Star Trail Photography

Taking star trails is one of the easiest forms of nighttime photography. it requires less equipment than full out astrophotography, only a camera that can take a long exposure and a tripod. In a pinch you can do without the tripod.

Three Lasers
Three lasers in operation, Subaru, Keck 1 and Keck 2, 23 x 4min with a Canon 60D
In star trail photography a long exposure is used to reveal the scene. With illumination provided by starlight the needed exposure will be minutes long, during which time the rotation of the Earth will cause the stars to trail. Each star will trace a short streak on the camera detector as it moves through the field of view.

For a number of reasons taking one very long exposure is a problem with digital cameras. Without getting into a technical discussion of noise, dark current and hot pixels we will simply advise taking short exposures. You can always try a twenty minute or half hour exposure and see for yourself. Thus the technique is to take a series of short exposures, usually one to five minutes long, and add these together in processing. By taking a series of short exposures, the final exposure length is limited only by the camera battery or the arrival of dawn.

If the camera is sensitive enough, and you have a fast lens, you might try starscape photography, where the stars are not trailed by the motion of the Earth. In contrast, star trail photography can be done by almost any camera that can take a long exposure. The difference is in the length of the exposures, long versus short, star trail or starscape.

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New Moon

Young Moon
A very young moon over Waikoloa, this is only 26 hours after new, visible to the unaided eye as a sliver in the fading glow of sunset
New Moon will occur today at 20:14HST.

An annular solar eclipse will be visible from Australia, Antarctica and across the southern Indian Ocean today. This is a somewhat odd eclipse as the center of the Moon’s shadow misses the Earth entirely. The eclipse will be quite short and visible over a limited geographic area.

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Diving the Naked Lady

A different sort of dive. There are few wrecks to dive on the Big Island, the Naked Lady is one of the few. An Easter Sunday morning spent out on the water, enjoying a beautiful day. As we came back across Kailua Bay from diving at Casa Cave we decided to dive the wreck as our second dive of the day.

Diving the Naked Lady
Andrew Cooper diving on the wreck of the Naked Lady, photo by Pete Tucker
The Naked Lady is a sailboat that burned and sank in Kailua Bay. Apparently the Naked Lady is not the vessel’s real name, simply the name acquired as a result of how it arrived on the bottom of the bay. Hard details are difficult to come by, but the story goes something like this… The sailboat was moored in the bay when the lady aboard needed to eliminate the “little green men” infesting her boat. The result was a burning sailboat and the lady arriving on shore minus her clothing.

It is 110 feet to the sand where the Naked Lady lies on the bottom. This is a short dive, at this depth our bottom time is limited to less than 20 minutes due to nitrogen absorption. Even with the safety stops on ascent the entire dive was about half an hour, I surfaced with over 1200psi of air left in the tank. Considering I often last over an hour with a 80cft tank this was a short dive indeed.

Deb and I did not bother with the mooring line as we dropped to the bottom. The water was clear enough we could see the wreck on the sand 100ft below. With no current we simply dropped, in the clear water this was a surreal, slow motion free-fall. Seeing the sand approaching I did not bother to trim buoyancy, but allowed myself to hit the sand a few feet from the hull. The gauge read 109ft as I knelt on the bottom. I took a couple photos, trimmed for neutral buoyancy and started exploring.

Sky at the Naked Lady
Sky exploring the wreck of the Naked Lady
The hull is more or less intact, with the mast lying to the port side. The entire upperworks are gone, consumed in the fire one would assume. The bowsprit and stern railings lie in the sand in front and aft of the wreck. Inside a few pipes and other fitting are all that remain of the interior.

Aside from a few colonies of cauliflower coral on the wreck itself there is no coral visible, simply a flat plain of sand that stretches in all directions. A swarm of fish surround the wreck, snappers and dasyllus the most numerous. Oddly there are numerous rough spined urchins on and around the hull.

There is little sign of life away from the wreck, the sand seems sterile from a distance. Upon closer examination even this sand desert teems with life. Burrows and tracks betray numerous residents. I take a few photos of a colorful goby I have yet to identify, it does not appear in the usual guidebooks.

The Atlantis Submarine that gives tourists a ride in Kailua Bay often tour the Naked Lady. The submarine was present when we arrived at the mooring, but had moved off by the time we dropped to the wreck. It would have been fun to wave at the tourists.

Naked Lady
Deb on the wreck of the Naked Lady
A lot of photos got taken, mostly of each other as we orbited the wreck. The remains of the sailboat on the sand makes an interesting subject, particularly with the divers poking about. Pete was diving his new 5DMkII rig with a wide angle lens. The wreck was a perfect wide angle target, I found myself wishing I had brought something wide angle like the GoPro. At 110′ there is only blue and more blue, so that the photos turn out rather blue. It becomes interesting to convert the photos to black and white.

The location results in a different dive profile as well. On this island we usually dive deep and then spend the rest of the dive slowly working our way back up the reef, ending in shallow water. A slow ascent eliminates the required safety stops used in recreational diving. Here there is no sloping reef, simply a drop to the bottom. Time to remember those safety stops and monitor the dive computer closely. This ascent required two stops, one at 50′ and another at 15′ to allow the nitrogen to transpire out of our tissues.

With two dives done it had been a great day and we were ready for more. Alas we had a pile of empty tanks and a distinct lack of full. Nothing left but a return to harbor, clean up the boat and an early dinner at the fish market. A great Easter Sunday, far more fun than sitting in church.

The Moon and Venus

Tomorrow morning, April 25th, will see a brilliant Venus paired with a crescent Moon. Look for the pair to rise about 03:41HST to be 30° above the horizon at sunrise. A 15% illuminated Moon will be a nice match for Venus shining brilliantly at -4.1 magnitude. Separation will be about 4&deg.

The following morning, April 26th, will see the Moon much closer to the horizon, over 11° west of the planet.