Project: Astronomy observatory

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We enjoy photographing deep-sky objects in the night sky. An observatory allows the telescope and imaging equipment to remain set up and ready to go.

We used this 8' x 12' roll-off roof observatory at our former house.

Here, we will build one similar to that, but slightly larger, at 10' x 14'.

The roof will be supported by hard-rubber wheels riding on 2x4 tracks. A garage door opener will open it for an imaging session, and close it the following morning.

Observatory site aerial view

We are fortunate to have sufficient land to accommodate a large open area for the observatory, giving us a 30° horizon in almost all directions. The yellow rectangle is where the observatory will be located in the clearing, and in relation to our round house (left), about 300' away. The observatory is oriented north-and-south, and north is up in this photo.

This photo looks east across the clearing with a side view of the observatory superimposed on it. North is toward the left, and the roof is shown rolling open and closed on tracks extending from the building in that direction.

Here is a 360° panorama from the observatory position at telescope height, and shows the horizon the telescope will see.

Here is the new horizon compared to our former site. The expanded viewing area is dramatic.


April 30, 2015 – Ethernet checkout.

The observatory is almost 300' from the house, and the Ethernet cable to it from the basement network closet is longer – close to the maxium length specified for Cat-5 cable. Consequently, we decided to check if a computer at the observatory site can communicate with the Ethernet switch in the house.

Mike put connectors on both ends of the cable, then connected it to the computer and the switch. Thankfully, the network connection works fine.


Roof opener plan

We plan to use a garage door opener to open and close the roof. This is a general plan showing how the opener will be attached to one side wall and the roof.


November 18, 2016 – Casting the telescope pier

At last we've started working on the observatory! Today we cast the 12" concrete pier to hold the telescope mount. The drawing above and this photo show how the pier will be located inside the observatory.

We began by using our power auger to bore a 16"-diameter hole 28" deep. We rented a concrete mixer, and Mike secured it to the tractor's front-end loader so we could lift and tip it to ease the work. Here it is ready to pour concrete for the footer into the hole.

After the footer concrete set slightly, we placed the 12" tubular form on it and used large wedges cut from 2x4 stock to shim it plumb (second photo below). Then we filled it with concrete. In this case, we shoveled the concrete out of the mixer into the form because we didn't want to dump it and risk spilling outside the form.

The pier has a long 12"-diameter base and a 10"-diameter top that is 18" tall. This smaller top will provide extra clearance for the telescope's imaging equipment when pointed high in the sky. The top of the 10" section is four feet above the ground, which made shoveling the concrete into the form a challenge.


November 19, 2016 – Pier complete.

The concrete hardened overnight, so Mike took a look at the pier today. The top section appears tilted slightly, but this is a cosmetic flaw only, as the black telescope mounting plate on top can be precisely leveled with the hex nuts beneath it.

Mike wrapped the pier with R30 fiberglass insulation to keep the concrete from freezing while it cures completely. After this photo was taken, he draped a tarp over the insulation to shield it from rain.


December 8, 2016 – Pier unwrapped.

The concrete pier has cured for nearly three weeks, so today Mike temporaily removed the insulation, then cut and unwrapped the cardboard form around it. He also backfilled the hole around the pier with dirt.

The pier looks pretty good, but the top section has some voids where we didn't stir the wet concrete well enough. These voids don't impair the pier's purpose of supporting 200 pounds of telescope and mounting, but we'll probably patch them later to improve appearance.

Mike replaced the insulation and tarp to allow the concrete to continue curing in cold temperatures.


March 26, 2017 – Burn pile cleaned up.

Ever since we moved into our new house in January 2011, we've been meaning to burn the brush and debris left on the burn pile by the contractor. A couple of weeks ago, we paid a team of workers to clean up debris along the driveway, and take the rubble from the burn pile as well. They took a lot, but left some partially rotted branches and stubble.

Earlier this week Mike attached the pallet forks to the tractor's front-end loader, and used them to carry the leftovers into the woods. Today he used the tractor and landscape rake to drag the rotten wood to the same spot, then smoothed the burn area.

Louise spread grass seed, but weeds are likely to sprout. Either way, Mike will be able to mow this area the same as the rest of the observatory clearing.


May 22, 2017 – Observatory project approved

Our rural subdivision has a property owners association with an Architectural Control Committee (ACC) that must approve any construction, even as minor as our 10' x 14' roll-off roof observatory. The ACC met this evening and approved the project based on plans and descriptions we submitted last week.

Now we can buy materials and begin construction (if it ever stops raining).


June 2, 2017 – Roof opener test

Calculatons indicate the roof will weigh about 400 pounds, so it's important to know if the garage door opener we have will move it (if not, we might need to build a smaller observatory).

