The Relay Clock

It may not look like it, but this is a clock, one of the world’s first digital clocks, circa 1973.

When I was twenty or so, I built a clock. It was a clock that used electromechanical relays to count the seconds, minutes and hours. I was early in my electrical engineering studies and barely understood Ohm’s law, but I was aware of electromagnets, and how they could be used to make mechanical movements. Some of us call them solenoids, coils of wire that magnetically push or pull an iron piston to make and break switch contacts.

My dad, in his ham radio hobby quest for cheap electronic components for whatever future project he might undertake, had acquired various relay mechanisms. He showed them to me and explained how they used electrical pulses to move a metallic wiper to a series of successive contacts. These were telephone relays, used when you “dialed” the phone. One relay, responding to a single rotary dial action could connect you to ten possible neighbors. Cascading it with another set of relays would allow calling up 100 neighbors. More phone digits would extend it even further, you get the idea. I barely understood how to deliver current to energize a relay coil, but I could figure out how to connect the contacts to make a sequence that counted.

Another item from my dad’s ham shack inventory of salvaged components was a numeric display, something you might see in an elevator (60 years ago) indicating the current floor. It used incandescent light bulbs to project a numeric figure on the screen. Ten separate bulbs, each behind a number glyph mask; one of which was selected for the current digit value. I figured out how to connect the telephone relays to the elevator displays to make a clock.

I was quite pleased with the result and when I got it working, I showed it off to my friends. But it had several drawbacks. First, it was noisy. Relays are mechanical devices that magnetically pull metal contacts against each other, resulting in a click-clack noise as they activate and release. The relays counted seconds, so there was a click-clack noise every second. And at ten seconds there was an additional click-clack, as the next relay responded to the carry pulse. And at 59 seconds, there was a carry to the minute-counting relay. As the carries propagated to the hours, a peak acoustic disruption occurred as the clock transitioned from 12:59:59 to 01:00:00.

The other drawback was that the clock got hot. As I said, I did not yet understand the relationships of voltage, current, power and heat. I just hooked up the components to make the displayed result I wanted. The numeric display, comprising light bulbs, used quite a bit of power. And the relays required power too, and my power supply was terribly inefficient. As a result the clock, in the glass case I made for it, built up an enormous amount of heat. I tried to ameliorate it by installing an internal fan, but this seemed only to make things worse (the fan used power too).

I kept the clock as a curiosity piece, displayed on a fireplace mantel in our home. It was intolerable to run continuously, so I would switch it on to show visitors that it actually worked, and then shut it down to stop the noise. Eventually, the clock got packed up during one of our moves and stayed so.

The boxed-up relay clock was in storage for at least 30 years, but I would occasionally encounter it hiding among my workshop parts and supplies. I recently ran across it. It had endured the desecration by (and excrement of) rodents, the decay of electrical components, and the binding of mechanical joints. I wondered why I had saved it all these years.

Well, the idea of resurrecting a contraption that I built half a century ago carried a certain appeal to me. Having since learned the principles of electricity, maybe I could bring it back to life and its former geek glory!

In the next series of posts, I will describe the process of restoring this pioneering clock.


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“Coffee Table Nightscapes” goes to print!

I finally caught up with my blog postings of past nightscape photos to reach the ones I made this last year. And I have now completed their assembly into a printed photo book.

I didn’t realize when I started this project that the pictures would span 25 years, and that they happened to straddle the transition from film photography to digital. The chronological order reveals the change in technology as I pursued my various night sky targets.

For completeness, I posted the preface and introduction as blog entries, but their real place is in the leading pages of the printed book where all the photos are collected under one cover. I was pleased to be able to give copies of it to my family and close friends this holiday season. Not all of them have coffee tables, but I hope they find a place for it.

Although this marks the end of this particular project, I doubt that I am really done. As mentioned in the epilogue, the capabilities of cameras just keep improving and so I am now excited to start the next 25 years of taking pictures of the night sky!

Epilogue for Coffee Table Nightscapes


The epilogue to my Coffee Table Nightscapes photo book project.


It has been a remarkable few decades since I began taking these pictures.  The world, and our understanding of it, have changed.  Space probes and telescopes have beamed back impressive imagery that reveal more and more of our amazing universe.  The pictures I have taken over this time may not be scientifically significant, but I hope they convey a sense of curiosity and wonder at what can be seen in our night sky. 

The tools and techniques for taking these pictures have also changed.  Although I don’t expect an equivalent to the digital revolution we have experienced, there are dramatic advances underway in “computational photography” and other imaging technologies that will provide even more opportunities to make inspiring and beautiful images of the night sky.  I will follow along as far as I can, so that maybe, someday, I will make a sequel to this coffee table book.  Just imagine what another 25 years of nightscapes will bring!

Thor Olson
December 2021

Introduction to Coffee Table Nightscapes


Here is the introduction to my Coffee Table Nightscapes photo book project.


This is a collection of photos taken over the course of 25 years with some stories to accompany them.  I call it “Coffee Table Nightscapes” to indicate that they are my favorites suitable for that artifact of an earlier time, a book of beautiful photographs and touching captions that adorned the low table in the formal space of a home.  This is my contribution to that genre.

