 | The MountNote: This astrophoto rig no longer exists since the destruction of my observatory (details on my observatory page), but I leave this page here simply for the history of my involvement with the Schmidt camera.Yes, this is not the same mount described in the text below, but it is close. Think of this a the Mk.1 mount and the current mount is the Mk.2. This is the only good scanable photo I could find of the mount, even though it is out of date. |
The Schmidt camera is mounted side by side with a classic orange Celestron-8 optical tube assembly which acts as a guide scope. Both instruments are mounted atop a circa mid-1960's Optical Craftsman German equatorial mount which once held a 10-inch Newtonian. The mount itself is bolted to a 10-inch steel pier which is filled with loose sand to dampen vibrations. The mount is all original equipment except I drilled the polar shaft and T-drilled the declination shaft to make a Polaris peepsight to aid in polar alignment back when the mount was used as a portable setup.
The original equipment clock drive gear is made of aluminum. When I bought the mount used at a garage sale in the late 1970's, the gear was so severely corroded that it would not work. After dismantling the drive assembly, I actually sandblasted the gear to remove the corrosion. Not being able to afford a new gear at the time, I reassembled the drive using the sandblasted gear. To my surprise, it actually worked. The drive has a 120 arc-second periodic error, which sounds horrible, but it is quite workable. This is no worse than the drive on my 1975 model Celestron-8. Needless to say, this drive keeps me wide awake while manually guiding with such a periodic error.
After some experimentation with a steel frame to support the Schmidt and its guide scope (as illustrated in the photo) , I realized that the more I reinforced it to stop flexure between the two instruments, the worse I made the flexure because of the added weight. I thus turned to a light-weight 3/4-inch plywood cradle reinforced with steel brackets to support the Schmidt and its guide scope. The cradle resembles a broad shallow box with twin semicircle cutouts on two sides to nestle the Schmidt and guide scope tubes. The instruments are then strapped into place with 1/2-inch steel banding material. This lighter assembly works well and has displayed no flexure at any shooting angle over 40-minute exposures. As a bonus, the lighter mass of the plywood mount required only half the counterballance and turned mounting the assembly back into a one-man job.
Go to next page ---- The Film