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Light Pollution is Ruining Our Night Sky

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Have you ever looked at a brightly lit building or street light in your neighborhood and thought it was excessive? You know, light shining in all directions or perhaps in your bedroom window, rather than only lighting up the intended area. That is light pollution

Light pollution is misdirected excess/obtrusive outdoor artificial light in a night environment. Too much light pollution washes out the night sky, interferes with astronomical research, disrupts ecosystems, wastes energy, and has adverse health effects.

Urban towns, cities, and suburbs are known for their excessive light. These light sources can be found by way of exterior/interior lighting, advertising, streetlights, parking lots, etc.

For non-stargazers, over-lighting or light pollution is likely a new concept and one they might not consider a problem. Even worse though, is the absence of a dark star-filled night sky is not even missed. 

Over-lighting has become a global problem in need of a paradigm shift. Before we can make positive change, we must understand the negative impacts of light pollution and strengthen our connection with the natural environment. 

light pollution example

Light pollution from a commercial greenhouse turns this Bortle Scale Class 3 location into an 8. 

Types of Light Pollution 

There are several different types of light pollution, including:

  • Glare: light reflecting off a surface making it difficult to see
  • Skyglow: light shining up into the atmosphere creating a yellow halo
  • Light trespass: light shining outside the intended area or where it is not needed
  • Clutter: bright, excessive groupings of light sources
  • Over-illumination:  the use of too much or excessive light

Sources of Light PollutionBenedek via iStockphoto. Let’s Talk Science 

Often when discussing the issue of light pollution, people discuss the matter of using lighting for safety reasons. While there has been no evidence from studies to suggest that lighting increases safety, the bigger issue is around selecting more efficient lighting to light up only the areas we need, when we need them. 

Neighborhood Lighting

Before and after neighborhood lighting change to direct light downward, where it is needed. IDA/Richard O’Brien

Light Pollution and the Night Sky

According to the International Dark-Sky Association (IDA), everyone had access to a starry night sky less than 100 years ago.

Now, there are millions of people living in urban cities that will never see the Milky Way from where they live or are stuck living under a permanent sky-glow. 

For example, on August 14, 2003, nearly 50 million people across Ontario and Eastern United States experienced a massive blackout and were left without power for a few days.

During this time, even in the core of downtown Toronto (which has a population of 250,000), there were people seeing the Milky Way for the first time ever.

Before and after light pollution

Light pollution before and after from the suburbs of Toronto during the 2003 blackout. IDA/Photo by Todd Carlson

Light pollution alters our view of the sky and makes it difficult to see smaller or faint objects.

It washes out stars, constellations, galaxies, and nebulae, reducing the overall contrast between these objects and the darkness of the sky, impacting astronomical research and the hobby of astrophotography. 

Light Pollution and Astrophotography 

The night sky viewed from a light-polluted city will not compare to the detail of what can be seen from truly dark skies.

While large objects, like planets and prominent constellations, can be seen from the city, fainter objects or deep-sky objects will need to be captured under darker skies. 

Astrophotography from a light-polluted area has its challenges. A light pollution filter is often your first line of defense against a washed-out sky.

Light Pollution and the Bortle Scale

8 levels of light pollution. The Orion constellation captured from Bortle Scale Class 1-8 locations. Credit to: Josh Wilson/ Richie Mills/ James Markgraf/ Remco Kemperman/ Robin Lim/ Andrew Wryghte/ Carsten Groinig/ Abhiroop Bhattasali

Popular light pollution filters include the Optolong L-Pro and Astronomik CLS. The filters do their best to ignore the bandpasses of the visible associated with artificial light.

Some photographers insist that shooting without a filter is best. In this scenario, you’ll need to have a solid game plan for processing the image to reveal your deep-sky object from a bright sky.

Deep-sky astrophotography is arguably much easier to accomplish from a light-polluted location than wide-angle shots or nightscapes.

