With the Spring unfolding and the Summer close by I decided it is the best time to finally start building my remote observatory. This requires a suitable position, solid foundation and structure, walls and roof, electricity, and equipment (telescope, mount, accessories, software & hardware). My aim was to have a roll-off observatory building with less than 1,000 EUR. That would be a significant saving from the cheapest I could find at 4,000 EUR without wood protection (+1,200 EUR with protection).
In this first part, I will talk about the location and setting up the foundation and structure.
Choosing the location
When choosing a place for your observatory you need to consider one important thing: once you’ve built it you won’t be able to move it if you later find the position you selected is unsuited.
With this in mind, you must consider the horizon profile. Usually, the observatory will be built in your home garden so there will be some buildings or walls blocking the horizon but that should not bother you as you should always aim to observe objects high in the sky. Unless there is a good reason for it (say location at higher latitudes requiring the observation of objects never reaching high altitudes), objects with elevation less than 15° should be avoided due to atmospheric refraction which makes stars twinkle horribly below that level. In my case (45° latitude north), the only issue is the low rise of the Scorpio constellation with its multitude of deep sky objects. Lower object elevations are also impacted by atmospheric seeing which becomes increasingly cumbersome as you drop below 45° in altitude. You can easily measure 15° by holding your hand at arm’s length and observing your tip-to-tip span between your index finger and your little finger.
In my case, there is a large tree just south on the meridian covering the sky as far as 25° in altitude but hopefully, in winter time the lack of leaves will make the observation of low-elevation objects better. Unfortunately, no other suitable location was available as the garden is full of trees.
In addition to this, the observatory walls will create an artificial horizon at a certain altitude depending on the height of the telescope mount. This can be improved by allowing parts of the walls to open. This is something I considered to have and will discuss in my next post.
Another thing I found useful was to use Stellarium to load a panorama of my summer and winter horizon to check the visibility of celestial objects at specific times and dates. You can easily build a panorama with your smartphone and load it into the software.
Setting the foundation
The foundation of the observatory is important. Some choose to use the ground to place their pier, others prefer a concrete floor, while some prefer to separate the area of the pier holding the mount from the floor. The latter has the advantage of restricting any vibrations on the floor made by walking. But for remote observatories, I doubt it makes a difference. To take it to extreme I have heard people saying that the mount should be encased in 1m3 of concrete to avoid vibrations. I believe these are a bit extreme for many of us who just want a permanent location for our amateur-sized telescope.
In my case, the location is in my back garden far away from the house and away from people and the main road thus in a low-vibration area. To build it I had to demolish a previous cabin that was already collapsing. From the image below, you can notice that it even has a small foundation (the ditches on the sides and through its middle) to properly fix to the ground.
The image below shows the concrete floor perfectly flat, although the team that built it wanted to give it a slope to avoid water from building up and eroding the floor. But that would have caused other problems like leveling the mount and also increasing the probability of the water entering the telescope and equipment area. Its dimensions are 4.4m x 2.4m with the long side having a North-South orientation. Overall it took one day to finish it.
Building the structure
I left the concrete to dry for one month before I started building the structure. To avoid any cracks it was periodically sprinkled with water but that still did not completely prevent small cracks. During this time I worked on the design of the roll-off observatory using Blender.
Before I continue describing the process here is a list of materials I used to build the4m x 2m wooden frame that will host the observatory.
- 11x wooden post
4000mm x 80mm x 80mm - 7x steel post
80mm x 80mm. Ideally, it should be 1mm larger than the wooden post but I could not find any. - 32x tie reinforced angle bracket
70mm x 55mm x 2.5mm - screws/bolts/dowels: 28x heavy-duty dowels for concrete (hex socket cap), 32x large screws for wood (hex socket cap), 100x small screws for wood (Phillips head)
- 2.5L protective wood paint (primer and varnish)
Installing the steel posts
A vital part of the process requires careful measurements and alignments. Any misalignment at this stage could lead to the nonlinearity of the entire structure and walls. I discovered that the easiest way to go was to use a water marker to signal the position of the holes and then drill the actual holes through the orifices in the steel posts. For the drilling, I used a percussion drill and then a hexagon nut driver to fix them (I simply rotated them till I couldn’t anymore).
Setting the wooden posts
Once the steel posts were in place I got to the part where the wooden posts had to be carefully cut and installed with the help of the reinforced angle brackets and wood screws.
The dimensions for the posts were as follows:
- vertical posts:
188cm(fitting one-and-a-half OSB board placed horizontally). The upper half is intended to open to lower the horizon of the observatory. - horizontal posts:
184cm(fitting a 200cm horizontal OSB board when the extra 16cm of the two supporting vertical posts is considered)
The first problem I encountered was that the wooden posts would not fit the steel posts so I had to cut 1mm on two adjacent sides. Not having initially a circular saw (I later rented one to cut the posts and triangular brackets) I used an angle grinder with a circular blade for cutting wood (which I was told is extremely dangerous due to its rotation speed and the fact that the blade is too rigid and does not break in case of stress leading to possible kickback and injury).
Once all 7 vertical posts were in position (6 for the walls and an extra one for the door) I continued with the horizontal ones. For them, I used the reinforced angle brackets to connect the joints. It was not always possible to place the brackets in the center due to wood knots. As a rule, I first placed one bracket and then using a level I placed the other. The horizontal wooden post came last. I positioned the horizontal posts in three rows, one just above the steel posts, another at 1210mm height (to match the height – 1250mm – of an OSB board laid out horizontally and leave 40mm for the one above), and a third at the end of the vertical wooden post.
The end result was a wooden frame like the one below which still needed reinforcing by using triangular wood brackets. These were placed in various locations in the frame to prevent it from shaking. I did not have these initially but after discovering how the entire structure shakes and speaking with some guys doing woodwork I decided to add a few.
As a final step, I painted the entire frame with a protective transparent coating consisting of both primer and varnish. At least 2 layers should be added. This protects the wood against UV, water, and insects.
The entire process of building the frame took 2 days and the end result looked amazing for a person that has never done this before. Quite sturdy too. Obviously, if I could do it again I would change a bit the way I designed the frame but for me, it was sufficient as it was.
The part on the left-hand side will be used to host the equipment and the part on the left to hold the roof in the open position. I consider covering it as well to be able to store additional equipment in that part as well but it remains to be seen. The entrance uses a sliding door concept. The next post will be about adding the walls and the third one will be about the sliding roof.
I am happy to provide consultancy services (for a fee) for people interested in building their own DIY observatory. I can advise on materials, and construction, and provide plans (my own or custom-made).
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