Building an observatory pier

15 years 10 months ago #6566 by albertw
Building an observatory pier was created by albertw
From another thread...

At the moment I'm building an observatory at home in Meath and would like some advice about the pillar for the mount. I know some people who have done this and have filled the pillar with sand to cut down on the vibrations, does anybody know what kind of sand would be best? I.E coarse or fine, wet or dry?


I asked a similar question a couple of years ago and the replies are still at

groups.yahoo.com/group/irishfas/message/1120

I never got around to doing it, but other may have experience to speak from.

Cheers,
~Al

Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/

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15 years 10 months ago #6568 by markdj
Replied by markdj on topic Re: Building an observatory pier
We are hi-fi buffs too and my brother Nigel built a pair of Side vivace enclosures for Lowther DX-3 drive units.

The enclosure was for a single horn-loaded drive unit and this required us to make a horn to amplify the bass from the single drive unit. The gaps were filled with play sand which was dried out in our boiler house over a few weeks. Play sand is used as it is sterilised and nothing will start to grow in it!!!

Use a thin stick to attack the sand as it settles in the tube. After you fill the tube, you will find that it takes a few days and some stabbing with a stick to get the sand to settle but it does work.

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15 years 10 months ago #6569 by Wallymee
Replied by Wallymee on topic Re: Building an observatory pier
Gary Nugent did a piece in Orbit within the last couple of years on the construction of an observatory. He in fact gave a talk to SDAS (back in Kenilworth days) as well.

That might be of some help.

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15 years 10 months ago #6570 by spaceboy
Replied by spaceboy on topic Re: Building an observatory pier
Thanks for these replies. I'll check out the links for ideas.

Cheers

Spaceboy.

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15 years 10 months ago #6571 by albertw
Replied by albertw on topic Re: Building an observatory pier
As well as Orbit, Gary has put similar articles into his own pdf ezine Photon. www.nightskyobserver.com/Photon/

issues 1 and 2 have articles describing the observatory, though I think he bought a pier.

Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/

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15 years 10 months ago #6573 by dave_lillis
Replied by dave_lillis on topic Re: Building an observatory pier
Hi Spaceboy,
I built a pier about 2 years ago for the 12",
It consists of a metal tube 6 feet long and 10 inch in diameter, the metal itself is 5/8 inch thick steel, its a serious weight!.
Then I got a local metal working company to weld on a square metal plate onto each end, each plate is 16x16x1 inches of steel.
I then got the entire thing hot dipped galvonised and then I painted it black using hammerite.

I had holes drilled onto each plate so that one end could be bolted into the ground and the other end could have another plate sitting on top of it using 4 thread bars +bolts (3/4 inch thick), this top plate could then be precisely leveled using the thread bars, and I had holes drilled in it so it could accomodate a wedge.

The reason why I used a barrel (aka supergun) 6 feet long was that I could bury half it in concrete if the need arose, to dampen any vibrations. It sits on a foundation 3 feet thick which sits on bedrock. It could easily accomodate a much heavier scope. Its rock solid and I can lean against it while using the scope with no noticable effects.

I had a hole made 2 feet from the bottom where i fed up a conduit for wires, so there will be no wires around the pillar. I filled the internal cavity with normal sand, there are no plants coming out of it yet :)

An observatory is going to be built around this over the coming months.
This might be over the top for alot of scopes, but its an idea of what you can do.
I'll put up a pic tomorrow.

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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15 years 10 months ago #6581 by DaveGrennan
Replied by DaveGrennan on topic Re: Building an observatory pier
I'm also planning an observatory here in rural Raheny!

I'm actually thinking of something like this

My problem ir that I plan to mount my 12.5inch newtoinian on an equatorial mount and I'm gonna need a lot of space so it can swing 360 degrees. One of my long term objectives is to make this fully automated and internet accessible. Thats a few years down the road and I may well relocate it to a less light polluted area.

I'll post info as it progresses.