We tested the opener on a patio by securing it to a 6x6 post and attaching the trolley to a dolly loaded with five 80-pound bags of concrete mix. (The attachment is hidden by the concrete in this photo.)

After a couple of glitches related to the optical obstruction detector (we won't use this, but it must remain connected), the opener moved the 400-pound load in both directions. Now that we're confident it will move the roof, we can start to build the full-size 10' x 14' observatory as planned.


June 6, 2017 – Framing lumber and hardware

Today we hitched the trailer to the pickup truck and brought home the lumber and hardware we'll need to build the foundation and frame the deck (floor). We bought:

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June 8, 2017 – Foundation stakeout

Yesterday Mike drafted a plan to stake out the locations of the foundation posts. It involves identifying the north-south line through the center of the telescope pier, then measuring from the pier to the post locations. Here is the plan drawing. Today's measurements are shown in red.

We strung a line between two lengths of steel conduit left over from our straw bale garden deer fence, and centered it directly over the north-south bolts embedded in the top of the concrete pier.

Then we marked the center and end post locations on a 10' 2x6, and laid this on the ground beneath the string. Louise dropped a plumb bob from the string, and Mike adjusted the 2x6 so the center reference mark was directly under the plumb bob.

Next we measured from the pier's north centerline, and rotated the 2x6 until the end marks were the same (and correct) distance from the pier. We were gratified that these measurements came out exactly right. We sprayed marking paint at each post's location. This photo shows the general setup.

We repeated this process on the south end, then measured between opposite corners and made minor adjustments to get the diagonals equal. One minor nuisance was the tape measure had only feet-and-inch markings, but Mike's plan showed all dimensions in inches. Thankfully, Mike has a construction calculator app on his cell phone, and this quickly converted inches to feet-and-inches.

The final step was to measure between same-side corners to locate the intermediate posts. In all, we accurately marked all 12 foundation posts. Tomorrow we'll bore holes for them.


June 9, 2017 – Foundation post holes bored

We used the power earth auger to bore holes for the 12 foundation posts marked yesterday. The job went very well, and we finished in less than an hour. The auger encountered only two rocks – unlike much of our land, where rocks are everywhere.

A depth gauge made quick work of onfirming the holes are at least 21" deep. Tomorrow we'll use a second gauge to check the depth is 18" after shoveling 3" of crushed stone into each hole. Then we can set the posts.


June 10, 2017 – Setting foundation posts

We began to set the 12 foundation posts and attach the cross beams between them. Even though we began in early morning, the full sun quickly became too much for us, so we quit at 10:30, and came back at 6pm, when the sun was behind some trees.

We made better progress in the cooler temperature. We first cut the two south corner posts to their respective lengths, then attached a 10' 2x6 between them. We poured 3" of crushed stone into each hole, and set the post-beam assembly into their two holes. We plumbed the posts, then measured from the pier's south centerline to the center of each post, and adjusted the posts until the distances were equal. When everything was right, we poured concrete into the two holes.

With light fading, we worked quickly to repeat this process for the north corner posts. We cut them to length, added the 10' 2x6 cross beam, set the posts in their holes, and plumbed them. We made minor adjustments until the posts were equidistant from the pier, then we secured them until tomorrow with large wedges made from old 2x4s.

Finally, we measured diagonally between opposite corner posts, and were estatic that both distances were equal to within a tiny fraction of an inch.

This photo shows today's progress at 8:44pm. The south posts and beam are in the foreground. The north posts and beam in the distance still must be adjusted to the same height as the reference post on the southwest corner (closest to the camera, near the black bucket). Then they too will be fixed in place with concrete.

We use an electronic water level to adjust each post to the correct height. It's accurate to 1/16".


June 11, 2017 – Setting more foundation posts

We got an early start this morning, but still set just two posts and their cross beam before it became too hot to work. Here is the morning's result. Only one pair of posts remain to complete the foundation perimeter.

We returned about 7:30pm and managed to set the final pair of posts and their cross beam. It was 9:15pm and almost completely dark as we collected our tools and headed for the house.

But oops! We didn't notice these posts and beam were offset 1" toward the west, and ½ too high. Mike had to fix these problems days later

Mike shot this northwest view of tonight's work the next morning, but we didn't work that day. The final post-beam assembly is second from the left. The remaining four posts to be set along the observatory's centerline are leaning on the other three beams.


June 13, 2017 – Foundation complete

We got another early start, and set the final four posts along the observatory's centerline. The foundation is complete. Next up – frame the deck.


June 14, 2017 – West frame boards

We need the frame's west side boards in place to be able to measure and mark locations to attach joists inside the frame. Tonight we cut and installed those two boards.


