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Of hawks, concrete, and the Driftway Observing Green

An observatory offers protection from the elements, convenience and a real sense of purpose. It also costs big bucks and with an Obsession 15 on order I wasn’t ready to take this major step to permanently house it, so I went half way. I built a protected, convenient, “observing green” behind my small observatory. After-all, one of the main claims to fame of the Obsession is easy to transport, set-up, and take down.

Driftway Observatory as it appeared this winter before the Obsession or it's "observing green" were even a dream. As with all images with this post, click it to get a larger version.

For the past decade I’ve enjoyed the convenience of a small – very small - rotating dome observatory. At five-and-one-half feet the dome is nice for an 8-inch SCT, but is crowded even by an 11 inch. It’s also crowded by more than one visitor at a time. There is no way it could handle a small group, and especially no way it could take a 15-inch Dob.

But I have reasonably dark skies – mag 5.5 on the best nights with some hassles from neighbor’s lights – so I wanted a relatively simple and inexpensive way to keep some of the advantages of an observatory while using the 15-inch. Here were my goals:

  1. Provide shelter from the wind – both to keep the telescope steady and me warm.
  2. Have a place I can safely leave the telescope set up for days at a time in spells of good weather.
  3. Provide for temporary storage of small objects, out of wind and dew, during observing sessions. (I’m forever taking off and putting on gloves and trying to find a handy place for items that include red flashlight, star charts, notebooks, small recorder, drawing pads, pencils, eyepieces, filters, binoculars, tea cup, Ipod, etc. Amazing how much stuff I seem to “need” at hand while observing.
  4. Provide a large enough area for small groups of visitors to stand, or sit, during observing sessions.
  5. Keep away unwanted guests. I love wildlife, but regular visitors to my yard includes foxes, raccoons, and skunks – and I especially don’t want to be sitting quietly, eyes glued to the telescope, when one of the little black and white charmers comes by!
  6. Provide that secure and familiar “sense-of-place” that makes for a perfect launching pad into the universe.

The almost complete observing green, set-up for a solar obsering session with the Coronado PST,

My solution was a tightly-fenced observing area of about 200 square feet with plenty of handy shelving all around the inside perimeter. Here's how I got there - with a few stumbles along the way.

First, on several nights I tested different sections of my yard for the best location, making notes of the horizon in all directions, but particularly the south. Factoring in view, convenience, and aesthetics – such a fenced in area wouldn’t look good just anywhere in the yard – I settled on the space directly behind the existing observatory. This area was overgrown with brush and included a large apple tree which I had planted more than 30 years ago. The tree – and some smaller ones – would have to go. The brush would have to be cleared, and since this was on something of a hillside, the land had to be leveled. But it offered a nice view in all directions – by that, I mean I can see anything that has climbed above 40-degrees and in some cases closer to 30 degrees and at that point the 6-foot-high fence would start getting in the way. Besides, I rarely want to look at anything lower because of the atmosphere.

From an aesthetic standpoint, this would be an improvement to the yard. A small hill, trees, and the little observatory hide the fence from view from most locations – and where it is visible it fits in with the existing observatory. Besides, my wife was delighted to have the brush cleared and that section of the yard reclaimed.

My next major decision was size and shape. I decided to go back as far as I could from the observatory so I could see over its dome to the south. Given my property line this meant 18-feet was the limit in that direction. Then I calculated how big the space had to be so the telescope could “see” over the fence at least to about 40 degrees above the horizon. That lead to a width of around 16-feet. One tricky question I was never able to answer is how close do I have to be to the fence for it to effectively block the wind that could shake the telescope?

So with an initial rectangle defined I got out my small chain saw and began clearing trees and brush and leveling the ground. (Yes, it was painful to take down the apple tree - but I've made amendasby planting others ;-) I built a low retaining wall of concrete blocks and my neighbor used his tractor to cart in several loads of dirt from elsewhere in my yard. This gave me a roughly level area – well, more level than before, though still with a slight slope from southwest to northeast.

I Then began my real wrestling match – what kind of surface did I want? I consulted with folks on discussion groups on the Web, weighed costs and my limited skills and energy, and seriously considered three alternatives: grass, wood deck, or patio blocks. I settled on patio blocks – flat, 16-inch square chunks of concrete colored brick-red and grey, I got four marble blocks that would provide a 32-inch square central area for the telescope base, then had 3-cubic yards of fine gravel brought in. I put this on top of a base of landscaping cloth (to keep the weeds down) and used it to make the area more level still.

I arranged the blocks in the gravel in an attractive – and accurate – compass rose, with the red ones acting as pointers. I figured this would be a nice conversation piece for visitors. But two things happened to change my mind.

First, on a sunny, mid-April day, as I was working hard on leveling the stone, a migrating broadwing hawk suddenly appeared, circling less than 30-feet up.
He made one circle, eyeing me, then headed to a tree about 100-feet to the south. Crows – who claim ownership to that section of woods, quickly chased him off his perch and the hawk came back and circled low over me again, then went back to the same tree,. This puzzled me. Hawks in my area usually depart quickly when humans show up, but this one seemed to be attracted to me – or at least just didn’t care I was there.

