Tuesday, April 22, 2008

Laser pointers, bans, and stupidity

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New South Wales just passed a law banning the use of high power laser pointers without a permit. See here. However, the effectiveness of law is already being questioned. See here and here. NSW is not the first place to put in place such a ban.

The ban was prompted by some recent misuse of laser pointers, where beams were flashed at the cockpits of aircraft that were taking off and landing. Let's make no mistake. There is simply no excuse for intentionally targeting aircraft (or any vehicle) with a laser. To do so is 1st degree stupidity at best.

Update: It turns out that the idiots pointing lasers at aircraft aren't the only stupidity in this story.

The real question is will the ban be effective? And by this I mean, are we going to see a meaningful reduction in the kinds of incidents that provoked this ban? Politicians seem to love to ban things. More often than not these kinds of bans are ineffective theatre designed to let them say they are taking action.

Such incidents are also not unique to Australia, they have been recorded in the US and Canada and there are incidents dating back to around 2003. See here and here.

Understandably the pilots union supports a ban on these devices. Thankfully they were open to legitimate uses such as astronomy.

Laser pointers can be invaluable for teaching astronomy to small groups of people. They can also be annoying to other astronomers if used carelessly. Like many issues, finding a balance can be challenging.

Incidents such as these are a natural consequence of technology, any technology, becoming inexpensive and widespread. I have a hard time believing that these could be accidents. How many of these incidents were fuelled by anger, alcohol, or drugs? How many were poorly thought out pranks?

Banning high powered laser pointers and requiring a permit will raise the bar for people getting these devices. Essentially there are three groups of people to consider. Those with a legitimate need that will go through the bureaucratic hoops to continue using one. Those that do not will circumvent the system with intent. And those in the middle that don't have a legitimate need or the determination to get a permit. A ban is really only going to affect the middle group.

Handheld lasers exceeding 500 mW are for sale! Also, there are widely videos showing you how to build your own high power laser using surplus CD and DVD lasers (specifications vary from 30 mW to 300 mW with 100-150 mW being common)!

The problem is not the inexpensive laser pointers available in dollar stars. They aren't very powerful, typically under 1 mW, and can be used for presentations and entertaining pets. While I doubt these would have any effect on pilots at range, I would err on the side of caution and not want to test the assumption.

Laser pointers used for astronomy are something else all together. For starters the human eye responds poorly to red and blue light compared to green. A green laser should give you the best visibility with the least power. But how much power?

A number of factors affect visibility. The thickness of the beam. The moisture in the air. Even light pollution.

Over the years I've borrowed a few of these devices to use as star pointers. The smallest was a 5 mW green laser. This just didn't cut it. It was only really barely visible on moist nights with dark skies. On the other end of the spectrum, was a 55 mW class IIIb green laser. This one seems to be visible in just about all nighttime conditions. While this is a far cry from the 500 mW ones I've seen advertised, it is still over powered for star pointing. I've had discussions with others that suggest a 15 mW laser should be adequate for star pointing. But what I'd really like to see is something with variable power so that you can get just what is needed and no more.

Safety with these lasers is a matter of awareness, attitude and responsibility. When I was a Scout, I learned to shoot a rifle. We were taught never to point a gun at anything we did not intend to shoot. Never under any circumstance. The same applies to a laser pointer. When I use one, I follow a few simple rules:
  • Keep control of the laser at all times yourself. Avoid rapid and wide movement. Don't let children use the laser.
  • Never point the laser at anything that might be an aircraft (or vehicle). Avoid moving objects and flashing lights.
  • If you need to point at a moving object, trail behind it. Do this even if you're sure it's not an aircraft. During Earth Hour, I was pointing out the International Space Station. Even though I was 99.99% sure it was the ISS and the laser couldn't affect the people on it, I still trailed the laser behind it.
  • Be aware, look around carefully before pointing.
  • Be respectful of other groups around you.
A NSW man was recently sentenced to three years in prison for shining a laser pointer at a police helicopter. See here. Others have been similarly convicted in other jurisdictions.

Now what will bans like these actually do?
  • It will probably raise awareness of the risks.
  • It may make it harder to obtain and use powerful laser pointers. Although without importation bans this will be less effective.
  • Fewer people will seek to own such devices. (probably)
  • Conversely by banning them, more people may want to own these devices.
  • It may promote more responsible behaviour from laser owners. More likely it will slow the growth of irresponsible owners.
  • And adds to the possibility of stiff penalties for abuse. Although, other laws can be used for this purpose and stiff penalties have already been handed out.
  • It may not even help police track down abusers, because you can't simply stop looking after you've checked out all the permit holders. The abuser probably won't have a permit.
  • It may criminalize people unfairly if not carefully applied (probably).
Will bans like this reduce such irresponsible incidents? That remains to be seen; but, I suspect that it will be less effective than its' authors hope. It also raises a lot of questions about what is considered "legitimate use" and who will be legitimate users. Lastly, I'm concerned about overzealous enforcement.