Capturing distant objects through a telescope has the advantage of isolating a very small patch of the bright sky, while a Milky Way panorama shows off nearly the entire sky.

separating a Galaxy or Nebula from a brown sky is easier than digging out each star and constellation of a nightscape photo. For this reason, I do not recommend capturing wide-angle photos of the night sky from a light-polluted location.

Bortle Scale 

Astrophotographers often use the Bortle Scale as a way to measure the brightness (or quality) of their night sky as it relates to light pollution. There are nine levels to the Bortle scale (Class 1-9) with Class 9 being the most extreme amount of light pollution. Five or under is required to see the Milky Way. 

How to find your Bortle Scale class

You can use the ‘Clear Outside’ mobile app for a rough indication of your current Bortle Scale rating. 

Light Pollution Map 

You can also access a light pollution map to determine your level of light pollution that will provide the Bortle Scale classification. This can come in handy if you are looking to travel to darker skies in order to capture a landscape photo of the Milky Way or a deep-sky object. 

light pollution map

A light pollution map displays the amount of light radiating from the largest city centers.

Impacts of Light Pollution 

As noted above, light pollution impacts the night sky and the hobby of astrophotography, but light pollution impacts more than astronomers/astrophotographers. 

Human Health

Life of Earth has always had natural sources of light by way of the sun and moon that produce a day-night cycle. This cycle, referred to as the circadian rhythm, acts as an internal clock that our bodies follow and is controlled by the light sources around us. 

Our bodies produce the hormone melatonin as a result of this cycle which is necessary for our overall health. Excess artificial light at night disrupts the cycle, suppressing melatonin production and negatively affecting human health. 

Light pollution also increases the risk of:

  • Sleep disorders
  • Diabetes
  • Weak immune system
  • Obesity
  • Depression
  • Certain cancers

Wildlife/Ecosystem Health

Much like humans depend on the day-night cycle for their health, ecological systems are dependent on this cycle for reproduction, nourishment, sleep, protection from predators, etc. 

There are several examples of these types of disruptions in nature affecting the existing ecological balance (migratory birds, turtle hatchlings, etc.). Declining insect populations as a result of light attraction can also negatively impact the balance of nature as all species depend on insects. 

Excessive artificial light:

  • Affects nocturnal wildlife who are active/hunt during the night
  • Changes predator/prey interactions
  • Alters species interactions
  • Confuses animal navigation
  • Affects plant/animal physiology
  • Draws in insects

According to research scientist Christopher Kyba, for nocturnal animals, “the introduction of artificial light probably represents the most drastic change human beings have made to their environment.”

Energy Consumption

Unnecessary use of resources is wasteful, which includes using too much light or lighting areas where it is not needed.

According to the IDA, it is estimated that at least 30 percent of outdoor lighting in the U.S. is wasted, mostly by lights that aren’t shielded. To put a dollar value on that, it adds up to $3.3 billion and releases 21 million tons of carbon dioxide per year.  

We can make better lighting choices to cut down on wasted energy and carbon emissions. This will save money, and ultimately allow everyone to enjoy the night sky. 

How to Reduce Light Pollution

Reducing light pollution involves reducing skyglow, glare, trespass, and clutter. 

There are several ways you and your community can take action against light pollution in order to minimize the risk to ecosystems, human health and protect the night sky. 

Start by assessing the light on your own property, and see if there are improvements you can make to your lighting. 

  • Look to reduce inefficient and/or unnecessary outdoor lighting
  • Reduce the intensity of your lighting and use minimum intensity
  • Adjust the orientation of your lighting making sure lighting is positioned downward, lighting only the area you need to light.
  • Consider installation timers on your lights or using motion sensors to use lights only when they are needed
  • Use soft or amber lighting over white light which contributes more to sky glow and health risks.
  • Use dark-sky-friendly lighting at your home. IDA works with specific retailers to establish IDA-certified lighting so you know it is light pollution friendly. 

Home Lighting

Non-Shielded versus shielded lighting to control light pollution. Lamps Plus.

In addition to adjusting your outdoor lighting, you might choose to become an advocate for light pollution.

