
![]() | Jeff placing that mirror. |
![]() | Yeah, not very flat... |
![]() | Martin was right: in the morning, it was on, but not tight enough to keep it secure while rattling across dirt roads in the Karoo. |
![]() | We're at the hotel restaurant, specializing in South Africa's favorite cuisine: red meat. Also, butternut, and beets. "Anne, certainly you'd like some of our springbok hot pot, would you not?" |
![]() | Charles, Aaron, and Jason talk with Martin Lyons. That's the moon rising behind them. |
![]() | Alex aligns his finder scope. |
![]() | DO NOT LOOK AT THE LASER BEAM!!! |
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![]() | Eliot and Alex work their telescope. |
![]() | Oooh! My green laser pointer comes useful, as we try to find our target field. Our star itself is a relatively nameless 15th magnitude object, but it is near the 2nd mag star Nunki (aka Sigma Sag). One week later, my discussion with immigration in Dubai went like this: Them: Sir, is that a laser pointer you have with you? Me: Yes, it is? Them: What color is it? Me: Green. Them: Please sign this form, and we will destroy your laser pointer for you. |
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![]() | And they are on the field! Amanda has put printed star charts in the 'Plankton,' which after some rotation eventually match what we see on the screen. |
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![]() | Anja, Alex, and Jason try to match stars. |
![]() | The next morning, back at the hotel. I'd forgotten about South Africa breakfasts, but this is a massive spread. Trina pulls out that map. |
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![]() | Aaron has his EMT outfit on, in case we have any medical emergencies at that breakfast buffet. He is a retired ski patroller, turned occultation chaser. |
![]() | And we're about to head off! Trina, Jeff, and Emily check out of one hotel and head to their bakkies to drive north. |
![]() | What an amazing set of choices we are offered!! It was hard to pick just one... |
![]() | Amanda's dad is a mechanic. "His advice? Get a new bakkie." |
![]() | We've made it about three hours up the N7 to Clanwilliam. The city is known as a major processor of Rooibos (South African honey-bush tea). |
![]() | In Clanwilliam, we drop by the Yellow Aloe guest house, with the very charming Anne. |
![]() | "Well, but you also need good weather!", someone points out. |
![]() | John Moore. |
![]() | Sam Strabala enjoys that tasty beverage! |
![]() | Our dark site near Clanwilliam is the Rondenberg Resort, which is an RV park ('caravan park') about 20 minutes outside of town. Many people stayed there, and we used it for meeting and night-time practice. Their website even has a big section covering the occultation, including articles in the Cape Times and the the local Afrikaans newspaper about the NASA group. |
![]() | Trina, Charles, Anne, and local SAAO postdoc Nic Erasmus, at the Rondeberg. |
![]() | Amir's bathroom has a tree, a climbing wall, and a stone shower. It was pretty incredible. |
![]() | Time to get those telescopes out! |
![]() | Yeah, a little bit of clouds... |
![]() | But we could see a lot of stars still. |
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![]() | Not looking too good here... |
![]() | But hey -- at least we get a nice view of that southern Milky Way! |
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![]() | By 3:30 AM it still wasn't clear, but we'd gotten aligned a few times, found the field twice, and basically knew what we were doing. |
![]() | At lunch the next day, Jeff and Simon scheme. |
![]() | While Emily plans back at the guest house. |
![]() | Oh, what I woud do to have the title Grant Spammer, Amagqwetha. |
![]() | Ted Blank. |
![]() | Just how far are we going? About 600 km, past Carnarvon, to Victoria West / Vosburg. This is solidly in the middle of the Karoo, in a very remote area of the country. |
![]() | As our chief predict planner, Simon stays at the Clanwilliam so he can be in touch with the Argentina team. |
![]() | RJ maps out his destination. |
![]() | John Wilson is among those of us who love oranges. |
![]() | Jason likes cats, and they like him (or at least his meaty sandwich). |
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![]() | A challenge to the reader: find all ten cats in this picture. Hint: they are all in a line. |
![]() | Christian reads out everyone's new assignments! |
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![]() | Con gets ready to drive: gas up, and buy those jerry cans! |
