Date: Thu, 13 Aug 1998 21:39:10 -0400 From: "Frank Schwartz" Subject: [M]: Concrete Permanent Pier I'm planning on building a permanent pier for my 8" LX-50. I don't have the cash for a steel tube, nor do I have the cash for something elaborate, but here's what I had in mind... At a local do-it-yourself center, I can get 8" diameter cardboard tubes. I was planning on getting 7' of it, cutting holes in the bottom half (I'll explain the holes in a minute) and filling it and the hole around it with concrete and filler rocks. 4' of it would be below ground, and with the holes, the concrete will ooze out the holes, connecting to the concrete outside the tube (thus making a wider base without having a straight concrete pillar). The remaining 3' of this tube will protrude out of the ground creating the pillar/pier. I will make sure the pillar remains level while setting, and on the top of the tube, I will have 5 bolts, 4 corners for leveler bolts, and 1 larger one in the middle for the wedge to screw onto. I plan to use the standard Meade wedge made for the LX-50. On the 4 leveler bolts, I will have an 8"x8" square metal plate (approx 1/2" thick) on which the wedge will rest, and a hole in the middle for the large bolt to stick through (coming from the center of the concrete pillar) to tighten the wedge down. Once the concrete is hard, I can cut the cardboard off or let the rain & humidity take care of it and throw away the shell, leaving just the concrete pillar. The location I have chosen is on top of a hill close to my house, on my property, and close enough that it's not a big deal to carry the OTA and accessories to it (I use a waggon to haul the stuff). It's an excellent location with a great unobstructed view in all directions. I'm in a fairly dark location many miles from the nearest town. I have been using the same spot for the past 6 months with my LX-50 and the standard tripod. It's just a pain to lug this huge tripod up the hill, level it, align it, etc. By creating this permanent mount and wedge, I can drop the OTA on, verify polar alignment, and get to work. Aside from the obvious tips like use stainless steel bolts, does anyone have any suggestions before I make this enormous piece of concrete in my back yard? Any help or suggestions would be greatly appreciated. If anyone has pictures or examples of something similar on the web, please give me a URL to check it out. Thanks Frank Schwartz schwartz@fast.net ------------------------------ Date: Thu, 13 Aug 1998 21:10:10 -0600 From: Barry L Johnson Subject: Re: [M]: Concrete Permanent Pier Frank Just poured my concrete pillar last week and am putting a dome around it now. I have 3 feet above ground (Pad) and about 8 feet below. The pier hole was 24 inch in diameters and I filled it to about 2 feet below ground level, then used a sonatube of 16 inches to come out of the ground from that level. I too put hole in the lower part of tube but also added lots of rebar across the bottom of the tube and sticking out into the concrete in the bigger hole. I also used lots of rebar in the pier, especially where the sonatube went into the lower concrete. One suggestion on the bolts I did not do but wished I had, if you know where you want the j-bolts to be, weld some rebar or crosspieces to ends of the J-bolts that will be in the concrete to from a cage. This will keep them aligned. I had some problems in keeping my 4 bolt holes coming up to be vertical although they were in a template. I later put down gravel and then a concrete pad being careful to isolate the pad and pier. The pad has three 5 foot footings to support it. From what I have read do not be scared of too much concrete. When I looked at the 16 inch tube I thought it may be too much but I am happy know that I did it. I love to overdo most things! Good luck on your pour. Barry ---------------------------------- Date: Fri, 14 Aug 1998 08:41:41 -0700 (PDT) From: J Nordby Subject: Re: [M]: Concrete Permanent Pier If it were me, I'd make the pillar about 23 inches high, so I could sit down at the telescope, at least for altazimuth use. I sometimes observe all night long, and because of sitting down, even after 8 hours I am not physically tired, just sleepy. Something to consider for when getting older. Another option which I've seen others use, is to stop the concrete at ground level with bolts inlaid, which then can hold various, removable piers, usually loaded with sand to stop vibration. This obviates the need for worrying about the appearance of a concrete pillar which in some venues would be considered an eyesore. ------------------------------- Frank, I see all the construction details, your and others, you are making it way too complicated and expensive. All it takes is 8 or preferably 10 inch sonotube that goes down a few inches below the frost line ---if