A new tour of the Gemini telescope

On Friday I got to go on a tour of the Gemini telescope building at the summit of Maunakea. In pre-COVID-19 times this would be something all new employees would get at some (not-too-long) point after joining, but since tours haven't happened since early 2020 there were something like fifteen of us who'd joined in the last two years who went along. Gemini North is in shutdown at the moment for recoating the primary mirror (for the first time in nine years!), which afforded a very rare opportunity to see an 8 meter-class telescope without its mirror installed.

I actually went on a tour of Gemini (plus some other telescopes) a decade ago back in 2012 while I was an undergraduate at UH Hilo, so for comparison, here's a photo I took then of the telescope with mirror in place and instruments mounted on it:

It's hard to capture the telescope from within the dome because it's just so huge, but the blue-painted parts are the telescope structure, with the various boxy things beneath it being the instruments, which are bigger than refrigerators. The silvery struts above hold the secondary mirror, which can be seen near the top of the image. Now, compare this with the panorama I took on Friday:

The panorama distorts some of the angles slightly, but you can clearly see where the mirror goes inside the telescope structure in this image. The flap covering the aperture there is half of the mirror cover, which folds up accordion-style over the mirror when it's in place. The blue circular thing behind the telescope on the temporary scaffolding holds the mirror from beneath; here's a photo of it I took from from up on the platform running around the telescope:

Here you can see the actuators (the white disks) which sit beneath (or behind) the mirror and help change its shape as it deforms under its own gravity as the telescope changes its orientation. As a reminder, the primary mirror for both Gemini telescopes is 8.1 m (26.6 ft) in diameter, so this is a big piece of equipment. While I did get to see the mirror, it's down on the floor below this one where the mirror coating chamber is, and was hard to get a good photo of as it's on a stand with a cover on top. I did get a photo of the mirror-coating vacuum chamber itself, which is pretty neat:

This flying-saucer-looking thing is the mirror-coating chamber. It wasn't in operation while we were there, but we got to hear a bit about how it works. Unlike most of the mirrors on the mountain which use aluminum, Gemini's mirror is coated with silver, which gives it a better infrared reflectivity. Silver, however, is more chemically reactive than aluminum, and would tend to tarnish quickly over time. To help prevent this, the silver is deposited as part of a sequence of several thin layers of various metals (which I can't recall now unfortunately) to help keep it from tarnishing too quickly.

Overall it was a great experience where I learned a lot about the telescope, marred only by me forgetting my coat and spending the entire time rather chilly. (Thankfully a coworker lent me a jacket.) It's easy to forget just how humongous the various telescope enclosures on the mountain are until you're inside them, at which point the cavernous volume becomes somewhat awe-inspiring. We left Hilo at 8:30 in the morning and didn't get back until 5:30 in the afternoon, so it was a long and intense day due to the altitude, but it was definitely a really cool experience that I'm thankful I got to go on. Though next time, I plan to remember to bring my coat…

Secret Hawaiian waterfalls

One unexpected benefit of flying drones around Hilo and up the Hāmākua coast is discovering waterfalls. The Hāmākua coast, lying on the windward side of Maunakea in the path of the prevailing trade winds, has some of the highest average annual rainfall values of anywhere in the world. Lava from Maunakea is also not very porous (which isn't true of Mauna Loa, which has almost no rivers on it), leading to a multitude of streams and rivers (many of them year-round) making their way down its slopes to reach the sea. The nature of that lava and its stratified layers also tends to result in lots of waterfalls along the way.

Some of these waterfalls are pretty famous (and rightfully so), or known tourist attractions, such as Rainbow Falls on the Wailuku river which marks the line between Maunakea and Mauna Loa lavas, or Akaka Falls a bit up the coast from Hilo on the Kolekole Stream. But something I've learned from flying around is that there are a lot more waterfalls along the various waterways of the Hāmākua coast, and I've been delightfully surprised at some of the examples I've randomly stumbled across.

For instance, here's a rather striking rock formation I discovered while flying up the Wailuku river in a portion that isn't easily accessible. This is actually only about 200–300 feet downstream from Rainbow Falls, but it's just around a bend from the official lookout platform such that I'd never seen it before. In fact, I have no idea just how many people have ever seen this particular part of the river – for being so close to a tourist landmark it really is quite isolated and wouldn't be easy to access on foot. Maybe from the right bank, where as you can see there's a private farm, but I don't know if there's any specific viewing area. (I've yet to see what it looks like when the river is in full flood, but I'm eagerly awaiting a large rainstorm to find out!)

But while the waterfall on the Wailuku river is probably not familiar to many people, it's at least on the edge of Hilo with a possible way to reach it from one side, and (crazy) people do occasionally kayak on the river. The waterfall above is on an unnamed tributary of Kawainui Stream, which sits between it and Waiʻaʻama Stream in a wild and untouched part of the Hāmākua coast, just a little ways south of Akaka falls. I found it entirely by accident while I was filming a timelapse video flying down the flank of Maunaka towards Hilo; at the end of it I looked down, and found this gorgeous little double waterfall. I was able to find it on Google Maps, and given its location in a thickly-forested area between two streams to the north and south, there really can't be many people other than pilots who've ever laid eyes on it.

I hadn't expected to find these picturesque waterfalls when I started drone, but it's really cool to be able to find ones that likely haven't been seen by many people before me, and then share them with the world. There are lots of places on this island I'm still looking forward to taking my drone, but it's also fun to discover these unexpected surprises. I'm sure I'll have more to share in the future, too! A hui hou!