How to find a Dark Site near You for Astrophotography
Updated: Jun 7, 2023
One of the most tiring aspects for us, or any amateur astronomer or astrophotographer is light pollution.
We have gone over it briefly during Episode 1 of Galactic Hunter and it deserves its own article to explain why it must be taken into consideration. Living in a city means there will be immense light pollution and that is true for Las Vegas as it is with other major cities.
Light pollution can be imagined as a bright blurry dome over the city that prevents starlight from shining through, however, the farther we distance ourselves, the more it loses its effect.
Unlike the other enemy we face when going out onto the field which we cannot control, clouds, we can escape the light pollution from the city. We do this by driving about 45 minutes out of the city and into the mountainous desert.
Over the years, we have found a few great spots for stargazing that have a good distance/darkness ratio. These places are also remote, usually in the "middle of nowhere" so it is very unlikely that people come through and disturb us.
It does not always mean that there are no people and occasionally we must share the space, but it is rarely an issue as most people tend to leave before nightfall.
The Milky Way from our Bortle 3 spot, and the Milky Way from our Bortle 2 spot.
The Bortle Scale
Also noted in Episode 1 of Galactic Hunter is the Bortle Scale. This scale measures the amount of light pollution distorting our view of the sky and has 9 levels, our main spot is a Class 3.
The area is optimal for viewing the sky and the distance is fair given the proximity to a major city. Any level under 5 is, in our opinion, the best you can do if you do not live anywhere near dark zones.
The dark zones, or level 1 zones, are what you should look for but most are found too far within reasonable traveling distance or over the seas in true pitch-black areas. Las Vegas is actually so bright that we still see the light pollution dome from each of our imaging spots! We face the opposite direction often while we are taking images but it shows just how radiant the light pollution really is.
Another thing you can do if you want to compare the quality of the sky in several of your favorite spots is to use a Sky Quality Meter.
A Sky Quality Meter (SQM) is a small device that you can point at the sky, and it will read how dark the sky is at the current place and time very accurately.
It is interesting to play around with an SQM device because the reading differs depending on where you point it in the sky, for example, it will accurately tell you that the sky is less dark if pointed towards a bright city light dome.
Sky Quality Meter devices give you a number in mags/arcsec square. To keep things simple, a number towards 16-17 means the sky is very light polluted, but a number near 21 means the sky is very dark. The highest number you can hope for is 22.0, meaning a perfect dark sky.
Dark vs Bright Sky
We wanted to know what M42, the famous Orion Nebula, would look like in a highly light-polluted area (our apartment complex parking lot) compared to our usual desert spot, so we made a comparison using our unmodified DSLR camera. As you can see below, the difference is HUGE! It would be interesting to make the same comparison for a galaxy or a cluster.
A few years ago, we took a trip to Tonopah, NV so we could witness for the first time what a Bortle 1 zone would look like. After a 30-minute drive to complete darkness, we were amazed at how beautiful the sky was. We took a 3-minute exposure on the Helix Nebula (which we were supposed to image for four hours but our laptop decided to die and ruin our night....). Below you will see the difference between our usual spot (Bortle 3.5) and a Bortle 1 zone when it comes to astrophotography. Not only does the image reveal much more under truly dark skies, but it also shows pretty much no noise at all (difficult to see on the image).
How to find Dark Skies near You
Depending on where you live, it will be either very easy or very difficult to find a good dark site. A great resource is available for free HERE where you can see a map with color-coded areas. The colors represent the Bortle scale. Areas colored in white are Bortle 9, so the most light-polluted places, usually large cities. Areas in dark gray are Bortle 1, which is what you should drive towards! Red, yellow, green, and blue areas are the Bortle zones in between. Our main imaging spot sits right in between a green (Bortle 3) and blue (Bortle 4) zone.
When consulting the map, be sure to select "World Atlas 2015" as the overlay in the settings on the right. This is the most accurate overlay so far.
To find a good spot near you, open up the map and find your city. From there, try to spot where the nearest dark site is located. You can then choose to drive towards this dark site and stop anywhere along the way when you feel like you don't want to drive further. Our main spot is a blue/green area about 45 minutes away from home, making it a good nearby-ish place. Our second main spot is 2 hours away, in a gray area (Bortle 2). We only go there when we plan on sleeping in the car as it would be dangerous to drive 2 hours back after a long night of imaging.
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Can't you do Astrophotography from the City too?
Yes! You can definitely do astrophotography from the city, many of our favorite images were captured from our Bortle 9 backyard. The problem is that to be able to image from heavy light pollution, you need special filters, and you are limited as to what you can image.
Using narrowband filters (Hydrogen-Alpha, Sulfur II, and Oxygen III), you can easily capture clean images of nebulae right from your backyard. The pictures below were all taken from our home in Las Vegas. The best types of targets using these filters are emission nebulae as they are rich in HA.
Nebulae shown above:
Broadband astrophotography (galaxies, clusters, reflection nebulae...) is also possible from the city, but much tougher. If this is something you intend on trying, be sure to read our Broadband Astrophotography from the City blog post!
The picture of Messier 94 below was taken from our backyard without any filters.
To learn more about doing astrophotography from extreme light pollution, be sure to read our full post about it and watch our video below!
Final Thoughts
To end, light pollution is a tiring aspect for us, as well as newcomers to astrophotography and fellow astronomers. It is not controllable but it is escapable. It is always good to find a class 5 level or less for optimal sky viewing. It is good to note that there is a huge difference of quality when imaging in a light-polluted area depending on if you are using broadband or narrowband filters.
When in doubt, simply drive as far away from the lights as possible.
Clear Skies,
Galactic Hunter
