Lancaster Observatory Dome
I purchased this unassembled 12-1/2' galvalume observatory dome on AstroMart in January of 2012. I was told by the seller that this dome is one of only two made by Lancaster Domes in Lancaster, PA back in the early 1990's, and is apparently the only one surviving. This dome was said to be the prototype for a dome built for one of their customers who was an amateur astronomer. That dome, as the story goes, has since been dismantled.
This prototype dome is a modified silo dome and appears to be closely modeled on an Ash Dome. It came with a set of uncut dome panels so if it was previously assembled as a prototype then the original panels were replaced with new ones when it was sold. I also received a generic Lancaster silo dome manual which explains panel assembly, but contains no information on how the custom base ring, aperture shutters and shutter tracks go together.
I did find an Ash Dome document online with some details on assembly, which helped me decipher the base ring and roller assembly, but unfortunately it's not a full construction manual. This dome has the two-piece rolling shutter as well as a drop-down shutter section.
This prototype dome is a modified silo dome and appears to be closely modeled on an Ash Dome. It came with a set of uncut dome panels so if it was previously assembled as a prototype then the original panels were replaced with new ones when it was sold. I also received a generic Lancaster silo dome manual which explains panel assembly, but contains no information on how the custom base ring, aperture shutters and shutter tracks go together.
I did find an Ash Dome document online with some details on assembly, which helped me decipher the base ring and roller assembly, but unfortunately it's not a full construction manual. This dome has the two-piece rolling shutter as well as a drop-down shutter section.
All The Parts And Pieces
Dome panels and base ring sections. The panels are galvalume while the base ring and track sections are galvanized.
Lower aperture fold out door.
These two sections of the shutter aperture tracks were damaged when I purchased the dome. Hopefully this won't be too hard to correct.
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Dome ring section. There are six sections to the ring. The diameter is marked as 12-1/2', but I have not assembled the sections to confirm this.
These look like parts of the shutter tracks.
The larger main shutter section sitting behind the dome panels.
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Lower Aperture Door Actuators
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I purchased these actuators for opening/closing the lower aperture door of the dome. They will replace the cable winch that came with the dome. The actuators are 38 inches long closed and extend an additional 30 inches. Hopefully I can make them work.
The actuators are rated at 12VDC @ 1.25A (no load) at 150RPM. That sounds like a lot of RPMs but it's not when you are just turning a lead screw. |
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This is a picture of the azimuth motor I plan to use on the dome azimuth drive. The motor is rated: - 12VDC @ 3.5A & 12RPM no load - 10 RPM @ 13A & 400 in-lbs of torque - 6 RPM @ 25A & 850 in-lbs of torque There is an electro-mechanical brake on the motor rated at 500 in-lbs. The motor was originally for extending a slide out on a camper. I also purchased a 12VDC 25A DPDT relay to control the motor direction. |
For comparison, one of the Exploradome automation packages uses a motor rated at just under 200 in-lbs of torque at 11 RPM to rotate the 8-foot Exploradome, which weighs in at about 225 lbs. I would guesstimate this dome to be in the 500 - 700lb range so I think this motor can do the job.
Drive Motor Power
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To power the azimuth motor I plan to use an old Compaq server ESP115 switching power supply. The 12-volt output of this supply is rated at 30 amps. I also used one of these to power the ExploraDome drive.
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Dome Rollers
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The dome rotates on 23 garage door rollers. I went the extra expense and ordered commercial car wash door rollers. They are 3-inch diameter polyethylene, sealed bearing, 4-1/2" stainless steel shaft rollers meant to survive wet environmental conditions. They are much higher quality than residential garage door rollers and should provide many years of trouble-free operation.
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Aperture Shutter Rollers
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The shutter rollers are 2-inch nylon, sealed bearing rollers with 6-1/2" zinc-plated stems. Not quite as high quality as the stainless steel dome rollers but still much better than standard residential garage door rollers. These are slightly larger in diameter than the metal wheels now on the shutters and I'm hoping that won't be a problem. But I won't know for certain until assembly time.
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Page created 11/27/2017
Last update 12/15/2021
Last update 12/15/2021
