Joshua Tree National Park – Skull Rock – Geminid Meteor Shower

This is the second of a set of articles on the Geminid Meteor Shower which makes an appearance every December, typically between the 12th and 14th. Geminid is in reference to the constellation Gemini from which the meteor showers ten to originate.

2017 was a great year because the sky was dark from a new moon. You can see about 120 an hour at the peak. That seems like a lot but it’s about 2 per minute. Some are faint and some are out of the view of your camera.

My wife Liz and I went to Joshua Tree National Park to see the shower. I selected that location because it’s a pretty dark place and it’s also warm. Temperatures for the eight days we were there were typically in the 60s during the day and the 40s at night.

If you can find Orion, Gemini is close by. In the feature image, look for Orion just over the “skull”.

Feature Image Details

The feature image is a shot in the waning moments of sunset two days before the best part of the meteor shower combined with images taken the night of the meteor shower.  Another image of Skull Rock taken at sunset, from a different angle is shown below.  We visited Skull Rock on several evenings during the trip.

There were plenty of people crawling around everywhere on the night of the meteor shower. Getting a land image at that time, with all the flashlights and traffic, was not possible.

Lights from others did not affect images I took of the night sky except when passing cars rounded curves and random light shined into the camera.

I only used one image of the land and eight or so for the sky. The process is as described in my previous article Joshua Tree National Park – Arch Rock – Geminid Meteor Shower.

Overall Process

  1. The image of the land is as described above. I used my Canon 11-24mm right at 13mm.
  2. For the sky, I used a modified EOS 5D Mark IV. I had Spencer’s Camera replace the low-pass filter with one that allows the full spectrum of light to come in. This makes the camera useless for daytime photography without special filters. The advantage at night is the camera picks up an extra stop of light. That’s the difference between a 15-second shot and a 30-second shot.
  3. The sky, minus the meteors, is a blend of eight images, 50 seconds each, taken back to back at ISO 3200, at F4.
  4. Because the stars rotate, and because of camera noise, you just cannot take exposures beyond a certain length or the stars will look like streaks rather than points of light. The rule is E = 400/FL where E is maximum exposure time in seconds, 400 is a constant, and FL is the focal length of the lens in mm. With a 24 mm lens you can only shoot for 16.66 seconds. I round to the nearest 5 seconds, in this case, 15 seconds. At  11mm I could go 35 seconds.
  5. I have an iOptron Skytracker Pro device that tracks the stars. With the Skytracker, one can double or triple the amount of time given by the E=400/FL formula. But you have to align the device to the North Star. However, I could not see the North Star as it was hidden by the arch. I estimated, knowing approximately where the North Star was. I added only an extra 15 seconds or so, making for a 50-second exposure.
  6. Bear in mind that by tracking the stars, the land will now be blurry. That was the point of blending the two images of the land together rather than trying to do this all in one take.
  7. I took eight images of the sky and made some basic adjustments in Lightroom. Next, I exported the images to Photoshop, opening them up as layers. Then I aligned the layers. To get align to work properly, you must first mask out the land or photoshop will attempt to align the images on the land, not the stars.  Next, I converted the layers into a smart object, then set the blend mode to median.  The point of this step is to reduce random noise. It also nicely eliminates any airplanes flying through. In eight images, only one of them will have a plane in the same spot. By telling Photoshop to use the median value of each pixel, blinking lights from passing planes vanish and random long-exposure noise is dramatically reduced.
  8. Finally, I kept taking images every minute or so for a couple of hours hoping for meteors. I took eight of the brightest meteors and masked out everything else and put them about where I recall seeing them in relation to Orion.
  9. Equipment-wise, I used two EOS 5D Mark IV bodies, one of them was specially modified, Canon’s 11-24 F4.0 L lens, an iOptron Skytracker Pro, and a Manfrotto 190 Tripod fitted with a Really Right Stuff BH-30 Ballhead and Panning Clamp.

Equipment

Those interested in my equipment and recommendations can find it here: Mish’s Equipment List.

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Mike “Mish” Shedlock

2 thoughts on “Joshua Tree National Park – Skull Rock – Geminid Meteor Shower

  1. Thanks for all the comments on the last post everyone. I was wondering why there were none. I forgot I had to approve them as I don’t on The Maven. I just found them today.

    Like

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