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The Basic Roll Off Roof Observatory

The roll off roof observatory was built in 1995 to house a C-8.   The scope has been upgraded to a C-14 with the C-8 now used as a biaxial guider.  The building has since been expanded to include a warm room with two computers.  One computer controls imaging [ST-10ME, ST-6B or ST-4 cameras] and the second computer controls the Astrometric Skywalker II drive system.  This is a custom installation.   [www.astrometric.com] .  

The images below are thumbnails and can be clicked on to see details.

On Aug 22, 2001, we had a small tornado come through our part of the county. It broke several large limbs from trees in the back yard and tossed them over the top of the house into the front yard. It reeked general havoc on the neighborhood ripping roofs off sun-rooms and blowing out windows. My electronic weather station on the roof of the house recorded wind gusts from the north at 46.3 mph at the height of the storm. The observatory came through unscathed except for little rain that blew into the side wall vents!

I would be glad to consult with anyone who wants to build one of these darn things.  Please let me know if you have any questions. I'm always happy to help. The advice is free...dumb looks cost a little extra.

The original 8'x8' observatory took about 2 weeks for my youngest son and me to build in our spare time.  It is constructed from 2x4 framing for the wall sections and reverse board and baton siding. The base is 3/4" marine plywood over a 4x4 pressure treated lumber frame on 24" centers. The roll off roof is again 2x4 construction with the same siding as the walls.  The roof is standard roofing shingles over 1/2" plywood sheeting. [total raw material cost ~$500]. Because the roof is not attached to the walls, the walls will "rack" or form a parallelogram, if not reinforced. It is necessary to install diagonal braces or gussets at the top of all of the wall corners. These gussets are only about 1 foot long, but they will keep the walls square when the roof is rolled off. Measure the diagonal across thewheelbox.jpg (39723 bytes) observatory's open roof before installing the gussets. Make sure that the diagonals are identical before securing the gussets. A gusset is shown here with one of the roll off roof roller wheels.

The observatory itself just sets on the ground. I have put a 3" thick concrete garden paver pad at each corner to keep the unit from sinking into the ground and to allow me to shim each corner separately when necessary to keep the unit level. The roll off rack has 2 - 4x4s at the corners which act as part of the wall framing for the warm room which was added in 1998.

The roll off roof is locked closed when not is use. The locking mechanism is simple...just two padlock hasps inside the observatory which hold the roof secure to the inside wall. I have a photo of one of the hasps here hasp.jpg (20060 bytes)

in the locked position. The twist part is attached to one of the 2x4's at the front edge of the roof and the hinged portion is attached to a 4x4 which is part of the wall plate. The hinge allows the hasp to fold out of the way when the roof is in use.


The observatory floor is made of 3/4" marine plywood on pressure treated 4x4's at 12" centers. The walls are standard stud construction on 16" centers. Wall height is 7 feet. The floor now sets on 24" square concrete pavers which are blocked to keep the floor level. [Click on picture for higher resolution image



This photo shows the detail of the 6" pier going through the floor of the observatory. There is a 2" clearance around the pier so that the vibrations of the floor do not transmit to the pier. I later had to affix a rubber boot around the bottom of the pier and attach it to the floor of the observatory. The reason was that mice were coming in through the clearance gap and making a home for themselves in my computer. The computer had a 7 watt bulb in it to keep the hard drive warm in the winter. The mice made them selves right at home. Eventually, the computer quit working and I had to take off the cover...that is when I found the mice. They were living in the Pentium Hotel!

I used roller blade wheels [urethane] for rollers to support the roll off roof in the original construction. In the winter, they became flat on the bottom and I had a hard time getting over any ice which had built up on the roll off frame.  In 1997, I welded up some 16' long 3/4" "V" tracks from 3/4' angle iron laying on its base.  I bought 4 - 4" diameter cast iron "V" wheel rollers from McMaster Carr [$24 each] and now the roof rolls on the 4 wheels. It crushes any ice which forms on the track and rolls off easily in just a few seconds. The "V" rollers are held in place by wooden boxes which are attached to the roof.  A close up of the wheel box can be seen herewheelbox.jpg (39723 bytes).   

The roof can easily be rolled back with one hand. 