Clear skies,

Dave.[/url]

Regards and Clear Skies,

Dave.
J41 - Raheny Observatory.
www.webtreatz.com
Equipment List here

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15 years 10 months ago #6591 by spaceboy
Replied by spaceboy on topic Re: Building an observatory pier
To Dave L, Thanks for that info. I'm thinking something similar might be appropiate for me and I don't have to go to a metalworks to get it done since I'll do it myself and lower the costs. :D

To Dave G, Will U be at the meeting on Tuesday evening? If so we'll have a chat.

Spaceboy

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15 years 10 months ago #6592 by dave_lillis
Replied by dave_lillis on topic Re: Building an observatory pier
Spaceboy,
Nice one if you can do the metal work yourself, i just wouldn't do the welding myself, since I need it to be good. :lol:

Heres a pic of the mount i use, I put the ETX70 on it for scale.

www.irishastronomy.org/user_resources/fi...254-Pillar+ETX70.jpg

I left the protruding bars underneath and will cut them off when I have the dome built.
Some of the bolts are slightly rusted, these I'll change over the next few months.

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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15 years 10 months ago #6596 by michaeloconnell
Replied by michaeloconnell on topic Re: Building an observatory pier
When it comes to filling the pier with something, sand is a reasonably good material. However, if dampness gets into it (which it could very well do) then the effective of the sand decreases alot. Basically, sand consists of alot of small round particles. The fact that they are round means that they don't compact too well. However, if you wet the sand, the viscosity of the water tends to fill up the void spaces between the grains and stick the grains together. Wet sand in a pier is not desirable as it will resonate vibration much easier bacause the vibration travels across from one grain to another through the water. You end up with a semi-sold internal portion to your pier.
If you are concerned about dampness hitting the sand, you might decide to select a material with larger particles, all of similar size. Therefore, coarse dry sand or small single-sized stone might make a better choice.
When selecting a small-sized stone to use make sure it is of roughly all the same size aggregate. Beach or river gravel would be much better than normal crushed stone as it is rounded due to the action of the water. Rounded particles don't compact too well (think of marbels) which is why river or beach gravel is never used (or at least SHOULD never be used) for constructing something on. The fact that they can't compact means that they have room to move around a bit. This is what you want in a pier as the movement of the particles actually disapates the energy thus reducing vibration.
A point will come of course when too large an aggregate size will mean that vibration will go up due to insufficient material in the pier to take vibration. However, my gut instinct tells me that this wouldn't happen until you were using something very large stone. Therefore, when selecting a material to fill the pier, I don't think people need to restrict themselves to only sand.
(end of geology lecture! :wink:)
Clear skies,

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15 years 10 months ago #6597 by michaeloconnell
Replied by michaeloconnell on topic Re: Building an observatory pier
Nice mount for the ETX Dave! :wink:

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15 years 10 months ago #6602 by dave_lillis
Replied by dave_lillis on topic Re: Building an observatory pier
Michael,
Going on what you say above, maybe something like sharp sand (for patios) would be a good choice as it compacts well.
By adding this sand or any material, you're reducing the resonant frequency of the pillar, which can be but isn' t always the best thing to do, so I've heard ?!?

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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15 years 10 months ago #6603 by DaveGrennan
Replied by DaveGrennan on topic Re: Building an observatory pier
I'm far from an expert on resonant frequencies etc. My understanding of the situation is this. What you need to do is either increase the resonant frequency so that the wavelenght is so short that it becomes undetectable at the eypiece or on film. The other option is to lower it so that it a very long wavelenght produces the same result. I remember reading a post from someoneone somewhere who said that if you tap the pier with a hammer (lightly) you should hear a dull thud. Makes sense to me. I *think* what I'm saying here ties in with what Michael says.

The obvious solution to me sounds like cement as the filler. I guess I'm missing the point here somewhere.

Clear Skies,

Dave.

Regards and Clear Skies,

Dave.
J41 - Raheny Observatory.
www.webtreatz.com
Equipment List here

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15 years 10 months ago #6604 by markdj
Replied by markdj on topic Re: Building an observatory pier
Yeah, the stuff we got for the speakers was very fine, I think it was called sharp sand now that you mention it...

