Scorpius

The main observatory floor has been framed but the “pod” has not. I hope to frame the pod floor this weekend so all the sheathing can be installed at once. Plan to use ¾” plywood coated with an epoxy paint containing a slip-resistant, grit-like material and that will be the finished floor surface. Used this in one of my storage sheds & it creates a nice weather resistant surface that holds up well. The observatory is 12 ft. square on the outside which translates to about 11 ft. 4 in. square on the inside. Been debating how large to make the pod & now I’m thinking of going a little larger than originally planned – probably 6 ft. x 6 ft. I’ll eventually construct a proper control room but have resigned myself to the fact that won’t happen this year. Therefore, the pod will give me a place to stay somewhat warm this winter & keep the dew (which often turns to frost) off me and the laptop. Like John who’s building a Fenland Observatory, I’m now in a race against mother nature to get this structure dried-in before ole’ man winter visits the Blue Ridge Mountains of Virginia once again. The roof is what concerns me most as I’ve never built a rolling roof before however, I usually do my best work under pressure so guess we’ll see...

I find it intriguing that discussion of pier design generates such strong opinions even more so it seems than choices of equipment like OTA’s, mounts and cameras. First and foremost, I’d like to say - I completely understand the need to forego a substantial pier solution when the proposed site may not be long term - which apparently is the case for many following this thread. Yes, there are codes which regulate foundations for houses and I happen to be very familiar with those in the US since I work as a building inspector (18 years’ experience) and have about as many years’ experience working construction prior to my current job. Foundations (footings) for structures must be placed on undisturbed soil of suitable bearing capacity and installed below the frost line to prevent a natural phenomenon called frost heave where frozen ground can actually lift tremendous weight and then lower it again as the ground thaws out. In terms of structures, it’s this up and down movement over time that can crack foundations and create other stresses that negatively affect a building’s structural integrity. Obviously, in warmer climates frost heave isn’t much of a concern (hence the more shallow code-defined frost lines in those areas) however, not everyone lives in a warm climate. So it’s a given that frost heave can exert the same type of force on a telescope pier which completely negates any attempt at permanent alignment and that’s the whole point of building an observatory where everything remains in place. However, this may not be a concern for a pier constructed “in the garden out back” since the scope is usually not permanently attached and this would seem to be a great application for the concrete block pier described here and other similar designs – especially when removing it at a later date may become necessary. But regarding your statement that damping vibration is a pier foundation’s main purpose, I disagree. My understanding is the primary goal of pier construction should be to reduce deflection – meaning the slightest movement at the top caused by the dynamic nature of the equipment supported. This article in particular seems to indicate vibration is of little concern if the pier is constructed to keep deflection to an absolute minimum. http://www.cloudynights.com/page/articles/cat/articles/how-to/pier-design-fundamentals-r1236 Here’s an excerpt from the link above which specifcally addresses the question of vibration: “Some astronomers concern themselves with vibrations, damping time and ringing. If you design your pier using my guidelines you can forget about these considerations completely. You will not worry about the period of oscillation (damping time) because your pier will not deflect enough to disturb imaging or observing, whatever the fundamental frequency may be. Similarly, your steel pier will ring with a crisp high C bell tone if you strike it forcefully with a hammer. Just don't do that while you are imaging or observing and the ringing will be of no consequence. There are no natural forces that can excite the ringing mode as long as you keep your hammer away.” At the end of the day, how one builds their pier is a personal choice which should not invoke cries of protest from others. If I choose to sink my pier deep in the ground and surround it with copious amounts of rebar and concrete that’s certainly up to me and by the same token if someone else chooses to connect some concrete blocks together - and this suits their purposes and circumstances - they will hear no further negative comments from me. It’s not about one-upmanship – it’s about what works for the individual and what will hopefully meet their expectations...