you live in that part of the country-- otherwise about 4 feet down. Let that project about 18 inches above ground. Fill with Sakrete or other bag ready mix and go EASY on the water. Mix outside the hole and then dump. The mixture should be grainy and somewhat dry. This makes increadibly tough concrete. Before filling the hole put in two pieces of 1/2 inch rebar spaced about 3 inches-- do not allow the rebar to show outside the concrete; top or bottom. Place a pipe flange with machine screws into the top of the concrete and level the assembly. Stainless steel is a waste of money for this job and may not adhere to concrete as well as plain steel. On the pipe flange will be screwed a length of pipe to the height you desire and at the top another pipe flange on which you attach the wedge. This arrangement is cleaner looking, more durable than all concrete and and and! allows you to change pier height as your needs change. I.E. Tall for zenith observations and short for horizon---etc. The pipe should be 3 or 4 inch diameter and can be found at any plumbing supplier that handles fire sprinklers and steam pipes. Dick, who's also a registered professional eng. -------------------------- Date: Fri, 14 Aug 1998 13:22:07 EDT From: DFranck@aol.com Subject: Re: [M]: Concrete Permanent Pier Ok, I have a question! I am having a new pad poured for my observatory. Right now I have a 12" Sonotube sitting in a hole 4 feet down. What is the best way to get the pier stable and yet, not have it pick up movement of the pad? I wanted to have a space around the pier, so that it is not touching the concrete floor. But, the constractor says the pier will move without alot of concrete around it. - - Don Franck ------------------------------ Date: Fri, 14 Aug 1998 13:15:08 -0600 From: Jim Waller Subject: Re: [M]: OT Concrete Permanent Pier - Question About the isolation of the pier from the pad, it really necessary. I understand why it's required in a big, professional observatory. Lots of things are happening in the building in addition to the operation of the scope. But, in a personal observatory, where's the vibration coming from? I have a 12'X 12' roll-off-roof observatory with a 12" LX200 on a permanent pier. The pier and the slab are one block of concrete. With just me and the dog around, I've never seen any evidence of transmitted vibration in the CCD frames I'm taking. Anyone else have any experience pro or con? Jim Waller ------------------------------ Date: Fri, 14 Aug 1998 14:20:46 -0500 From: Gene Horr Subject: Re: [M]: OT Concrete Permanent Pier - Question It is quite necessary. Taking photos guided with ST-4 + 1,000mm refractor you can see the guiding "jump" when someone walks by 3' away when the mount is on dirt. When the mount is on concrete you can see it happen when someone is 5' away (and on the same slab). Gene Horr genehorr@swbell.net ------------------------------ Date: Fri, 14 Aug 1998 12:21:45 -0700 (PDT) From: J Nordby Subject: Re: [M]: Concrete Permanent Pier In later life my father was a builder/contractor, and I worked with him seven summers during college, of which some experience was laying concrete. That is some years ago, though, and I only worked there, didn't enjoy it that much so I can't really call myself an expert. But from that limited experience, plus what I have read about telescope piers, I believe that the telescope pier could remain free of vibration from the pad if there were some air space between the pad and the pier. How to achieve that is the question. I have seen some arrangements where the pad was made of 2x4 flooring, arranged as for a patio deck, where the 2x4's are spaced the width of a 16-penny spike apart,which allows any water to drain down. The crowns should be up, to help drainage. The 2x4's should be waterproofed. This 2x4 flooring comes within an inch or two of the pier, but never touches it, with framing around the pier but not touching, for strength. Any walking around is done on the 2x4 flooring, which makes contact with the ground several feet away from the pier. Of course, to support such 2x4 flooring, one would need floor joists, perhaps 2x10s or perhaps the more modern engineered joists which are lighter but just as strong. These would probably be spaced at 16 inches on center, and would contact their support ends (concrete?) several feet away from the pier. Now, I'll leave it to somebody else to figure how to meet these specs in an observatory setting. I'm thinking here in terms of a regular building, such as a house, or house attachment. ---------------------- Date: Fri, 14 Aug 1998 15:46:14 -0500 From: "R. A. Greiner" Subject: Re: [M]: Concrete Permanent Pier DFranck@aol.com wrote: > Ok, I have a question! I am having a new pad poured for my observatory. Right > now I have a 12" Sonotube sitting in a hole 4 feet down. What