A major technological revolution over the last quarter century began when homes really did have coffee tables with books on them.  This revolution changed the way we take pictures.  The transition from film to digital has had an enormous impact on our lives, how we interact and communicate with each other, and how we experience the world. 

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Preface to Coffee Table Nightscapes


Here is the preface to my Coffee Table Nightscapes photo book project


This story begins nearly thirty years ago.  My nine-year-old son asked me to go out to help him identify some constellations for a school project. We drove a few miles to a park where we watched the stars emerge from the twilight. We discovered that the moons of Jupiter could be seen through binoculars, located constellations with familiar zodiac names, and saw the Milky Way splashed across the sky. It was an enchanting experience.

I wondered what else could be seen in the sky.  I had friends with telescopes who were kind enough to let me peer into them to view “deep sky objects” (galaxies and nebulae).  It was fascinating!  The idea of ancient photons being collected by a telescope lens and then focused on my retina made a powerful impression on me and continues to do so even to this day. 

I soon began acquiring my own equipment and immersing myself in the world of amateur astronomy. 

Having been an amateur photographer my entire life, it was not long before I wanted to capture those views on film.  During this time two bright comets appeared in two successive years.  They provided my first photographic targets and begin this collection. My son has grown up and now has sons of his own.   He will likely encounter a similar experience while helping them with school assignments.  Meanwhile I’m still investigating the night sky, attempting to capture its romance and magic through the lens of my camera.  I hope you enjoy my favorites from the first 25 years

Milky Way Sails the Playa

Racetrack Playa is a dry lakebed in Death Valley.  It is a vast expanse, miles by miles, of dried mud cracks.  It is flat and nearly level, the north end merely inches higher than the south.  The occasional stone can be found on the playa, delivered by erosion forces on the surrounding mountains, falling down and rolling out onto the lakebed.  They are stones, not boulders, maybe a foot or two across, heavier than is convenient to carry away, but not heavy enough to protect them from magic seekers.

And the magic they seek is that many of the stones are found at the end of a long, physically engraved trail, recording their traversal of the ancient lakebed.  How could these stones have moved across the dry playa?  It has been a mystery to geologists for years.  Various theories have been proposed, and some have been tested, but it is a difficult research project.  The stones lie inert for years, and then, when next inspected, they have moved.  With new trails marking their path!  This is the magic that the stone thieves are after.

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Polaris on the Playa

One of the active topics in modern photography is the distinction between “blends” (combining multiple exposures from a single camera viewpoint), and “composites” (which combine unrelated images into a synthetic scene).  Both are valid uses of photography, but I prefer to limit my efforts to the former, hoping to reveal some scientific beauty in the result.

In this case the relative motion of the stars is “stacked” (added) from 2,335 10-second exposures.  Each frame looks like a normal picture of the sky, but when accumulated creates the star trail effect.  The frames were selected from the period after “astronomical twilight” when the sun is more than 18-degrees below the horizon.  On this date, official night lasted over six hours, and the star trails cover more than 1/4 of a full circle (and even Polaris shows that it is not exactly on the north celestial pole).

Although it was “night”, it was not completely dark.  The moon was up and illuminated the scene until it set around midnight.  This allows the foreground to show, including the “sailing stone” with its path on the dry lakebed trailing behind it, a contrast of time scales against the motion of the sky.

A final detail to explain:  the streaks below and to the left are the result of trains of Starlink satellites moving across the sky.  Dozens of satellites follow each other into and out of the sunlight at their altitude, reflecting it down to our observing position on the playa and creating its own trail on this image.

For more of the backstory on making this image and the next, see “A Night on the Playa – Part 2“.

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19 May 2021
Racetrack Playa
Death Valley National Park CA
Canon EOS Ra with EFS 10-22mm
2335 exposures, 8 sec @ f/4, ISO 3200 (6-1/2 hours)


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Holiday Card History

My grandparents’ Christmas card, circa 1950

I grew up watching my father, following his father’s example, coming up each year with handmade Christmas cards that nearly always included a family photograph.  They were both avid amateur photographers and would corral and cajole my siblings and me into a studio-like set in the living room with carefully positioned lights and a camera mounted on a tripod that would be aimed at a scene of dressed-up children surrounding their proud parents.   This often occurred at our family Thanksgiving gathering, allowing just enough time for my mother to get prints made, mounted into cards (often with her hand-stenciled or stamped cover designs), personal greetings inscribed, and envelopes addressed and stamped, all before the week of Christmas.

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Wupatki Startrails

“The Citadel” remains the focus for this startrail image.  The moon dominates the scene, and this blend of exposures shows its path among the stars.

The cloud persisted above the monument over the course of the exposure, growing and shrinking, but never moving away or evaporating.

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15 May 2021
Wupatki National Monument
Flagstaff AZ
Canon EOS 6D with Sigma 14mm f/1.8
458 exposures, 8 sec @ f/2, ISO 3200 (76 minutes)


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Wupatki Moon

“The Citadel”, one of the structures built by indigenous people who lived here from 500-1200 CE, provides a focus for a nighttime exposure.  The Arizona skies are clear except for a cloud condensed by the contrasting air flows over the monument. 

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15 May 2021
Wupatki National Monument
Flagstaff AZ
Canon EOS 6D with Sigma 14mm f/1.82 sec @ f/2, ISO 3200


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