Actually, there's a cubic yard below ground & roughly a 1/2 cu. yd. above ground. There were several reasons I formed & poured the above ground portion - mainly because the only suitable pipe I could find for the pier was too short - hence the extension legs I welded to the bottom. Then the legs provided a way to weld on a baseplate for it to stand on. This allowed the pier to be freestanding in the hole prior to placing concrete making it unneccessary to suspend it somehow which I knew would be problematic. Also, I wanted to get the obsy floor up off the ground & once that was decided, I knew I'd need some concrete above ground if I wanted to encapsulate the upper sections of rebar I had already welded to the pipe. If it weren't for these factors, I would not have placed any concrete above the ground although I figure it certainly can't hurt...

Hi Jim - Thanks for the response and the link. Looks like this is one of those areas of obsy construction where there's no set way to do it or a specific parts kit designed for the purpose. I need to do some more research on this but it sounds like V-groove rollers running on an inverted V track work well opposed to a recessed channel with flat rollers since debris can build up in the channel causing problems with smooth operation of the roof. Maybe some long pieces of 90 degree angle iron with the corner turned up could be used as tracks if you could find the right size V-groove rollers to fit. But then there's the problem of how to attach the angle iron to the beam without obstucting the corner which forms the track and there'd be nothing with this type design to hold down the roof since it would just be riding on top of the track. Oh well - at least I've got some time to think it over since I haven't even started building the obsy yet but thanks once again for the info..

Darn it! I probably should have added a couple more tons of concrete and a few more miles of rebar but oh well - maybe it will hold up for a little while...

Removed the forms today and the pour looks good. I used to apply a thin coat of motor oil to the inside of forms to provide a smooth finished surface and prevent the forms from adhering to the concrete. However, my wife mentioned she had read somewhere you can use cooking spray instead. So tried it and it worked great as you can tell by how nice and smooth the sides turned out. So the pier is set and I need to finalize the building design. It will definitely be standard post and beam construction and the bottom of the floor joists will be about 2 inches above the concrete to isolate the pier from the floor system. Finished floor of the obsy will be about 30 inches above the ground and I'm seriously considering adding a bump-out (Pod) for quick access to the scope during alignment and for other maintenance-type tasks. I do plan to have a warm room but just in case that doesn't happen until next spring, the pod will have a shelf for the laptop and a conduit routed under the floor to the bottom hole in the pier. The pod will be recessed in the obsy wall and covered with a simple, sloping, non-moveable roof to prevent me and the laptop from being covered with dew until the warm room is done. But for now, the next task is to set some posts which means more scratching around in the dirt. Fortunately, my father in-law has a tractor with an auger which will simplify that process and save some wear and tear on my back...

Well Friends - today the pier was finally poured !!! Seems like it took forever from the first day when I found the 3/8” wall - 8” dia. steel pipe at the local junkyard. Then came some fabrication and the welding of extensions since it was all that I could find but was too short for my purposes. Next there was a lot of sanding and 3 coats of primer before it was placed in a 3 x 3 x 3 ft hole. Then plenty of rebar was added and the above grade forms were finished yesterday. Finally the concrete truck arrived today and Windy Knoll’s pier is set once and for all. It may be overkill to some but to me it’s the heart of my future observatory and should remain rock steady both now and in the future regardless of the type of equipment placed upon it. Next on the agenda is Phase II – Observatory Construction...

Greetings All, After looking back at my previous post, it occurs to me my last comment was inappropriate so my apologies to anyone who may have been offended. For what it’s worth this was not my intent and I do realize what works for some doesn’t necessarily work for all. Since these block piers seem to be so quick and inexpensive to build, I may end up installing one outside my future obsy for visual use. Hope everyone has a great weekend and best of luck with your future astronomical adventures… Regards, Scorpius

A tripod works because the legs extend outward thereby distributing the load over a much wider footprint but the whole point of a constructing a pier is to create something far more stable than a tripod, is that not correct? Otherwise, why even have a pier at all and just leave the tripod setup and cover it with something to protect it from the elements. I don’t believe I insisted that the OP do anything more than he planned so not sure where you came up with that idea? I’d say if someone wants to build their pier out of popsicle sticks that’s certainly their prerogative but how well it performs in the long term will be governed by the laws of nature (frost heave) and the laws of physics (top-heavy with inadequate foundation). As I said – best of luck to the OP and sorry for having an opinion different than most. To be honest, I suspect the popularity of this type of design stems more from an aversion to manual labor than anything else but pretty sure that won’t be a popular opinion either.