is the best way > to get the pier stable and yet, not have it pick up movement of the pad? I > wanted to have a space around the pier, so that it is not touching the > concrete floor. But, the constractor says the pier will move without alot of > concrete around it. > > - Don Franck You MUST have a concrete floor isolated from the pier. It is not a question of vibration but is a question of shifting of the image if, or when, one walks around on the floor. We have many concrete pads at our dark site. They are fine for viewing but even though they are 6 feet square and a foot thick, they move significantly when persons step on and off the pads. Telescopes mounted in houses have the same problem. When people move about in the house the house flexes enough to give noticable motion of the telescope. If your tube goes down about the same length as it sticks out of the ground and below the frost line, if any, your pier will be solid and not move over the period of imaging times. Doc G ------------------------------ Date: Fri, 14 Aug 1998 17:53:55 EDT From: JohnLX200@aol.com Subject: Re: [M]: Concrete Permanent Pier In a message dated 98-08-14 16:50:36 EDT, Doc G wrote: << You MUST have a concrete floor isolated from the pier. >> I hope Doc means that IF your floor is concrete, it must be isolated from the pier. This is true whatever the flooring material, so I think the word concrete can safely be removed from his sentence above. As the post (no pun intended!) on wood decking correctly stated, the important point is that the point where the flooring or decking load gets applied to the ground should be isolated from the pier, and preferably as far away as possible. For this reason, I believe the wood decking solution which gets it several feet away is preferable to a concrete slab, isolated or not. Another way to improve the isolation from vibration is that if the scope pier goes to bedrock, perhaps the deck piers should not, or vice versa. Obviously our ability to do this depends upon your depth to bedrock, soil type, building codes, and other factors which you may not be able to control. I plan to also put heavy-duty expanded polystyrene foam ("styrofoam") below and around any ones not going to bedrock. I'll use the pink or blue variety, which are much more rugged than the granular white ones. John ------------------------------ Date: Fri, 14 Aug 1998 18:37:12 -0500 From: "R. A. Greiner" Subject: Re: [M]: Concrete Permanent Pier JohnLX200@aol.com wrote: > In a message dated 98-08-14 16:50:36 EDT, Doc G wrote: > > << You MUST have a concrete floor isolated from the pier. >> > > I hope Doc means that IF your floor is concrete, it must be isolated from the > pier. This is true whatever the flooring material, so I think the word > concrete can safely be removed from his sentence above. > Absolutely. A Deck such as I use also has to be isolated. My deck is on posts that are about 3 feet from the pier. If I jump up and down, I can get tiny vibrations in the pier through the ground. I was thinking about those cases where you have a concrete pad that you set a pier or tripod on and then walk around. > As the post (no pun intended!) on wood decking correctly stated, the important > point is that the point where the flooring or decking load gets applied to the > ground should be isolated from the pier, and preferably as far away as > possible. For this reason, I believe the wood decking solution which gets it > several feet away is preferable to a concrete slab, isolated or not. Another > way to improve the isolation from vibration is that if the scope pier goes to > bedrock, perhaps the deck piers should not, or vice versa. Obviously our > ability to do this depends upon your depth to bedrock, soil type, building > codes, and other factors which you may not be able to control. > Very good analysis John. I can see that you really are an ME. :-) > I plan to also put heavy-duty expanded polystyrene foam ("styrofoam") below > and around any ones not going to bedrock. I'll use the pink or blue variety, > which are much more rugged than the granular white ones. > > John Doc G ------------------------------ Date: Fri, 14 Aug 1998 22:10:00 -0500 From: "Herman Zwirn" Subject: Re: [M]: Concrete Permanent Pier R.A. Greiner wrote:"You MUST have a concrete floor isolated from the pier. It is not a question of vibration but is a question of shifting of the image if, or when, one walks around on the floor." Of course this is absolutely correct. Another option is to build a deck around the pier (no contact). It's easier to build, easier on the feet and does not transmit vibration. I have two piers in my observatory. The foundation and floor is a strong deck about 6" off the ground. The decking is about 3" away from all sides of the piers. You can jump up and down like when you discover you are