You could do this by speaking with your friends and neighbors about the importance of reducing light pollution, engaging a greater community online through social media, setting up an outreach table at your local event, or advocating for a lighting ordinance in your town.

Check out the IDA and their resources to support any of these options. 

Compensating in Astrophotography

It is often said in the astrophotography world, “there is no substitute for dark skies”. This statement is very true, as you will always take better images from a location with an unspoiled sky.

In the past, I have traveled from 1-4 hours to enjoy a dark sky. The best time to enjoy a dark sky location is during the new moon phase, so you can fully appreciate the number of stars you will see in the sky.

The reality is, most of us spend the majority of our time under a light-polluted sky at home. To photograph the deep space objects in the sky, we must get creative with our approach, and/or utilize specific filters to get the job done. 

The Milky Way

The Milky Way photographed from a Bortle Scale Class 3 location.

Short Exposures / No Filter

One technique that you can try, is to shoot several short exposure images without the use of a light pollution filter. This method has the benefit of capturing the most natural-looking star colors, but will significantly reduce the exposure time of your individual images.

For example, I was able to capture the Trifid Nebula from my Bortle Scale Class 7 backyard sky without using a filter. The sub-exposures were limited to 2-minutes each, using ISO 1600 on my Canon EOS Ra camera.

The trick is to shoot enough sub-exposures to overcome the noise (through integration) and use multiple gradient removal techniques to separate the deep-sky object from the bright sky. You may be surprised to find high-quality data buried beneath a washed-out sky.

deep sky astrophotography

Optolong L-Pro Filter

There are many light pollution filters available for astrophotography from the city. The Optolong L-Pro is my number one choice when it comes to a broad-spectrum light pollution filter that captures natural-looking images. 

The biggest difference you will notice when using a filter is the contrast between the stars/nebulae/galaxy and the sky. A filter helps to separate the object from a bright night sky, at the expense of altering the natural colors of the area slightly.

You will need to make some careful color adjustments to the stars (and your subject) to restore a natural look.

Optolong L-Pro filter review

Before/After using a light pollution filter from the city (Optolong L-Pro Filter). 

Dark Sky Organizations 

There are organizations with the mission to protect the night from light pollution. The International Dark sky Association is the main recognized authority on light pollution and is the leading organization combating light pollution worldwide.

While celebrating dark, star-filled skies, they also advocate and educate about light pollution, provide resources for individuals/policymakers/industry, and promote responsible outdoor lighting.

AstroBackyard is an IDA member which means we pay a membership fee to support their preservation efforts to protect our dark skies. It’s a great way to support the dark skies we all crave as astrophotographers. 

Here in Canada, Ontario Parks and the Royal Astronomical Society of Canada (RASC) are working to protect and preserve our night skies in partnership with the IDA, and are designating locations (mostly Provincial Parks) as Dark Sky Preserves based on the following criteria: 

  • Control of local lighting
  • Outreach programs aimed at the general public and neighboring municipalities
  • Good nighttime lighting practices

There are many other local organizations that are also discussing the issue of light pollution and raising awareness in their communities. Feel free to drop the name of other organizations you know who are advocating for dark skies in the comments section. 

If you are an astrophotographer who appreciates dark skies, I would encourage you to look into/connect with an organization in your community or otherwise to see how you can make a difference and help protect our skies. 

Dark Sky Locations

As part of the work being done by the IDA, they also designate locations as part of the International Dark-Sky Places Program. These locations offer dark skies for those looking to escape light pollution with some facilities geared towards astronomers/astrophotographers. 

I have attended the Cherry Springs Star Party for several years, which is held at Cherry Spring State Park, an International Dark Sky location. 

For a full list of parks/locations that are part of the IDA Places Program, click here

International Dark-Sky Week

The International Dark-Sky Association also hosts International Dark-Sky Week during the month of April to help raise awareness about light pollution.

Keep an eye out for activities each year presented by the IDA.

