Ground breaking at Mintaka Hill for Orion’s Belt Observatory began in May of 2016.
I decided to go with a sliding roof design. Several reasons. First is that having a dome requires control of aperture rotation. Not easy to have that work consistently. Second is the advantage of being able to install more than 1 pier in a larger structure with a sliding roof. Finally is the appreciation of the night sky we are fortunate to have here . One of my favorite activities is binocular observing. Often when I am up here I can do that in the observatory at the same time as projects are running. The 2 disadvantages for those thinking about this is that you may be more exposed to wind and if you are operating the observatory remotely, your scope will have to park properly before the roof can close. This may be problematic if the observatory is trying to shut down because of weather and your scope can’t park!
After researching several possible contractor sources we decided on Backyard Observatories. They have built several observatories here and around the country. Everyone I spoke to has been very happy with their choice. It’s a little different process though from other building projects you may have been involved with. They don’t do everything from top to bottom. You are responsible for preparing the site and creating the foundation depending on which type of infrastructure you decide on. Either a deck type which requires a square cement footing with cinderblock or a cement slab. Several folks expressed some concern regarding their cement slabs creating a large heat sink which possibly can degrade seeing due to convection created in the observatory. Therefore we decided on a deck design. We went with the size of 15′ 6″ square of which 5′ 6″ x 15′ 6″ consists of warm room. This was felt to be more than sufficient. This will allow 2 piers to be placed roughly 5′ apart.
The bedrock in the construction zone was down about 2-3 feet. The above image shows the initial site work and creation of the forms for the footings. You can see the holes dug for the piers. The decking sits about 9 1/2″ above the top of the cinderblock and the tops of the piers will need to be approximately level with that so the pier forms will seem to sit pretty high up.
The next step in the project was to figure out the location of true North. This was for the purpose of correctly positioning the pier bolts for the telescope pier. Much of this will depend on what mount and pier you decide to use. To clarify then, there are cement piers in the ground anchored to the bedrock and telescope piers that sit on top of the cement, usually bolted to it. For myself, I am a long time Software Bisque user and have set up permanent mounts before so that’s what I use. The Bisque piers are steel piers of varying heights with a half inch base that has 4 slots in them for the bolts. These slots are 1 inch and do allow for +/- 5 degrees of azimuth correction to the pole if you are slightly off but the key is to align the bolt orientation as closely as possible to true north. The risk is that being significantly greater than 5 degrees off will make it impossible to polar align your mount! For true north alignment therefore I rely on Polaris. I would not recommend a compass as there are magnetic sources everywhere which will throw things off.
For aligning the pier to the true north-south line I used a device called a theodolite (see above). This is the yellow object in the image. It is commonly used by surveyors. There is a 20x sight tube mounted on a calibrated altazimuth base. I align the base to the pier such that the site tube is parallel to the edges of the pier which are square and then tape the base down. Then I raise the sight tube in altitude to, in this case ,34 degrees which is the elevation of Polaris above the horizon for our lattitude. If Polaris is not visible I move the pier, not the theodolite in azimuth until Polaris is centered. Now the square edge of the pier marks the north-south line! We can then stake out the north-south line the following day and run a line between the stakes parallel to the square edge of the pier to show more clearly the line.
Next we create the templates for the pier bolts. We set it on a plywood square that will be slightly larger than the dimensions of the actual wooden pier form so we can adjust the alignment to the north south line. You can see the curved slots in the pier base. We ream 4 holes centered in the slots and place the 4 J-bolts measuring 1/2 inch by 12 inches
Template completed! The blue tape marks the north south line. The circles indicate where conduits are to be embedded in the cement for electric and for data. Those of you thinking why did I put the conduits in the pier and not outside is because it’s much better for cable management to have the conduits right there and being only 2 of them it is quite unlikely they will cause excessive vibration inside the pier which is quite large by comparison. No evidence to date that they are causing an issue.
The pier forms are wooden squares. One is a 3 foot and the other a 2 foot. The forms go down close to 2 feet to the bedrock. The cement is anchored to the bedrock with rebar that is drilled down into it. This is definitely more than adequate for amateur imaging! After all, we’re not trying to discover gravitational waves (I don’t think)! If there is an earthquake there might be some pier movement but otherwise I believe we will be OK. You can see that the templates are placed on top of the forms and oriented so they are parallel to the north -south line indicated by the blue tape and in the far right image you can see the white cord on the right indicating the north south line. The builders oriented the forms to that line. I fine tuned it again with yet another Polaris alignment just before they poured the cement. I had to rotate the template just a few degrees! The conduit circle cut-outs are also seen in the templates.