in a "sucker hole") and not transmit any vibration. By products of this approach are it's easier to stand on, does not absorb heat or give off heat, not as cold in the winter, softer on eyepieces than concrete and the decking board separation combined with the elevated deck allow excellent air circulation. Herman ------------------------------ Date: Sat, 15 Aug 1998 09:41:51 EDT From: RZP1@aol.com Subject: Re: [M]: Concrete Permanent Pier Frank, Ref. The contractor and the concrete pad. What part of the country are you in? What sort of soil? I doubt that even in lose sand that 4 foot depth on the pier is going to let it move. I'd also go for a MINIMUM of 1/2 inch spacing all around the pier; an inch is better. After the concrete cures fill the space with sand. If you are subject to frost heaves then you better dig down another foot and have about 5 feet into the ground. Dick PS. For what it's worth. My concrete pad moves when I walk around it. Discovered this by having the telescope on a tripod. I can see my target star shift slightly as I walk around the telescope. That was the reason for my pier. ------------------------------ Date: Sat, 15 Aug 1998 09:51:18 EDT From: RZP1@aol.com Subject: Re: [M]: Concrete Permanent Pier To J. Norby: I've built such a floor for my roll off roof observatory which is 10 by 10 feet. However I didn't use such outrageously large lumber (and expensive). I used 2x8 joists 24 inches apart on which I laid 3/4 plywood flooring. In the center is a cut out 2 foot square for my pier. Testing the floor for flexure with a telescope on a tripod I can say the movement due to a person walking around is almost undetectable. This floor sits 24 inches above the ground supported by 6 4x4 posts. Dick ------------------------------ Date: Sat, 15 Aug 1998 10:18:14 -0700 (PDT) From: J Nordby Subject: Re: [M]: Concrete Permanent Pier Yes, I'm sure that in many cases, 2x8's at 24-inch centers would suffice, especially for shorter spans like 10 feet. When I've been in the basements of some old houses, I've seen where the builders used 2x8's and then years later someone came along and nailed 2x10's alongside them when it became evident that the 2x8's didn't stand up; but of course floors in houses obviously need to support more weight. Not sure how many overweight people your obs floor would support though! :) - ---RZP1@aol.com wrote: > > To J. Nordby: > > I've built such a floor for my roll off roof observatory which is 10 by 10 > feet. However I didn't use such outrageously large lumber (and expensive). I > used 2x8 joists 24 inches apart on which I laid 3/4 plywood flooring. In the > center is a cut out 2 foot square for my pier. Testing the floor for flexure > with a telescope on a tripod I can say the movement due to a person walking > around is almost undetectable. This floor sits 24 inches above the ground > supported by 6 4x4 posts. > > Dick > == J Nordby jmnordby@yahoo.com "Godspeed, John Glenn" (October, 1998 launch date) _________________________________________________________ DO YOU YAHOO!? Get your free @yahoo.com address at http://mail.yahoo.com ------------------------------ Date: Sat, 15 Aug 1998 14:18:15 EDT From: DFranck@aol.com Subject: Re: [M]: Concrete Permanent Pier It looks like the best idea is to isolate the pier from the pad. Which I also agree with after seeing images move on my concrete driveway. So, what is the best way to do it? I am down to the frost line and will have 36" above the poured pad. Will the pier be stable if I hard pack soil around the outside of the sonotube( 8 foot tube) and fill the inside with concrete? Contractor says it will not be stable with just hard pack. I plan now to have about 3 inches spacing between the pier and the pad. Leaving the forms around it in place. - - Don Franck ------------------------------ Date: Sat, 15 Aug 1998 14:26:59 EDT From: DFranck@aol.com Subject: Re: [M]: Concrete Permanent Pier RZP1 (Dick), The soil here is rich black dirt. And is fairly hard packed near the base of the hole right now. The hole is 4 feet deep and should be below frost depth. I do know I can just go with the contractor, and later not move around as images are being taken. The pour should be early next week, so one way or the other, I have to decide now. - - Don Franck ------------------------------ Date: Sat, 15 Aug 1998 13:50:10 -0500 From: "Joshua Kent" Subject: Re: [M]: Concrete Permanent Pier I realize that this topic is being discussed to death. But since this is an important topic... go here . They have lot's of info and ideas... Joshua Kent LX50 Web site and more.... ------------------------------ Date: Sat, 15 Aug 1998 21:48:45 EDT From: RZP1@aol.com Subject: Re: [M]: Concrete Permanent Pier I think the 2 x 8 joists will support as many people as can fit into a 10 x 10 building with a large refractor