🔭 Updates an earlier post to include recent changes and new information.
As an amateur astronomer, I use desktop planetarium software to plan viewing sessions and keep track of the planets and Moon. There are many products available for all computer platforms and smartphones. A Google search yields links to many sources. I downloaded and use the open source Stellarium on my desktop computer. It can be customized to your location and is free. For Android and Mac phones and tablets, I like SkySafari. It isn’t free but is inexpensive.
Online planetarium sites are popular and offer many features. Below are highlights of some I find interesting. Each has multiple features, a unique look and feel, and different levels of detail. They can help satisfy your curiosity about astronomical events.
I have included only a few select sites and links since so many are available. I welcome reader questions or reviews about using these tools or others you find helpful.
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The eruption of Mt. St. Helens in Washington State 37 years ago was a spectacular event. Upwelling of magma caused the mountain to be forced slowly and strongly from below. On the morning of 18 May, a huge landslide occurred on the north slope face of the mountain. Rock, timber, snow and ice, slid down the face. The event allowed the volcano to release pressure and begin its eruption.
Ash was projected high in the sky and was caught in the high altitude westerly winds. The dense cloud of ash drifted east blocking out the midday sun across the state. Ash settled down on communities causing confusion and havoc.
In the path of the settling ash was Manastash Ridge astronomical observatory run by the Dept. of Astronomy of the Univ. of Washington. Douglas Geisler was working at the observatory throughout the night of the 17th into the early morning hours of the 18th. He said the skies were excellent for telescope observations. He went to bed at about 5 am.
A loud ‘boom’ barely interrupted his sleep. He went back to sleep until about noon. When he got up to go outside, it was dark.
“Yikes! – There is no day. It’s completely black; thick, inky black with visibility ~10 feet (with a flashlight), & it stinks. This is the end of the world.”
In the logbook for the 19th, he noted for the record the sky condition was black & smelly. He also noted he lost 6 hours of observing due to volcano (good excuse, huh?)
He thought he might be the last survivor of the war as he remembered hearing a ‘boom’. He turned on the radio and heard ‘cha cha’ music. Why was the world playing music at the end of the world? Eventually the radio station from Yakima said that Mt. St. Helens ‘blew its wad.’ He was relieved.
It remained dark until mid-afternoon. Several inches of ash settled on the ground. Visibility improved to about 1/2 mile by dusk. He covered the telescope and instruments to prevent damage. He took some pictures of the dome and surroundings thinking he might make a lot of money on his story. But, he never followed through.
A prism of high quality glass sits in a south window above our mantle. It is part of a surplus optical instrument from WW-II. The window crank gives a sense of its 2″x1″x1″ size.
When the Sun is low in the sky during late fall and winter, light through the prism casts a large full spectrum on the wall on the opposite side of the house. This is a closeup of the spectrum. It is always a delight to see the colors move slowly across the wall during the middle part of a sunny day.
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A story on 16 Dec 2016 from the NASA Earth Observatory site said the Antarctic and Arctic sea ice amounts for November 2016 were both at record lows for that month. The Arctic is in the process of refreezing the surface sea ice as it goes into the winter months. The Antarctic is in the process of melting the sea ice as it goes into the summer months. A chart from the story shows the total amount of sea ice north and south from 1 Jan 1979 to 14 Dec 2016. There has been gradual decline in the total. For 2016, the total is significantly less for the last months of the year. An animated version of this chart is in the linked article.
Sea ice forms from water already in the oceans. Changes to the total does not alter sea level. Melting of land based ice drains into the oceans and does raise sea level. The decrease in total sea ice is due to shifting winds and warmer temperatures of the water. The underlying reasons and prognosis for future effects is an area of intense scientific study.
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Position a satellite camera 1 million miles from Earth directly toward the Sun, 4x the distance to the Moon. Keep it at that location and make it stare toward Earth. Eventually, this happens.
The Moon orbits Earth in a 5˚ tilted plane relative to Earth’s orbit plane. Rarely does the Moon pass directly between the camera location and the Earth. It happened twice in the past year. This pass was captured on 5 July 2016 by the camera on the satellite. It did so once before on 16 July 2015 shortly after the satellite became operational. The Moon passed behind Earth on 27 Sept 2015 as captured in this video. A solar eclipse was captured on 9 March 2016 as the umbra of the Moon’s shadow crossed the Pacific.
These views of Earth are provided by NOAA’s DSCOVR satellite. It is located at a point where the gravitational pull of Earth and Sun on the craft are equal and opposite. This stable location serves as an early warning site for geo-magnetic storms from the Sun. The Space Weather Prediction Center will begin using DSCOVR data on 27 July 2016 to monitor conditions and make predictions.
In much the same way distant off-shore sea buoys serve as early warning beacons for tsunamis, this satellite gives Earth 15-20 minutes of warning for solar storms that might affect Earth.
Recent true color views of Earth are available at this site. You can navigate forward and backward in time by clicking the right and left margins of the screen.
Scientists with the DSCOVR mission have compiled a video from over 3000 images of Earth taken by the EPIC camera on board during the year from July 2015 to July 2016. Notice how the tilt of the poles changes between summer and winter.