![]() | Eliot and Mike get ready to pack up. |
![]() | Mike Skrutskie put that Celestron tripod to good use. |
![]() | Swapping off some keys and drivers! |
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![]() | And we head out once again into the beautiful South African countryside. It's sunset, and we're just about to start our 600 km trip. |
![]() | Jason Mackie is coming along with us. Originally we had two floaters, but with one telescope out of commission, we're effectively up to four floaters now. |
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![]() | Jason calls around to see if he can find us space in a guest house in Vosburg. Success! |
![]() | We head up with Nic as well. |
![]() | Fueling up at our last chance for awhile... |
![]() | Looks like we have about six hours and 600 km ahead of us. |
![]() | I took a lot of photos, but I look forward to seeing Jason's movies -- he filmed a lot on that tiny GoPro. |
![]() | What a beautiful country it is... |
![]() | Time for a quick breakfast. Well, 'quick' may not be possible in the Karoo... but with only one restaurant in town open, we were happy to partake. |
![]() | And here we all are! That's the proprietor's dogs and 4-year-old below (all of whom run around a lot). |
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![]() | It's a South African breakfast: lots of meat! |
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![]() | And there's the meat building: Die Vleisfabriek = Meat Factory, in Afrikaans. |
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![]() | Our lines are spaced every 10 km. So we drove down the road, and pulled off at the closest ranch to each line. |
![]() | Although the owner wasn't around, we did find the families of the farmhands across the road. |
![]() | Sheepies! |
![]() | So, we struck out on a few, but we continued on. By the side of the road we spied what looked like ruins -- old decayed brick buildings, and a nice rusted out vehicle to the side. |
![]() | "That's from a predator!" |
![]() | Here's the site that he directed us to. It's super: easy access from the road, and a good block from the wind... not to mention some nice scenery. |
![]() | Jason is in charge on the way back to Clanwilliam. |
![]() | Meanwhile, the rest of the teams have done a great job scouting (in cooperation with super friendly locals), so while we have some good backup sites in hand, we aren't going to end up needing them. |
![]() | We meet back up with Ted and Paul. They've been out scouting as well, and have found a great location for their telescope. They'll set up on an ostrich farm, next to a small church as a windblock. |
![]() | Eugene gets that braai going. How long does it take? "If you want to do it right -- seven hours." We've got about three -- so we talk him into the express version. |
![]() | Even standing right in front of the braai, it's cold! |
![]() | Charl gets those boerewors going. |
![]() | Ted pulls up the secondary, and mounts the camera in the eyepice tube. We're using a low noise CCD from QHY. |
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![]() | Now it's time to collimate: set the mirrors so they are aligned with each other. The laser beam makes that easy. |
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![]() | And there's the beautiful southern sky! The Milky Way is running top-to-bottom, and the two clouds to the left are, appropriately, the Small and Large Magellanic clouds. The faint green banding is real: that's airglow of oxygen at 557 nm -- in a way, a very low-level aurora generated in the Earth's upper atmosphere. The glow silhouetting the mountain is from another city maybe 15 km to the south. |
![]() | An hour to go before the start time, and we get a message: FLOATER NEEDED NOW! Aaron and Jason hop in the bakkie, and take off. Those are their headlamps as they went on either side of me. |
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![]() | On the target. |
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![]() | That's our target field! |
![]() | And... occultation complete! We recorded a full 5400 frames at 2 Hz. Ted and Paul have turned back on their lights, and are backing up the data from the laptop to an external drive. NASA also used this shot for a press release... it's definitely one of my favorites. |
![]() | And here are where all the teams ended up. We found great sites, and the weather more-or-less held in Clanwilliam, so every team ended up getting usable data. |
