A gentleman's observatory: this backyard structure recalls classic tastes of the Victorian age.
Having made a Victorian-style telescope and mount several years ago (S&T: May 2011, p. 64), I had the idea of creating a permanent home for a similar instrument that matched its style and that would optimize its usefulness in the British weather. In the United Kingdom you can often spend an hour setting up a telescope only to have the clouds to roll in. Conversely, even on cloudy nights there are often periods of clarity that a rapidly deployed telescope can take advantage of. Our winter nights also tend to be cold, damp, and windy! So having the telescope permanently mounted in an observatory offers significantly more opportunities to observe and to do so in far greater comfort.
Constructing observatories in the Victorian style in its heyday was the sport of English Lords and American industrialists. Since I'm neither of the above, it was quite a challenge to work out how to make something that would have a similar feel yet still fit into the corner of my modest English garden while adhering to a sensible budget.
My starting point was to study as many 19th-century observatories as possible. Some, such as Yerkes Observatory in Wisconsin, are masterpieces of classical architecture, but their scale is far too Olympian for the aesthetics to work in a domestic garden. Others, such as Ladd Observatory at Brown University in Rhode Island, are more modest in size but still very beautiful. At the small end of the scale, the Aldershot Observatory in the UK manages to elegantly capture the essence of Victorian design in a relatively tiny building.
I concluded that a small circular structure with brick walls and a copper dome would best encapsulate the look I was after. I began my design by making sketches before moving on to scale models constructed of cardboard and glue. Even after being an artist for many years, it still surprises me how different a design can look on paper compared to when it's transformed into three dimensions.
One thing that came to light during the modelling process was that the building looked much better if it had windows, especially if the tops were rounded. Of course, from a practical perspective, windows in an observatory are not necessarily a desirable thing, but this was one of several cases in which aesthetics won out over practicality.
Inside the model observatory, I also made a moving model of the telescope and mount to ensure it wouldn't hit the roof and walls as it went through the complex gyrations of slewing a long refractor on a German equatorial mount. This also enabled me to experiment with various shutter designs.
Dome shutters have always presented a headache for observatory designers. Geometrically, a hemisphere really doesn't want to open into a slot that will give wide access to both horizon and zenith. There are several solutions to this problem, none of which are entirely perfect. My preference was for a shutter that rolled back over the dome because it best preserved the classic look of the roof. However, such a shutter wouldn't have been able to slide back far enough to give me a good view of the zenith, so my shutter has two parts. Rolling back just the main shutter allows access to the sky from 30[degrees] to 110[degrees], providing excellent access to the zenith. With both parts rolled back, the sky window is -10[degrees] to 70[degrees] offering a good horizon view. Having a working model enabled me to refine this double-shutter design and choose the optimal point at which to split it.
The final revelation that came from playing with the model was that the roof would look much better with a little dome or cupola on the top. I guess that's something the great Renaissance architects of Italy discovered centuries ago, and many domes since have incorporated such a finishing touch. Once again, aesthetics triumph over practicality, because adding a cupola does nothing to improve the running of a shutter. It did, however, offer the opportunity to incorporate a weatherproof vent fitted with a solar-powered fan to suck out hot air from the roof in summer.
Upscaling the Model
Having established the aesthetics of the building, it was time to consider the engineering that would translate this into a real brick-and-mortar structure. I imagine the observatory will have a useful life of perhaps 100 years, significantly exceeding my own!
Regular bricks retain a lot of heat, which isn't ideal for an observatory. Bricks also generally come in rectangular shapes that don't lend themselves to creating tight radius-curved walls. I have no doubt that the Victorians would have solved the latter problem by creating special curved bricks, so I decided to do the same. Since I don't have access to a brick factory, I used colored concrete impregnated with fiberglass reinforcement instead. With the mixture just right, the end result is very brick-like indeed. Making my own bricks also made it possible to reduce the thickness to about 1/2-inch, reducing thermal mass.
The bricks were made in a special silicone mold that accommodates five bricks at a time, with a day of setting in between each batch. A total of 450 bricks were required for the observatory walls, making this the longest and most tedious parts of the entire build. Brick-making spanned almost four months, each day taking out a set batch of bricks and mixing another five to go.
Such thin bricks are incapable of supporting any real load, so the observatory required an internal structural frame. This was made from welded galvanized steel covered with thin perforated mesh. The frame provides a very strong and rigid structure to support the roof, and the perforations in the mesh offer an excellent gripping surface for the foam adhesive that holds the bricks on.