Helpful Resources:

What is light pollution?

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Canon Rebel Astrophotography

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The very first camera I used for astrophotography was an old Canon Rebel Xsi (450D) DSLR. Even though the production of this camera was discontinued many years ago, I still use and enjoy this camera today.

A DSLR camera like the Canon Rebel 450D is a versatile choice as it can easily be attached to a telescope for deep sky imaging using a T-Ring and adapter. You can also use this camera with fantastic camera lenses such as the Rokinon 14mm F/2.8 for wide-angle nightscapes and Milky Way photography.

I’ve used many types of cameras for astrophotography from monochrome CMOS imaging cameras to cooled one-shot-color models. My Canon Rebel DSLR’s continue to produce amazing images, and they are one of the best ways to get started in the hobby.

The Milky Way

The Milky Way captured with a Canon Rebel T3i on a SkyTracker Pro Mount

Astrophotography with a Canon Rebel DSLR

I eventually upgraded my DSLR camera to a (slightly) newer Canon EOS Rebel T3i (600D), and it came pre-modified for astrophotography. The modification that was made to this camera is known as the “full spectrum modification”, which involved removing the stock IR cut filter inside the camera body.

Although there are many choices to consider when it comes to choosing a camera for astrophotography, an entry-level Canon Rebel series DSLR offers a unique combination of value and performance.

In this post, I’ll share my personal results using the Canon Xsi DSLR for astrophotography, and give you my recommendations for a beginner DSLR camera.

Canon Rebel Xsi for astrophotography

The Canon Rebel XSi a popular DSLR camera for amateur astrophotographers

If you don’t own a telescope yet, but want to get into astrophotography using a DSLR, have a look at the following resource page: Astrophotography Tips You Can Try Tonight

Capturing Deep-Sky Targets with a DSLR

The moon’s glaring presence has subsided, and it is now time to gather more RGB (color) light frames on my coveted summer deep-sky milky way objects. This is now my 5th summer as an amateur astrophotographer, and I don’t like to waste time when choosing my target for the night.

During the months of May-July, the Messier objects located near the core of the Milky Way have my full attention. My favorite summer deep-sky objects lie within the Sagittarius region of the Milky Way Core. Many of them are bright and colorful such as the Lagoon Nebula, Eagle Nebula, and the Swan Nebula.

The Lagoon Nebula is one of my all-time favorite targets and a worthy photo opportunity for any DSLR camera and telescope. The summer emission nebulae in Sagittarius are so bright, it is possible to photograph them from a light=polluted area such as your backyard in the city. My backyard skies are rated a Class 8 on the Bortle Scale.

From my latitude in the Northern Hemisphere (Ontario, Canada), the main aspect to consider is having a clear window of sky to the South, as most of the summer Milky Way targets travel Southeast to Southwest throughout the night.

Canon rebel astrophotography


The Lagoon Nebula using a Canon EOS Rebel Xsi

The photo of the Lagoon Nebula above was imaged over several nights last week. I set up my telescope gear on June 30th, July 2nd, and July 3rd over the Canada-Day long weekend in my backyard. It’s rare that we have such a long stretch of clear nights, especially on a long weekend.

This colorful nebula does not rise very high in the sky from my latitude in Southern Ontario. In fact, it just barely clears the height of my backyard fence. When planning a deep sky imaging session, it’s important to have a clear view of your target for an extended period of time.

I consider myself very lucky to be able to photograph such a glorious night-sky treasure from home.  You can view the specific photography details for my final image on my Flickr profile. I also managed to squeeze in some more imaging time on the Eagle Nebula, as well as the Elephant’s Trunk Nebula over the weekend, as you will see further down the post.

Capturing Galaxies

I have photographed many galaxies with my Canon EOS Rebel Xsi from the backyard. One of my most successful images was the Triangulum Galaxy. A long stretch of clear nights allowed me to collect over 7 hours of exposure time on M33.