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15 years 10 months ago #6605 by albertw
Replied by albertw on topic Re: Building an observatory pier

I'm also planning an observatory here in rural Raheny!

I'm actually thinking of something like this


Some of you may know Carsten Arnholm from imaging newsgroups. He built a similar observatory to the one linked above from a flatpack garden shed. More details at www.arnholm.org/astro/observatory/index.htm

For a pier he went with re-enforced concrete www.arnholm.org/astro/pillar/index.htm

Dave, the biggest issues I can see with perhanent observatories in suburbia (after light pollution!) is security. I'm not sure I'd feel confortale with a converted shed to store expensive optics and a computer. Building a proper dome in the garden is a bit overkill though!

Cheers,
~Al

Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/

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15 years 10 months ago #6606 by DaveGrennan
Replied by DaveGrennan on topic Re: Building an observatory pier

Dave, the biggest issues I can see with perhanent observatories in suburbia (after light pollution!) is security. I'm not sure I'd feel confortale with a converted shed to store expensive optics and a computer. Building a proper dome in the garden is a bit overkill though!

Cheers,
~Al


Al,

Yes both of those are my biggest concerns. As for the LP well theres not much I can do about that except have a chat with the people in St Josephs Hospital which over looks my back garden. They have huge halogen lights looking down on their grounds. They arent very well aligned. One of the shines outward rather than illuminating their property. I'm sure I can have them adjust this. If that fails there's always the commando option;) Only kidding! I really plan to do CCD/Webcam imaging at home through my 12.5 reflector and possibly consider buying this klevzov cassegrain . I have a 16inch truss tube dob which is eminently portable for taking to dark site observing sessions.

As for security, this is really my biggest concern. My back garden adjoins a public park the local gurriers often have drinking sessions right behind my back wall, On the other side is the DART track which further exposes my site. What I do have on my side is bloddy great big snarling mutt who goes ballistic if anyone comes within 100 yards of our property. When she pops her clogs I plan to get two doberman!! I'm thinking that with the mutt and a couple of IR passive sensors hidden well within the observatory and linked underground to the house alarm should mean that no-one can get in without at least waking a couple of cemetaries.

Thing is after lugging heavy scopes around for years you do eventually get tired of it. It can be hard to get motivated especially if the night is not absolutely perfectly clear. I personally feel that building this observatory will give me new impetus for astronomy. I work in I.T., spent many years as a software engineer and have a bit of elecronic engineering experience too. I think I should have enough expertise to do a lot with the observatory with regard to automation etc. I reckon the whole observatory thing could become a sub-hobby in itself to tide me through the cloudy nights!.

Sorry for the long winded post. I find it hard to stop sometimes:)

Best wishes and clear skies,

Dave.

Regards and Clear Skies,

Dave.
J41 - Raheny Observatory.
www.webtreatz.com
Equipment List here

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15 years 10 months ago #6607 by michaeloconnell
Replied by michaeloconnell on topic Re: Building an observatory pier

Michael,
Going on what you say above, maybe something like sharp sand (for patios) would be a good choice as it compacts well.
By adding this sand or any material, you're reducing the resonant frequency of the pillar, which can be but isn' t always the best thing to do, so I've heard ?!?

Dave,
I don't think compacting the sand is a good idea.
What you need is one of the following:
1) Coarse sand or small rounded single-sized gravel loosely thrown into the pier
or
2)Reinforced concrete.
Anything in between is exactly what you don't want.
i.e. it either needs to be very loose material which can move slightly and distribute the vibration through itself due to the looseness of the material
or
it needs to be extremely stiff and able to withstand a nuclear bomb (note slight exageration! :) )
Anything in between will allow a certain resonance that may not be desirable. This ties in with what Dave Grennan said:

I'm far from an expert on resonant frequencies etc. My understanding of the situation is this. What you need to do is either increase the resonant frequency so that the wavelenght is so short that it becomes undetectable at the eypiece or on film. The other option is to lower it so that it a very long wavelenght produces the same result.

