Solicitation for Comments

[KenMiller]

A Bisque Paramount.

However, I am currently using a Takahashi EM-400 and would like to mount that first and characterize it so I can compare its performance to the Paramount.

I need to do some research today about how to faciliate the mounting of either (and potentially others).

[BT Technologies]

mmmmmmm, Paramount ME....

[Bob_riggs]

Originally Posted by KenMiller

My area of greatest concern is the piers (I'm planning for 3).

I am tentatively planning on using 12" diameter concrete piers isolated from the pad of the observatory by an expansion joint. The piers would be sunk into the ground 4'.

Is there any better pier solution than a big chunk of concrete?

Will the expnansion joint be sufficient for vibration isolation?

The pier positions I am planning are 2' from the edge of the dome and 6' between piers. Do these sound like reasonable spacings?

All observations and suggestions welcome!

Hello Ken,

I install telescope piers for a living, and may be able to offer some insights. As you are in Florida, I'm guessing frost line is not a factor and 4' of buried depth is just fine, especially in sandy soil. I would suggest you consider using a 12" diameter pier foundation only up to 10" diameter fork mounted OTA's. You can downsize with GEM's due to the better balance. Bigger is truly better in this instance. An 18" Sonotube (or equivalent) costs roughly $8/9 per foot, uses little more concrete, but yields so much more stability.

The subject of steel reinforced concrete piers versus steel piers has pros and cons. Unquestionably, the concrete pier is subject to virtually zero vibration and flexture, and is much less expensive. On the other hand, if one is to move, that concrete hard to take with you, and it's nasty to remove. A steel pier is more portable in this sense, and gives somewhat greater ease of polar alignment.

If you chose to go with a concrete pier, you could bring your greater diameter up to grade/ground level, and pour a smaller diameter up to finished height.

There are good steel piers available for well under $1,000, and of course you can pay more for more features. If you'll PM me, I'll offer specifics. As to size, I mounted a 14" RCX400 on an 8" steel pier this last fall, supported on a 18" Sonotube column to floor height, under which was a 3 x 3 x 3 steel reinforced concrete block. It's "rock-solid".

I agree with your later post to install your pier(s) and build your obs around them, having determined the minimum working space needed. If your scopes are presently tripod mounted, you can arrange them in closest proximity to one another and see what's needed. Larger scopes require more clearance than smaller. Too much room is far better than too little. More concrete is better than not enough.

Hope this helps. Best wishes with your project.

Clear Dark Skies!
Bob

[KenMiller]

Thank you for your observations and comments Bob.

I know what you mean about the concrete being problematic. I once moved from a house in which I had installed a 60' tower (I'm an amateur radio operator). One of the conditions of sale was that I "get rid" of the 3' x 3' concrete slab in the back yard.

The wording of the agreement was such that I simply had to reduce it to the point that grass would grow and the back yard would appear normal. Which turned out to be a good thing. The actual size of the "slab" was 4' deep and 4' square at the bottom - tapering to 3' x 3' at the top.

After two of us worked for 4 hours with sledges and only managed to remove the four corners, I rented an electric jack hammer. Even at that it took 8 hours to remove the top 4" of concrete.

I had mixed it by hand with the help of a mason friend. It was the first batch of concrete I had ever mixed and when he asked me how hard I wanted it I told him "hard enough to withstand a nuclear blast." He obviously took me literally.

I had no idea concrete could actually be that hard. I also had no idea how much work it was mixing that stuff by hand (and that was when I was a young buck). Fortunately, a pier doesn't requrie anywhere near the volume a 60' tower does

As to the piers, I have consulted with a mechanical engineer with expertise in pilings and such regarding the design. He recommended essentially the same design you have so that's what I'm going to do.

I'll post some pictures when I get underway.

[Bob_riggs]

Hi Ken,

Nice to know your ME friend agrees with my approach. Since you have prior experience "bustin' rocks", I'll toss another tip your way. You can end your main pier foundation below grade, say a foot below, and carry your reduced diameter up to finished floor level, or even up to scope height (if you're not going with a steel pier). Of course, your rebar must run from nearly the bottom to nearly the finished level. But, the point is, you will have to chew through far less concrete, if required, if you move to another locale.

Yes, do send those pic's...lookin' forward to 'em.

CDS!
Bob

[KenMiller]

I'm a slow learner - but I'm a good learner.

You can bet I was already planning on tapering below ground level

[BT Technologies]

Ken, did you already start on your permanent setup?? Am I reading this correctly?

Originally Posted by KenMiller

I'm a slow learner - but I'm a good learner.

You can bet I was already planning on tapering below ground level

[KenMiller]

Yes Brian, I'll be ordering a Paramount soon

I have made the decision and ground-breaking is imminent.

I have a concrete mixer being delivered this weekend.

I'm going to put one pier in and see how things go. I'll almost certainly add a second. We'll see from there.

For the time being I'm going to just cover the mounts and carry the rest of the gear in and out.

After I settle on how many piers and their spacing I'll worry about getting a building up around them.

There are just too many variables for me to decide on a building size yet and too many benefits to the permanent pier not to do it ASAP.

[BT Technologies]

WOW!! You don't mess around!!

I look forward to seeing your progress on this project. Please let me know how everything goes.

Originally Posted by KenMiller

Yes Brian, I'll be ordering a Paramount soon

I have made the decision and ground-breaking is imminent.

I have a concrete mixer being delivered this weekend.

I'm going to put one pier in and see how things go. I'll almost certainly add a second. We'll see from there.

For the time being I'm going to just cover the mounts and carry the rest of the gear in and out.

After I settle on how many piers and their spacing I'll worry about getting a building up around them.

There are just too many variables for me to decide on a building size yet and too many benefits to the permanent pier not to do it ASAP.

[KenMiller]

My original post was over three weeks ago. Normally, I would say that would qualify me for "lolly-gagging."

But as someone else owns the property I'm putting all of this on, some “persuasion” time was necessary