It is a good time to clean out your rain gutters before the fall rains start in earnest and you can slip in some astronomy by checking the debris for meteorites.
We are familiar with meteors or shooting stars that leave streaks of light as they burn up in Earth’s atmosphere but 5 to 300 tons of space dust and debris hit the Earth’s surface every day. Impacts of large meteorites are rare but micrometeorites, those that are smaller than a grain of rice (50 µm to 2 mm in diameter) are quite common. A rough estimate is that one micrometeorite lands in any square meter per year so your roof might bear a number of micrometeorites.
The challenge is separating the micrometeorites from the other terrestrial debris and using a good magnet to pull out nickel and iron laden rocks is the key. An easy way to collect them is to place some strong magnets in a plastic bag and hang it near the outlet of the rain gutters. The magnet collects the nickel- and iron-laden micrometeorites, plus other magnetic debris, as the rain washes them off the roof. The next step is to use a microscope to separate the good stuff: micrometeorites are spherical and have a glass coating formed as they heat up when passing through the Earth’s atmosphere.
There is a good chance that some of the “micrometeorites” you’ll identify are actually formed in terrestrial processes that put particles with the appearance of micrometeorites into the air, such as volcanic eruptions or burning coal. Jon Larsen’s Project Stardust Facebook page has detailed tips on correctly identifying the micrometeorites. Hundreds of fascinating images of micrometeorites are included in his book “In Search of Stardust“.
Good collimation is important for getting the best performance from a telescope. I recently installed Bob’s Knobs on my Celestron SCT to help with collimation – mostly to reduce the risk of damaging the corrector lens when fumbling at night with a screwdriver. Unfortunately, installing the knobs put the telescope way out of collimation – it wasn’t just a minor mis-alignment, in-focus stars were comet shaped and the out-of-focus stars appeared as crescents rather than the desired donut pattern. I spent a couple of hours, over two nights, trying to improve the collimation to no avail but some Google searches and building an incredibly simple artificial star helped.
An artificial star is a small point of light that is used for collimation or optics testing. With an artificial star, collimation can be done during the day and doesn’t require clear skies or good seeing conditions. Artificial stars are available commercially from $25 USD but a precision artificial star is not required for rough collimation so I “built” one for free using a bike light and aluminium foil.
I started by poking four small holes in a piece of aluminium foil with a sewing needle while varying the pressure to produce holes of different sizes. The foil was then wrapped around a bright MEC bike light and secured with a rubber band.
I set up the telescope on its mount in my yard and aimed it at the artificial star which was placed on on barrel about 20 meters away. The second largest hole produced the best image when viewed through the telescope so I put a bit of tape over the other holes to block them out then followed these instructions to restore rough collimation in about ½ hour. A few minutes of tweaking at night produced a much improved view and the expected donut pattern on an out-of-focus star.
This year’s Perseid meteor shower is expected to peak late on Thursday Aug 11 or in the early morning on Friday Aug 12. Under good dark-sky conditions, you can expect to see 40 to 80 meteors per hours. Be patient, the Perseids do not create a blizzard of streaksthrough the sky: 60 meteors an hour means an average of just one per minute, and that includes many faint ones. From locations in the Lower Mainland with moderate light pollution, you are more likely to see one meteor every two or three minutes.
There is often a good show of meteors several days after the peak so the Perseid Meteor Shower Watch event on Saturday at Aldergrove Region Park is great chance to the shower.
Ten Perseid Meteor Facts:
The Perseid Meteor shower has been observed for over 1000 years. In 33 AD, a Chinese skywatcher reported that “more than 100 meteors flew thither in the morning” but when the shower first occurred is unknown.
The Perseid meteors are caused by the Earth passing through the debris trail left by Comet Swift-Tuttle which orbits the sun once every 133 years.
The meteors are the pieces of debris, usually no bigger than a grain of sand, that enter the Earth’s atmosphere.
More meteors are expected this year because the Earth will be moving through a thicker clump of debris from Swift-Tuttle, created partly from the influence of Jupiter’s gravity.
The Perseid meteors strike the atmosphere at a high velocity, about 60 kilometers per second, which tends to produce bright meteors and an unusual number of super-bright meteors, called fireballs.
The Perseid meteors appear to come from the same place: the constellation Perseus, also called the “radiant.” Perseus is found in the northeastern part of the sky.
Light from the moon will interfere somewhat this year but the moon sets at 12:53 AM on August 12.
People have claimed to hear sounds associated with meteor: hissing, sizzling, or pops. Scientists have recently proposed that that very frequency radio waves created by meteors could vibrate metal objects on the ground.
An astronaut on the International Space Station, Ron Garan, watched the Perseid meteors from space by looking down at the Earth.
BC’s Knowledge Network recently launched a program called “Space Suite II” and it’s a follow-up to their popular series of short films that comprise the original Space Suite. The video below is one of ten short films that make up Space Suite II. The piece is titled “Clearer From Afar” and explores the context of the planet Earth from those who have been lucky enough to see it in its entirety.
At the next monthly meeting, we will have a silent auction of several old telescopes and accessories that were part of the telescope loan program. We are doing this to clear space in the storage area and to raise funds for some new telescopes and mounts.
Below is a list of the items we plan to sell. The show-case item is a Celestron Nexstar 8” with GOTO mount.
In addition to this list there will be several eyepieces and odds-and-ends for sale.
There will be minimum bids. We may be able to issue tax receipts if the final bid amount exceeds the item’s value by a certain amount (if 80% of the bid is above the value of the amount, a receipt can be issued for the difference).
The days are long and the nights are short around the summer solstice that occurred a few days ago at 03:34 PM PDT on June 20th, 2016. How late should one stay up to observe the stars in a dark night sky?
At this time of year, Vancouver resides in a twilight zone where we never reach a fully dark night sky. Instead, we experience different levels of twilight. Twilight occurs when the sun is below the horizon, but there is still light in the sky caused by the refraction and scattering of the sun’s rays in the atmosphere. Astronomers define three different types of twilight depending on how far the sun is below the horizon.
Civil twilight starts when the sun dips below the horizon and ends when the sun is 6 degrees below the horizon. There’s enough light to see, but people turn on their lights to drive a car, and the streetlights are starting to come on.
Nautical twilight begins when civil twilight ends and lasts until the sun is 12 degrees below the horizon. The sky can still be distinguished from the distant horizon when at sea, allowing sailors to take measurements of bright stars (hence the name).
Astronomical twilight ends when the sun moves below 18 degrees from the horizon. Night finally begins and you can observe the stars in a dark sky – assuming that there is no bright moon and there are no clouds are in the way.
But at Vancouver’s northern latitude (a bit above 49º north), the sun does not make it below 18 degrees from the horizon during June and during good chunks of May and July. We don’t experience night, with fully dark skies, during these months but remain in the twilight zone until sunrise the next day.
What can observers do? One option is to travel south – traveling a few hours south to Seattle lets you experience close to 1 ½ hours of night according to timeanddate.com. Another option is to observe bright objects that are visible during twilight such as planets, the moon, or bright double stars.