OK - So I get the fact that a lot of folks are fans of low-tech, low cost solutions. But just how low-tech can you go before the laws of physics take over? There are sound engineering principles behind the idea of a solid foundation (concrete plug) for a telescope pier and I just can’t understand how a couple of cinder blocks glued together that depend solely on a “floating” paver for support could be substantial enough to carry expensive astronomy equipment. Guess I’m in the minority here but I’d rather over-engineer something than under-engineer it but maybe the conventional wisdom of pier construction is wrong. I will say however, an unsecured paver placed on top of a tree stump (which will eventually rot away) can’t possibly be sturdy enough to limit movement to a fraction of a mm. Then there’s also frost heave – a proven phenomenon - where the earth above the frost line moves up and down. This type of movement in and of itself would seem to prohibit any type of permanent PA in areas which experience prolonged temperatures below freezing. The whole idea just sounds flimsy to me but apparently many folks have had great success using this method and materials. I’ll just never know from personal experience since I’m gonna bury an 8 inch steel pipe 3 ft. in the ground and surround it with copious amounts of concrete and never have to worry about it again. Best of luck but I’d at least find a way to tie it to the ground or the whole thing is liable to tip over and damage or destroy your equipment…

What about lightning protection? Not so much from a direct strike but from an indirect strike nearby. After I read this article by Dr. Clay Sherrod of Arkansas Sky Observatory this has been a nagging concern and since I plan to pour the pier plug on Monday – I need to decide if I’ll embed grounding (earth) connections into the concrete plug as descibed in the article. http://www.arksky.org/surge.htm Has anyone here ever had any electronic circuitry (mount, cameras, etc) damaged by power surges associated with indirect lightning strikes traveling up through a steel pier or via the rebar in a concrete pier? Thanks in advance for any guidance... Paul

A few progress pics...

Still a ways off but looking for some ideas on a track & roller system for my roll-off roof obsy. Any info and pics of successful designs would be much appreciated as I’m trying to plan ahead so I’ll have all the parts needed once it’s time to construct the roof. Got the conduit installed this weekend and the pier has finally been set in the hole. Then I leveled it up and installed the mount temporarily to make sure it’s aligned with the NCP. Then last evening, I hand mixed 10 – 80 lb. bags of concrete and poured 6” in the bottom of the hole to stabilize everything in the event it gets bumped during the main pour. I’ll build the above grade forms this weekend and then the truck will arrive on Monday afternoon to pour the remaining 1.5 yards of concrete.

This sounds right and I had the same issue with my 80mm ES refractor before I purchased some extension tubes. I believe you can put the camera in the diagonal to see if focus can then be achieved which would confirm it's a spacing issue.

No kidding - so I've been doing it a** backwards this whole time? Think maybe it's time to have another go at some of my old subs and then compare the results... Thanks for the advice and specific instructions

Seems like the trick is to get enough RGB to let you adjust the color layer transparent enough for the L to show through without washing out the color. Which reminds me of something I've been meaning to ask - is there a rule of thumb for how transparent the color layer should end up in PS if you've got the right amount of RGB? Are we talking 25, 50, or 75% - just wondering if there's a ball park number or is it simply dependent on too many other factors?

Your knowledge of electronics is so far over my head it isn't even funny. Guess I was thinking more about some kind of external force that could slam the roof down on the scope. At the risk of sounding like a broken record - first thing that comes to mind is the wind. But guess the weather station would tell you it's too windy to raise the lid in the first place. So unless something in the roof-raising mechanism fails after the scope is deployed (physical hardware connections) looks like you've got all the bases covered. Ingenius concept and superb implementation - anxious to see some pics once it's officially up and running.

