A step by step diary on the construction and cost of building a roll-off observatory with an identical shed

·        AN OVERVIEW-

The Dogpatch II Observatory is a 12' x 12' square "standard" roll-off roof observatory and 12' x 12' shed combination built during the spring and summer of 1999. The buildings are separated by 15' which is the area the roof rolls into. It originally housed a 10" f/6 reflecting telescope and a computer system for controlling the telescope and a Cookbook 245 CCD camera. It now is home to a Nexstar11 GPS and an SBIG ST-8XE and the computer system to control them. Due to covenants in the community it had to be covered in vinyl siding to match the siding on the house. The roof is white aluminum roofing panels to allow for quick cool-down and there is ventilation provided to minimize temperature buildup inside during the day. The roof rolls on (8) polyurethane V-groove wheels, 4" diameter x 2" wide, with roller bearings, purchased from McMaster-Carr. The only difference between the two buildings is the roll-off roof and the hardware to accomplish it. The basic idea in the two identical buildings  is that there needs to be some place for the horizontal roof supports to be anchored. My lot is large enough to accomplish this by having the two buildings back to back with the roof space between.

All costs listed are to construct BOTH the shed and the observatory since I was buying materials for both and building both at the same time.

In case you want to skip all the gory details below (although it is interesting reading about my foul ups) go here for the pictures.

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 Friday, 4/2/99

Dug the pads out today. The yard slopes down hill at a rate of about 5" in 12'. This causes the front of the pad to be buried almost up to the top of the form and the back to be sticking out of the ground about 1 1/2" to 2". In leveling them out as best I can I'm going to end up with a tapered pad thicker to the south to minimize the amount of concrete needed. I estimate an average thickness of 4 1/2" to 5" which works out to between 54 and 60 cubic feet. A yard of concrete is 27 cubic feet. It will take a little more than 2 yards a piece to do them. Dug the pier by hand, 18" square and 3' deep and the two support post footers 12" diameter and 24" deep. I will pour them only if there is enough left over to do it. I placed a 3" OD PVC sewer pipe in the ground for running the coolant lines and cabling under the pad to the CCD and scope. A 25-pin connector will pass through it easily. The last thing to do in the observatory will be to cut them off flush with the concrete. I'll leave them capped until then to keep all the sawdust, dirt, and bugs out of them.

Suggestion: (1) always run a piece of string through the tube tied in a loop or pull another string through with the cable. This will make it easy to pass cables through it in either direction and (2) make sure that the joints are SEALED to keep out water.

 Saturday, 4/10/99

Poured the concrete this morning with four friends to help. I ordered 5 yards and had the contingency of pouring a 4'x4'x6" deep step/ramp into the shed and a 3'x3'x6" deep step into the observatory along with the footers for the roof support columns and the pier for the scope. These items could be done with bags of cement if necessary but not the main pads. We did the pads and the pier first and had enough left over to do the steps. I believe the driver left with about 1/4 to 1/2 yard left on the truck. The only scary part was a loaded concrete truck rolling around on the grass and it rained heavily last night. When I called about the condition of the ground I told the operator that I had no problem driving my pickup on the ground but it doesn't weigh what a loaded concrete truck does. It would be the driver's call on whether or not to try it. I don't know what he would do with 5 yards of concrete if he couldn't make it to the pads. They are 100' behind the house and about 250' off the road. When he got there he asked if we would be able to get him out if he did get stuck...I don't think so! Two F150 Fords and a Toyota T1000 ain't gonna move him.

Suggestion: ALWAYS make sure there is more concrete than you need unless you are mixing it up yourself. If necessary find another project for the excess.



