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.

Yeah, the stuff we got for the speakers was very fine, I think it was called sharp sand now that you mention it...

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

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.

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,

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 ?!?