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Observatory Construction

Updated: 06/05/2012

The Hidden Loft Observatory arose from a desire to have a permanent observing position for CCD imaging that would be consistent with the covenants and restrictions of our homeowner's association. No outbuildings were permitted so a conventional observatory was out. Since I had a single bay garage for a workshop and astronomy storage area attached to the house, I decided to design an observatory with a roll-off roof in that garage. This design would keep the roll-off structure below the parapet that surrounded our home and, as such, was compliant with the association’s restrictions.

In addition to the roll-off roof, I had to build a platform or deck approximately 8 feet off the garage floor, install an isolated concrete footing and pier and run the necessary cables to the office for remote telescope control. In order to clear the parapet that surrounded the existing roof, an elevating pier was needed. With the Pier-tech 2, I thought I would be able to raise my scope above the parapet for a clear view to the horizon, except where mountains got in the way. The design also had to insure the scope would fit below the roof so that the roof could be closed. This required very careful analysis and modeling.

The design work started July 5, 2001 with many revisions and checks.  Here are drawings for the south elevation view, the east elevation view and the concrete plan. 

 

South Elevation

East Elevation

Concrete Plan

 

Basically a 6½ ‘ square hole was cut in the roof of a single car attached garage. The roof rafters were supported on either side of the opening by (2) 4 x 12 beams resting on 4 x 6 posts. A deck was installed at 8 feet above the garage floor supported by a frame of 2 x 8’s attached into the posts and wall studs. Folding attic stairs were originally used for deck access. I later replaced them with permanent stairs.  The deck was covered by ¾” CDX plywood. The roll-off roof frame and tracks were constructed in another garage and checked for squareness and function. Angle iron was used for the track and (4) 4” V-groove wheels from McMaster-Carr were used to carry the roof. It was then disassembled, hauled up to the roof and reassembled. The roof sheathing and roofing material was then applied to the roll-off roof. The tracks were sealed and painted. I added a thermostatically-controlled exhaust fan to minimize the heat buildup during those hot Tucson summers.

Actual construction started July 17, 2001.  Here are some photos of the process.  Click on them for a larger image.

 

Cutting the hole in the roof. Big first step!

Deck framework and stairs

Deck hatch open

Deck hatch closed

View from the deck to the south.

Roll-off roof frame and rails

Cut here!

2 feet deep and lined with foam.

3 ton pad poured.

Bracing for pier pour.

Looking down the empty sonotube.

Pier poured and mounting plate installed.

Bracing removed.

Telescope in place.

Roll-off roof closed.

Ready for business!

 

The pier footing was approximately 48” x 48” x 24”. Rebar was in place for the pier before the footing was poured. An 18” sonotube was slipped over the rebar and filled from the top. The top view of the pier shows the nails that were used to gauge the concrete fill level. North was determined by a compass, offsetting for the magnetic declination. It was confirmed by checking the shadow cast by a plumb line as the sun crossed the meridian.

Outlets were liberally provided. Lighting consists of two circuits – a red one and a white one. The red circuit is on dimmers and controls red rope light that runs along the east and west side of the observatory. Power supplies for the camera, mount and pier are located under the deck flooring and are accessible by a removable panel. Power is controlled by an X-10 power line controller from the office, as are the red lights. All AC is on a GFI circuit. A web cam is used to view the telescope during slewing if desired.

The observatory is connected to the office by a 1 GHz Ethernet network. The actual run is around 60 feet.

First light was on September 18, 2001 and boy do I love it! There is enough space for my scope and one or two observers. Not any more - with the new scope, it is considerably tighter.  I leave the elevating pier in its down position for CCD imaging, raising it only for visual work. I have approximately a 15° to 20° horizon with the pier in the down position. In the design I had provisions for a garage door opener to open and close the roof. This turned out to be unnecessary. Given the pitch of the roof, all I have to do is release the locking hasps and untie the rope. The roof opens smoothly. There is very little effort required to close the roof by pulling on the rope and tying it off to a nearby cleat.

Once the roof is open, all other control is from the office. I use my X-10 controller to power up the system. Most image capture, along with dark frames, is acquired by CCDAutoPilot4 so it occurs while I sleep. In the morning, I power down the system from the office and close the roof. The only real back-and-forth between observatory and office is if I need to take light box flats.  I generally prefer sky flats and most often use them.

I hope this gives you some ideas for your observatory!

Macedonian translation of this web page (by Web Geek Science

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