(8) wheels, McMaster-Carr, polyurethane, 1/2" shaft, P/N 22835T51


(8) 2x4x12' for forms

8' of 3/4" galvanized all-thread w/nuts and washers for bolting down buildings (cut to 6" lengths), for (8) per building

(1) 12" diameter x 4' long form tube cut into two pieces (Home Depot)


8' of 3" OD PVC thin wall Sewer pipe + (2) 90 degree elbows + (2) caps


(5) yards of ready-mix concrete, 3000psi, delivered*


*Note- There was a price break if quantity ordered was over 4 yards

Total costs to date- $520.00

 Sunday, 4/17/99

Went to the lot and removed the forms. Had to "dig" out the (4) 2x4's framing the pier. It is difficult to remove them during the setup of the concrete because (a) you aren't sure how well it is setup internally and (b) there is a large amount of suction holding them in. It had rained on them during the week and water had puddled up on top, swelling the top part of the wood. The only way to get them out was to drill holes through from the top and bust them out with a crowbar and chisel. Some concrete had run under the forms around the pier but it was easy to break out and remove so now there is a nice 1 1/2" gap between the pad and the pier. I'll fill it with play sand when I get it covered over to eliminate any sag in the indoor/outdoor carpet I put down. The sand will not transmit vibration to the pier. The pier base doesn't have to be pretty so plan ahead. I used the concrete covered 2x4's that warped or broke to make up some cheap sawhorses to keep on site and the better ones will be the base parts of the walls, cleaned up a little of course.

Suggestion: make the pier form collapsible from plywood and stakes driven in between, or anything that will avoid getting the things jammed in there if doing the pours all at once.

Tuesday, 4/20/99 

A local metal supplier in Easton, MD., has the 1 1/2" x 1 1/2" x 1/8" aluminum equal angle for the wheel tracks at $21.23+tax each in 25' lengths. I originally intended to cut the parts out of an 8' 2x2 or 2x4 treated wood but thought better of it after trying out a test cut on my table saw. The thought of trying to make 8' long saw cuts and keep them to some consistent size has made me decide that discretion is the better part of valor and $45 is a reasonable price to pay.

 Saturday, 5/8/99

The FIRST of our two moves this spring/summer is done so work can begin for real this coming Friday.

 Friday, 5/14/99

Went to LOWES lumber store and got (104) 2x4x8' and (20) 2x4x12' in addition to 15 pounds of #10 galvanized nails, (28) truss hangers, 56 mending plates to make up the trusses and more nuts and washers for the 3/4-10 all thread I'm using to hold down the buildings for another $402.42 . I'll probably need a few more 2x4x8' and I know I didn't get enough 2x4x12' but that was all I could haul reasonably.

 Saturday, 5/15/99

My son and I worked on the observatory walls today. All four walls are up with the doorway outlined. I've decided to do a type of garage door entry into the observatory that will roll up into the roof section and out of the way. It will aid in security too although crime is not a problem where I live. I will have to check with a local garage door company about the costs of getting the C-channel frame and other door hardware. Had to stop early since the wife is taking me out for dinner and a movie for my birthday.

 Sunday, 5/16/99

Went back to the lot early this morning and managed to knock out the shed walls and the door frame without my son to help. It was a full day though from about 8:30 AM to 7:00 PM. Tomorrow I'll se if I can get to the lot in time to do any work in the evenings since I work a 10-hour day and commute for another 3 total. I have pictures but they are still in the camera. So pictures will be slow coming.

Lumber + truss stuff + nails + tie-down hardware


Total spent to date- $924.42

 Monday, 5/17/99

 Got all the roof trusses cut tonight and one assembled. The longest time in the building process is the layout and cutting of things. The actual assembly goes like a snap. Tomorrow I hope to get the rest assembled and put in place on the shed.

Monday, 5/24/99

During the past week, I managed to get all the shed trusses made and in place. I worked Friday, Saturday, and 12 hours Sunday to get the entire roof and side panels up except for two on the south end which will be done tomorrow. I received my McMaster-Carr order that included the tie-down screw eyes that replace the 3/4-10 nuts bolting the observatory to the ground and installed them. The problem with doing the two buildings at once is that the greatest urgency falls on the shed first due to the need to store home stuff like appliances, bathroom equipment, all the nice things that have to be ordered for new construction and STORED somewhere. Once the shed is roofed over and lockable the observatory will fall into place.

More nails, 2x4's, stud hangers, mending plates, and (29) sheets of 4'x8'x3/8" CDX plywood for the roof and walls


Total spent to date- $1273.81.

