Supplies for building a homemade telescope

Finished scope with a child for scale.

Finished scope with a child for scale.

Everything that went into the scope

This list is based on the list from the SF Sidewalk Astronomer telescope plans, but contains only the supplies I used. In most cases, I’ve tried to be clear where I found the supplies, and costs.

Concrete column form (Sonotube) (1): This is for the tube. If you’ve researched homemade scopes, you’ll have heard the word Sonotube mentioned repeatedly. Sonotube is a brand of concrete column form used by construction companies. I never managed to find an actual Sonotube, but other brands are readily available. Even Revy and Home Depot had a number of diameters in stock. I phoned around and found some at BrockWhite, a construction firm with offices in Winnipeg. Cost was less than $8. for a 12 foot length. They cut it into two five-foot lengths for me, and discarded the last two feet. I figured that if I ruined the first five feet, I could start again on the second. This was very sturdy cardboard tube that felt almost like wood. Thickness of the walls was between 1/8 inch and 1/4 inch.

Exterior grade plywood (1): One sheet, 4′ x 8′ x 3/4″. The lumber yard made the cross cuts for me, five of them, according to the SF Sidewalk Astronomy plans. Like the plans said, I used only half the sheet of plywood. Total cost, including the cuts, was about $34.

Paint and painting supplies: I used a whole can of flat black spray paint for inside the tube. I purchased a small can of primer/sealant and a small can of exterior gloss latex paint for the tube and mount. Total cost, including a paint brush, about $40.

Sheet Metal Screws: Panhead, size #8, 3/4″ long. I got a small package for less than $2. I used these to hold various items in place on the tube.

Nails: I got one small box of 1-3/4 inch box nails at a cost of about $2.50. These are used in the construction of the Dobsonian mount.

Machine Bolts (3): I got a small container of 6, 1″ long; 3/8″ in diameter. Cost was about $2. These are used as the collimation bolts on the mirror cell.

Lag Screw with matching washer (1): One lag screw, 3″ long; 1/2″ in diameter. I bought these as separate items at Revy. These are used to hold the top of the mount to the base. The lag bolt is the pivot point for azimuth movement of the mount. Cost was about $ .80 total.

LP Record (1): We used to have these around the house, but apparently we got rid of them all in a garage sale. I was about to purchase a sheet of plastic laminate 2′ by 4′ from Revy for $2.47, when I thought to call my in-laws. My in-laws gave me four LPs they had in their “throw out sometime soon bin.” I ended up using a Mario Lanza record. This forms kind of ball bearing that rides on top of three pieces of Teflon on the mount base, and allows really smooth azimuth movement. Cost, $0.

Chrome-plated Brass Tubing (PVC tubing): The plans called for chrome covered brass, but I found two lengths of black plastic PVC pipe that looked perfect. One of the alignment check, one for the inside of the eyepiece tube. In the end, I think it’s necessary to find the chrome plated tube. The black PVC is hard to see when doing alignment. I managed, but I think the chrome plating would have made the job easier. Total cost, $3.50

Cedar Shim Shingles: Revy had nice little packages of cedar shims, about 8″ long, for under $4. I bought a package. Probably 12 or more shims in the package. These will be used for making the vanes on the spider, to hold the secondary mirror in place.

Wooden Dowel: The plans call for a dowel 3-1’2 inches long, 1-3/4 inches wide. I bought a 4 foot length from the lumber yard in case I made mistakes. This is attached to the vanes and becomes part of the spider. It’s used to hold the secondary mirror. Cost, about $5.

Cardboard “Mailing” Tube: One piece, 1-1/2″ inside diameter, about 2″ long. Staples had these mailing tubes in a number of diameters. This is used to make the focuser. The 1-1/2 inch tube was $1.57.

Thumbtacks (3). I bought a small package for $1.50 from Revy. These are used in the construction of the tailgate, primary mirror cell.

Leather Scrap: Three small pieces-about 1/2″ square. I cut these from an old belt with a broken buckle. These are used as a base for mounting the secondary mirror.

Sticker or Decal (1): This was to mark the centre of the mirror to aide in collimation. When my mirror arrived, however, it had a tiny black spot in the centre from a marker. This worked perfectly, so I didn’t bother getting a sticker. I had planned on using paper reinforcers for binders.

Masonite: More generically called hard-wood. These come in nice smooth sheets. I purchased a 2′ by 4′ piece for $4. To be used as backing for the eyepiece tube and for mirror supports on the tailgate.

Teflon: (7) I needed 7 pieces, three for the base 2 each for each side of the tube-box cradle. I purchased a package of 7 pieces from Peek’r Technologies, where I purchased my primary, secondary, and eyepiece. Teflon is used to allow smooth movement along the azimuth axis, as bearings between the base and top of the mount. Four pieces are used in the cradle as altitude bearings.

Furniture stop nails (4) The plans call for Furring nails. Furniture stop nails have plastic or Teflon tops, about 1/4 inch high and wide, to protect doors and furniture from hitting things. These worked fine for me. They’re nailed into the small pieces of wood used to mount the primary mirror (mirror mount blocks), and stop the mirror from falling out of the front of the telescope tube. A small box was $1.50.

Glue: I bought one tube of some kind of wood-bond. Cost was $5.00 approximately. I also bought a tube of silicone glue to reinforce some of the bonds, cost another $5.00.

Telescope Objective Mirror (1): I looked around, and ending up in an email conversation with Ken Saumure of Peek’r Technologies. Although the cost of his mirrors was more than other places I looked, I liked the service, and ordered through him. Cost: $225 for a six inch mirror at 1/8 wave. I placed the order on a Monday afternoon, the mirror (and everything else from Ken), arrived two days later by Greyhound Bus Express Delivery, at a cost of $20 for shipping.

Cardboard: The back of a cardboard breakfast cereal box works nicely. And that’s what I used. Used as part of the tailgate/cell assembly to support the primary mirror.

Telescope Diagonal Mirror (1): I asked Ken at Peek’r Technologies what size of secondary I needed, and he told me. I ordered it with my primary. Cost, about $40.

Eyepiece (1): Again, I ordered a 20 mm Plossl from Ken at Peek’r Technologies. Cost. $85.