Dobsonian Project

After considering my options on a larger telescope the astronomynut decided to attempt his first homebuilt Dobsonian. The Dobsonian takes its name from the designer of the mount John Dobson who belongs to the San Francisco Sidewalk Astronomers. The mount allows easy tranportation to and from the field because as you can see in the example below the scopes tube and base can be easily separated. This tube size limits my primary mirror size to 6" and will have a F/8 focal ratio (remember focal ratio is 6 x 8 = 48 inches or the mirror diameter x the focal ratio of F/8 which is 1218mm). This should give the scope plenty of light gathering power, and the focal ratio will give it enough magnification for planetary observation, but being a smaller dobsonian will allow me to keep the object being observed in the field of view for longer periods of time.

There are several things to consider when you build your own scope. One is finances, as much of the components for the scope will end up costing close to if not more than a scope built by a reputable manufacturer. Second to consider is ability. Are you able to build or are you willing to get into such an undertaking as building your own. Third do you have the proper equipment to build this design.

If you do decide to build your own please wait till you have at least some idea of what focal lengths, aperature, and even the amount of patience you may need when you discover you have miscut a piece or you forgot to do something. Now, when you are ready, go to the internet, (link provided below) and download the plans. Then second head for your local Home Depot, or Lowe's and buy the materials needed such as tube, paint and wood. Then do what you can to find the formica needed for the bearing in the base (I will tell you that I used vinyl floor tiles for the bearing in my base with a small amount of Vaseline in between the two tiles which works well for me as I could not find any Formica). Then head to the garage, or workshop, or backyard and get to work.

The hard part is getting the middle of the tube painted you should have seen my arm!

The wonderful news is that the cost of the basic material is not very much. I bought half a sheet of three quarter inch plywood for about $8.00. The tube, which is a basic form for concrete (can alo be found at local hardware store in the concrete aisle), cost me about $6.00. Since I live in an apartment my father-in-law had all the appropriate tools at his home and was more thn happy to help with the cutting and construction of the base and prep of the tube. As I said before I used simple vinyl floor tiles that after testing several glided over each other well. I purchased three total at a cost of $1.50 apiece. The nice thing about these tiles is that they are also pre-glued and will stick to the wood in the base nicely. After I installed the two tiles into the base and finished the assembly of the tube I wanted to be sure the bearing would work, so I set the whole thing up (minus the optical components) and the bearing worked wonderfully.

Now assuming that you are getting close to finishing the main tube and mount you will want to start looking for the optics. Once again the internet can and will be your best friend. You can click on the links below to start your search for the perfect mirror, spider, and focuser. Or you can use the simple focuser and spider in the plans. I myself am going the commercial route so there will not be any errors in my construction. So keep an eye to the heavens and the other eye right here at The Universe to see the end results of my first homebuilt Dobsonian.