8 inch f8 Dob

This was my first telescope project. The mirror was picked up at a good price because it was only so-so. The scope performs quite well up to about 160 power (10mm plossel). It is great for planets and brighter deepsky objects.

The construction is typical dobsonian. The base and rocker are made of exterior grade 3/4" plywood with a sink cutout used for the formica/teflon azimuth bearing. The tube is a mailing tube from Yazoo Mills. The mirror is mounted with silicone in a push-pull cell. The focuser is a homemade crayford type. Finding a source for the small bearings proved to be a challenge but I located them at Tower Hobbies. The bearings are used for R/C model cars.

After I finished the scope I decided I wanted digital setting circles (DSC) on it. I looked at the black box options but decided instead to link the encoders to my laptop. I built the shelf (left) to support the laptop and built a narrow battery box (shown below) that holds 2 gel cell batteries on top of each other. This setup is self contained with no wires leaving the scope to trip over












I decided on the Ouranos interface (attached to computer at left) and optical encoders by U S Digital.
For the altitude I used the T2 Inclinometer (left).
The Inclinometer lets you do away with the linkage between the bearing and rockerbox.
For the azimuth I used the standard S2 Encoder (below).








I use the planetarium program ECU for tracking the encoders. You can use it as as you would standard DSC or you can set the program to keep the scope position on the chart. As you move the scope the chart on the screen moves also creating a 'Virtual' finder scope that you can zoom in and out. I have had good results using the encoders except near the zenith where it is hard to maneuver the scope anyway. I just wait till the object is in a better position.