This is a diffuse deep-sky object which can make it difficult to observe visually, but through photography, we can reveal the beautiful structure and color of this galaxy. The telescope used to capture the image below was an Explore Scientific ED80 with a focal length of 480mm.

Triangulum Galaxy

The Triangulum Galaxy using a modified Canon EOS Rebel Xsi

For Beginners / Newbies

You can view the equipment I use to take images like the ones on this website here or watch this video as I take you through my complete setup for astrophotography.

If you already own a DSLR and telescope and have started taking your own astrophotos – you may benefit from my astrophotography tutorials about image processing.

I connect my Canon Rebel DSLR to my laptop computer using a USB cable and control the camera through a software application known as BackyardEOS.  With this application, I can tell my DSLR to take multiple exposures of varying lengths and ISO settings.

Backyard Telescope

My Canon Rebel Xsi attached to an astrophotography telescope

I can also use this program to focus the stars, and make sure that my astrophotography subject is in the center of the frame. A typical session in my backyard will last all night long and have my Canon Xsi set to take anywhere from 30-60 three to four-minute exposures on a nebula or galaxy.

Dark frames of the same temperature are also captured during the night to reduce noise in the final image. As a general rule of thumb, the colder your digital camera is while imaging, the better!  Long-exposures taken during a hot summer night will produce even more noise than usual.

The Canon Rebel series DSLR cameras are also well-suited for Moon photography. If you connect the DSLR camera to a telescope, you benefit from its long focal length (compared to most lenses) for an up-close look at our nearest celestial neighbor.  

Moon through a telescope

If you are interested in this aspect of solar system astrophotography, be sure to have a look at my Moon photography tutorial. The Moon is an excellent target for your DSLR camera at any focal length. 

Hot Summer Nights

On a recent attempt to gather some H-alpha data on the Elephant’s Trunk Nebula, I discovered the limits of my DSLR when imaging in the hot summer heat.  On this particular night in Mid-June, the temperature remained over 30° well after midnight.

This was just too hot for my Canon 7D to capture any useful data on my deep-sky target.  (I use a different DSLR for my H-Alpha captures, as my Canon Rebel Xsi has the LP filter fitted to it at all times)

The hot hazy skies, combined with a dangerously hot sensor produced a red, noisy mess of an image.  An exposure of 30 seconds to a minute may be fine in this heat, but I was shooting 7-minute subs at ISO 1600 to pick up faint nebulosity through a narrowband 12nm Ha filter.  Lesson learned!

I have since returned to the Elephant’s trunk nebula in the constellation Cepheus, and let me tell you – it is faint!  Photographing IC 1396 from a light-polluted backyard in the city has proved to be quite the challenge.  I was able to capture about 2 hours of exposure on this nebula last week, which is not enough to produce a pleasing image.

By stretching the data far enough (using curves in Adobe Photoshop) to show the rim of the nebula, the background stars become blown out and noisy.  It takes many hours worth of imaging to produce a decent portrait of this DSO.  Here is my early result with limited exposure time:

IC 1396 - Elephant's Trunk Nebula

The Elephant’s Trunk Nebula in Cepheus

Best Beginner DSLR for Astrophotography

I have stood behind the Canon brand of DSLR’s from the beginning. Based on the advice I read in the Backyard Astronomers Guide back in 2010, I chose to start my photography adventure using Canon digital cameras.

At the time, they were the clear choice for astrophotographers, offering the only DSLR built for astrophotography (They later released the Canon 60Da)  Nikon has come a long way since then in the way of astrophotography, but my heart still belongs to Canon.

The Nikon D810A is a camera intended for astrophotography, as you may have gathered with the “a” designation in the title. This is Nikon’s first DSLR dedicated to long-exposure astrophotography. This camera body was based on the original D810, but include a sensor that is four times more sensitive to H-Alpha red tones than an ordinary DSLR.

Canon EOS Rebel T3i

In 2015 I upgraded to Canon EOS Rebel T3i camera for astrophotography. The T3i (600D) came pre-modified by an astro-modification service known as “Astro-Mod Canada”. I have used this camera to capture many deep-sky objects using various clip-in filters.

