Dome Construction at the SFA Observatory
A 10-foot Diameter Pro-Dome


The Forms

  • Grass was removed and dirt was added with a front-end loader.
  • 1 by 6 boards were used to hold the circular forms in place.
  • 2-foot metal stakes with nail holes were used to hold the forms in place.
  • A transit (a theodolite with the telescope) was used to level the forms.
  • And 4-foot by 8-foot piece of mansonite was cut into four strips to make the circular form.
  • The length of each mansonite strip Pi * 119" / 4 (the arc length of a quarter section).
  • These forms are for a 119" diameter concrete foundation.
  • Reinforcement mesh wire was cut to fit the circular form.

Electricity

  • 1" gray PVC pipe was used to carry wires for electricity, phone and the alarm system.
  • The PVC pipe comes out through the masonite form as shown on the image to the left.
  • The pipe was set 12" to 24" underground with a ditch witch.
  • Two 5" diameter PCV floor cans was used for the outlets.
  • The placement of the floor cans are shown in the images to the left.
  • The outlets placed close to the center will be used to power the telescope and CCD camera.
  • The outlets placed close to the southeast edge will be used to power the computer and dome motors.

The Pier

  • Redwood forms were used to make a 18" by 18" by 36" block of concrete for the telescope pier.
  • The redwood pieces were used to isolate the pier and therefore were not removed from concrete.
  • The redwood forms and reinforcement bars are shown in the image to the left.

The Concrete

  • The image to the right shows the pier anchor bolts with wooden circular templates.
  • 2.5 cubic yards of concrete was needed for the 4" concrete pad and pier platform.
  • Thirteen 1" by 8" J-anchor bolts where also placed around the edge of the wet concrete.
  • These J-anchor bolts were used to attach the wall ring to the concrete pad.

The Concrete

  • The pier bolts with wooden templates are shown to the left in the redwood box.
  • The 5" diameter floor cans for electrical outlets are also shown.

The Location

  • The coordinates of the site was measure in two ways:
    • Internet Maps
      • Latitude: +31d 45' 35.3"
      • Longitude: -94d 39' 40.5"
    • GPS Unit
      • Latitude: +31d 45' 34.7"
      • Longitude: -94d 39' 38.5"
  • Note: 1 arcsecond of latitude (1") corresponds to about 31 meters on the Earth.
  • GPS units have a built-in error of about 100 meters.

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Price List

  • 2 yards of concrete = $140
  • Reenforcement Steel = No Cost
  • Redwood Board 1"x6"x8' = $8
  • Masonite forms 1/4"x4'x8' = $10
  • 2 Electrical Floor Boxes @ $11.35 = $22.70
  • 2 Electrical Floor Receptcals @ 13.67 = $27.34
  • 120' gray PCV conduit 3/4" = $12.91
  • 6 PVC Elbows @ 1.57 = $9.42
  • 3 rolls 500' wire (white, green, black) 12 gauge stranded @ $20 = $60
  • 3 male PVC adapters @ $0.50 = $1.50
  • 2 PVC sleeves 3/4" @ $0.50 = $1.50
  • PVC glue 1 pint = $3.00
  • 1 transfer wall through box = $5.00
  • Total = $301.37
  • Businesses = FEW Concrete, McCoy's, Elliott Electric


Still under construction...