Laser Return Photometery

A different use for amateur astrophotography gear.

An amateur CCD camera can do more than take pretty pictures. There is no reason why any decent telescope, however small, and a CCD camera can not be used to do real science, or real engineering in this case.

The goal of the night was to perform proper photometry on the laser returns with independent equipment. We want to quantify the performance of the Keck adaptive optics laser systems. We launch two powerful lasers into the sky, one from each telescope, to allow analysis of the atmospheric distortions through which the telescope is observing. Using the data the system can correct for this atmospheric distortion and create much sharper images of distant stars and galaxies.

The lasers pass through a layer of sodium atoms about 90km (55miles) above the ground. There the 589nm yellow light excites these sodium atoms creating a glowing beacon, what we call the laser return. This return is what we look at to analyze atmospheric distortion. A brighter return allows better data and better performance of the system.

Both Keck lasers in operation
Both the Keck 1 and Keck 2 lasers in operation under the light of a nearly full Moon

Amateur astrophotography gear is perfectly capable of doing this task. A portable telescope, a proper CCD camera, combined with care to acquire calibrated images. All that I needed to add to the setup was a photometric V filter.

It was a perfect night for it, clear, dry and cold. Best of all, there was no wind to bounce the telescope around and chill anyone working outside. The winds are nearly constant atop at 14,000ft peak, calm nights are unusual, I was lucky indeed.

I setup the telescope atop a crust of ice and snow. The snow was convenient as it allowed me to set down gear on a cleaner surface than the gritty volcanic cinder underneath, keeping everything quite a bit cleaner. The altitude and cold made setup and breakdown a slow, laborious process, and added unique difficulties. I had to be very careful moving the heavy gear, so as not to slip on the icy snow. When I went to move the telescope tripod I found it frozen into the snow and cinder! I had to heave hard to break it free.

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Some Holiday Diving

Boat dives are always a treat. We generally shore dive, where the only costs are the tank fills and a little gas to drive to the site. Many sites along the Kohala Coast are easily reached from shore. There are a number of great sites that are more difficult to reach, sites for which a boat provides a nice alternative. When going with a dive boat you also have the crew to assist in rigging gear and getting in and out. They also provide drinks, snacks and friendly conversation while you wait through a surface interval between dives. A holiday treat? A mutual Christmas gift? Whatever you want to call it, we booked a dive with Denise and Dave from Blue Wilderness for a day of diving.

Deborah Descending
Deborah descending to the bottom

There were several divers beside Deb and myself. Ben, from London, had left his girlfriend back at the resort for a morning of diving. A family from Saskatchewan was escaping the winter with a couple weeks in Hawai’i and a morning of diving. The wife and daughter were simply snorkeling. The father, an ex-navy diver, was introducing his son Brett to the sport.

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Postcard from the Summit – White Christmas

Regular snowfall has accumulated at the summit. It is patchy, the wind sweeping the snow off the slopes, creating substantial drifts behind buildings and against guardrails. If you want to sled or snowboard, some of the north slopes have a bit of accumulation. Try the small bowl between Keck and Subaru. Need to have a white Christmas in Hawai’i, we can provide this year…

Icy Summit
The Sun setting over an ice and snow covered Pu’u Hau Kea

Light Snow Makes for a Pretty Day

A light snowfall delayed our arrival at the summit this morning. It was really only a few inches, but as usual it drifted into all the wrong places. Thus ice and drifts on the road meant we were waiting for the snowplows to break through.

Waiting was no problem, the Sun was out, creating a very pretty mountain. Olivier and I walked up to Keck from below Subaru as the snowplow cleared the last bit of road. We both had cameras in hand, enjoying the scenery. Not a lot of snow, but a fair amount of ice on any exposed surface. A few days before Christmas it all seemed appropriate.

After a quick job in the AO bench we needed to wait for some adhesive to cure. I ended up joining in with the snow shovel crew, clearing our doors and walkways of small drifts. Shoveling snow is not easy at nearly 14,000ft. Breathing hard, but having fun…

Light Snow
A light snowfall atop the summit of Mauna Kea

Green Flash

It was a beautiful evening as I drove home from work. The clear air allowing appreciation of all five volcanoes that loom over South Kohala. Indeed, the horizon was completely clear, the island of Kaho╩╗olwe visible over 60 miles away.

As I drove I noted the Sun beginning to settle into the distant horizon. At the wheel I couldn’t look long enough to be certain, but I thought I saw an Etruscan vase effect as the solar disk made first contact with the horizon. Curiosity peaked, I pulled over to properly watch the end of sunset. A pleasant surprise rewarded my view, a decent green flash was apparent as the last glimmer vanished.

Better yet, the camera caught the effect as well. Of the dozens of sunsets I have stopped and watched, this was the best green flash seen yet from such a high elevation. Still, it was modest compared to a couple flashes I have seen from sea level. I can only wonder how good this evening’s flash was as seen from the shoreline, 2,000 feet below.

Green Flash
A modest green flash as seen from the Mamalahoa Highway outside Waimea, 1 Dec 2011

Postcard from the Summit – Colorful Commute

As winter descends on Mauna Kea, commuting to and from the summit had become… interesting. Fog, snow and ice being regular features of the drive. Winter weather has also brought fantastic cloud formations, all the more interesting as you drive into them. The later dawn and earlier sunset means that our usual arrival and departure times are filled with dramatic light. All elements become part of a spectacular show.

Colorful Commute
Shane, a Mauna Kea Ranger, heading down the mountain into a rainbow

Diving Black Friday

Black Friday, a phrase that brings to mind stores jammed with shoppers seeking the first Christmas sales. Not my idea of fun and something to be completely avoided if at all possible. Better to spend the day where credit cards do not work… Possibly under water?

The plan was to return to O’oma and the dive sites near the popular Pine Trees surfing breaks. The area is very good diving, with many sites and entries to choose from along a half mile of coastline, From OTEC to Kaloko. The area is popular with the dive boats as well, we were dropping into the water mere yards from the moorings used by the Honokohau diving operations. As we prepared for the dive we watched as the boats did as well, we just did it without paying $150 per person. The only disadvantage? We had to walk across 50 yards of pahoehoe lava to get to the lava, not a problem with the very gentle swell of the day. Entry was quite easy with a sheltered shallows available just in from the popular Suck ’em Up cave and dive site.

Olivier and Camera
Olivier Martin with his camera rig on the reef at O’oma
We again had a large crew… Mark, Patti, Dennis, Sky, Olivier, Pete and his two off island friends.. Isaac and Jeff. Mark and Patti took advantage of the holiday camping at O’oma to camp out on the beach for a couple nights. While parts of the beach were crowded with campers, the popular spots were those adjacent to the surf breaks. Much of the remaining shoreline was quiet, where you could have a nice stretch of sand to yourself. Not that the peace was totally uninterrupted… The rest of our crew invaded their peaceful campsite, for a time turning it into a diving base camp, with vehicles, wetsuits and tanks everywhere. But then, they did invite us.

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Postcard from Hawaii – Too Many Bananas!

A third bunch of bananas in as many weeks! Yeah, just a few too many bananas around here. Did the cooler weather bring them all on at once? Look for bunches of apple bananas in the Kohala break room at work tomorrow!

In the meantime… Banana smoothies! Two bananas, a cup of plain yogurt, a bit of milk to thin out the mixture, a handful of ice cubes, and a couple heaping spoonfuls of my sister-in-laws strawberry jam. Blend and enjoy!

A bunch of apple bananas from the backyard banana patch