Forms are ready for pouring! Conduits are installed. Foundation is complete with J bolts for attachment to the observatory frame
We tested the fit of the Bisque pier on the cement and 4 bolts after cement was poured and everything hardened. Everything looks good! The pier base is level.
A trench has to be brought up from the house to carry 2 conduits, 1 data and 1 electrical. The trench is around a foot+ deep and 18 inches wide. There is no set depth and width as long as the conduits can be separated so there is no electrical interference.
Not to be overlooked is the site work that must be done around the observatory to manage ground water and rain. We don’t get much rain up here but when it comes it arrives in sudden bursts of large quantities of water, occasionally causing local flooding. 2 large berms were created around the perimeter of the north end of the property and additional gravel placed in the immediate vicinity of the structure. This is the view from the east end of the clearing looking west. You can see the foundation in the foreground.
Framing and completion of the observatory structure
On July 30, 2016, the BYO crew arrives!
Day 1 consisted of completion of the subflooring, completing the conduit from the piers to the warm room and to the electrical panel and 2 walls built. No disasters so far. The foundation walls were a tad off level to the north and west so they had to put shims but no other issues.
Finally the floor is done and 2 walls built, ready for assembly!
July 31, 2016
The day started out sunny and seasonable but rapidly declined to stormy and rainy. Walls went up today as well as the inside framing for the warm room.
August 1- Wall completion.
South wall with 2 foot fold down panel to improve access to southern sky
Inside the walls
August 4, 2016- Observatory completion!
Structure completed! Inside the observatory showing south wall with the drop down panel. Actually there are 2 separate panels due to the weight. The wall height is 85″. The height with the drop down open is 62″. Note the insulation under the roof which keeps the heat from building up in the summer. The building has been wired with multiple outlets and a few wall lights
And now 3 years later, the mock WordPress interview with Dr Dave on the evolution of Orion’s Belt Observatory:
WP: I bet it’s hard to believe it’s been already 3 years almost to the day that the observatory was built.
DD: Sure is! It’s amazing to think in those 3 years I have been able to install 2 piers with fully operational equipment I am now routinely operating remotely! Truly is a dream come true.
WP: Anything looking back you wish you had done differently?
DD: Remember this is something I have been waiting for most of my life so I had done a ton of research during that time. I feel I have made mostly really good decisions. I think I really am a roll-off fan for the reasons I stated earlier. Despite the issues with scope parking etc., a roll-off is MUCH easier to operate remotely than a dome. BYO roll-offs are well known in the US for their excellent quality construction. They were efficient and finished the job when they said they would. I would highly recommend the hardy board which is basically a cement based siding instead of wood. It still looks brand new. Wood gets destroyed by the high altitude Sun here. The only thing I think I would have changed is I would not have had them install that dreadful M1OASYS roof control which is totally unworkable for anyone but software engineers. I am sure for a home security system it’s great, but for a 16 foot structure and your average amateur it’s basically expensive junk. I would have saved quite a bit there.
WP: How about the general area you’re in? Are you happy you chose this site?
DD: Excellent question. Really the New Mexico Skies area is the one I had my eye on for years. It was the premier observing site possibly in the world when it first started now almost 20 years ago. The one thing you don’t have any control of is the weather. Climate is changing for better or worse. It has to change. It’s a fluid situation. It’s Earth’s atmosphere. Our telescopes are not in Space. When you pick a site for a permanent installation there is always going to be that uncertainty regarding the stability of the local seeing. When this development first started there were routine 1 arc second seeing nights. I never came here with a seeing monitor to confirm that. I saw all the observatories here and figured it must be amazing seeing all the time. Since building the observatory 3 years ago I have to say honestly the seeing at least in the last 2-3 years has been pretty average. I’m almost thinking the seeing in our home residence of Las Cruces is better than here! I mean there is an amateur who has multiple observatories about 200 yards from me and has a seeing monitor up all the time. I have looked at that thing every clear night for the last 2 years. I’m going to say conservatively the seeing has never been below about 1.7 arc sec and when it has it’s only for an hour. Typically after an hour the seeing steadily declines. Probably it averages all year somewhere between 2 and 2.5. Now having said all that would I move? Definitely not. There is still an amazing dark sky here and I am very fortunate I am only just under 2 hours away from my home. So if I have to get up here I can easily do it even during the work week which is fantastic. I would go out of my mind if I was 1000 miles away and something happened where I really had to get there. I do have a lot of patience but not that kind! The other great thing about this location is the people here. The astronomy community is fantastic. I can’t tell you how much I have learned and how many new friends we have now, really great people we can routinely get together with and share our common passion.
So the answer to the question is no, I am not moving my gear to Chile! Who knows, in another 5 or 10 years the seeing may come back!