2. Astronomy

Observatory Construction

In my 20s and 30s I built two observatories and two observatory telescope mounts (among a number of smaller portable telescopes and mounts). The logistics of handling parts too large and heavy for one person to pick up are interesting. The photos in this gallery will give you a feel for what those projects were like.
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Polar drive assembly.
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Polar drive assembly.

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  • 66. MOVING DAY! A few friends gathered to help move the telescope parts up to the observatory. The parts were too large to fit through the door so they had to be passed through the dome slot. I barrowed a farm tractor with a front bucket to lift the parts up to the slot. The mount base is being connected for the lift in this photo.
  • 68. The heaviest part was the 480 pound fork. This was about the lifting limit of the tractor.
  • 70. Five of us carried the fork from the edge of the slot to the center of the dome and connected it to the hoist on the tripod.
  • 72. The telescope truss tube is ready for transport. The mirror cell is on the right. The ring in the middle is a 16" diameter clutch drum.
  • 74. Just reached the top of the hill with the truss tube in the trailer. The Gravely tractor has the engine in the rear, good for traction but not much weight on the front wheels. When the fork was placed in the trailer the front wheels lifted off the ground so a bag of cement was put on the hood to keep the front end down.
  • 76. This astronomer is happy because 1200 pounds of telescope is out of the garage and in the observatory. The next weekend it snowed and it would have been months before I could have moved the parts up the hill. (It was nice to get the cars in the garage for winter!)
  • 78. The scope sits on top of the tower welded up in the basement. The position of the scope is adjusted with the 1-1/8” diameter bolts on top of the tower (bottom of photo).
  • Polar drive assembly.
  • FLASH BACK 17 YEARS from 16” mount construction! While still in college I had the opportunity to cast and machine a 12 inch bronze gear in anticipation of building a large telescope mount with a big gear drive. After helping to setup the foundry in the new building at university shop this gear blank was the first item cast.
  • After cooling, the sand mold can be opened up to inspect the casting. After the third time to cast the gear blank I got a solid blank with no voids. (This was my first three times to make a casting ever.)
  • I used a horizontal mill to machine the teeth into the gear blank. The shop didn’t have a machine that was designed to cut worm gear teeth, so I modified this mill and the indexing head to do the job. I mounted the gear cutting hob and a spur gear on the mill arbor. A custom gear train was constructed between the mill arbor and the input to the indexing head. This rotated the gear blank at the proper speed while 240 teeth were cut into the periphery.
  • This photo shows the mill in action while I’m applying cutting oil. The mill had to run slowly to prevent vibration due to the very long arbor. It took close to 8 hours of machining to complete the gear.
  • The completed 12” worm and wheel set provided a 240 to 1 gear ratio.
  • 80. After the telescope was painted the mirror was installed in the mirror cell.
  • 82. The 100 pound mirror and cell assembly is carefully raised into position with a hydraulic jack and bolted in place.
  • 84. This night exposure of the observatory with the constellation Orion in the background was a little less than a minute long. The dome slot is only 5 ft wide, but by rotating the dome during the exposure the whole inside of the dome is revealed.
  • 86. There are three instruments on the massive fork mounting. The largest telescope has a 16” f/4.8 reflector. The long white scope is a 7.5”, f/10 refractor. In addition to observing, this scope was used to guide the 16” scope during long photographic exposures. The shorter white lens near the fork is a Canon 600mm f/4.5 telephoto lens fitted with a wide field eyepiece and used as a finder scope. This lens was also used for wildlife photography when not attached to the scope. The clock drive uses a 12” diameter bronze gear to move the scope and compensate for the Earth’s rotation. Over 125 pounds of welding rod was used in the construction of this telescope. The large wrench is used to align the fork mount with the Earth’s polar axis for tracking celestial objects. It took a year of spare time to build this telescope.
  • 88. This observatory was a pleasure to use until we moved in the mid 90s. The scope and observatory were sold with the house.
  • 90. Near first quarter Moon.
  • 92. Lunar close up.
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