My ongoing astro work is going well. With Larry Scott's help with the calcs, I'm showing sub 2.5" standard deviations on my observations.
It's going so well, I think I'm running into the limitations of my tripod. When I remove the solar filter to go to reverse (I must...it won't swing), there are signs I'm screwing up the setup, to the tune of multiple (possibly 10 or more) seconds. Plus, the tripod is partially on ledge, partially in the dirt around it. Not the best setup.
I want to build a permanent observation pier. I've got my primo network control point on a rise in my largest open field. It's currently a magnail in solid rock ledge. See sketch.
I've thought of setting up a rigid (bar) plumb bob, and carefully filling it with concrete, but am concerned it may shift during the pour. Or does it matter, so long as I mark my spot at the top of the pier? I'd then put a top plate on with a permanently mounted tribrach.
Ideas on how to do this?
[USER=6521]@Shawn Billings[/USER] built something similar years ago. They used it for GPS antenna but you could work it for what you're doing. Take a 2 3/8" piece of drill stem tubing, dig a 3' hole, bevel out the bottom, drive the pipe in the ground until it's solid AND at the height you want to run an instrument from, fill the hole and the inner part of the pipe with concrete, and before it dries, take a busted old range pole with right 5/8"x11 threads and sink it in the concrete. Let it set for several days. Then screw the tribrach onto it, put the gun in the tribrach and turn the hell out of some angles.
They did something similar in the 60's when they built the Astrodome except they hardmounted a Wild T3 if I remember right.
Build a mini tower (tiny oil derrick) out of angle iron with a permanent 5/8" threaded stud. That way the monument is available and the tower removable.
Or pour a concrete column Sono tube, well into the ground with a 5/8" stud. As a new point, not over the existing mark.
A true Astro post.
(That won't elevate the potential of disturbing your backsight obs by filter removal and replacing.)
I like steel better than concrete. i can fab a 4" schedule 80 pipe, with flange, and chemical anchors into the rock. That way, I can check for plumb from time to time after earthquakes. 😀 I'll drill the 5/8"-11 stud so that an optical plummet will still work.
I want to keep my point. It's in rock, not soil. What's not to like? Also removable, but I'd have to cut the anchor bolts off.
But that's for another day.
I think I'm coming into it.
rfc, post: 371937, member: 8882 wrote:
I like steel better than concrete. i can fab a 4" schedule 80 pipe, with flange, and chemical anchors into the rock. That way, I can check for plumb from time to time after earthquakes. 😀 I'll drill the 5/8"-11 stud so that an optical plummet will still work.
I want to keep my point. It's in rock, not soil. What's not to like? Also removable, but I'd have to cut the anchor bolts off.
But that's for another day.I think I'm coming into it.
I like the beer bracket a lot!
Ah yes - the beer leg!
Did you cut a section right thru your beer cozy/coozie/koozy/definitely not "beer cossy"? If not, do account for the extra diameter. Also, you'll need a light to see that mag nail...
I used to find these permanent stands over bronze disc set in concrete. Build one of these.
That's an Ashtech antenna propped on rocks.
But a 5/8 stud would be better.
Northern Argentina, circa '96. A few km south of Bolivia. 
rfc, post: 371928, member: 8882 wrote: My ongoing astro work is going well. With Larry Scott's help with the calcs, I'm showing sub 2.5" standard deviations on my observations.
It's going so well, I think I'm running into the limitations of my tripod. When I remove the solar filter to go to reverse (I must...it won't swing), there are signs I'm screwing up the setup, to the tune of multiple (possibly 10 or more) seconds. Plus, the tripod is partially on ledge, partially in the dirt around it. Not the best setup.I want to build a permanent observation pier. I've got my primo network control point on a rise in my largest open field. It's currently a magnail in solid rock ledge. See sketch.
