I am getting back into astronomy (since my youth) and wishing to build a pier and observatory and tossing up what sort of pier to use; fabricate my own 12" (300mm) concrete pier (but where can I get the formatube ) vs. a 165mm metal pier (available from one of the telescope companies here in Oz). It is to support my CPC1100 and wedge and as I wish to get into astrophotography it needs to be stable so any ideas and experiences with either pier out there? Any help is appreciated. Thx.
I looked exactly what you looked into....
I found Concrete was more expensive, almost 1 cubic meter (about $300 from concrete taxi) and about $60 for a formatube..
I got my steel from direct steel at ipswich and total cost was $79
it consisted of
300 x 300 x 20mm mild steel base plate
2of 200 x 200 x 20mm mild steel top plates
165mm OD pipe ( i actually went 150 od pipe as they were out of stock of the 165)
+ bolts total cost is about $100... even if you factor in a cheap bunnings welder + gear at about + $150 or so its still cheaper then concrete and a commercial product.
Stability should be about equal as well, especially if filled with sand. if its out in the middle of the yard on a windy night things might be dodgy. there are members on here who use smaller diameter steel and its still uber stable.
linked is a cad drawing of it.
if you cant DIY find someone who can weld for u.. clean up only needs a cheap angle grinder. IIS members are uber helpful. If you willing to wait a few months i will make mine, i will make you 1 as well.
Another idea is to incorporate a stubby (ie. not full height) concrete pier with the pier foundation, which typically would also be concrete. Then, a steel pier can be attached to the top of the concrete pier to attain whatever height is needed. Future equipment changes can be accommodated by replacing the relatively cheap steel pier with a shorter or longer one.
I bought a length of Formtube from the supplier in West Heidelberg, Melbourne, and would be surprised if there wasn't an equivalent in your part of the country.
Thanks Chris and Steve; that gives me some great ideas and suppliers also. The designs are great Steve and I will have a chat to my local suppliers next week. That was a big hole you dug for your pier Chris and what an awesome looking observatory. I'll have to get my pier started as I am putting an astrodome over it once it is in so I can leave my scope permanently setup. Adds so much more to viewing time and then I can get into the photography. Thanks again guys. Peter
Whether you build some concrete formwork for a full or partial concrete pier, or just do a straight steel number like Steve's, you will still need to lay a solid concrete base for the whole thing. A block of concrete a metre deep and say 400x400 will be less than 1/4 m3. I'd do it with bags of premix. Work on about 15 bags worth. I think they're about $10 a bag these days. And you have the additional option here of getting a longer bit of steel pipe and burying it (with suitable bits of steel welded to the foot to make it solidly anchored in the concrete base - eliminating the baseplate and associated bolts involved in Steve's design. Of course you don't have the option of removing it later on - apart from digging the whole thing up again.
I have one pier that is of this kind and it's rock solid. I also have one that is a store-bought steel one bolted into a slab. Both are rock solid. One cost me $1000 plus the concrete base. The other cost me the same amount of concrete base and the rest was less than $100 in scrap steel pipe. I know which was I'm going next time (there's always a next time).
Peter
Steve, you might wanna check your maths.
There is no way you'll fit a cubic meter of concrete in a 300mm tube unless it's about 6 meters tall.
LOL fail maths.. ur dead right.. 60cm high and 300 wide is about .42 cubic
Quote:
Originally Posted by pmrid
Whether you build some concrete formwork for a full or partial concrete pier, or just do a straight steel number like Steve's, you will still need to lay a solid concrete base for the whole thing. A block of concrete a metre deep and say 400x400 will be less than 1/4 m3. I'd do it with bags of premix. Work on about 15 bags worth. I think they're about $10 a bag these days. And you have the additional option here of getting a longer bit of steel pipe and burying it (with suitable bits of steel welded to the foot to make it solidly anchored in the concrete base - eliminating the baseplate and associated bolts involved in Steve's design. Of course you don't have the option of removing it later on - apart from digging the whole thing up again.
I have one pier that is of this kind and it's rock solid. I also have one that is a store-bought steel one bolted into a slab. Both are rock solid. One cost me $1000 plus the concrete base. The other cost me the same amount of concrete base and the rest was less than $100 in scrap steel pipe. I know which was I'm going next time (there's always a next time).
Peter
This is quite a good idea. Ive always been in the habit of over engineering stuff.
After reading everyone comments on this.
I think I will go 4 Star pickets driven into the ground to reduce change of the ground around the block dissapearing and the block starting to move/shake if pushed.
400 x 400 x 1m block poured on the star pickets reinforced with rebar
4 m16 threaded rods with their ends bent welded to the rebar, these bolts will be used to attach the steel pier
steel from direct for $100
Should i put styrofoam around the sides of it to isolate it from the ground or is just isolating it from the pad ok?
and yes I partly have hijacked Helo (peters) thread. I'm asking the same question as him
4 m16 threaded rods with their ends bent welded to the rebar, these bolts will be used to attach the steel pier steel from direct for $100
I did something similar, here is a picture of what it looked like. The wood held the threaded rod in the right position during the welding and concrete pour.
