Category: Sky Events
Sky events
Spot a Young Moon
At sunset this evening the Moon will be less than a day past new, about 20 hours old and only 0.7% illuminated. It is possible, if somewhat challenging, to spot this very thin crescent in the evening sky deep in the bright glow of sunset.
This evening the Sun will set at 18:39 and the Moon will set at 19:21, about ten degrees behind the Sun. Thus a low and clear western horizon is a necessity for locating the Moon tonight. Optical aid will also be very useful, once the correct area is located the Moon can often easily be found by sweeping the area with binoculars. A small, rich field telescope with a field of several degrees across can also be used.
The effort is aided a bit by the presence of the bright planet Mercury in the sunset this evening. The planet will be seven degrees higher in the sky and just a bit north of the Moon. If you find Mercury at 19:00HST, the Moon will be 5 degrees below the planet and four degrees to the south in azimuth.
In several cultures with lunar calendars the spotting of a young crescent Moon like this marks the beginning of the month. Often Moon sightings are used to determine religious holidays and other important events of the year. It is also an good challenge to practice your observational skills. have fun!
Full Moon
This full moon will feature a penumbral lunar eclipse visible across the Pacific region. It will be well placed for observers in the Hawaiian Islands where the entire eclipse from beginning to end will be visible. Do not expect much, penumbral lunar eclipses involve only a slight dimming of the Moon, it is unlikely to be noticeable without instrumentation.
Vernal Equinox
The vernal or spring equinox occurs today at 18:30HST. Today there will be little difference between the length of the night when counted against the number of daylight hours. This is the first day of spring as marked by many cultures in the northern hemisphere.
| 2016 Solstices and Equinoxes | ||||
|---|---|---|---|---|
| UT | HST | |||
| Perihelion | Jan 2 | 22:49UT | Jan 2 | 12:49HST |
| Vernal Equinox | Mar 20 | 04:30UT | Mar 19 | 18:30HST |
| Summer Solstice | Jun 20 | 22:34UT | Jun 20 | 12:34HST |
| Apehelion | Jul 4 | 16:24UT | Jul 4 | 06:24HST |
| Autumnal Equinox | Sep 22 | 14:21UT | Sep 22 | 04:21HST |
| Winter Solstice | Dec 21 | 10:44UT | Dec 21 | 00:44HST |
| Source: USNO data Services | ||||
March 8, 2016 Solar Eclipse from Kawaihae
The seeing was terrible, but at least we could see the Sun while much of the island was overcast and raining. I had hoped to set up in the parking lot for Puʻukohala Heiau but arrived a few minutes after they closed the gate. Instead I set up just below at Spencer Beach park.
Of course the telescope drew a crowd of folks who wanted a look. No matter, an eclipse is a slow motion affair with plenty of time to share the eyepiece. I showed my guests how to take photos with their cell phones at the eyepiece, so everyone got a photo or three of the event.
New Moon
This new moon will feature a total solar eclipse that sweeps from Indonesia across the central Pacific. It will be visible as a deep 50% plus eclipse in Hawaii.
Solar Eclipse Reminder
| Solar Eclipse Data for March 8th, 2016
|
||||
|---|---|---|---|---|
| Mag | Begin | Max | End | |
| Hilo | 55% | 16:37 | 17:37 | 18:32 |
| Honolulu | 63% | 16:33 | 17:36 | 18:33 |
| Lihue | 67% | 16:31 | 17:35 | 18:33 |
| Kahului | 60% | 16:35 | 17:37 | 18:33 |
| Kona | 56% | 16:36 | 17:37 | 18:32 |
| Mauna Kea | 56% | 16:37 | 17:37 | 18:32 |
| Midway Is | 97% | 16:04 | 17:20 | 18:29 |
| All times HST | ||||
| Source: EclipseWise Interactive Map | ||||
A Leap Day
Today is February 29th, that odd date that only occurs every four years.
The reason for a leap day inserted into the calendar, the existence of February 29th, is ultimately astronomical. Perhaps a little explanation is in order…
We originally defined days as the time it takes the Earth to rotate. While we define years as the time it takes the Earth to orbit once around the Sun. The problem is that these values do not divide evenly into one another.