This is the DSLR I always recommend to beginners. First of all, it is the successor to the Canon Xsi which I use now and can provide actual results (my photo gallery) of the astrophotography performance of this camera. Second, it is a great value.

Canon Rebel T3i

You will find used models of this camera body at online retailers (such as Henry’s in Canada) for a fraction of the price of a new CCD Astronomy Camera.  You can no longer purchase this camera new, so if you can’t find a used body at camera retailers, you will have to search online forums such as Canada Wide Astronomy Buy and Sell, or Astromart.

This camera can also quite easily be modified for astrophotography by yourself or a professional.  The features of the camera itself are quite standard of all models these days, but this DSLR is capable of taking astonishing deep-sky and landscape astrophotography images.

My favorite feature of the T3i is the flip-out LCD screen. This comes in very handy when shooting deep-sky astrophotography images because the camera is often in an awkward position when connected to a telescope.

Tilting the screen to a more accessible angle allows me to focus the telescope using the 10X live-view function of the camera. I can also review the histogram, make changes to the exposure time, and review my light frames as they are being captured.

The Canon T4i and T5i are also excellent choices but are a little more expensive.  The Canon T5i can be purchased in a kit including an 18-55mm lens.

Recommended Clip-in Filters

I have used a wide variety of clip-in light pollution filters with my Canon Rebel DSLR cameras. For deep-sky targets containing hydrogen-alpha emission data such as the Eagle Nebula, a narrowband filter like the 12nm Astronomik Ha is an excellent choice.

For capturing broadband RGB data on my targets, the SkyTech CLS-CCD filter allows me to block a healthy amount of city glow. This filter creates an impressive amount of contrast between your object and a light-polluted sky.

For broad-spectrum targets such as galaxies or reflection nebulae, I recommend trying the Optolong L-Pro filter. This multi-bandpass filter is less aggressive and helps retain the natural colors of the stars in your image.

DSLR camera filter

The Optolong L-Pro filter in My Canon Rebel 600D

Why use a DSLR?

There are many different types of astrophotography cameras available, other than Digital SLR’s. Dedicated thermal-cooled CCD cameras are much better at producing deep-sky images with less noise, but are much more expensive and less user-friendly.

Webcams can produce stunning images of Solar System planets and the moon and can be inexpensive and easier to use. The Altair Hypercam 183C is an example of a dedicated astronomy camera that can bridge the gap between a DSLR and a CCD.

I still enjoy using a DSLR because it’s an enjoyable experience. You can’t beat the value and versatility of the Canon Rebel series cameras.

Light Pollution Map

I often speak of the light pollution from my backyard in the city.  I love to get away from home to image under dark skies at my astronomy club’s observatory (RASC Niagara Center) – but I rarely have time to drive 40 minutes with all of my equipment to this special place.

To maximize my time under the stars, it makes more sense for me to get as much astrophotography in at home, in the backyard. (Hence the name of this website) The light pollution produced by the city I live in is quite heavy, especially in certain areas.  My house is in the worst of it, being located in the central area of town.

I found this helpful Light Pollution Map that shows just how bad it really is:

Light Pollution Map

Light Pollution Map for my Backyard

The Bortle Scale

Do you see that?  I am in a Red Zone!  I would estimate that my location is either a class 7 or 8 on the Bortle Scale, although I have not yet taken an accurate light pollution measurement.  The Bortle Scale states that a class 6 zone (NELM 5.1-5.5) will have your surroundings easily visible and that the Milky Way is visible only at the Zenith.  

These characteristics are true of my backyard and is referred to as a bright suburban sky. How much light pollution is in your backyard?  You can use this nifty interactive map to find out: Light Pollution Map

To view all of my best images captured with a Canon Rebel Xsi and T3i, check out my photo gallery.  I wish you all the best in your future astrophotography endeavors, clear skies.

Helpful Resource: Getting Started with Deep Sky Astrophotography

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