Astronomy Basics

-4.9 magnitude? Inferior conjunction? Maximum elongation? 3.4° separation? To explain many of the basic terms I use to describe sky events I really need to post some explanation. Something I can link to in order to explain myself. Using the magic of hypertext as it was originally meant to be used.

I have written a couple more astronomy basics posts to go along with the sky events postings. I have copied over a few more posts from the old DV blog, updating and refreshing them as I did so. Expect to see a series of astronomy basics posts through the month as I get everything setup in the new blog.

Postcard from the Reef – Fine-Spined Urchin

Fine-Spined Urchin (Leptodiadema purpureum)
Fine-Spined Urchin (Leptodiadema purpureum) in a cave at 30ft depth, Kohala Coast

A pretty urchin found in a cave. Apparently this is the rule for these urchins, found under rock and rubble when small, larger individuals found in caves or deep crevices with an active aversion to light. Most urchins move pretty slowly, the motion barely perceptible. This echinoderm was moving, tube feet furiously propelling it along the cave roof as it tried to avoid our lights.

Mucking About in Themes

Yes, I have changed the theme. Sorry.

The theme currently displayed is Blogum. I think this is the way I want to go. The original appearance was back on white. Not really appropriate for a blog called Darker View. I have edited the CSS for a gray on black appearance closer to the original DV. A few things do not work quite right, particularly the tables I had so neatly laid out for the earlier theme. Just more work ahead, bear with me.

The Moon and Pleiades

Tonight a bright gibbous Moon will be just under 3° from the Pleiades star cluster. The Moon will be 84% illuminated, bright, but the cluster is bright enough to be seen even against a bright Moon. As the Pleiades move to the west over coming months there will be a few more lunar conjunctions, with increasingly smaller crescents.

Perihelion

Today the Earth is closest to the Sun, a point called perihelion. We will be about 147,098,290km (91,402,639miles) from the Sun. Compare this to the 152,098,232km (94,509,459miles) we will be at aphelion on July 4th, a difference of about 5,411,169km (3,362,344miles) occurs throughout one orbit.

It may seem odd that we are actually at the closest for the middle of northern winter, you just have to remember that proximity to the Sun is not the cause of the seasons. The seasons are caused by the axial tilt of the Earth, creating short and long days throughout the year, with a resulting change in the angle and intensity of the sunlight.

2012 Solstices and Equinoxes
  UT HST
Perihelion Jan 5 03:59UT Jan 4 17:59HST
Spring Equinox Mar 20 05:14UT Mar 19 19:14HST
Summer Solstice Jun 20 23:09UT Jun 20 13:09HST
Apehelion Jul 4 23:59UT Jul 4 13:59HST
Fall Equinox Sep 22 14:49UT Sep 22 04:49HST
Winter Solstice Dec 21 11:12UT Dec 21 01:12HST
 
Source: USNO Data Services Website and the NASA Sky Calendar

 

Site Appearance

Yeah, I am not happy with the appearance of the site either.

The current theme just has a number of annoying “features” that just bother me. I am experimenting with another theme, one with an even cleaner and more minimalistic layout. So expect the appearance to change some time. In the meantime if you happen to stop by Darker View late some night to see an entirely different look… It is just me working on another layout.

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.

Continue reading “Some Holiday Diving”

Quadrantids

The first meteor shower of 2012 is likely to be a good one. The Quadrantids are a reliable shower, producing 60-120 ZHR, one to two meteors per minute. The Quadrantids are named for the obsolete constellation Quadrans Muralis, now part of the constellation Boötes.

For viewers in the mid-Pacific the peak will arrive early on the morning of January 4th. The radiant rises around 2am, creating a pre-dawn event. Set the alarm clocks early for this one. While the predicted peak is January 4, 07:20 UT (January 3, 21:20 HST) the show should be quite decent for hours either side of this time. Unlike other showers where activity can occur for days or even weeks, the Quadrantids have a sharp peak, activity falls off rapidly on the preceding and following nights.

The Moon is still a few days short of full, allowing several dark hours before dawn for meteor watching. Moonset will occur about the same time the radiant rises, about 2am, giving observers about three hours of good dark skies to enjoy the event.

Watching meteors requires no more equipment than your eyes and a dark sky, and can be enjoyable for just about anyone. Set the alarm clock, this one should be worth the early morning wake-up.