Mon, 04/18/2022 - 11:15

Richard Berry presented a wonderful webinar on observatory construction. I just wish he had done it 20+ years ago before I built MY roll off roof observatory!

Over the years I've identified flaws with my design. The major one wasn't seen until years after construction.

That flaw is in using V Groove wheels on both sides of the roof, both running on inverted V angle iron tracks. Why is this a flaw you ask?? Because over the years of weathering and settling those angle iron tracks are no longer perfectly aligned. That means that at some point in opening and closing the roof the wheels on one side or the other are actually being pushed slightly "up hill" on the tracks. Its not too bad, but pushing the heavy roof up hill takes an effort. To counter this I have installed a manual boat winch to open/close the roof.

Longer term, erhaps this summer, I will replace the track and wheels on one side with flat track and wheels, thus eliminating the up hill pushing issue.. 

OK, what mistakes did YOU make??




American Association of Variable Star Observers (AAVSO)
Dome vs rool off

My biggest mistake was going with a dome instead of a roll off.  As I got older, physically navigating the dome became more difficult where as a roll off wouldn't be a problem.  The dome also adds complication to automation. 

If I had it to over, I would install a really nice roll off with lots of room. 

American Association of Variable Star Observers (AAVSO)
Pier location

My biggest mistake was in setting the pier in the center of my 10x12 ROR observatory.  With equipment hanging off the back end of my SCT I have very little clearance between my work area and the scope.  With next ROR observatory being constructed next year I will offset the pier to the south.

American Association of Variable Star Observers (AAVSO)
Flat Track and Wheels

Hard rubber wheels on a flat track has worked well for me for the past 25 years.  Some people caution about the wheels flattening under the weight, but to avoid this make sure you use enough wheels.  For example, if your roof is estimated to weigh 500 pounds and a wheel can handle 50 pounds maximum each, then that would call for for 10 wheels total, or 5 each side.  Add more to keep the weight on each wheel lower than the maximum (say 60%) and you should get good service for many years.  I have wood strips on the outside of each track to ensure the roof doesn't wander off the tracks (never has).

American Association of Variable Star Observers (AAVSO)
A roll-off roof that doesn't…

A roll-off roof that doesn't roll easily is a pain that appears twice every night!!  Didn't think about the observatory shifting and "pushing" uphill.  I will have to check the level of the rails and walls.  Thanks.

Mine used ball bearings in a race and I am trying to fix after 23 years.

Other mistakes I have made with past observatories......

Adapting a "old" observatory to a new site.  It is easier to just build a new one.

Thinking a small leak is tolerable, particularly since I live in a desert.  Nope, change design and construction that water goes away rather than towards.  After a bit of time, it is impossible to seal!!

Not putting in additional storage or a warm room.  Everything migrates to the observatory over time. 

Putting in a drop wall to the south.  Easier to take a scope outside.  Don't remember using it at all.

Having a low roof.  I have been wearing a hat for 23 years inside the observatory to somewhat protect my skull. 

The mistake I made was thinking I would ONLY use the observatory with the roof open.  You end up spending lots more time out there than you realize.

One thing I did just recently, was buy a Quark Chronosphere.  That meant I could use the scope and my gear during the day.  That is real helpful in making sure everything functions at night!!  Hopefully, I will no longer waste a night with gremlins and instead will deal with them during the day.

All that said, the worst observatory in the world is much better than setting up every night.

American Association of Variable Star Observers (AAVSO)
What I learned from the first iteration

The first iteration of my observatory roof blew off in a night of high winds and rain, and landed up-side-down about 100 feet away.

I built the observatory as a deck with four-foot-high walls. The roof rolled on the top 2x6 pressure-treated lumber top rail of the wall on hard rubber tires. The first roof had been too low, so I could not stand full height and could not exercise the scope through its full range of motion. I designed a new roof with 24-inch side walls, providing ample headroom. With the roof rolled off, the telescope was fully open to the sky, but the observer felt enclosed by the four-foot high walls.

The first roof had used hard rubber tires running on the 2x6 wood rail of the wall. Over time the wood splintered and that made it increasingly hard to roll the roof. I retained the rubber tires system for the new roof for a while, but finally the deteriorating rail decided me to install a vee-track and grooved wheels. Aleko sells both the track and wheels for rolling gates. Installing the tracks and wheels without removing the roof meant lifting the roof one side at a time, removing the old wheel assembly and putting in the vee-groove wheels, then slipping the track segments under the vee-groove wheels onto the top rail. 

In retrospect, I got something important right: instead of screwing the rail down tight, I tacked it lightly using galvanized roofing nails. The holes in the track were considerably oversize for the shafts of the nails, so the track was free to move a bit side to side but still could not escape. Once I set the wheels back on the tracks, the tracks shifted to bear the load equally. I was delighted: with steel vee-groove wheels on steel track -- I could roll the roof with one finger. Furthermore, because the track was able to move a little bit, the wheels never did bind as time passed. Buildings should be "live" and able to adjust as time passes.

Although it was feasible to route power to the observatory from the nearby barn, getting Internet connectivity was more difficult. I actually rolled out 450 feet of Cat 5 cable for a short time around the 2017 solar eclipse. I liked it so much I wanted a permanent setup. The solution was to install a point-to-point wireless bridge from the house to the observatory. In theory, the bridge had a range of 3 km, so it worked great at 100 m and did 25 mbps reliably. I used Chrome Remote Desktop to run my observatory computer from my home office, and could allow students to operate the telescope and camera remotely from Portland (or anywhere).


American Association of Variable Star Observers (AAVSO)
Observatory Mistakes??

These are great stories from the collective wisdom of AASVO observers!  I have a 8x8x5 roll-off now, but will be moving soon to a site just east of Mt. Pinos at 5,500 feet and will need to build a new roll-off.   I agree with Richard Berry, those hard rubber wheels on a steel U-track (I think these are used for the sliding shower doors) have worked great for  me for the last 15 years and I will use these.   However my roll-off roof, while fully leak proof, used interlocking flat galvanized aluminum sheets which are probably a poor choice in an area that gets snow fall.  I will probably need to get an angles roof with tile to survive the winter storms near Pinos.