Astrophotography: The Skyglow Blues


When you look outside at night…what do you see? A rusted sky? Perhaps a gang of street lamps…loitering at the end of the block…smoking cigarettes or drinking beers…

Many of us no longer have the luxury of being able to bask under a truly dark sky. It’s heartbreaking. Sodium vapor street lamps tarnish the night sky, smearing a nasty orange glow across the cosmos. Meek starlight can’t compete against the bombardment of countless street lamps, so the night sky becomes veiled behind a curtain of impenetrable pollution.

…What’s the matter? Are you going to be bullied by sodium vapor? Roll up those sleeves, put on your angry face, and let’s go to war!

The Skyglow Blues


**Here’s what you’ll need **

  • Light polluted night sky image (RAW file)

  • A RAW Editing Program


Don’t let sodium vapor bully you! Sodium vapor may own the streets, but we can take back the night!

I’ll show you how we’re going to do this:

  • Utilize RAW Photographic File Format


I’m not going belch a song and dance, or wax lyrically about the superiority of RAW over JPEGS. Although not a necessity—a RAW photographic file will make it much easier to combat light pollution. A RAW file grants access to the following: white balance (fine tune temperature), color tone, brightness/contrast, and a variety of other fine adjustment parameter settings.

I used Canon’s Digital Photo Professional for this demonstration, but you can use any program (as long as the program can edit RAW files). Adobe Photoshop will work, and if you don’t have access to either of these programs, try downloading GIMP. However, I don’t think GIMP can read RAW files.


** Step 1 **


  • Convert Image to Monochrome


Canon’s Digital Photo Professional interface is user friendly and everything is pretty much self explanatory, but since I’m a nice guy, I’ll walk you through the basics.

To covert an image:

  • Select ‘picture style’

  • Select ‘monochrome’.

  • Done!


** Step 2 **


  • Apply Blue Tone


After an image is converted to monochrome, a few slide bars will become available: filter effects and toning effects. There are few different toning effects—select the blue tone.


The image is too damn blue! Is that what you’re thinking? I know, I know. Calm down.

Don’t worry…we’re not done.

** Step 3**

  • Adjust Saturation


Use the slider and manually decrease the saturation until the image becomes slightly pale. Pay attention to the color of the sky—The idea is to roughly simulate a dark sky—while masking light pollution. Environmental objects will also maintain a blueish tone, so keep that in mind.

You can adjust the saturation to your liking, but don’t decrease the saturation too much or the image will revert back to monochrome.

In Canon’s Digital Photo Professional:

  • Hit the ‘RGB’ tab

  • Locate the saturation adjustment bar at the bottom (can’t find it? Take note of the magical red markings)

I kept the numerical value of the saturation between 40 62. The numerical value will typically change and it’s not meant to be a static value (for a variety of reasons).

Experiment and see what works!

After the photograph’s blue tone is adjusted—the rest is up to you. Contrast and brightness adjustments can be tweaked, or you can try dodging the image Here’s the fully processed image, which gone through the guide’s demonstration:

No loitering? Says who? Oh…

The next step is not necessary, but it’s worth pointing out:


** Bonus Step **


  • Fine-tune color adjustment


Once again, hit the ‘RGB’ tab, and then locate the ‘blue channel’ (labeled as a capital B). Lower the blue curve slightly and the image will take on a silvery appearance. The sky will look more naturally, especially compared to a light polluted photograph.




See? That wasn’t so bad! Here’s a comparison:


Of course, when photographing stars, it’s best to get as far away as possible from artificial light sources. Duh. No brainer. But some of us don’t have that ability. Streetlamps and a variety of other photon nuisances dominate the night, and it can be damn near impossible to completely hide from artificial light sources.

There are more sophisticated ways of masking light pollution, but they’re not too simple, that’s why they’re… ummm…sophisticated! Specialized filters can help mask light pollution…for a price. The idea presented in this guide is simply a quick solution, especially if you’re new to astrophotography, or plan on imaging the night sky under a canopy of orange haze.

Don’t be intimidated! Aim your camera at the night sky! It’s a war of lights out thereraise two middle fingers to all those sodium vapor bastards—and go fire off some exposures! That’s an order.

Published by FlyTrapMan

I have no idea what I'm doing.

6 thoughts on “Astrophotography: The Skyglow Blues

  1. Very useful article, funny, whenever I look at the sky these days I think about you!! I wonder if others suffer from this syndrome, I am not looking for a cure as I rather like it!!
    Took some pics last night of a tiny slither of moon but there was still a disk visible, not sure why…I shall process the raw soon and show you.

    Liked by 1 person

    1. Hmmm…I think you’re describing Earthshine, that’s my immediate suspicion. Sunlight can bounce off Earth and illuminate the dark portion of the moon, depending on the moon’s phase, and the clarity of the atmosphere — it’s possible to see a fully illuminated disk (even though a crescent moon would only typically be visible).

      More information:

      Liked by 1 person

  2. This is incredible; to call myself even an amateur astronomer would be ego-maniacal; I just like to look up at the night sky, and light pollution is my foe. Granted, I’ll have to read your post a dozen or so times before I can utilize the info, but I surely appreciate it. (Saves me some jail time from smashing street lamps. Just kidding) Thanks.

    Liked by 2 people

    1. Light pollution is certainly a pain in the ass. Some locations are far worse than others, especially in highly populated cities. I contemplated sabotaging a local light bulb a few years ago, but didn’t follow-through with my plan…I should have.

      Liked by 1 person

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