Starlight Cascade Piers and Observing Deck

Page last updated: 2003 September 17

Start of the Project: 2002 August 26
Completion of Project: 2002 October 06

Intro

We moved out of the city of Kingston to a dark-sky site (at least relatively speaking!) about 30 minutes away in the summer of 2002. The first thing we need is a place to observe and the best spot looked like out in the back yard, but tripods are most always inferior to piers, especially if you want to polar align an equatorial scope.
So we decided to put in a couple of piers and an observing deck to get up off the ground as a precursor to a full blown observatory (coming next year!).

Benefits

  • a pier would give us the ability to accurately and permanently polar align an equatorial mounted telescope.
  • a deck would get us up off the cold ground

    Pier Design

    We tried out a pier designed by Mark Kaye made out of four 2x4's with sand in the middle to dampen vibration.
    Parts List
    One pier:
    four 2"x4" x 8' regular (non-pressure treated)
    #8 by 2.5" wood screws
    carpenters glue
    one bag dry sand
    two bags of readymix concrete (just add water)
    
    Deck:
    x10 5/4"x6"x10' pressure treated decking
    x2 2"x6"x10' pressure treated (long outside support)
    x1 2"x6"x10' pressure treated (short outside support)
    x4 2"x4"x10' pressure treated (short inside supports)
    
    Mount:
    1'x2'x 3/4" plywood
    
    Supplies needed:
    drill, robertson screwdriver, concrete mixer, level

    The Assembly

    The Pier
    1. Predrill pilot holes for the screws into a 2x4. Put glue down along the edge and put two pieces of 2x4 together into an "L" shape. Screws should be no more than 12" apart.
    2. Repeat for the last two 2x4's. You now have two assemblies of two 2x4's.
    3. Put the two assemblies together with glue and screws as above. Let dry
    4. Dig a hole on the pier spot below the frost line or down to bedrock. We went down about 28" to solid rock.
    5. Put the pier in the ground and mix up the first bag of readymix concrete. Pour it in the hole around the pier and tamp it down with a spare 2x4. Mix the second bag (as many as necessary) and fill up the hole to just below the surface (so you can cover it up with dirt, grass or sod and not have to worry about the lawnmower). Tamp it down to release air bubbles. Use the level to insure perpendicularness and tamp concrete to suit. This stuff hardens within 20 minutes. Cover and leave to cure overnight.
      That went so well that we went off and gathered the materials for the second pier and the deck, and within a short time, the second pier was in.

    The Deck
    We used pressure treated wood, 1.25"x6"x10' decking
    The trick here is to ensure that the deck does not come into contact with the piers and you can notice the 2x4 supports grouped close to the piers and the decking cutouts around the piers.

    The mount
    The last step was to assemble the mount.

    1. A suitable height was determined by measuring the primary observer's height and the estimated height of the telescope with mount. The pier was cut off to that height using a skill saw along all four sides.
    2. scrap 2x4's were then mounted around the pier to create a larger top surface, making sure that they are level
    3. fill the pier with dry sand. It doesn't take all that much, maybe 1/2 bag or so. Our sand was wet and we had to spread it out and let it dry first.
    4. Two circles of plywood are cut out, approx 12" in diameter (or whatever size your largest dinner plate is). Drill 1/4" holes through the centre of both circles. We mounted a 1/4 x 20 3" bolt from the bottom up, gluing it in place on the bottom so it doesn't turn. Glue and screw the first circle onto the 2x4's.
    5. The second layer is meant to fit overtop of the bolt and move around until the most accurate polar alignment can be made, then it is permanently screwed into the first bottom circle.
    6. With our particular metal mount, the tightening knobs extend below the bottom surface of the metal mount itself, so we had to make another circle, smaller than the others, to place the metal mount on. We measured to suit, drilled a 1/4" hole in the centre as well and mounted the small circle to the top larger circle.
    7. With the 2nd large circle still "loose" on the platform, we then placed the metal mount on top, used a large washer and a wingnut to tighten the entire assembly together
    8. That night we polar aligned the best we could, tested it again the next night and finally secured the second circle to the first one with three more screws.
    9. The telescope and metal mount came off and the whole thing was varathaned several times, with some decoration (stenciled stars) put in first.

    After the fact

    The piers and deck have survived the winter and we actually got out and used them quite often. The decking does need some kind of anti-slip treatment, especially in the ice and snow.2003 July 15: We found some sticky antiskid tape in a local hardware store after months of looking. We've been using a heavy guage plastic bag that fits over the mount and pier and is secured with bungie cords. The plastic has not survived the winter too well so we are looking for a better, heavier-duty UV resistant kind of cover, possibly the alumnized mylar/tarp material.
  • 2003 September 03: Extended the deck from 5'x10' to 8'x10' in preparation to cover it with a metal shed that will be used as an observatory.