This is my son Aaron, who helped build the observatory, showing how easy it is to roll the roof off. It takes about 10 seconds.




These are three photos of the observatory [pre warm room] with the C-14 in place and operational.

This image shows the scopes and mount.  It also shows the entrance to the warm room off to the right.MVC-564S.JPG (128828 bytes)  The small fan that you can see just below the monitor runs all of the time.  It keeps condensation from forming on the pier and the mount when the temperature rises rapidly [common problem here in Indiana in the spring].


The observatory is painted white to minimize heat build up. I have also installed 4"x8" passive louvers in the side of the roll off roof and in the lower west side of the observatory to let out any heat build up that might occur.  It typically takes about 60 minutes for the C-14 scope to settle down on summer nights. [Much less time in the winter] In 1999, I added a powered vent on the high portion of the roll off roof.  

Click Here MVC-559S.JPG (119012 bytes)to see a photo of the vent fan.  This fan is set to come on at 80F. It pulls ambient air into the observatory and keeps the building from being hotter than the outside air.  I have found that t his also helps the scopes come to equilibrium more rapidly in the evening.  It is imperative that the scope be covered with a cloth when using a powered vent, otherwise the dust buildup on the scopes and related equipment is devastating!                                            

This is a view of the interior of the warm room.  Definitely a great invention on those cold, breezy nights.  MVC-569S.JPG (146646 bytes)When I built the observatory, I buried a CAT3 [use CAT5 these days] computer cable along with the AC power line and phone lines from the house to the observatory.  An Ethernet hub in the observatory attaches the two computers to the network.  I am now able to control both the scope mount and the cameras from two computers in my house.  [Which is great on cold Indiana nights!]  I am using Microsoft NetMeeting software for the remote control.   This runs over a simple Ethernet system and is isolated from the internet by a router.  This is great for long runs and cold nights.  It is theoretically possible to remote control the observatory computers from anywhere in the world.  

One that that I wish that I had done differently was to have run conduit from the house to the observatory.  I just buried the cable in the ground and now I am stuck with CAT3 cable.  If I had run PVC conduit, I should have been able to updated the wiring as needed.

MVC-396S.JPG (107645 bytes)I am in the process of building a flat field screen.  TheseMVC-399S.JPG (64363 bytes) images show two perspectives of the screen and the reflector.  Essentially, I shoot through a piece of translucent Plexiglas which has been front illuminated by arrays of incandescent halogen 10 watt, 12 volt garden spotlights mounted to the Plexiglas and pointed at a reflective white screen on the observatory wall.  I run the spots at 5-7 volts for flats in the R and V bands and at the full 12 volts for flats in the B band.

You really can't go too far wrong with the system as long as the roof rolls off easily and the floor does not touch the pier. My pier is concrete filled, I have heard that it will "ring" less if you fill it with sand rather than concrete. The pier is 6" cast iron pipe sunk 3' into the ground in lots of concrete. Make sure that the pier is absolutely perpendicular before the concrete sets.

The warm room [see photo to right] was added to the observatory in the summer of 1998. It really helps keep me out of the wind on those long winter runs and allows me to sit down to run the computers. MVC-569S.JPG (146646 bytes) The photo shows the computer on the left for controlling the CCD camera, the computer on the right for controlling the mount, and, above to the left,  the video monitor for the TV camera.  

I have also "piggybacked" a C-8  under the C-14 for MVC-567S.JPG (99175 bytes) lower power viewing and in line guiding. The C-8 can be adjusted separately [biaxial adjustment] for RA and Dec so that I can do guiding at high power on the C-8 and the ST-4 while imaging through the C-14. The photo on the left shows the biaxial adjustment details. 

 Another addition was a CCD video camera which I have mounted to a 1.25" tube so that It can be put in place of any eyepiece. I can actually draw a "+" sign on the screen of the monitor and use it for guiding from the lower power [C-8] scope or I can put it on the higher power scope to show groups of visitors what the scope is "seeing"

I have also found the TV camera invaluable for scope collimation. I set up the scope for eyepiece projection but use the video camera rather than the CCD camera. I can adjust the secondary mirror on the SCT's while simultaneously viewing the concentric ring image in real time.