Two weeks ago I photographed these star trails over Fool Creek Peak in the Canyon Mountain Range near Scipio, Utah — along with a 6% Waxing Crescent Moon. I did a two exposure HDR in order to capture some reflective "Earthshine" on the Moon.
Here's a RAW image blend of the mountains and star trails before I did additional post processing on the sky and mountains (Canon 6D + 70-200mm • Mountains and star trails @ 200mm • f/4, 5-minutes, ISO 800 for mountains • star trails are a 2nd single exposure @ f5.6, 80-minutes, ISO 160 in LENR mode):
The crescent Moon required a 3rd exposure on the following day due to incoming cloud cover (f/5.6, 1/8 sec, ISO 100) + a blended 4th exposure to capture the Earthshine of the Moon (f/5.6, 1/4 sec, ISO 320) — both using a 600mm lens:
The crescent Moon blend was processed the accentuate the Earthshine detail and then composited in the correct astronomical position with the blend of the star trails and the mountains. If I would have been able to shoot all three (the stars, mountain and moon) the same night (from the same tripod position) this would have technically been called a "focal length blend" rather than a composite/blend.
LENR Method of Star Trails Capture: Although the above example was more complicated than normal, the "Long Exposure Noise Reduction" (LENR) mode is one of the more simple ways to capture star trails.
The process: Anytime you take a very long exposure (more than 30 seconds) with your digital camera your camera's imaging sensor starts to heat up and produce considerable digital noise. To combat this noise build up, your camera's menu has a shooting mode called LENR or "Long Exposure Noise Reduction." In this shooting mode (you are typically using the "Bulb" setting, which requires a remote release) your camera is actually taking two exposures: the actual exposure and a "black" exposure for comparison — in this exposure, the imaging sensor heats up for the same period of time as the real exposure and the camera's onboard computer compares the build up of noisy pixels in the black image and removes them from the real exposure.
For this reason, a 30-minute star trails exposure that you take in LENR mode will actually take you an hour: 30 minutes for the actual exposure and another 30 minutes for the "black" exposure — plus a couple of minutes for the onboard computer to do its magic.
Exposure settings: On pages 174 and 175 of my new eBook (included with your Supporting Patreon membership), I give the settings to the simplified LENR method for star Trails:
Turn on your camera’s “Long Exposure Noise Reduction” (LENR) function.
Set your camera to Bulb Mode and use a remote release or intervalometer to control the shutter time.
Set your ISO to 125 or 160.
Use f/4.0 for a 30 minutes star trails exposure.
Use f/5.6 for a 1-hour star trails exposure (or f/4.5 for 45 minutes).
Use f/8.0 for a 2-hour star trails exposure (or f/6.3 for 90 minutes).
Your camera’s on-board computer will take a 2nd “black” exposure to compare and eliminate hot/noisy pixels from your image. The black exposure will take another 30-minutes to 1-hour, depending on the exposure you chose. TIP: You can pack away your camera and tripod and go to your next location while it processes —just don’t shut off the power! Remember to turn off LENR.
LENR is more simplified than other standard methods like star stacking, which often requires hundreds of stacked exposure (usually 30-second exposures) and lots of post-processing in Lightroom and StarStaX to compose the images into trails.
LENR method has limitations: The LENR method does a beautiful job for 30 minute and 1-hour star trail exposures. As it approaches 2-hour exposure times it becomes less effective; and, beyond two hours the typical noise build up is too great for LENR to handle. Images also become flat, lacking in contrast, and are difficult to post-process. The image below is from page 6 of my eBook:
Besides LENR and stacking in StarStaX, what are the other 3 ways to capture star trails? That will be the topic of my presentation at the upcoming Nightscaper Photo Conference next month in Kanab, Utah. I hope many of you will be able to attend. I will also demonstrate several ways to improve your star trails in post-processing. If you are interested in the conference and my presentation, you have less than seven days left to get your discount tickets. The Early Bird discounts expire on August 31. Use code "EarlyBird2" to get $100 off the full price for in-person tickets, or "EarlyBird2Replay" for $25 off full price for replays-only tickets (if you cannot attend in-person).
One more super-easy way to do star trails: Next week I'll share one of those 3 other ways to capture star trails. Stay tuned to this "channel!"