in the middle and a bookcase and chart table. By actual test about 3 people total. BTW, the building inspector suggested 2 x 6 on 16 inch centers. Then I looked up the allowable stress/deflection data for the type lumber I used---long leaf yellow pine about the same as oak. The tables said I could go 12 feet with a live load of 40 pounds per square foot. Since there is really no furniture or appliance floor loading worth noting I went with the book specs. Testing with a telescope on a tripod shows almost no deflection or shake when people walk on the floor. But as you say maybe in a few years...... Dick ------------------------------ Date: Sat, 15 Aug 1998 21:58:25 EDT From: RZP1@aol.com Subject: Re: [M]: Concrete Permanent Pier To D. Frank, Sounds OK to me. About the same type soil as here in Iowa. You are down 4 feet and that's below frost for you---great. Go with it. Make sure you put the two pieces of 1/2 inch rebar as I said before. No need to use more. Forget the rock packing and all the other crap. Nothing is going to move that pier. The builder is thinking in terms of a support column for a building. He has no experience with a short concrete column used to support not more than a 100 pounds. As for the gap around the column and the the pad---- 1/2 inch is OK and 1 inch may verge on too much. If you get frost you have to pack the joint with tarred felt to prevent the ice from breaking things. Maybe not this year but it will eventually. That's why the gap should not be overly large. Don't worry about your pad floating around. No matter what you do it will float unless it has 4 foot footings--ridiculous! It will really move around during the rainy season. It's just one of those things. Since it's not connected to the pier it won't matter. Are you going for the pipe pier or solid concrete all the way? Dick ------------------------------ Date: Sat, 15 Aug 1998 22:36:59 -0500 From: Michael Hart Subject: RE: [M]: Concrete Permanent Pier On Saturday, August 15, 1998 8:58 PM, RZP1@aol.com wrote: > To D. Frank, > > Sounds OK to me. About the same type soil as here in Iowa. You are down 4 > feet and that's below frost for you---great. Go with it. Make sure you put > the two pieces of 1/2 inch rebar as I said before. No need to use more. > Forget the rock packing and all the other crap. Nothing is going to move that > pier. The builder is thinking in terms of a support column for a building. > He has no experience with a short concrete column used to support not more > than a 100 pounds. > As for the gap around the column and the the pad---- 1/2 inch is OK and 1 inch > may verge on too much. If you get frost you have to pack the joint with > tarred felt to prevent the ice from breaking things. Maybe not this year but > it will eventually. That's why the gap should not be overly large. > Don't worry about your pad floating around. No matter what you do it will > float unless it has 4 foot footings--ridiculous Six to twelve inches of large aggregate is enormously helpful at minimizing or preventing concrete pad movement- this is common practice for highway construction. The aggregate allows space for moisture and frost to expand and move away from the underside of the concrete with little to no concrete movement. It is not a practice for sidewalk and driveway construction, which is unfortunate. Much aggravation and premature failures are produced by concrete slabs rising and moving about which could be minimized or prevented by a few dollars of rock under the concrete. I have seen newer concrete slabs with full reinforcing rebar fail when laid directly on soil, while older un-reinforced aggregate supported concrete remained intact. Dick is quite right about builders thinking in terms of supporting large loads and over-building the pier. The purpose for the rock under the concrete is to redistribute the load in the soft ground. This prevents settling and allows a heavy structure to reside below the frost-line and above bedrock with little to no movement. In soft soils, this is arguably more important than rebar. Rebar is useful to support shear, shock, and vibration loading. It also increases the tensile strength of concrete. A typical short pier used for a telescope has predictable loading. Typical concrete has a compressive strength of 2500 to 5000 psi and I suspect this is quite adequate to support 100 pounds as evidenced by several piers in excess of 5 years old with no signs of concrete failure. > It will really move around > during the rainy season. It's just one of those things. Since it's not > connected to the pier it won't matter. > Are you going for the pipe pier or solid concrete all the way? > > Dick > - -- Michael Hart Husen Observatory mhart@netexpress.net ------------------------------ Frank, I sent this to MAPUG a while back. Hopefully it will have