The Earth takes about 365.24219 days to obit the Sun, when measured by the Sun’s position in the sky, what is called a tropical year. There are different ways to measure a year, but if one is concerned with keeping the seasons in sync with your calendar, then you are interested in tropical years.
It is that bunch of decimals, the 0.24219 etc., that is the problem, every four years the count drifts out of sync by roughly one day. The insertion of an extra day every four years helps bring the calendar back into synchronization with the orbit of the Earth and with the seasons.
Even leap years do not quite fix the problem as 0.24219 is close, but not quite 0.25 or one quarter of a day. Thus additional corrections are needed… Enter leap centuries.
Our current calendar was instituted by Pope Gregory XIII in 1582, setting up a standard set of corrections for the fractional difference between the length of a year and the length of a day. Scholars knew that errors had been accumulating in the calendar for centuries, resulting in a drift of several days. Religious authorities were concerned that this drift had displaced important celebration in the church calendar, in particular the celebration of Easter. After much argument it was decided to reform the calendar. The current solution was devised by a number of astronomers, including Aloysius Lilius, the primary author of the new system.
The Gregorian Calendar uses an extra day in February every four years, unless the year is divisible by 100, then there is no leap leap day that year. However, if the year is divisible by 400, then it is a leap year. While this may sound odd, it does create a correction much closer to the ideal value of 365.24219 days per year.
I am a geek, so let us put that into code…
Even this is not perfectly precise. The correction is close but will drift given enough time. The length of a tropical year also changes slowly over time. We will eventually have to add another correction to keep the calendar and the seasons in sync. But not for a few millennia, good enough, for now.
As 2016 is divisible by four and not divisible by 100, there will be a leap day added to the end of this February… Today.
Full Moon
Total Solar Eclipse March 8, 2016
On March 9, 2016 a total solar eclipse will sweep across Indonesia and into the central Pacific. This will be an late afternoon eclipse, with maximum occurring just before sunset at around 17:37 HST (5:37pm HST).
Note, you might be confused by some references that state the eclipse occurs on March 9th. It does occur on the 9th! For our islands greatest eclipse occurs around 03:30 on March 9th universal time. If we convert to Hawaiian Standard Time this will be the 17:30 (5:30pm) on the afternoon of March 8th. You must remember that universal time is ten hours ahead of Hawaiian Standard Time.
A deep partial can be very interesting. Even people not expecting the eclipse may notice a dimming of the Sun and an odd, subdued nature to the sunlight. Even a quick glimpse of the Sun will reveal that half of the disk is covered. Eclipse glasses or a welding filter will provide a nice image of a partially eclipsed Sun. Tree leaves and other makeshift pinhole cameras will show crescent images of the Sun on the ground. For best viewing a small telescope with a solar filter, or a pinhole camera will allow excellent images of the eclipse. My standard eclipse viewing setup is a 76mm refractor with a Baader film solar filter. I assembled this gear for the 2012 Venus transit and it has seen several eclipses since.
| Solar Eclipse Data for March 8th, 2016
|
||||
|---|---|---|---|---|
| Mag | Begin | Max | End | |
| Hilo | 55% | 16:37 | 17:37 | 18:32 |
| Honolulu | 63% | 16:33 | 17:36 | 18:33 |
| Lihue | 67% | 16:31 | 17:35 | 18:33 |
| Kahului | 60% | 16:35 | 17:37 | 18:33 |
| Kona | 56% | 16:36 | 17:37 | 18:32 |
| Mauna Kea | 56% | 16:37 | 17:37 | 18:32 |
| Midway Is | 97% | 16:04 | 17:20 | 18:29 |
| All times HST | ||||
| Source: EclipseWise Interactive Map | ||||
As you can see the magnitude of the eclipse increases notably the closer you are (further north in the main islands) to the path of totality. The timing does not vary by nearly as much, with maximum eclipse occurring around 17:36 for the islands.
If you would like to see precise information for your location, or for someplace other than the islands, just use the interactive map and click on your location for data.
There are no further solar eclipses near the Hawaiian islands until 2031 and 2035, the path of totality for both of which pass well south of the main islands. There is also an annular eclipse in 2024, for which the center line also passes well south of the islands.