Astronomy laser pointers are very useful tools for backyard stargazing. Due to miniaturisation and affordable technology, green laser pointers are now cheaply available for every amateur astronomer.
They are very handy for pointing faint objects in the night sky, especially for showing others what you're looking at. Used at a star party, there'll be fewer moments when you say “No, not that one, I’m talking about THAT one right there!”
But, as useful as laser pointers are for astronomy, they can land you in serious trouble if you’re not careful and don’t know the rules of using them.
In this article, we share everything you need to know for their safe and fun use.
Best Astronomy Laser Pointers
Click on the links in the table to check prices and customer reviews on Amazon
Laser Pointer Basics
Lasers are used by many backyard astronomers and are commonly referred to as either pointers or astronomy laser pens because of their pen-like shape and dimensions.
A laser pen's small, round shape is ideal for backyard astronomers because they will fit in the finderscope holder on your telescope tube. This makes such lasers ideal to use both as a pointer and a convenient finderscope.
When aligned with your telescope, a laser pointer used alongside a traditional finderscope produces great results. Even before looking through the finderscope, the green laser light shows you exactly where the telescope is pointing.
In fact, keep reading and you'll find another neat trick with astronomy pen lasers to show you exactly where your telescope is pointing.
Why are Astronomy Lasers Green?
Lasers come in all sorts of colors, but, the ones used for our purpose are green. This is because the human eye is most sensitive to colors from the green-yellow spectrum, so following them up in the night sky is a breeze.
Additionally, green lasers are brighter than red and blue for any given amount of power. This makes them ideal as small, powerful, handheld instruments running on a battery.
Laser Power and Brightness
The brightness of a laser is determined by its power output. The higher the power, the brighter the laser. Although this is only true for a fixed wavelength (color).
For instance, a green and red laser at the same power output will not have equal brightness. In this example, the green laser will be brighter.
Also, keep in mind that when it comes to power output, higher is not always better. Don't be tempted to buy a high powered laser: you won’t need it for backyard astronomy purposes.
And that’s a good thing!
For one, high powered lasers are more expensive. Secondly, a high power laser will cause your eyes to refocus every time you use it. This causes unnecessary discomfort and upsets your night vision.
The key is to buy a laser pointer bright enough for the laser beam to be clearly seen but not so bright that your vision suffers.
To help you decide, here is a little chart (originally on this site) on how much power you will need under different conditions:
5 mW - 30 mW
15 mW - 100 mW
5 mW - 50 mW
50 mW - 150 mW
50 mW - 100 mW
100 mW - 300 mW
How to Use an Astronomy Laser Pointer
Now that you know the basics, it’s time to actually start using your green laser pointer for astronomy!
Below, we explore the ways you can use a laser pointer for stargazing.
As a pointer
For starters, the most obvious use of laser pointers is, well, pointing! You can show your friends around the night sky accurately with lasers, especially when you are addressing to a group of people.
Making sure you follow the safety advice below, and only use a laser pointer that is not 'always on'
When you want to point out an object to a friend or fellow member of your astronomy club, make sure no aircraft can be seen or heard nearby, press your laser on and point the beam exactly where the object can be found.
As soon as the person can see where you are pointing, turn the laser off again.
This is a quick and very effective way to give newbies a tour of the night sky and veterans a pointer to the sight you want them to find.
As a finderscope
You can use your laser pointer as a finderscope. The finderscope holder on your telescope tube can hold the laser pointer, as in the picture below.
This is not in place of your finderscope but alongside it.
In combination, these two tools can work wonders for increasing the speed and accuracy with which you get the telescope objective on point!
Some backyard astronomers prefer using a laser to a finderscope. The main reason is lasers don’t need you to bend over and look through them every time you hunt an object down.
This is especially helpful when the scope is set at a low height, requiring you to stoop, sometimes for a few minutes at a time or if you have back problems.
Laser Pointer Laws and Guidance on Use
A laser is a highly focused beam of light. It can travel a long distance without diverging too much. This makes it useful for pointing out stars on a dark night... and also potentially dangerous to people in the air.
There have been many cases of people pointing lasers into planes and helicopters, only to land themselves in trouble.
What you may not realise is that your point-sized laser beam can fill an entire cockpit in a stinging green light.
For example, at a distance of 500 ft, what looks like a laser dot can be a circle of high-intensity light about 6 ft wide.
Such a laser can temporarily blind the pilot and the crew, putting their lives in danger and those of all their passengers. It's equivalent to a camera flash in your eyes whilst driving a car on a pitch-black night. You can understand why the rules on using laser pointers are strict.
This excerpt from astronomyforum.net highlights the legal penalty and the incidents of lasering aircraft:
“Interfering with the operation of an aircraft is a crime punishable by a maximum of 20 years in prison and a $250,000 fine.
In 2009, there were 1,489 laser events logged with the FAA—that is, pilots reporting that their cockpits were illuminated by the devices. The following year, that figure had nearly doubled to 2,836.”
The latest FAA data for 2016 shows there were 7442 incidents, which is over 20 per day.
Key advice on astronomy laser pointer safety, includes:
- Never shine a laser pointer toward any person, aircraft, or other vehicle.
- Never look directly into the beam of any laser pointer
- Do not allow children to use them unsupervised
- Don't aim a laser skyward if you can see or hear any type of aircraft overhead
- Don't use laser pointers within 2 miles (3 kilometers) of an airport
- Pointers must have a 'caution' or 'danger' sticker on them. Don't buy without.
Buying an Astronomy Laser Pen
Having read the precautions, here are a few things to keep in mind when buying a laser.
Lasers come in all sorts of fancy shapes and sizes. From small keychain lasers to large, lightsaber style torches, if you happen to be a Star Wars fan!
As a backyard astronomer, all you need is a medium sized green laser pointer. Laser pointers especially developed for astronomy are easy to find, and we've recommended three in the table below.
One final aspect that most people overlook when they buy a laser is its operating temperature.
If you live in a cold place where snow is common, you may find that the laser malfunctions in the chill of the night. Most common laser pointers malfunction when the internal temperature drops below freezing, so keep them out of the cold, or...
Buy one that's cold and frost resistant. These are easily available (but expensive) and we've recommended one in the table below. They can be used well below freezing point.
Our Best Green Laser Pointers for Astronomy
Click on the links in the table to check prices and customer reviews on Amazon
Summing Up Astronomy Laser Pointers
Green laser pointers are a cheap, portable and really effective piece of astronomy equipment.
You have to use them safely and they're not to everyone's taste, but...
If you are involved in outreach or regularly view the night sky with fellow astronomers, you will not regret having one in your collection.
Oh, and that last neat trick? Point the laser down the eyepiece of your telescope and watch as it shoots out the optical tube into the sky to show exactly where your telescope is pointing.
Written by Adish War