Sunday, April 20, 2008

April - Last chance to see DDO Canada's largest telescope

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I just received confirmation that the David Dunlap Observatory is shutting down tour operations. I expect this is the first step in the shutdown relating to the sale of the property.

There is a brief window of opportunity for any groups remaining to see it and I wanted to get the word out.

Any Scouting (and Guiding) groups from wishing to see the largest telescope in Canada have one last chance to visit. The staff can accommodate all age ranges from Beavers through to Rovers. But you must act fast to secure a spot.

The following dates are available April 21, 23, 25, 27,28, and 29th. No tours will be run after April 30th.

Group size is not important at this point. It can be 10 people to 70 people and can include family and friends. The fee is $5 per person. The minimum deposit is being waived.

If you know of groups that could be interested, please pass the word.

To arrange a tour contact the DDO by email tours@astro.utoronto.ca or see http://www.astro.utoronto.ca/DDO/public/tourschedule_scouts.html

The 433rd Cubs recently visited the DDO and had a great time.

Thanks, Mang

Monday, April 7, 2008

Navigation without a compass (or GPS)

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Every good Scout should be able to find their direction. Even without a compass! Or a GPS unit. But how?

How many ways are there to find north and south. It turns out there are a lot. Most methods that take advantage of basic astronomy that allow you to find true north and south. These are methods that could come handy in a survival situation.

The picture above illustrates one of my favorites. It isn't taught as much because watches have gone digital and the method is seen by some as anachronistic because of this. The picture pokes a bit of fun at this because I borrowed a cellphone that had a "retro" watch face. The setup shown is northern hemisphere during standard time (it wasn't but it's just an example). The yellow line shows north.

If you've become lost the simplest recommended method is the Hug a tree approach. This prevents you from getting further lost and facilitates rescue. Navigation methods like the ones described here are a bit more advanced. Nonetheless they are worth practicing! They won't easily help you find a small site like a camp, but wide things like highways and major rivers are another matter.

Watch Method

This method is fast, portable, and reasonably accurate for these kinds of general methods. And even if you don't have an analog clock face, then you can draw one easily enough. It's not perfect (see below), but handy.

Cast a shadow across the watch face.
  • In the northern hemisphere, align the hour hand to the shadow. You will now need to bisect an angle (find the halfway angle) between the hour hand and noon (or 1pm if you are on daylight savings time). The line running through the bisected angle will run true north-south. North will be the side of the line closest to 3 o'clock in the morning and 9 o'clock in the afternoon.
  • In the southern hemisphere the approach is almost identical (it would be if you had a clock that runs anti-clockwise). In the southern hemisphere align noon (or 1pm if you are on daylight savings time) to the shadow. Bisect the angle to find the north-south line. North will be the side of the line before 12 in the morning and after 12 in the afternoon.
If you're lucky enough to have a 24 hour analog watch face, you don't need to bisect the angles.

Some drawbacks include that you can easily be off the width of a timezone which is typically an hour but can vary. Knowing if you are close to a timezone boundary will help with this. It's also not supposed to very good if you are either too close (under 20°) or too far (more than 70°) from the equator.

Sun Methods

There are several methods for using the Sun to find direction.
  1. Knowing that the Sun rises in the east and sets in the west. You can figure an east west line at sunrise or sunset. There will be some variation depending on the time of the year and length of day, but the Sun should be due east/west at 6 o'clock am/pm.
  2. "Shadow Tip" methods. These are described in detail in an article below. Basically, there are different ways to get an east-west line. The one that makes the most sense involves taking measurements on equal times before and after mid-day. While I haven't tried the others, I have a hard time believing that drawing a line between two shadow tips at 20 minute intervals around 7am will result in an east-west line. (But perhaps I missed something.)
Star Methods

Locating direction using stars can be accomplished by several methods.
  1. Use sticks to track the rise and set of different obvious stars. This is a method that was believed to be used by the ancient Egyptians to layout the pyramids. The line between the rise and set of a bright star should be an east-west line. Of course, this requires you stay put for a while.
  2. Locate a landmark beneath the pole,
    • In the northern hemisphere, this is beneath the north star located by using the pointers in the big dipper. See the Astronomers badge.
    • In the southern hemisphere there is no easily visible pole star so it's trickier. You need to find the long axis of the Southern Cross (Crux), the pointers in Centauri, and Achernar in Eriandus. These intersect over the south pole. Some of the diagrams on the web don't show the pointers and this intersection. For more detail see here. Also, be wary as there are false pointers, a false cross, and the diamond cross to confuse you. For more see here. (As I've never been this far south, I'd love to hear from someone who's actually done this. Musca where are you?)
Moon Methods
  1. This is another approximate method. Basically, the phase of the Moon will tell you the location of the Sun. Additionally, if the Moon rises before the Sun sets it is trailing the Sun and the bright side will point approximately west. If the Moon rises after midnight it is leading the Sun and the bright side will point approximately east.
  2. Another interesting looking trick is described as a "finger of shadows" on a nearly full Moon to point due north. It can be found here. I may be wrong but, this sounds overly wordy and colourful.
  3. The previous trick got me thinking about a crescent Moon. The line between the tips of the crescent should run approximately north-south. This makes sense if you consider that the Moon orbits close to the ecliptic (within about 5°) and will be illuminated from north to south.
Mobile Software