 Monday, 5/31/99

During the holiday I finished the shed except for doing the aluminum roofing, the siding and the door. I went back to Lowes and got the two 16' long 4x4's I needed for the roll-off roof. I had the aluminum angles delivered from Eastern Steel on Friday at a cost of $48.07. Each individual piece was only $22.89 so adding ~$2.00 for delivery was a no-brainer. The only problem was they were supposed to be delivered before lunch...they weren't. When I went back to the lot Saturday, the pieces were there and the invoice WITH MY CREDIT CARD NUMBER was blowing around the lot. Good thing I found it. I installed the 4x4's today and the angles. Turns out I have about 1" misalignment over the 15' span between the buildings due to assuming the front of the observatory and the back of the shed were aligned within about a half an inch...they weren't. Suggestion: when building a system like this GO with the sides as the alignment since the rails HAVE to be parallel. Above all else the supporting beams can be longer or shorter as necessary BUT they must be parallel to each other.

Since I intend to build a play area in the space between the rails, I added a couple of 2x4x10' to take up the misalignment and give me some place to attach the extra stuff to such as a platform and sliding board and whatever. I said this would be a "warts and all " diary. I never claimed to be a #1 carpenter. That's why I'm adding these suggestions to show what to look out for after I didn't. The extra 2x4's really added to the stiffness of the beams too. I've redesigned the trusses for the ends of the observatory to REALLY increase the stiffness since almost 12' between the wheels. Don't want any sag when the roof is open for half the night. Once the shed is roofed over and lockable the observatory will fall into place.

(2) 4x4x16's + (1) 4x4x8' + (2) attachment brackets


Total spent to date- $1319.30.

  Sunday, 6/6/99

Went up to Lowes in Dover and ordered the roofing, 20 panels of 36" wide x 8' long white "Classic Rib" aluminum from Metal Sales Manufacturing. The price had gone up since I priced it last. It is now $2.50 a foot instead of $2.19 so it came out to $400.00 even for both buildings. I also bought the bolt/axle hardware for the rollers, more CDX and the 2x4's for the observatory trusses. In the past week I've managed to get all the trusses build for the observatory, the end trusses done and the roller sections done and installed. Do they roll smooth and quietly or what! I spent half of yesterday getting the last minute items to complete the roof. I picked up the fascia and soffit for the roof ends and will borrow a friends bender to shape the pieces to cover the plywood. I have worked every night during the past week (about 1 1/2 hours per evening) and the weather is getting hot (90's) and fortunately breezy. There has been no rain so the ground is getting hard as a brick. The deer flies are thick though so "OFF" has been a necessity. No work today... grandson's birthday. The roof will go on the observatory this week. The only remaining costs will be the doors for both buildings (probably hand built), finishing the inside if the observatory with wiring and outlets, and a GFI circuit breaker in the house for both since there will be water at the shed. Almost forgot one big item..the siding but I don't know the estimate on that yet.

(8) 1/2-13x4 1/2" bolts, nuts, and washers


(1) 5# box of galvanized #10D nails,


(12) additional rafter ties and (18) additional mending plates


(4) anchor down plates for the rail support posts


(4) 1x8x12' for the roller sections


(20) sections of aluminum roofing (special order)


(31) 2x4x8' to finish roof trusses


(8) 4x8x3/8" CDX for end panels


Total spent to date- $1972.59

   Sunday, 6/13/99

Finished up the roof truss installation on the observatory this afternoon between spritzing rain showers. When it was all done I stabilized the four walls so they wouldn't rack diagonally and pushed the roof down the aluminum angle track for it's first test roll from end to end. It rolled about halfway and stopped. Seems the amount of misalignment was LESS than I had figured. What I should have known was to fix one track and let the other find it's own free position, which is what I did. I removed the screws on the west side wall beyond the observatory and rolled the roof almost to the end. I put the screws back into the new position and rolled it back. Now it rolls completely with no binding. When the roof panels are in place I probably will install another winch system to move it. It will he heavy enough to require a little boost.

I worked yesterday an the roller assemblies finishing the attachment to the end sections. I also made up the doors for the shed. Still haven't decided what to do with the observatory door. The garage door style rollup is intriguing but probably too expensive for this project.

