David Trowbridge

May 152016

On a rafting trip through the Grand Canyon in March-April, 2016, I captured images of the sky that I assembled into time-lapse videos. On clear nights, I set up my camera on a tripod and recorded two photographs each minute for several hours through the night. Audio was added later.

Canyon walls were illuminated by moonlight when the moon was up. The rapid streaks you see are airplanes flying over the canyon.

See the Equipment for Time-lapse Imaging page to see details about camera and power supply.

Canon 6D camera with Rokinon 14mm lens, 12V battery, DC-DC converter and intervalometer

Canon 6D camera with Rokinon 14mm lens, 12V battery, DC-DC converter and intervalometer

For highlights of our rafting trip, check out the video Running the Colorado on YouTube.

Oct 062015

Waning-crescent-moonIn the early morning hours of Oct 5, just before closing down the observatory, I decided to try capturing the crescent moon while the seeing conditions were still good. Here is the result. Click to open a full-size image.

This image is a mosaic of three images: northern, mid-section and southern, each of which was created from several hundred frames of a 60-second video clip. Frames were sorted by quality, aligned and combined using Autostakkert!2 software by Emil Kraaikamp of the Netherlands.


Oct 052015


In his book, The Messier Objects Stephan James O’Meara calls this galaxy ‘The Phantom,’ writing “No object in the Messier catalogue has proven more troublesome, more elusive, more provocative to amateur astronomers than this giant spiral.” M74, also known as NGC 628 is galaxy with 40 billion stars and a diameter of 97,000 light years. Compare this to our own Milky Way galaxy which has at least 100 billion stars and a diameter of 100,000 light years. While more diffuse than the Milky Way, M74 has a similar armed spiral structure.

I was drawn to trying to capture an image of M74 as I can imagine a sentient being on a planet around one of those stars looking up in their night sky and contemplating us in a galaxy 32 million light years away that looks not that much different.

This image is a combination of thirty 6-minute exposures on the night of October 4-5, through a Takahashi Mewlon 250 telescope operating at f/19.2 with a Canon 6D camera.



Oct 052015

On September 27, 2015 at dusk, we observed the full moon rising over the Cascade mountains when it was already in eclipse. At first it was difficult to see as the sky was not very dark yet. Then gradually as the moon rose and the sky darkened, the dark red orb became more apparent. As the moon moved through the Earth’s umbra shadow, patterns of brightness changed until it finally emerged as our familiar bright full moon.

Lunar Eclipse 2015-09-27

If you were standing on the surface of the moon during this eclipse, you would see the Earth blocking the sun, and surrounded by a ring of red-orange light. In essence you would be seeing all the sunrises and sunsets of planet Earth at one time. The center of the Earth’s shadow is toward the upper right in this photo and the lower left is not as deep in shadow.


Final stage of lunar eclipse

This is a “phase” of the moon you will never during a typical month — a bite taken out of the full moon as the moon emerges from the Earth’s shadow or umbra.

These images were taken with a Canon 6D DSLR camera with an f/4 300mm fixed lens on a tripod.

Oct 042015

Sun in H-alpha

This is my first successful image of the sun, taken through my new Coronado Personal Solar Telescope (PST). The PST uses a Hydrogen Alpha filter to block out all wavelengths except a narrow 0.5 Angstrom band (the spectrum of visible light ranges from 4,000 to 7,000 Angstroms). One advantage of using such a narrow bandwidth is that glowing hydrogen gas that moves toward us or away from us can be seen as a slight darkening or brightening relative to the background. For example, solar prominences are plumes of hydrogen that erupt from the surface of the sun. Seen edge on, they appear as dark ridges because the wavelength of light they emit is reduced slightly and consequently blocked by the H-alpha filter.

In this image, you can see dark “cracks” on the face of the sun that are actually prominences viewed edge-on. Prominences can also be seen on the limb (the edge of the sun’s disk) as red bumps on the right-had side of this image.

This image is not the result of a single snapshot, but rather the sum of over 1200 frames taken from a 2-minute video taken at 30 frames per second on October 1, 2015. Software is used to analyze the quality of each one of 3600 frames (120s X 30 fps = 3600), sort them by quality, then align and add together the best third and discard the rest.

Camera used was the Canon 6D shooting at 1/30th sec, ISO 6400 for 120 seconds. I then used PIPP (Planetary Imaging PreProcessor) to open the source .MOV file and AutoStakkert!2 to align, combine and sharpen the images. Original video was shot in monochrome. Red color to approximate what our eye sees when it views a Hydrogen Alpha source was added to the final result.

Compare the image above with a single frame of the video below. Note the vastly improved quality that results from aligning and combining hundreds of individual frames.

Single frame from video sequence, 1/30th sec exposure, ISO 6400.

Single frame from video sequence, 1/30th sec exposure, ISO 6400.

Jan 192015

Comet Lovejoy

This photo of comet Lovejoy, C/2014 Q2 was taken on the evening of January 14, 2015. The original photo was a 60-second exposure in color, but to increase the visibility of the tail, I converted it to black and white. The tail points directly away from the sun, a result of light pressure on the ionized gas released from the comet.


Here is the corresponding color image. The green glow of the comet’s head results from fluorescing carbon atoms (C2) in ultraviolet light from the sun. For further explanation of the origin of the green color, visit the Planetary Society page. Camera was a Canon 6D on a Takahashi FSQ-106 at f/5.

Comet Lovejoy C/2014 Q2’s orbital period around the sun is roughly 11,500 years. If you miss it on this pass, it will return in about 8,000 years hence.

Aug 232014

North America Nebula

The North America Nebula looks like a map of North America. The nebula on the right resembles a pelican. Together, the North America and Pelican Nebulae are known as NGC 7000. This image was taken August 21, 2014. It represents a total exposure of 2 hrs 20 min, the result of 28 5-minute exposures.


Aug 052014

Visitors to the Observatory often ask whether it’s possible to see the International Space Station (ISS) through the telescope. I finally decided to give it a try, aided by new features in TheSky X, software that controls my mount. It’s a bit tricky to follow, since you need to set up for high magnification and the satellite moves rapidly across the sky. But after a few failed attempts, I was able to capture this movie on August 4, 2014 around 10:10 pm. The sounds you hear are the of the mount tracking the satellite and the dome rotating (near the end of  the video) to keep the slit in the proper orientation.

Jul 312014

M51, Whirlpool Galaxy

This image of the Whirlpool Galaxy was captured thje night of July 29-30, 2014. It represents a total exposure of 3 hr 40 min (44 5-minute exposures). The Whirlpool Galaxy, M51 is 23 million light-years from earth. M51 interacts with its companion galaxy NGC 5195 (above). ImagesPlus 5.75 and Photoshop were used for image processing.