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![]() | We make it back to Cape Town amid a huge rainstorm (and the first one they've had in months). A good sleep, and then in the morning, it's time to pack up some telescopes! |
![]() | Trina and Charles bring in their OTA. |
![]() | Amanda gets those collimators checked out and packed up for Chile. |
![]() | 2000 kg of telescopes! And 2000 kg more to Argentina! It took a 53-foot trailer to get them delivered to Boulder. |
![]() | Check out those data! Ted is among the first to turn in his USB stick to Simon. That's the whole goal... |
![]() | Meanwhile, Jeff assesses one more mirror situation. (We've already looked at Amanda's, but now this one fell out as well!) |
![]() | For some reason, the mirror has come loose again, even though all the bolts were apparently tight. It's not the adhesive failing like before, but some situation with self-loosening bolts. |
![]() | We flip it over and do our best to lock things down this time. |
![]() | I document it... |
![]() | Sam and John go through their checklist of cables. These telescopes are headed straight to Argentina for the July 17 event -- so everything must be ready for the next observers. |
![]() | Con and Jef pack up that telescope (again). |
![]() | Con and Michael haul off those crated side pieces to their vehicle. |
![]() | "How big a crew do we have? Two guys. Tomorrow afternoon, they're going to carry every single one of your telescopes into the truck, drive to the airport, and drop them off." |
![]() | The UVA team packs up at Federal Clearing. |
![]() | Meanwhile, back at the hotel, Eliiot is compiling a list of 'lessons learned' for the next occultation trip. Paul has made a pretty great start with his 50 hand-written suggestions. |
![]() | Paul is a really experienced observer, and has a ton of useful input. |
![]() | We head down to the Cape Town waterfront for some dinner, and a beatiful picture of Table Mountain. |
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![]() | Don't bother Simon! While we're eating, he's processing light curves. |
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![]() | We're flying out in the evening, but with the telescopes off, we have most of the day free around Cape Town. Five of us gather at 6 AM for a hike up Table Mountain. |
![]() | No stargazing allowed! We're headed up the Platteklip Gorge trail, which starts just past the cableway, and ends on top (obviously). |
![]() | Christian and Charles have set a pretty bruising pace on the way up! This route is 2 km, but with 0.8 km of vertical elevation gain! Looks like Charles is photographing a protea, which is the South African national flower. An amazing fact I read: there is a greater number of plant species on Table Mountain, than in all of the UK. It could well be true: Table Mountain tops out at 1100 meters, which is only slightly lower than the 1300 meters of Ben Nevis, the UK's highest point. |
![]() | Go go go! |
![]() | Nearing the top... |
![]() | Hey, we're 3/4 of a mile higher than the airport... |
![]() | Last time I was on Table Mountain, it was a white-out, with visibility of not much more than few meters. Also beautiful, but it was great to be able to see the whole surface. It's really surreal. On the horizon behind us is the real summit (which is on the far end from the cableway). We've almost made it out there. The round trip on top added 2 or 3 km to our escapade. |
![]() | For a few brief seconds, Trina no doubt has the highest feet in Cape Town. |
![]() | Behind us is 'Maclear's Beacon' -- the true high point (16 meters higher than the other end of the plateau!) |
![]() | This is cool: "His tribute to this mountain was his naming of Mons Mensa (Latin for Table Mountain) -- the only constellation named after a geographical feature in the world." |
![]() | Just about to head down the cableway. You can see the 2010 World Cup soccer stadium just below to the left. |
![]() | Have to talk to the rock hyraxes ('dassies') first! A cute little animal, whose closest relative is the elephant. |
![]() | And in the cablecar... 6 minutes and we're down. |
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![]() | In the evening I head back to India. En route I have a layover in Dubai, and meet up with a friend there. |
![]() | John and I go out and look for camels. |
![]() | Eventually, we called for professional assistance. |
![]() | Where are we? Kind of near a road that's buried, and in the middle of a bunch of sand dunes? The closest business to us was a place called Camelicious. Apparently it's a camel milk processing factory. It's 10 km away. |
Last modified 11 Jun 2023