Amazing display of ingenuity and knowledge of electronics. Surely marketable to the masses once tested and refined. Just one question - is there absolutely, positively no way the roof could close electrically - or by external force - when OTA is deployed? Looking at that beautiful scope (Williams Optics?) just the thought of such a castastophe would give me the jitters!

Doubt it will ever need to be removed since the obsy and four season gazebo in the pics will be/are located on a 160+ acre farm belonging to my wife’s parents. My hope is to spark some interest in astronomy with my grandkids so it will continue to be used by future generations. Every time I see her - the oldest keeps asking - Paw Paw, when can I see that planet with the rings and I keep telling her it won’t be long now. Of course she could still observe Saturn with the scope on a tripod but she’s still a little young to stay up that late. Anyway, if someone ever does try to remove the pier, they better have a truck load of dynamite at their disposal because once I build something - it’s usually there to stay. My in-laws have told me this little plot of ground is mine to do with what I choose so the gazebo is my man cave although we use it for family get togethers as well. Having it close by the obsy will be nice when a hot cup of coffee in the middle of the night would taste mighty fine or a nice comfortable bed really fits the bill after a long night of astronomical adventures. There’s a bunk in there, a wood stove, a cook stove, a kitchen sink, a TV, solar powered LED lighting and various other comforts of home. This is not where my house is located - although that’s only a half mile down the main highway – which is roughly the same distance my remote site is from the same road. Only difference - you won’t see any vehicles back there (other than my old Toyota pick-up) and the only pedestrians to worry about are the deer, turkey and other wildlife. There’s no way I’d go to this much trouble if my obsy had to be built at home since there’s too much LP from neighbor’s street lights and cars going by at all hours of the night casting headlights into dark adapted eyes. Anyway, although progress has been slow – I’ll just keep plugging along until Windy Knoll Observatory transitions from a dream into a reality…

Well, decided to go ahead and sand it down to bare metal - then gave it 3 coats of primer to protect it from the weather until the obsy is under roof. Next is to trench in the conduit to the warm room then try to figure out how I’m going to get this beast of a pier in the hole. After that I’ll build some forms to extend the pier plug about 12 inches above the ground. And then finally it will be time to pour some concrete so I can get this obsy build underway...

Worked all weekend and got the legs and baseplate welded to the bottom of the pier. Also cut a hole near the bottom to route cables down through and then out into an enclosed area beneath the floor. This is where I’ll install 110V power for the mount and anything else that needs it. The below floor area will be accessed through a trap door in the obsy floor. This way there will be no cables to trip over since the only wires/cables will exit through the owl’s nest before connecting to the mount, cameras, etc. The conduit from the warm room will terminate inside the pier at about the same level as the bottom hole so I can either route wires into the below floor compartment for connection to USB hubs, etc. or I can continue them on up through the pier and out the owl’s nest. It needs to be this tall (about 8 ft) because the floor of the roll off roof obsy is going to be about 30 inches off the ground. I’m doing this to get the scope a little higher - which should help me see lower on the horizon - and also should put it high enough to see over the roof of the warm room which will be constructed at grade level. Plan to use a standard height door between obsy & warm room - which will swing into the warm room eliminating any height issue if it were to swing into the obsy. The door will open to a short flight of stairs (about 4) in order to make the transition in floor level. The pier height will be 36 inches above the obsy floor. Said I wouldn’t start a build thread until the pier was set in concrete but after working like a dog all weekend to finish the fabrication, I decided to go ahead and go for it. Knowing me - I’m sure progress will be slow however, progress will be made little by little and I’ll post updates to this thread as I go... You may see some logging equipment in the background but that’s a story for another day. Just suffice it to say – I’ve got some friends who are helping me expand my horizons...

I agree - Don't know what I was thinking