something you can use in it. Like you, I'm budget minded (occasionally) and this pier has and is serving me well. Subject: [M]: concrete pier for LX200 (way long) From: Bob Freeze Reply To: mapug@shore.net Date: Sat Jun 20 05:42:25 1998 Sorry for the lengthy post, but there were quite a few requests for this description. The following is a step by step of concrete pier construction for a 12" LX200. Without pictures this may not be clear, so please feel free to let me know which parts need clarification. Materials - 4 ft. length of "Quik-Tube". "Quik-Tube" is a cardboard tube made for use as a concrete form. Made by the same folks that make "Quik-Crete". I only found one building supply in the Knoxville area that had it in the size I wanted. All-Thread small. 3 12 inch lengths for the small wedge mounting bolts. All-Thread medium. 1 12 inch length used for tangent mounting. All-Thread large. 3 12 inch lengths, 1 for the wedge central mounting and 2 used as "rebar". I don't remember the exact sizes of the All-Thread pieces - I took the wedge nut and bolts to the hardware store with me to match sizes. I also got a handful of nuts and flat washers to fit each size. Scraps of plywood and 2" X 4". 30 - 40 60# bags of "Quik-Crete". (delivered along with other observatory building materials by Home Depot for $25.) "Quik-Tube" preparation. I drilled holes ~4 inches from the bottom of the tube such that the medium all-thread could be inserted in a cross pattern and double-nutted into place. I calculated (estimated) how much tube I needed above ground to give the desired above floor height of the pier. I drew a line around the tube with a "Sharpy" so I could judge the proper depth of the tube when pouring concrete later. The pier was done first with the observatory built around it later. ~4 inches from the top, I drilled two more holes, over-under fashion for the tangent mounting bolts. I cut one of the 12 inch large all-thread pieces in half, bent each 90 degrees and double-nutted in place with about 1 1/2 inches outside the tube. The point of the bend was different on each so that they wouldn't create a single weak spot inside the pier - staggered about 3 inches and pointed different directions on the inside. These are what I planned to mount a piece of angle iron to for azimuth adjustment. This still isn't done. In four places between the bottom of the tube and the ground level line, oval "windows" were cut out of the tube to allow concrete to flow through. The tube was left on the pier above ground to help control crumbling. Below the main concrete mass the tube will probably eventually rot away. These windows keep this from being a concern because below ground level this is a single mass joined through these "windows" and the bottom of the tube. Wedge mounting preparation. The wedge hole pattern was traced onto a piece of scrap 3/4 plywood by placing the wedge on top of it and marking the holes with a pencil. The North direction was also marked at this time. Before drilling the template, a circle the size of the tube was marked using the center wedge hole position as a guide. All-Thread was double bolted into the holes with double flat washers and plenty of extra thread above. I didn't plan to use a plate, but one will be added some time in the future if I ever unmount the 'scope. The extra thread will be handy here. A plate should make the azimuth adjustment "smoother". A plate could also take the place of the tangent mounting and could also have holes for hanging the keypad, etc. Again, the point of bend in these pieces of all-thread were staggered and pointed away from each other on the under side. The North line was transferred to the top and, as a final step, three scraps of 2 inch thick wood were screwed to the bottom just outside the circle marking the tube diameter. These were a big help keeping the bolt template centered on top of the tube later. Hole preparation. The center of the hole was marked by using stakes and line, offset by the radius of the tube in both directions. This offset allows the tube to be centered later by "resting" in the corner of the cross. The hole was dug 3 feet in diameter and 3 feet deep. These dimensions were somewhat arbitrary. I went with what I thought was certain over-kill. This size has been more than adequate. The bottom of the hole was flared outward for the last 8 inches or so to prevent "rocking" later. Pouring. 