My scope is a 10" dobsonian design from Berry's book. The tube was constructed with 2"x 1/4" fir strips ripped from 6' 2"x 4"s The strip tube was covered by one layer of fiberglass. The tube rotates so the eyepiece is at a convenient height. The base is oak plywood. A variety of lead counter weights were formed by poring different amounts of lead into diet coke cans. The weights have a 1/4" hole drilled in them that slides on two 1/4 bolts. One bolt on either side of the tube base. A variety of weights were pored to match various cameras and eyepieces. A video camera is shown on a wooden camera mount held on the tube by a shock cord. Both video and 35 mm. cameras fit the mount. The dust cover on the end of the tube has a solar mylar filter which can be removed to give a variable aperture cover for viewing the moon and the brighter planets. The scope fits on an equatorial tracking table designed by Chuck Shaw (see http://www.tiac.net/users/atm/platform.html). The scope and accessories was awarded best first scope at the 1995 Table Mountain Star Party held near Ellensburg, Washington.

This is an image of my telescope Click for larger image.

A shock cord mounted camera mount holds either video cameras or 35 mm cameras aligned with the eyepiece.

Camera Mount Click for a larger images.

A solar mylar filter is mounted on the dust cap of the scope for solar observing. By removing one screw the top layer can be removed that has the solar filter exposing a variable aperture cap to control the light entering the scope when observing the moon and brighter planets.

Solar Filter Click for a larger images.

Variable Apeture Cap Click for a larger images.

The equatorial table designed by Chuck Shaw (see http://www.tiac.net/users/atm/platform.html) keeps the scope tracking. It is powered by a 6 volt battery. The control box varies the voltage supplied to a small motor. The voltage variation controls the motor's speed which is further reduced by two model car gears to drive the horizontal screw rod which moves the table supported on two aluminum rails ground for the local latitude. The rails are supported on 8 surplus bearings. A digital volt meter reads the voltage being applied to the motor and allows very accurate control of the tracking rate.

A new improved stepper motor ribbon drive and detailed pictures of the tracking table.

Tracking Table Click for a larger images.

A new improved stepper motor ribbon drive

A laser collimator built from a surplus lecture laser pointer, a few nuts and bolts, some scrap plastic and a film can. Disks A and B are 1 1/4 inches in diameter with a 2 mm. in diameter hole in the exact center of the disks. Disks C and D are 3 inches in diameter with a 2 mm. in diameter hole in the exact center of each disk. Disks A and B are held exactly aligned by three bolts. The A B disk assembly slides into the focuser tube to have the laser beam aligned with the focuser tube. For this reason, they should fit snugly into the tube with no play. Disk C is screwed to disk B. Disks C and B need to be aligned so their center holes are exactly aligned. Disk C and D are held together by three bolts. There is a spring placed around each of these bolts holding the disks apart. This spring makes adjusting the alignment of these disks easier. The three bolts are used to aligning the laser beam with the holes in Disks A and B.

A box that fits the laser unit firmly, so there is no play, is attached to back disk D so that the laser beam passes through the center of the hole of disk D.

To aligning the beam, you need a "V" trough that is about 1 1/2 inches on a side that joined at a 90 degree angle. This trough is attached to a solid base at a convenient height, about shoulder high is best. Disks A and B are laid in the trough. By rotating the unit 90 to 180 degrees and watching the laser spot on a wall 20, or more, feet away you can see if the beam is exactly aligned with the disks. If the beam stays fixed as the unit is rotated, it is aligned. If the beam moves, the screws holding Disk C to Disk D are adjusted until the beam is aligned and does not move when the unit is rotated in the "v" trough.

You will need a target for the beam illuminate. I found I could not make disk A and B far enough apart so that disk A was at one end of the focuser tube when disk B is at the other end. If I used screws that long, I got play in the unit.

I took a plastic 35 mm. film can and drilled a 2 mm. hole in the exact center of the base of the can. There is usually a bump on the base to help determine the exact center. I painted the bottom of the can white.

Prior to aligning the mirrors you should check that the focuser tube is exactly 90 degrees from the axis of the telescopes tube and that the diagonal mirror is aligned in the exact center of the focuser tube when you look down the central axis of the focuser tube. The center of the primary mirror should have been marked by a felt tip marker or a notebook paper hole reinforcer.

To use the calumniator slide the film can, white side toward the diagonal mirror, into the focuser tube from inside the telescope. Next, slide the laser unit into the focuser tube from the outside. Disk A is then deep in the focuser tube, disk B is just inside the tube and disk C is resting on the lip of the focuser tube. Turn the laser on and the beam will hit the diagonal and be reflected to the primary mirror.

Adjust the diagonal mirror so the laser beam lands on the exact center of the primary mirror. If it does not hit the center of the primary, adjust the diagonal mirror until the beam hits the center.

The beam is then reflected back to the secondary mirror and from there onto the white surface of the film can. If the reflected beam hits the hole exactly everything is aligned. If it misses the center of the can, adjust the primary mirror to move the laser beam to the exact center of the film can. Most scopes will require a second person to adjust the primary mirror mounting while the first person watches the bottom of the film can and directs the person adjusting the primary mountings.

Once the beam hits the hole in the can from which it started, your mirrors are aligned. Alignment typically takes 2 -3 minutes and can be done in the daylight.

Laser Collimator Click for a larger images.

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