Again the crows came out and chased him away and again he came over me, circling low. But this time he circled once, then twice, and with each circle he rose higher. The third time he got high enough to head off to the north, continuing his migration. Then it dawned on me. I had the only non-grassy patch of ground around. In the sun the gravel and concrete had apparently heated enough to create a little thermal and this had given the hawk enough of a pop to gain altitude with little expenditure of energy. This is typical of how these particular hawks migrate, so . . .

OK – I can’t prove that was the case, but it made me reconsider the issue of heat retention. What I had learned on the Web discussion groups was that the general opinion was that grass and wood weren’t a problem, but concrete was. Concrete as an observing surface had two disadvantages. One is it would retain the day’s heat and contribute to bad seeing at night as it slowly released that heat. The second is eyepieces, when dropped, don’t bounce well on concrete. But I liked it because it would be dry underfoot and it would be easy to clear off the snow in the winter. Besides – by the time the lesson of the hawk sank in, I was all done! It was time to start work on the fence. And then I got cold feet – or should I say, hot feet.

I started asking people – including Dave Kriege at Obsession – and the majority opinion was that concrete was a bad idea. So I gulped hard, then began the tedious process of removing about 70 patio blocks, as well as the 3-cubic yards of gravel. I briefly toyed with the idea of building a wood deck, but that would require more in terms of skills, energy and expense then I was ready to tackle. So I opted for grass – and again, the majority opinion from my queries of experienced observers seemed to favor this solution.

So all was removed – even the landscaping cloth, and the ground was turned over and on a conveniently rainy weekend I brought in rolls of sod. The cost was less than $100 to cover the whole area and when done I had to admit it looked pretty good. This also gave me a new name for the area – the “observing green.” I like it – sounded, well, environmentally sound and socially inviting.

With a budget already cramped I decided on a stockade-style fence of unfinished spruce which cost less than $30 per 6-foot, pre-assembled section. But before making my final decision I considered once more the question of shape. The rectangle bored me. So I decided to cut off the corners – go for a sort of modified octagon approach using the rear of the observatory as one side. This turned out to be a fortuitous choice because it made connecting the individual fence panels easier. I didn’t use the type where the rails go into the posts. Each panel is like an independent fence with two posts supporting it. But by choosing the octagon each panel reinforces the other and makes for a much sturdier fence.

What I did, once it was up, was tie the sections together by running 2x4 supports at mid-level from the post of one section to the post of the next. These supports cut the corners and tied each section together making the whole structure even stronger. (And as I write this we’re in the midst of a three-day nor’easter with wind gusts above 50 and the fence hasn’t budged an inch.) Then I cut shelves from half-inch plywood and fitted them in each of these corner sections, supported by the fence rail, plus the 2x4 braces. This added rigidity – but more important, it means that no matter where I stand in the small enclosure, there’s a shelf nearby - very handy, especially in the dark when your main focus is on the telescope.

All of this was sort of planned – but it’s been one of those projects that grows out of experience as well. As I worked on it, I would visit the area on clear nights, binoculars in hand. I’d park a lawn chair in the middle and sit a while, enjoying the night sky. One thing that slowly dawned on me – it’s a lot brighter than inside my little observatory. Of course it is – it’s open to the entire night sky, not just a two-foot-wide slit of it. This gives a different feeling that is neither good nor bad. I like the “window on the universe” aspect of the observatory dome with its viewing slit, but I also like the idea of being open to 360-degrees of sky where I catch glimpses of meteorites and have a difference sense of the whole.

One thing that became clear, though. On a dewy night the shelves wouldn’t be much help. I may find a way to make them more useful in this respect, but my immediate solution solved other problems. I bought a large, poly tool box on wheels. This can hold folding lawn chairs, as well as two other plastic containers that have drawers in them. One has a single deep drawer – good for the binos, for example, The other has three shallow drawers – holds charts, drawing paper, flashlight, recorder, etc. Since it’s on wheels I can move it to where I want it while observing. During the day the two plastic containers fit inside the tool box and the whole thing is weatherproof, so I can just leave minor stuff out there.

I also purchased a weather proof cover from Astrosytems ( This is NOT a permanent storage solution. What I like to do is observe in the early evening, leave my telescope set up, get four or five hours sleep, then come out for another hour or two of observing before dawn when the seeing is frequently better. I figure this cover will protect the telescope from a sneak shower or two. I can also leave it on during the day when we have a stretch of good weather and I feel its safe to leave the telescope set up.

So – the result. I don’t have the convenience of a full-blown observatory – but I also don’t have the cost or the hassle of building one. I do have many of the advantages of such an observatory and there are some advantages I didn’t count on. For example, I find this a wonderful spot to spend time during the day. Nice place, for example, to set up my Coronado PST and observe our nearest star. It’s also a quiet, private place that gives nice views of the surrounding trees and since after astronomy, birds are my first love – well, it’s proving to be a good bird blind as well. And yes, it does meet my major goal which is to provide a convenient, comfortable launching pad for exploring the universe.

Now all I need is for the rain to stop – I’m getting the new telescope curse in spades! Maybe I should have ordered an ark ;-)

Posted by Greg Stone at May 27, 2005 04:49 AM Comments? Please email me:

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