Clear skies,

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15 years 10 months ago #6609 by dave_lillis
Replied by dave_lillis on topic Re: Building an observatory pier
Michael,
Thats fine, the sand in the pillar here is not cmpacted, and filling it with concrete is out of the question, if I ever move house I dont want to have to hire a helicopter to move the pillar.

Albert, I once thought that have a dome in suburbia was abit much also, but once you surround is with abit of trellesing it can go along way to disguising it, it would also depend on your local surroundings and mine are ok for it.
And pictures I got over the last year or so have convinced me that I can get some decent images here, and for visual observing, its far from perfect but its not as bad as I've seen elsewhere.
Its what I have for now and I'll just have to make to most of it!

I will not have a permanent PC out there, I'll just bring out the laptops needed, and obviously the scope is insured and the structure will be wired into the alarm system.

I have to say that a roll-on roll-off shed is looking very appealing also, this might be the solution for alot of people.


Dave Grennan, That looks like a fine scope, how do you intend to mount it. I'll probabily go for a big trus dob in the next few years, did you ever make up drives for it ?
Would it be feasible to incline the whole thing on a very low wedge and make it polar, you might get some great images with that kind of aperture ?!?

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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15 years 10 months ago #6614 by michaeloconnell
Replied by michaeloconnell on topic Re: Building an observatory pier
I should mention of course that the material you use to fill the pier is minor in comparison to the diameter, height and stiffness of the pier itself. This should be the main priority by far.

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15 years 10 months ago #6617 by DaveGrennan
Replied by DaveGrennan on topic Re: Building an observatory pier

Dave Grennan, That looks like a fine scope, how do you intend to mount it. I'll probabily go for a big trus dob in the next few years, did you ever make up drives for it ?
Would it be feasible to incline the whole thing on a very low wedge and make it polar, you might get some great images with that kind of aperture ?!?


Dave L.

The 16 inch is currently dob mounted. The scope was designed and built by Phil Lardner and I must say Phil builds the best big dobs I know of. I am in the process of installing Mel Bartels homebuilt drive system (have you seen it> If not check it out The biggest problem I'm having is mechanically attaching the stepper motors. Actually attaching them is not the problem. The problem is that the scope is acting like a big amplifier, amplifying the vibration from the steppers. I need to mechanically isolate the steppers so that the vibration doesnt get to the scope assembly at all.
The main problem photographically with this setup is of course, field rotation. Once I get the drive system working properly then I can knock together a field de-rotator. Of course with programs like registax around tracking problems like this can be overcome a lot easier so maybe I wont need the de-rotator at all.

The 12.5inch is mounted on a synta/skywatcher EQ6 mount. See Here for image of 12.5 fully mounted . I may have mentioned in another thread that I plan to replace the drive system on the EQ6 with AWR Tech's EQ6 kit to enable full GOTO and for generally better performance. In the photo you can see the 12.5inch has a split ring system so that the OTA can break in two for easy transport and storage. When I get around to affording the klevzov cassegrain I guess it will also go on the upgraded EQ6. The nice thing about the EQ6 is that its rock solid and has a nice easy release system so that scopes can be interchanged easily.

Regards and Clear Skies,

Dave.
J41 - Raheny Observatory.
www.webtreatz.com
Equipment List here

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15 years 10 months ago #6627 by dave_lillis
Replied by dave_lillis on topic Re: Building an observatory pier
Dave,
Gosh, the tube looks massive on that mount!, I can see why its giving some problems.
As for the Dob, sounds like you need some sort of dampening ?
How will you mechanically, presumabily physically isolate it, maybe using drive belts ??

Ive read up on field derotaters and they work fine but can be real finicky gadgets to get working right, could you just incline the base of the scope by placing a triange wedge underneath it and then one motor is all you need for tracking, lock the declination axis, and you wont need a field derotater ?!?

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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15 years 10 months ago #6629 by DaveGrennan
Replied by DaveGrennan on topic Re: Building an observatory pier

Dave,
Gosh, the tube looks massive on that mount!, I can see why its giving some problems.
As for the Dob, sounds like you need some sort of dampening ?
How will you mechanically, presumabily physically isolate it, maybe using drive belts ??