Non-GPS software is available for a number of mobile phones and PDA's. I'm most familiar with Palm OS based tools, but I understand there are versions for other devices such as Windows mobile. Possibly the Blackberry and other devices? I'd love to see comments on recommendations.
Some odd time pieces, compasses, and related items
  • I wasn't kidding about backwards or reversed clocks. They are commonly available for left-handers or as novelties. One example see here. (It would be exceptional to see one with a 24 hour dial.)
  • Surveyors used very accurate Solar compasses because magnetic compasses could often be thrown off by deposits of magnetic minerals. A photo of one can be found here.
  • I recently saw design for an unusual clock called the "Bulb Dial" clock, here. It's sort of a minimalist and Rowland_Emett-ish at the same time. (Emett is known for his wacky art-inventions that were featured in the movie Chitty Chitty Bang Bang and regularly displayed at the Ontario Science Centre in "The Magical Machines of Rowland Emett").
Sort of related DIY projects
  • While I 'm not certain you can find north-south with it, a related find was instructions for a do it yourself Sextant using a CD case and Lego, here. (Careful about the sun filter).
  • Earth dials are interesting and would make an interesting school or Scouting project. This Planetary Society article provides instructions on how to build one.
Other methods and links
  • For more information on these methods see this Wiki How To article. This covers many of the methods mentioned in more detail including using a digital SLR camera and a cell phone as well as the watch method, shadow stick, and star methods.
  • Another explanation of the clock method with diagrams can be found here.
  • Yet another explanation of several methods can be found here.
  • The Planetary Society posted an article on Earth Dials (see below) with links that include a sites that calculates magnetic deviation for your locale and several links for teachers and kids including Astronomy with a Stick.

Wednesday, April 2, 2008

Browser wars part deux!

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Most people take browsers for granted and think of the browser wars as ancient history. Well they're back.

Some of this diversity is a good thing. But the problems of security and compatibility lurk beneath the surface.

Browser diversity

There are a surprising number of browsers out there and even a small site will get a fair spread of visitors. Judging from the visitors to this site (and discounting my own activity), we have:
  • Internet Explorer or IE (50%) with 3 versions
  • Firefox (36%) with 6 versions
  • Safari (7%) with 1 version
  • Opera (1.3%) with 5 versions
  • Others (5%) including Konqueror, Camino, Netscape, Mozilla (pre firefox), and the ever popular blank or noname.
I have yet to see a visit by a Flock user.

Recently Apple has been trying to make a big splash with Safari. They got themselves into a bit of hot water by being aggressive and misleading using the iTunes updater to install Safari on Windows, here. And looked a bit silly because the click through license disallowed installs on Windows, here.


Older browsers are vulnerable to all kinds of security problems and are actually unsafe on many pages.

Unpatched security vulnerabilities make it possible for criminals to easily infect computers by planting malicious code on web sites and waiting users to visit. It's been called "drive by downloading". It's not just reserved for fake websites and spam blogs, many legitimate web sites have been laced with nasty malware.

Security studies in 2005 and 2006 comparing IE with Firefox found that IE (v6) was unsafe 98% of the time! In fact, about 30% of our visitors are running unpatched browsers.
  • About 20% of the visitors to this site are running the insecure IE v6!
  • Also about 2.5% of visitors to this site are running insecure versions of Firefox.
Of course, not all vulnerabilities are equal and if you want to do some research, vulnerability information can be found at Secunia.com as well as numerous other websites. Click on one of these links for a vulnerability summary for IE7, IE6, IE5.5, IE 5.0, Firefox 2, Firefox 1, Netscape 7, Camino, Opera 9, Opera 8, Safari 1, and Flock 1.

Firefox can be supplemented by a variety of Add-ons which can improve both functionality and security. A few of my favorites are NoScript and Adblock Plus.


Older browsers are also functionally problematic. It goes beyond not supporting newer web functionality, some of them don't follow standards and require web developers to go through all kinds of quirky hoops to get even simple web pages to display properly in all browsers. IE6 and earlier were notorious for being non-standard. Developers even have a name for one of the problems, it's called Quirks Mode. It's been argued that Microsoft likes this because it promotes their lock-in. Developers by and large hate it because it destroys interoperability and promotes lock-in.

By way of example, when our web developer put together the "Forest Friends" page for the 433rd website the animals originally lined up properly only in IE. The site looked nasty in every other browser. Some experimentation and adjustment was required to get it working for standards based browsers like Firefox and Opera. If you look in the page source, you will see comments describing the gory details of how the page was adjusted.


One web developer has been so miffed by these problems, he started a campaign called End6! to get rid of IE6 (and earlier) non-conforming browsers. This was picked up by another group, here, and caused some controversy, here. Just to be clear, he's not trying to get rid of IE. Just old non-conforming IE.

Take the End6! test, here. Of course it requires JavaScript to be enabled.