June 15, 2017 – Frame perimeter complete

This evening we attached the rame's east side boards to complete the perimeter. One of the 2x6 cross beams is nearly ½" too high, so we'll have to remove it and mount it lower so all framing is at the same height.

Louise marked the locations for joist hangers on the framing boards. The next step is to nail up 64 joist hangers, then cut and install the joists. to prepare for this, Mike made a simple jig to hold a joist hanger and position it correctly on a beam for nailing.


June 19, 2017 – Oops! Fixing an error

The final posts and beam we installed when it was nearly dark ended up being offset an inch toward the west, and ½" too high. Yesterday Mike lowered the beam, and today he notched the west post to remove the 1" bow in that beam. Then he cut off the tops of the posts level with the beams.


June 20, 2017 – Shims and joists

Today we installed shims on two posts on the north end beam to correct an error in those posts' locations. When we measured opposite corners, we saw exactly 17' - 4" on both diagonals, indicating a perfect rectangle. Whew!

Next we began installing joists in the deck framing. Louise had already marked the locations, so we held a joist hanger in Mike's jig, and used a palm nailer to nail it to the beam. We did this for all joists in the southern bay (photo below).

Then we cut 2x6s to the needed lengths, and set them in their hangers. Unfortunately, the 2x6s aren't the same height, so some joists were up to 1/8" higher than the beams. We brought these into the shop, and Mike will use the band saw to cut shallow notches in the bottom, so they'll sit lower in the hanger.

Tomorrow we'll use a different technique to accommodate joists of varying height.


June 21, 2017 – installing joists

Mike's shallow notches in the ends of the south joists did the trick. When he put them back into their hangers, all the tops were at the same level as the adjoining beam.

We turned out attention to joists in the north bay. Our revised technique involves first measuring and cutting each joist to its final length. Then, as shown in the photo below, we clamp a joist hanger on the bottom, and a piece of wood on the top of each end of a joist. We set the joist in place between the beams, with the wood supporting the weight and holding the joist at the correct height. Next we nail the joist hangers to the beams.

The final step is to drive two 3½" nails at an angle through the joist and into the beam. We did this on all joists in the north and south bays.

Here is this evening's work. Tomorrow we expect to install three short joists in the gap in middle of the north bay, and install most of the joists in the center bay.


June 22, 2017 – installing more joists

We changed the plan slightly to use one long joist in the north bay in place of three short ones. We also adjusted the joist spacing in the center bay to eliminate two short 2x4 blocks by the pier.

Working in the evening kept us out of direct sun and heat, but the humidity was high. We installed the long north bay joist, than cut and installed the longest joists in the center bay. Only 11 joists remain to be cut and installed. Mike measured the needed lengths for eight of them, and Louise wrote those measurements on the designated boards for quick reference.

Mike snapped this photo of this evening's work the next morning after light overnight rain.


June 23, 2017 – installing still more joists

This morning, Mike used the tractor to bring the boards for the next eight joists into the shop, where he used the chop saw to cut them to the needed lengths. This was much easier than cutting them on-site with a handheld circular saw.

In the evening, Mike took the joists to the job site and installed them in the middle bay. He then measured and marked locations for three short joists in the pier bay, and took those boards to the shop, for cutting tomorrow.

Here is today's work. The three joists in the pier bay will complete the deck framing.


June 24, 2017 – framing complete

We installed the final three joists in the pier bay, and the deck frame is complete. Next up: lay some plywood and build the walls.


June 25, 2017 – what a day!

Today started off well enough. We hitched our 4'x8' utility trailer to the truck, and set off for Lowe's, 40 miles away, to pick up an order of a door and five sheets of ¾" plywood.

Halfway there, driving on the Interstate, the truck began having trouble maintaining speed. A glance in the rearview mirror showed smoke streaming behind us! But the dash instruments didn't show any engine problem, so what was wrong?

Fortunately, an exit was in sight, so we took it. As we turned into a gas station, Mike discovered the smoke was coming from the left trailer wheel – the bearing has seized, the tire was shredded and the wheel was destroyed. We left the trailer in the parking lot, and continued on our way.

Louise remembered that Lowe's sells trailers, so we bought a 5'x8' steel trailer with a drop ramp. It's rated for nearly twice the capacity as the now-dead 4'x8' trailer, so it will be suitable for hauling the tractor, should it need dealer servicing. We loaded the plywood and door into the truck bed to keep the new trailer empty.

We returned to the gas station to rescue the old trailer. With the help of two strong young men and a couple of 2x4s we'd brought from home, we muscled the old trailer onto the new one, and carefully drove home. Once there, we unloaded the plywood and door from the truck, then Mike used the tractor to unload the old trailer. Here are photos of the ruined tire and the tractor unloading the old trailer.

Now we can get back to building the observatory.

Updated June 25, 2017