Lori Carey Photography

Friday, February 4, 2011

Twilight Phenomena

Minotaur Rocket Streak - Minotaur rocket with streak payload launched from Vandenberg Air Force Base in California on September 22, 2005.  This is a classic example of the Twilight Effect, which occurs when the ice crystals catch the light of the sun which has already set and is below the horizon.

No, not vampires!

Shortly after I moved to California we were having dinner one evening when I looked out the window and saw the most amazing sight in the evening sky. I had no idea what it was so I did what any photographer would go - grabbed my camera and started bracketing like crazy, then ran to the computer to find out what it was.

It didn't take long to find the news about the spectacular twilight launch of a Minotaur rocket from Vandenberg Airforce Base. The twilight phenomenon shown in my image can occur when a launch takes place approximately 30-60 minutes before sunrise or after sunset when the sun is still below the horizon. Ice crystals in the contrail - unburned fuel particles and water drops that freeze in the less-dense upper atmosphere - reflect high altitude sunlight and produce a rainbow of colors, and high altitude winds can twist the exhaust plume creating a corkscrew effect. The result is a breath-taking sight that can be visible for hundreds of miles. Although Vandenberg AFB is located on the California coast about 140 northwest of the Los Angeles the contrail in my image above was seen as far away as Nevada, Utah and Arizona.

The twilight phenomenon is relatively rare since it has to do with the timing of the launch and the weather. The sky in the area must be clear and dark and the sun must be below the horizon. As the missile rises out of the darkness the twilight effect may occur. Out of over 1,800 missile launches since 1958 at Vandenberg, only a very small number have resulted in the amazing light show.

Tomorrow morning early risers in SoCal may have the opportunity to see and view another launch that may result in the twilight effect. Vandenberg is scheduled to launch a Minotaur 1 rocket carrying a national security payload for the National Reconnaissance Office on 5 February at 4:26am.

Don't be discouraged if you don't live near Vandenberg. I'm approximately 200 miles south in coastal south Orange county and most launches, including day time launches, are clearly visible from my backyard in the WNW sky. I took the photo above from my backyard.

The twilight effect for pre-dawn launches is usually more subtle than for evening launches, but if you're interested in heading out in the wee hours for the possibility of seeing and photographing what could be a truly breathtaking sight, Brian Webb's Space Archive site is my bible for Vandenberg launches. It has a wealth of information, including a page devoted to photographing launches, and up-to-the minute Vandenberg launch information. Get on his mailing list if you want to know about future launches, it is a great resource.

Luck is when preparation meets opportunity! My alarm will be set. If we're fortunate enough to have another amazing twilight effect and you get photos, feel free to link to them in the comment section.


  1. What a fabulous photo! And thanks much for the explanation.

    --- Denise

  2. Thanks Denise! Great to see you :)

  3. Just wanted to post update since several people have contacted me - this morning's launch was scrubbed after 1.5 hour delay due to technical problems with ground equipment. Looking for possible reschedule in next 24 hours.

    Shame too, the two-hour delay they were originally looking at would've increased chance of good twilight phenomenon.

    Forgot to mention that Vandenberg posts updates throughout a launch on their Facebook page, one of the best Facebook pages I've ever seen - http://www.facebook.com/30thSpaceWing?v=wall

  4. The launch has been rescheduled for 4:26 a.m. (PST), Feb. 6, pending
    resolution of the power issue.