  Monday, 6/29/99

I've had to wait to finish the roof while a former neighbor with access to a break for doing the soffit was on vacation and unavailable in addition to us getting some badly needed rain. Also there was a necessary repair to my boat that consumed two Saturdays. Turns out the break isn't around for me to borrow so it's off to the rental store this Friday. Since the last report I've finished framing the soffits and aligning the roof angles, added the doors to the shed and installed the lock and hasp. It is now holding half the bath accessories and a propane fireplace for the new house since it's still not lockable...another necessary delay for the observatory. I've decided that the observatory door will be a hand made door that will utilize two lock sets given me by my son. It will be split at the wall joint and the roof will carry the upper portion with it. It will save some money over the garage door style. The basic spending is done except for the materials to house the computer and installing the pier. The roof and outside should be done by Saturday evening, except for the siding.

  Monday, 8/2/99

I've been a busy man for the past month. I have finished the roof work, built an insulated computer box large enough to accommodate two computers and monitors, installed the winch stand, and completed all the interior and exterior wiring. The contractor installing the septic system at the house dug me a trench (a canyon is closer to fact) to run the power wires and the network and phone cables. There is no reason for the trench being so large. The well line and the hose line back to the observatory are to be run in it also. Just killing multiple birds with one stone I guess. While the roof does roll fairly easy it will be better to pull it open and closed. I've got my shelves put in and it's time to begin work on the pier. I'm going to use the steel pipe that came with the Meade GEM I bought years ago. It will be temporary since one of my near future projects is to computerize the drive ala Mel Bartel's system and redesign the scope housing to lighten it. I have to rent a drill to install the bolts into the pier and get a piece of aluminum or steel plate to attach the pipe to the pad.

To top it off I had to fire my builder. After 8 weeks the house is STILL being framed in. It AIN'T that big. Turns out he wasn’t paying the framer and the HVAC guy he hired had no clue what was needed for the heat and air. I’m on my own. Oh, Brother!


130' of 3/4" PVC tube for the network/phone line conduit


(15) outlet boxes, cover plates and (5) switches


50' of additional #14-2 underground cable


(4) barrel bolts for computer box


(2) eye bolts 1/2"x6" for moving roof


Total spent to date- $2010.27


We got moved into the house in May…18 months after signing our contract for an 18 week construction schedule. That was just to get the occupancy permit. Half the stuff in the house wasn’t finished like the trim and so on. That had to come before much more got done on the Dogpatch II.

Using the GPS in my boat which is parked next to the observatory and since Pres. Clinton was kind enough to turn off the Selective Availability (SA) I have determined the Dogpatch II's location to be N38° 47' 18" W75° 56' 35". SA is the way that the Defense Department degraded the GPS signal so that foreign governments couldn't use it to have their missiles use it for guidance. Yeah, like an H-bomb gives a damn if it's off by a couple of hundred yards!!! Since I'm getting a very nice Nikon Coolpix 880 digital camera for Christmas I'll be updating the interior/exterior shots of the DP II details. I finally got the carpet installed and it helps (a) cushion a lens if I happen to drop it and (b) helps to keep your feet warmer in the winter since the bare concrete is like standing on an ice cube.


I purchased a Celestron Nexstar11 GPS in June of 2002 and replaced the 10” homebuilt Newtonian I was going to use the Mel Bartel’s system upon. The 6” Newt I used as a wide field scope on it has become my grandson’s first real telescope. Better that than one of those cheapo refractors that discourage so many new to astronomy. This summer the space between the two buildings will be enclosed with the roof retracting into the shed. I will accomplish this by rebuilding the shed two feet wider on both sides. There is a nine and one half inch drop in elevation between the two buildings. Stay tuned.

Update 3-16-16

After 13 years of the NexStarGPS and the other telescopes I dismounted the 11" OTA from the form mount and purchased an Orion HDX-110 GEM mount with a 100 pound carrying capacity. The NexStar was pretty much loaded to the max and I thought it was creating some of tghe imaging problems I experienced. It took about a month of playing with the EQMOD software ans AstroTortilla program to get the hang of controlling a GEM. It's a little different than a fork mount scope.

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