Bakersfield Night Sky – October 18, 2014
By Nick Strobel
As a followup to the total lunar eclipse we experienced ten days ago (well, the early risers anyway), we will get to experience a partial solar eclipse on Thursday, October 23rd when the New Moon will cover up to 36% of the Sun's surface. The inset of the attached star chart describes the particulars of this eclipse as we'll see it from Bakersfield.
How can you observe the partial solar eclipse safely? The Sun is extremely bright and you can damage your eyes within a few seconds if you look at the Sun without protection. To view the Sun during a partial or annular eclipse you need to either look at a projection of the Sun or use a special-purpose solar filter—very dark sunglasses do NOT protect your eyes. Other things to NOT use (they are NOT safe) include: smoked glass, stacked sunglasses, crossed polarizing shades, photographic neutral-density filters, or a filter designed to block visible light for infrared pictures. The items in the previous sentence do not block the UV or IR that can also damage your eyes. What follows are safe ways of viewing the Sun.
The simplest thing to use is a pinhole projection. Poke a hole in an index card with a thumb tack or sharp pencil, face the card toward the Sun and hold a second card three or four feet behind it in the front card's shadow. A big hole makes a bright but fuzzy image and a small hole made a dim but sharp image. You can reduce the daylight glare on the viewing card by enclosing the setup in a long box.
A sharper and bigger Sun image can be made by projecting the Sun's image through a small telescope or binoculars onto a white card behind the telescope or binoculars. Do NOT look through the telescope or binoculars without a special-purpose solar filter! You will need to have the telescope or binoculars on a mount. Point the telescope or binoculars toward the Sun using the device's shadow. When you are pointed at the Sun, the telescope's shadow will be smallest. At that time a bright image of the Sun will shine from the eyepiece onto the card. Turn your focus knob and adjust the distance of the card from the telescope until the Sun is sharp and as big as you want.
For direct viewing you can use an arc-welder's glass of shade #14 (NOT a lower-numbered shade) or special "eclipse glasses". High-quality and safe but inexpensive eclipse glasses are available from Thousand Oaks Optical and Rainbow Symphony, both U.S. manufacturers. The best views are through a properly-filtered telescope.
Solar filters for your telescope or binoculars can be found at Astro-Physics, Thousand Oaks Optical, and Orion Telescopes & Binoculars. The solar filters come as either wispy sheets of metallized film, metallized black polymer plastic, or metallized glass with the metallized film ones usually providing the very best view but all being very good. These filters fit over the front of the telescope or binoculars. Do NOT use small filters that fit over the eyepiece since the magnified and concentrated sun's energy can easily shatter an eyepiece filter (and then fry your eyeball). More details about observing the sun is posted on the "How to Observe the Sun Safely" page.
Tomorrow will be another exciting event in astronomy when Comet Siding Spring (C/2013 A1) buzzes Mars. The nucleus of the comet, the dirty iceberg from which all of the dust and gas in the comet's atmosphere and tail come, will pass within about 87,000 miles of Mars (about a third of the distance between the Earth and the Moon) at 11:27 am moving at 126,000 mph. Since this is in the middle of the day, the inset shows the previous night and tomorrow evening's position of the comet and Mars. The comet will be visible only with a telescope but you can see Mars without a telescope as orange-red star low in the southwest in the early evening sky next to the brightest part of Sagittarius. Mars is also going through the brightest part of the Milky Way.
Like Comet ISON last November/December, Comet Siding Spring is making its first trip from the distant Oort Cloud into the inner part of the solar system and like Comet ISON it will be studied by a suite of spacecraft. However, this suite of spacecraft will be different than what was used for Comet ISON. Because Comet Siding Spring is passing so close to Mars, all of our Mars orbiters and rovers will be taking a close look at the comet (and I mean close!).
Because the comet is passing so close to Mars, there is the very real risk that some of the bits of rock from the comet could damage an orbiter. NASA and ESA have maneuvered their orbiters to be on the far side of Mars when Mars runs into the dust trail from the comet nucleus about 90 minutes after the nucleus passes by Mars. The danger will last about 20 minutes, so NASA and ESA scientists will be experiencing their greatest worry from about 1:00 to 1:20 PM Pacific Time. I haven't heard what the Indian space agency is doing with its MOM spacecraft but I'm assuming they are protecting their orbiter in the same way. The rover teams have nothing to worry about because Mars's atmosphere, though quite thin, is still thick enough to make any rock bits burn up before they reach the surface.
Comet Siding Spring will be the first comet from the Oort Cloud to be studied up close by spacecraft. We observed Comet ISON from a much greater distance. Comets, especially those from the Oort Cloud, are primitive objects that are made of the same stuff (water and carbon compounds) from the birth of the solar system 4.6 billion years ago. They haven't changed since that time, so they are a window on the birth of the planets and the Sun.
In my previous column, I described how the Mars orbiters were going to study Comet Siding Spring. Other NASA space observatories such as the Hubble Space Telescope, Kepler, Swift, Spitzer, Chandra, NEOWISE, STEREO, and SOHO have been observing the comet along with the ground-based Infrared Telescope Facility on Mauna Kea, Hawaii and the BOPPS balloon-carried telescope. Images and updates of the comet's visit to Mars is posted on the website http://mars.nasa.gov/comets/sidingspring .
The two to three days following the Comet Siding Spring close encounter with Mars (October 20-22) will be the peak of the Orionid meteor shower. These are the result of the Earth passing through the dust trail left behind by Comet Halley. Those bits hit the Earth's upper atmosphere at 41 miles per second. They appear to streak out of point just above Orion, so look for Orion in the southeast after midnight. Up to 20 meteors can be seen in an hour under a dark sky. The Moon will be a very thin Waning Crescent those nights as it heads for its conjunction with the Sun on the 23rd. Therefore, the Moon will be rising close to sunrise and the moonlight won't interfere with our view.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com