3 Tips For Milky Way Photography f/98
Milky Way Over Clark Dry Lake Borrego Springs
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Show Notes
In early April, I headed into the Southern California desert for some astrophotography. Clear skies and a new moon were perfect conditions to capture the Milky Way. And I learned a few things during this star gazing adventure. I have 3 tips to share with you for better photos of the core of the Milky Way. I hope you enjoy the episode.
Tip 1 - Planning Is Important (If Not Vital)
Astrophotography needs certain conditions to be met or your photos will fall flat. You need to know where and when to go for the best Milky Way photos. The location you choose needs to have low light pollution. Without a dark sky, the stars and Milky Way won’t be visible. Use tools like the interactive map at lightpollutionmap.info to find a dark sky. I recommend using the World Atlas overlay to view sky brightness. Also, click on a location for a Bortle scale reading. The lower the number on the scale, the darker the sky. Look for places with a score of 4 or lower.
Next, you need to know when to go. The folks at capturetheatlas.com publish a yearly calendar that lists the best dates of the year to see the Milky Way - and when the galactic core will be visible. There are different calendars for different latitudes on Earth (free with mailing list signup). Choose the one that is closest to the location you plan to visit.
Finally, you need a clear sky. Fog, rain, or clouds will obscure the night sky. Reaching a dark sky is a longer journey for most of us, so check conditions before you go. Use your favorite weather forecast app (or multiple apps) to check the forecast. My go-to app is Yr.no which has great micro forecasts. I also check several other apps as a sanity check.
Bonus Tip: Explore the Night AR mode of the smart phone apps Photo Pills. You can move the night sky forward and backward in time relative to a location and see how the Milky Way will rise and fall. And you can do this all in your living room - before you’re in the field.
Tip 2 - Choose The Right Lens And Camera Settings
The galactic core of the Milky Way will stretch across a wider part of the sky, so you want a wide angle lens to capture its breadth. Other types of astrophotography that capture specific celestial bodies or regions of space may use telephoto or other lenses. For the Milky Way, go wide. A 24mm focal length is good, 20mm is better, and 16mm is great.
You also want fast glass that can gather a lot of light. Remember - you are in a dark place and will need your lens to capture as many stars as possible in a reasonably short amount of time. Use a lens that has a wide aperture, like f/2.8. You can get away with f/4 (and I’ve done that) but will need to compensate for the smaller aperture with increased ISO.
Speaking of ISO, that brings us to camera settings. The ISO will need to be increased. This will increase noise in the photos, too. Astrophotography is a tradeoff between star detail and digital noise. An ISO in the range of 1600 to 6400 is typical for Milky Way photos. I start with an ISO of 3200 for an aperture of f/2.8. It is high enough to capture more stars in the sky, yet low enough that modern noise reduction software can eliminate most of the noise in the scene.
Finally, you must choose an exposure time, how long the shutter will remain open. The longer the shutter is open, the blurrier the stars will become. Why? They are moving subjects relative to the Earth. As our planet rotates, the relative position of the stars moves. This is how to capture star trails … drag the shutter longer and the stars become arcs of light. But for crisp Milky Way photos, your goal is pinpoint stars.
There are two methods to calculate how long you can expose without introduction blur due to the Earth’s rotation. There is the 500 Rule and the NPF Rule. The former is basic math, divide your focal length into 500 for the exposure time and the latter accounts for more variables, including the focal length, aperture, and megapixels of your camera. The web is full of articles explaining the details and the math. I use the Photo Pills phone app to calculate the exposure time. This app has a Spot Stars calculator and gives exposure times for both rules. With modern cameras, I recommend the NPF calculation method.
Summarizing my recommendations for lens choice and camera settings for astrophotography:
Use a wide angle lens, 24mm or wider
Use a wide aperture like f/2.8
Increase ISO to 3200
Set exposure time using the NPF calculation in the Photo Pills app
Start with these settings and then tweak and experiment in the field.
Tip 3 - Manual Focus For Tack Sharp Stars
For the most accurate and tack sharp stars, use manual focus. The auto focus in your camera will not do justice to the night sky. Even if you’re able to get auto focus to lock on a bright star, it may not be focused at infinity. The process I use to manually focus for Milky Way photos:
Turn off auto-focus in my camera and, if applicable, on my lens
Turn on any manual focus assists or magnification features in my camera
Turn off focus peaking
Frame a bright star in the night sky in the viewfinder
Rotate the focus ring until that bright star is as small as possible
My Sony A7Rii has a manual focus assist feature that does a 5x magnification when manually focusing. That makes it much easier to get perfect focus. That bright star I’ve selected to dial in focus grows and shrinks (kind of like a bokeh ball) as I adjust the focus ring. I’ve also found turning off focus peaking helps, so I can clearly see my reference star.
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