Astronomy Basics, So Far…

I have completed the first set of the Astronomy Basics posts I intended to do. I really wanted to get these posted as support material for the astro-events posts.

As I finished these I realize I should probably continue and hit a few more subjects. Look forward to a few more Astronomy Basics posts in the coming months.

Degrees, Arc-Minutes and Arc-Seconds

How do we measure things in the sky?

Throughout the descriptions of astro-happenings here on Darker View, I use the terms degrees, arc-minutes, and arc-seconds. This is how astronomers measure size and separation of objects in the sky.

The degrees used by astronomers are the same as those you learned in high school geometry, the same as marked on that old school protractor forgotten in the back of the desk drawer. 360 degrees mark a circle, 360 degrees reach once around the sky.

Degrees measure rotation, and just about everything in astronomy rotates… As the Earth rotates on is axis, the sky goes wheeling overhead. When we move a telescope from one point in the sky to another we rotate the telescope about its axis. How far does it rotate? That is measured in degrees.

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Counting Whales

It is that time again! Time for Ocean Count 2012… A morning spent spotting and counting whales for the Hawaiian Islands Humpback Whale National Marine Sanctuary.

The sanctuary staff recruits teams to crew sites all around the islands. All together, 61 teams with over 950 volunteers observed whales from Kauai to Hawai’i today. Twenty one teams set up to cover the Big Island from South Point to Opolu Point. The procedure is to observe whales from 8am to noon, recording the behavior in half hour time slots. Every blow, dive, breach or other activity is recorded. The technique is to work in teams of two, one person spotting, binoculars in hand, the other writing as the whale activity is called out.

Counting Whales
Deb Cooper counting whales north of Kawaihae

A bluff overlooking Pelekane Bay has been our site for the last three years. Mile Marker 7 is a perfect place to observe whales. A bluff well above the water. A rocky knoll covered with lawn chairs, coolers, and well over twenty observers peering through binoculars.

This year was much like the last several years. We counted dozens upon dozens of whales from the MM7 site, while other sites around the island are lucky to see a handful. There are some sites that did not see a whale all day. We count as fast as we can write, activity everywhere.

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Polishing an 8m Mirror

My friend Dean Ketelsen has posted another great bit of video from the Steward Mirror Lab where he works. This time it is time lapse of polishing one of the eight meter GMT mirrors.

Somehow the video does not do justice to the sheer size of an eight meter mirror, it looks smaller than it really is. Be sure to read his description for all of the technical details.

The Moon and Venus

This evening a nice crescent Moon will join Venus in the dusky sky. The pair will be reasonably close, about 8° apart. Venus is currently shining very brightly at about -4.1 magnitude, contrasting nicely with a 9% illuminated Moon. The two will still be close tomorrow, about 9° apart with the Moon 15% illuminated.

Meteor Watching

Watching meteors is one of the simplest forms of astronomical observing. Just about anyone can enjoy meteor watching, from just about anywhere in the world. Enjoying the show takes only a couple things… A dark sky and a comfortable place from which to watch.

Leonids in Orion
A pair of Leonid meteors streak through Orion
Meteors are simply small bits of debris hitting the Earth’s atmosphere at very high speed, typically tens of thousands miles per hour. Our solar system is rich with this debris. Most of these bits are quite small, about the size of mote of dust or a grain of sand. Something the size of a pea would create a spectacular fireball that lights up the whole sky. While they often seem close, they are actually quite high, 60 miles (100km) above the ground when they flare into short lived fireworks.

The mechanism for the show is simple. When something hits the very thin air high in our atmosphere at very high speed it compresses the air in front of it. This compression also heats the air, causing it to glow white hot. Heated enough, the air becomes a plasma, the molecules shredded and electrons freed from the atoms. It is not the meteor itself that you see, but the glowing plasma around it.

There are a number of questions many people ask about meteor observing. You can find many of the answers below. Watching a meteor shower takes no special equipment, expert knowledge or extravagant preparation. This is an activity nearly anyone can enjoy, one of the spectacles of nature available to all.

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Postcard from the Reef – Bigeye

Common Bigeye (Heteropriacanthus cruentatus)
Common Bigeye (Heteropriacanthus cruentatus) in a cave on the Kohala Coast
Shine a dive light into any small cave along a Hawaiian coast and you will see a swirl of red fish… Soldierfish, squirrelfish and bigeyes. They are all some shade of red and all possess large eyes for foraging in the night. During the day these fish shelter in caves, crevices and overhangs. There are a couple dozen species, identifying each is a bit of a challenge…