60# bags of concrete were mixed 2 at time in a wheel burrow. Yes, really. I didn't count, but I ended up using something close to the 30-40 bag range. The concrete was mixed slightly on the dry side at this point. Once the level was high enough that about 6 inches of tube would be below, the tube was placed into the concrete. The position was determined by putting the line back on the stakes and leveled across the top and on the sides with a 24 inch level. Depth was guestimated with the previously marked "ground level" line on the outside of the tube. Once positioned, a late model "wife" was used to hold the tube steady while concrete was added around it. Concrete was added in stages - as the outside level reached 6 inches or so above the inside level, concrete was added to the inside of the tube. At a couple of points the tube was checked level and North pointing (tangent bolts south) and it was allowed to sit for 30 minutes while things firmed up a bit. Once the inside and outside concrete levels were at ground level, I wet the concrete on the inside of the tube and let everything set up for about an hour and a half. The tube was then topped off with a slightly wet mixture. While filling, the concrete on the inside of the tube was lightly tamped with a 2" X 4" scrap ever other shovel full. The tube was filled so that concrete was bulging above the top. The all-thread mounted to the plywood was carefully "worked" into the top of the tube while watching the North line for orientation. The plywood was forced down to the top of the tube. Final steps I let this set up for a week before I messed with it. The following weekend I unbolted the plywood template and checked it out. Lucky again, the flat washers were slightly above the rest of the concrete and provide a level 4 point surface for the wedge so rest/mount on. Being concerned for the safety of my LX200, I went out to the pier several times over the next week and leaned on, stood on, kicked, slapped, banged with a rubber mallet, and then mounted the 'scope. THIS THING IS SOLID! Gotcha's. During the pour, the tube sank about 3 inches lower than I had planned it. This turned out not to be a problem. I was determined to have a single, monolithic mass when I got done, so two steps were out of the question. Starting out with the "ground level" line a few inches higher would have solved this problem. I checked and adjusted the level very frequently. This is a must - by the time I got to the point of topping off the tube, further adjustments were not possible because of the setting of the concrete. It probably could be forced, but after setting up to this degree you would almost certainly weaken the mass. I was lucky - the level was on the money. Plan for a plate between the pier and the wedge. This will make azimuth adjustments much easier. I haven't been able to get anything mounted rigid enough to act as a tangent. A plate mounted over the all-thread with a hole for the tangent pin would be held in place automatically by the all-thread. There would be no need for the tangent bolts I included. The concrete in the top of the tube shrank away from the plywood very slightly. This turned out to be a good thing so that the wedge doesn't rest directly on concrete. Make sure you tamp the concrete in the tube during the filling process or the concrete may shrink down too far. This pier is absolutely solid. However, others have recommended using a larger diameter tube. Bob http://www.usit.com/rfreeze rfreeze@usit.net -----Original Message----- From: Frank Schwartz To: mapug@shore.net Date: Thursday, August 13, 1998 9:56 PM Subject: [M]: Concrete Permanent Pier >I'm planning on building a permanent pier for my 8" LX-50. I don't have the >cash for a steel tube, nor do I have the cash for something elaborate, but >here's what I had in mind... > >At a local do-it-yourself center, I can get 8" diameter cardboard tubes. I >was planning on getting 7' of it, cutting holes in the bottom half (I'll >explain the holes in a minute) and filling it and the hole around it with >concrete and filler rocks. 4' of it would be below ground, and with the >holes, the concrete will ooze out the holes, connecting to the concrete >outside the tube (thus making a wider base without having a straight >concrete pillar). The remaining 3' of this tube will protrude out of the >ground creating the pillar/pier. I will make sure the pillar remains level >while setting, and on the top of the tube, I will have 5 bolts, 4 corners >for leveler bolts, and 1 larger one in the middle for the wedge to screw >onto. I plan to use the standard Meade wedge made for the LX-50. On the 4 >leveler bolts, I will have an 8"x8" square metal plate (approx 1/2" thick) >on which the wedge will rest, and a hole in the middle for the large bolt to >stick through (coming from the center of the concrete pillar) to tighten the >wedge down. Once the concrete is hard, I can cut the cardboard off or let >the rain & humidity take care of it and throw away the shell, leaving just >the concrete pillar. > >The location I have chosen is on top of a hill close to my house, on my >property, and close enough that it's not a big deal to carry the OTA and >accessories to it (I use a waggon to haul the stuff). It's