I've thought of setting up a rigid (bar) plumb bob, and carefully filling it with concrete, but am concerned it may shift during the pour. Or does it matter, so long as I mark my spot at the top of the pier? I'd then put a top plate on with a permanently mounted tribrach.
Ideas on how to do this?
Hello rfc,
My experience with steel pillars is that steel bends like a banana when the sun hits one side. And you'll get differing movements as you move around and shadow and in-shadow it. If you must use steel then I'd recommend fashioning a fabric skirt that will drape over the pillar when in use and prevent any full sun from hitting it at all. Otherwise having ur own pillar is pretty cool.
If you have data on that nail already, can you accurately enough reference it out to three other monuments, put a concrete pier in place, and then set a 5/8 bolt over the original nail by the ties to the reference marks? I can see you might lose 0.01 or 0.02 ft in the process.
Stolen from a friends Facebook page.
She was involved in the construction of a CORS site.
The concrete apparently goes 5m below ground level.
Larry Scott, post: 371944, member: 8766 wrote: I used to find these permanent stands over bronze disc set in concrete. Build one of these.
That's an Ashtech antenna propped on rocks.
But a 5/8 stud would be better.Northern Argentina, circa '96. A few km south of Bolivia.
Very cool looking tower, but I want something slender...don't want to have to lean over the tower to sight (or always need to use the right angle view finder).
Bill93, post: 371969, member: 87 wrote: If you have data on that nail already, can you accurately enough reference it out to three other monuments, put a concrete pier in place, and then set a 5/8 bolt over the original nail by the ties to the reference marks? I can see you might lose 0.01 or 0.02 ft in the process.
I'm now thinking that if I leave a small amount of adjustability to the 5/8 stud (Like an oversize hole, with a washer under the head of the bolt), I can use the optical plumet to dial it in, then tighten the bolt. (I'd leave cut-outs at the top of the post, beneath the top plate). If I got a tribrach with an optical plummet I could always check centering before and after use. Thanks for the suggestion though.
Conrad, post: 371953, member: 6642 wrote: Hello rfc,
My experience with steel pillars is that steel bends like a banana when the sun hits one side. And you'll get differing movements as you move around and shadow and in-shadow it. If you must use steel then I'd recommend fashioning a fabric skirt that will drape over the pillar when in use and prevent any full sun from hitting it at all. Otherwise having ur own pillar is pretty cool.
Excellent point. If my wife will let me, I can paint it white, or better yet, put a section of airconditioning duct insulation (fiberglass), with the white vinyl cladding.
Or I could go full hi-tech International Space Station look, and get the kind with aluminized mylar covering. 😀
Add a few satellite dishes next to it and I'll really have my neighbors wondering.
When we build a robotic telescope pier we always put in at least a cubic yard of concrete in at the base of the pier below the frost line for stability. For GNSS antenna pier ideas, see UNAVCO.
astrodanco, post: 371987, member: 7558 wrote: When we build a robotic telescope pier we always put in at least a cubic yard of concrete in at the base of the pier below the frost line for stability. For GNSS antenna pier ideas, see UNAVCO.
A cubic yard? Whoa. This and the CORs mount Seb posted are certainly beyond my budget. But I'm fairly certain my "platform" is solid rock...not granite perhaps but very monolithic biotite quartz. I'll know in a heartbeat after I put a hammer drill to it.
The little steel mini tower is reminiscent of the old bilby towers. And you won't have to be too concerned with sunlight. When you get serious about Astro, it'll all be night work.
Solar azimuth first, stellar Lat/Long next.
Take a look at some of the stands and pillars as well as the information about training on astronomical observations here: http://www.ngs.noaa.gov/corbin/class_description/Astro_12.shtml
A wooden stand like those in some of the photos are cheap, easy to build and with the platform around the stand isolated from observer movement.
Photos also show a concrete pillar. Folks at the NGS facility would most likely be happy to provide specs.
HTH,
DMM
Especially if you have a 35 lb T3.