The roof, an aluminum skeleton with riveted metal sheet cladding, is very similar in design. I didn't use real copper for the exterior because it's heavy, expensive, and difficult to shape into the decorative parts required by the aesthetics of my design. So instead, I used aluminum sheet for the panels and fiberglass castings for the cupola and decorative corbels. After much experimentation, I developed a paint effect that gives any surface a very similar look to verdigris on copper.
When it came to the interior, my wife Asia and I wanted the observatory to be a fun place to hang out. It needed to feel cozy in spite of being essentially an unheated outdoor shed. As artists, we were also very keen that it should be a beautiful celebration of the night sky. Since the internal ceiling is a dome, we thought it would be great to have stars on it--even better if they were set amongst mythological figures.
In the library of my alma mater there's a celestial globe that a colleague had created from engravings by the great 17th-century cartographer Vincenzo Coronelli. Seeing this magnificent globe made me determined to use the same artwork on the inside of our dome so that, in effect, you'd be standing in the middle of Coronelli's universe.
One problem was that, like most early globe makers, Coronelli imagined that the stars existed in a fixed crystal sphere around the Earth. So what he drew was a view of the constellations as seen from outside of that sphere, looking down on the stars and the Earth below. The trouble with translating such a globe onto the internal roof of an observatory is that an observer looks outwards from within the sphere, not in from outside. As a result, everything, including the order of the constellations around the sky, is left-right reversed compared to the globe. Of course, the star patterns and the illustrations around them can easily be flipped over, but Coronelli also included thousands of star and constellation names, inscriptions, notes, and markings--each one had to be manually reversed in Photoshop so they weren't backward when the main artwork was reversed. I'm sure my wife recalls my complaints once or twice about this tedious job.
The final artwork was printed out onto aluminum panels using a big industrial sign printer and UV setting inks--which are 100% weatherproof and in theory should last a lifetime. The panels were then bent into the proper contour using rollers and then riveted onto the interior frame of the roof.
The finished observatory is a lovely space to sit and enjoy the magnificence of the night sky. We're lucky to live on the edge of the Exmoor National Park Dark Sky Reserve (https:// is.gd/dark_sky), so the skies are particularly dark and stunning here. With the observatory's interior red lights dimmed, the real stars shining through the shutter sit beautifully alongside Coronelli's fantastic creatures progressing around the ceiling. Even on a windy night observers stay reasonably warm and the telescope remains steady. The interior is far from roomy, but it's big enough for two people.
Setting up for an observing session simply involves unlocking and opening the shutter, then removing the lens caps from the telescope, all of which takes less than a minute. Perhaps most importantly, there's no heavy lifting or straining involved. Having once owned a very large "portable" telescope that was a real workout to move, I really appreciate that avoidance of physical exertion. The prospect of heavy lifting is especially daunting at the end of an observing session when I'm often cold and tired. It's not something I miss at all.
Not everyone is lucky enough to have the ability to build an observatory, but if it's feasible for you to do so, I would highly recommend it. Having a permanent home for your telescope will significantly increase your observing time.
TIM WETHERELL is an accomplished artist and amateur astronomer. Visit his website at timwetherell.com.
Caption: STELLAR SHRINE British amateur Tim Wethereli's observatory is designed to complement the Victorian aesthetics of his home, garden, and even the telescope it houses.
Caption: WINDOW TO THE UNIVERSE The aluminum panels on the interior of the dome were custom-printed with mirror-reversed images from Vincenzo Coronelli's celestial globe.
Caption: STEEL SKELETON The walls of the observatory were constructed of welded galvanized steel surrounded by perforated mesh used to secure the adhesive to affix the brick facade.
Caption: BRICK MOLD To reduce thermal issues from traditional bricks, the author fabricated custom "bricks" from a concrete and fiberglass mixture in a custom mold designed to match the radius of the walls. Right: Each brick was then mounted using a foam adhesive and strapped into place using bungee lines while the adhesive set. The final structure is 2 1/2 meters (8.2 feet) in diameter by 3 meters tall, with a 60-centimeter-wide (24-inch) slit.
Caption: SHAPING THE ROOF Each section of the dome roof was bent into shape using a large slip roller.
Caption: BEAUTY WITHIN The author with his wife Asia and the premier instrument of the observatory, an attractive, Victorian-style 7-inch f/7 apochromatic refractor.
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|Title Annotation:||OBSERVATORY AESTHETICS|
|Publication:||Sky & Telescope|
|Date:||Sep 29, 2017|
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