an excellent >location with a great unobstructed view in all directions. I'm in a fairly >dark location many miles from the nearest town. I have been using the same >spot for the past 6 months with my LX-50 and the standard tripod. It's just >a pain to lug this huge tripod up the hill, level it, align it, etc. By >creating this permanent mount and wedge, I can drop the OTA on, verify polar >alignment, and get to work. > >Aside from the obvious tips like use stainless steel bolts, does anyone have >any suggestions before I make this enormous piece of concrete in my back >yard? > >Any help or suggestions would be greatly appreciated. >If anyone has pictures or examples of something similar on the web, please >give me a URL to check it out. >Thanks >Frank Schwartz >schwartz@fast.net > > > ---------------------- Hi Frank, It's easier for me here than AOL. Their system is too slow. Re: pilar. Just like I wrote before. Straight column into the ground. No need for anything else. Don't let it touch the pad as I mentioned before. Keep enough gap but not too much see prev. mess. If you are going to stand out there in the weather a concrete pad is fine. I built an observatory around my column. The roof runs off on a track. The floor is wood and raised 2 feet above ground. That's so moisture won't be a problem for equipment inside and also to raise the sight line above the peak of the roof on my house enough that I can see down to 20 degrees above the horizon. That's plenty good considering the distortions of more air at lower angles. If you can view pictures in the .PCX format I can send you one of my observatory. One of roof closed and one of roof open so you can see how it is. Prior to the observatory I used to get into a snow mobile suit and brave the minus 20 "warm" Iowa winter evenings. I've gone soft and demand my comfort such as stereo music and no snow blowing in my face. I doubt your frost line extends down as far as mine. In any event 4 feet deep should be plenty since my frost line is 42 inches according to the building department. The only reason for this is not permanence but to keep the pilar from moving at all in winter. Otherwise it would move up in winter and back down in spring so you'd have to polar align every time the weather changed. That is if you are leaving the telescope mounted. If not you have to re polar align anyway. I see you are thinking in terms of a deck now. Just a word on expenses. If you build it up at least 18 inches above ground you do not have to use pressure treated lumber which is at least a 50% savings in expense. My floor is 3/4 inch flooring ply on 2x8 joists spaced 24 inches. It is a 10x10 foot floor. It is very sturdy. It is supported at the corners by 4x4 posts sunk into the ground below frost level. I also have one post midway on each of the header joists for a total of 6 posts all around into the ground. I went for a wood floor which is harder to build than concrete because concrete gets damn cold in winter and stays cold. Very hard on the feet. Also I once dropped a 2 inch star diagonal with a $230 eyepiece on the concrete pad behind the house. Total cost of that mishap was close to $500. No more concrete under my telescopes ever again! My pier ends 6 inches above the floor. To it is attached a pipe pier on which the telescope is mounted. This makes a less bulky-- neater installation than concrete all the way. It also allows me to change the height of the pier if I want by merely substituting different lengths of pipe. While the suggestions for all the rock fill and all the other ground preparation are nice and according to the book they apply to larger structures. My club built a 20 by 48 foot slide roof observatory as an addition to our other set ups. We also have several concrete pads. None of thbuildings of pads ahve any special ground treatment other than the minimum required by the building codes and that is footings on the building corners down to below frost. None of the piers have any special ground treatments. My own concrete pad--really a patio slab part of the house is just 4 inches of concrete on top of the dirt. It goes up with frost and comes down with the thaw. Has been doing it for 25 years and it still is unbroken and in the same place. It is 20 by 12 feet. However in the rainy season you can detect a slight motion of the slab by walking around the telescope. Never bothered me--just a point of information or amusement. BTW, whatever you do let the concrete sit undisturbed about a month before putting any stresses on it. So we are talking long term. Start now you may have something by late fall. If there are any points you need clearing up get me at this URL rzp@JUNO.COM Clear skies, Regards, Dick Director, staff & janitor of HillSide Observatory _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call