Should i put styrofoam around the sides of it to isolate it from the ground or is just isolating it from the pad ok?
You don't isolate the pier from the pad. That would defeat the whole purpose and leave the pier inadequately supporded/rigid.
You isolate the pier/pad as a whole from whatever other floor you decide to put in your obs - so when you're bumping around in the middle of the night, your movements are not translated from the floor to the pad/pier/scope etc.
There was a paper issued by a guy in the US about pier design.
As I recall its the diameter of the tube that is more important than the steel thickness. 250mm diameter tube is a lot more stable than thicker 165mm tube. So you want maximum diameter.
The usual design is a large pier/base that is heavy and supports the steel or concrete pier (as wide as possible) and then a levelling plate so you can get perfectly level mounting for your scope.
You want the pier isolated from the floor if you were planning to do a slab floor (I like pavers instead of slabs, less heat retention, no vibration transmission and easy to lay).
and then a levelling plate so you can get perfectly level mounting for your scope.
I think this is where the design of a lot of (most?) piers falls down. People go to all the trouble of building a fairly rigid pier, then mount their top plate on four long bolts. These four long flexy bolts then become the deciding factor for the rigidity of the whole mount.
If you do have to use a top plate mounted on bolts, these should be kept to the absolute bare minimum length possible to avoid flexure.
You don't isolate the pier from the pad. That would defeat the whole purpose and leave the pier inadequately supporded/rigid.
You isolate the pier/pad as a whole from whatever other floor you decide to put in your obs - so when you're bumping around in the middle of the night, your movements are not translated from the floor to the pad/pier/scope etc.
Just an idea, but for my pier I built a round tube of decking timber I had lying around. I screwed the timber onto 2 metal bands on the inside, one at the top and another at the bottom, and formed a tube that way. The inside diameter is around 30 cm. And then I filled it up with concrete. It didn't have to be watertight since the concrete doesn't really ooze out unless there is a significant gap.
This was built on top of a proper concrete base into the ground.
It was very simple and yet very decorative in the end, since I could stain the timber. I'm very happy with its performance and it looks great. I would post some pictures of it but they are on another computer. If anyone is interested then I'd be happy to post the pics later.
Starting to think seriously about a pier setup now, my EQ6 Pro has arrived and I just found out how big and heavy it is !!
May go for a trolley setup for a starter but long term I think a pier and 'Ob' makes for better option. I have a suitable location at home. Just got to find all the bits and this is all good info to consider.
I am starting to think the combo pier might be the way to go (concrete base with shorter steel pier so I can adjust in the future - just in case). Does anyone have any tips for exactly aligning south or having some leeway in the mount to adjust for any error when I place a wedge on top?
I am starting to think the combo pier might be the way to go (concrete base with shorter steel pier so I can adjust in the future - just in case). Does anyone have any tips for exactly aligning south or having some leeway in the mount to adjust for any error when I place a wedge on top?
You probably will need an adapter plate of some sort... just allow it to be moved at different mounting points..
E.g. my plate (attached) will have 6 holes (red) drilled in the outside for bolts, this will allow it to attach to my pier plate and a 7th hole(green) for the mount peg. I will align the peg hole to south including magnetic deviation as accurately as possible.
the attachment bolts will be drilled about 30 degrees either side of the peg hole.
6 bolts are 60 degrees seperate.
The end result is the adapter plate will be aligned for south, where as the pier can be facing anyway as long as the holes match up.
Also i am sick atm so my explanation might not make sence
Diameter of the pier is extremely important. Get 200mm and above for diameter. It really does make a huge difference. 150 will be too narrow for astro imaging with bigger gear. This is something you only want to do once in my opinion, so get the largest diameter possible. Wall thickness contributes but not as much as diameter.
I will align the peg hole to south including magnetic deviation as accurately as possible.
It's better to use the Solar transit method. It is more accurate than using a magnetic compass and you don't have to worry about magnetic deviation or the influence of things like the rebar cage inside your concrete pier that might throw the compass needle off.
Suspend a plumb bob from a string so that the shadow of the string falls across the top of your pier. Using your favorite planetarium program, look up the time when the Sun transits the meridian on the current date. At that exact time, mark a line where the shadow falls across the top of your pier. For good measure, mark it not just on the top, but on the sides as well. The line runs North-South and is very accurate.
I think you've overdone the rebar James.
But that's ok -
You've used about the same amount of reinforcing as for a pontoon gangway mounting block. There's very little stress on the block and the rebar is only for crack stopping. F62 mesh would be more than adequate two pieces about 600mm apart vertically
) vs. a 165mm metal pier (available from one of the telescope companies here in Oz). It is to support my CPC1100 and wedge and as I wish to get into astrophotography it needs to be stable so any ideas and experiences with either pier out there? Any help is appreciated. Thx.
and I just found out how big and heavy it is !! 