Its not so much that the size/weight of the scope causes problems its more that the standard eq6 drive system is not the best at all. The step sizes in the motors is too big hence there is a detectable vibration at high powers also the whole deal is really only suited to short exposure photography. I plan to invest in a decent CCD camera in the new year and I really wanna be sure that the scope/mount/drive system will be up to the job. As for the dob you are exactly right, belt drives are the way to go. I have gottem hold of some rubbery sef adhesive anti vibration material from a friend of mine and this in conjunction with a belt drive should more than do the job.

Ive read up on field derotaters and they work fine but can be real finicky gadgets to get working right, could you just incline the base of the scope by placing a triange wedge underneath it and then one motor is all you need for tracking, lock the declination axis, and you wont need a field derotater ?!?


Agreed 100% but if you saw the size of the 16inch you'd agree that in its current form inclining it at 53.5 degrees is just not really a goer!!! Also the mirror cell uses a sling to hold it. I'd pretty much have to re-engineer the whole scope to do that. Actually to be really honest I reckon the 12.5inch and perhaps the new 8inch klevzov I mentioned will satisfy my photographic needs. Really the 16inch is just for observing the faintest fuzzys any as I mentioned earlier registax can sort a lot of problems out. Field rotation on the 16inch is really at the end of my astro priorities list.

Clear Skies (Which we havent seen too much of of late:( ),

Dave.

Regards and Clear Skies,

Dave.
J41 - Raheny Observatory.
www.webtreatz.com
Equipment List here

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15 years 10 months ago #6633 by Seanie_Morris
Replied by Seanie_Morris on topic Re: Building an observatory pier
I have been doing a little research myself from whence I started building my 2 scopes, and one thing that was always mentioned but I hardly ever see put to use is that fact that the larger the scope, the closer to the declination axis it should be.

For example, while Dave Grennan's scope looks slightly as if its going to topple over at any moment, if the tube was closer to the polar/declination axis the better. I know that Dave's mount can't do this, as it is factory built, but when building your own mount, this should be taken into consideration. On that mount, it looks like there is about a 8 or 9 inch gap between axis and tube.

If this gap could be brought down to about 2 or 3 inches (which can be done when building your own mount), there is then less need to 'dampen' the scope's movement, as it has a lower center of gravity, and therefore easier to balance, and then manipulate.

One other factor is also to find the tubes center of gravity. This is not always half way down the tube, but should be about 1/3 the distance of the tube from the mirror. This is because of the weight of the tube versus the end weights of a) the focuser, spider/secondary, and finder scope versus b) the mirror and cell.

Just a few things that have helped me in balancing on my mounts!

Seanie.

Midlands Astronomy Club.
Radio Presenter (Midlands 103), Space Enthusiast, Astronomy Outreach Co-ordinator.
Former IFAS Chairperson and Secretary.

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15 years 10 months ago #6655 by dave_lillis
Replied by dave_lillis on topic Re: Building an observatory pier


Agreed 100% but if you saw the size of the 16inch you'd agree that in its current form inclining it at 53.5 degrees is just not really a goer!!!

Clear Skies (Which we havent seen too much of of late:( ),

Dave.


Hi,
Fair enough, I've never owned a big dob and experiance is everything.
It always looks simple until you try it.

as for the weather, its a major bummer :cry:

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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15 years 10 months ago #6709 by albertw
Replied by albertw on topic Re: Building an observatory pier
Was chatting to an Uncle about a pier earlier, knows little about astronomy but a lot about building.

He reckoned that reinforced concrete is the way to go. To have a 9" pier a meter above the ground, he reckons you would need to go almost as far underground.

Dig down, and create a wide base to stick the reinforcing bars into. Then buy a 9" diameter concrete pipe, put that in place, level it, support it with wood, and then pour concrete in, then sink in the mount base into that. Concrete should be mixed with one part sand and two parts gravel (or just gravel, I have some sand I'm trying to use up).

So now to find someone who can weld a mount base for me...

Cheers,
~Al

Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/

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