Pier question

[Leo.G (Leo)]

My son got a big hole dug in the back yard for me to finally put my pier in. As I live in a department of housing house I need something I can remove if necessary and I'm planning on a solid concrete cube base in the ground but contemplating a sand and cement mix only for the top 6 inches of the pier foundation. Any need to remove the item I crush up 6 inches of easy broken stuff, cut off the rebar and stainless steel mount studs I'll be concreting in and bury with at least 6 inches of topsoil.


I've seen the bases done with blocks, I'd get it more accurate pouring concrete.



I did some rough maths on the weight yesterday and the block I am going to pour, 25x20Kg bags of concrete in total, plus aggregate and sand adds up to a lot of weight beyond my removal capabilities.

Of course I'll only leave here if I drop dead or win the lotto so I want it to be solid.


Will this work or do I need something more substantial for the heavy steel pier?


My other option is to dig deeper and weld up a steel riser I can remove if required, I have an equivalent size steel tube with thick wall here I can cut and weld but I'd rather not do that if I can get away without the extra work. Plus I'd require some extra solid steel plates at 12mm and steel is now far from cheap.

[doppler (Rick)]

The sand and cement spacer idea would work, but you would have to use a quality mortar mix to avoid shrinkage and cracking of the mortar as it dries.
I wouldn't worry about reo in the concrete block, the weight of a home astro setup would not be enough to stress crack a solid block of concrete.
Rick

[Leo.G (Leo)]

Thanks Rick!


The rebar isn't so much to prevent cracking, I'm driving some into the ground radiating outwards at a 30 odd degree angle to minimise on the size of the pad a little and I'll drive some more vertical rods down to tie my stainless threaded rod to so it doesn't move during pouring.
I could drill holes post block but I used to install car hoists and know what sort of dramas can arise drilling through concrete.

[muletopia (Chris)]

Hello Leo
My pier sitting on a 1.3 metre cube of concrete suffers seasonal movement as the soil expands and contacts with the annual variation in moisture content. I suspect that a pier on a shallow base will suffer more, i.e. more frequent polar alignment will be required.
Chris

[Leo.G (Leo)]

I have clay at 600mm depth. I did a lot of reading on Stargazers and it's a common theme in England (probably plenty of other places too) and everyone says their clay is extremely stable.
Comparing Britain's temperatures to Lithgow, well, we don't get as much rain, occasional snow and -12C at night through winter.


1.3 M^3 would be a lot of concrete for me to mix and I wouldn't get a truck into my back yard, bags would cost me a fortune.
Add rental (department of housing, I'm not leaving till I drop dead or win Lotto and I have the strangest feeling I know which will come first). That's why I wanted something easily disposed of to a certain depth.
I already own the pier and since I bought it I'm determined I'm going to use it. I was going to weld my own up and have everything here to do it but a great offer came up locally.



I did just look up the concrete pads Bunnings sell:


https://www.bunnings.com.au/anston-6...-slab_p3451565


I can easily stack and drill 3 of them to add the extra 150mm height, removable in the case of my leaving this plane of existence, death or big win, run my stainless threaded rod through into the concrete pad (set during the pour) and the pier and nut tension would hold them in place on top of a semi decent concrete pad tied into the ground with the radiating reo bar driven in to around .8-1 metre diagonally at 30 odd degree angle.


Alignment is always an issue, I am just beyond the mountains and can't pick up stars as easy so I generally forego it and rely on a good solar noon for south and currently markers on 3 pavers set level in my sloping yard.
I obviously haven't gotten to anything beyond 180 second exposures as of this time but hoping a permanent pier and more permanent set-up will allow me a little better. Plus I would put more time into getting accuracy suitable for my low level of equipment.

I can drift align possibly but besides the mountains to my east I have trees everywhere surrounding my yard ( immediate neighbouring houses) at around 30-40 feet high. It used to be so much better here before I got so old and the trees grew so high.


I keep telling everyone I should sell everything astro related and buy a motorbike I can still ride when it's raining or cloudy, one of my few other passions I can't currently afford on disability pension.


I've made up my mind, I just need to win Lotto!

Had I not disturbed this thing I could have bolted my gear to it but I dug a trench for electrical to a garden shed. Guess where it was?
Around 3 feet from my destination at the far end of a trench already dug over a period of several days, RIGHT in the middle of my path.......

Had I just dug 12 inches to the left or right of it.....
It's over 24 inches width on the large side.

[doppler (Rick)]

My thoughts on piers is that if you can setup a scope on a tripod and get no vibration while imaging then it doesn't really matter how small your footing is as long as the ground is firm enough so your setup wont tip over. Any pier is a 100% better than a tripod.
My pier is in the backyard with no dome so I have alignment markings that when I put my rig back on polar alignment is usually good enough to start imaging a just a few minor tweaks.
My pier hole was 600mm deep and has a small 300x300mm footprint at the top, slightly pyramid shaped at the bottom of the hole. My ground is fairly hard I needed a crow bar to help dig it.

Rick

[Leo.G (Leo)]

Thanks Rick!
Yes, the pyramid with the smaller opening at top is always a go to for any structural I've ever done for posts being concreted in (mostly carports and garages when younger).
My tripod was quite good just sitting on 3 pavers set on a gravel base with sand on top for levelling. One paver was set down around 6 inches, one around 3 inches and one at ground level, the joys of a sloping yard. I used a laser level (green one I can see in daylight) and checked the other day, with a lot of rain in recent months (about 48 of them from memory) there was a total difference of around 1.5mm over the three and I set them in at least 6 months ago I think (or yesterday, I just don't remember stuff any more).


I did dig a drainage trench for the 2 set below the ground level so they wouldn't float.
I was getting good 3 -4 minute exposures with an RC8 pointed at Orion (M42) and that's with a modified EQ5 PRO mount (tapered roller bearing on RA and high spots removed from alloy worm gears.
I had the one half a star in every frame over 250 x 180 second exposures, not the slightest drift and all of this done by a total idiot (myself).
I just sat the tripod in the perfect place on that occasion.


Plus a pier would significantly reduce set up time. I have also considered making a lockable water/bug proof cover for the head sitting on the pier and leave it out permanently. Hopefully reducing the need for alignment other than perhaps a quick check here and there. I have to learn to weld alloy first. I excelled in it when I did my fabrication engineering well over 20 years ago and have a very nice 200 Amp TIG welder here I just can't remember how to use.
Maybe a spool gun on my MIG will do, not as pretty though.

[joshman (Josh)]

oooh. I'm definitely paying attention to this. I'm about to embark on putting in a pier at some point in next few months, so I'm very keen to see everyone's ideas.


What's the final design and dimension for your pier? slightly pyramid shaped, with steel driven into undisturbed dirt radiating out underground?

[Astronut07 (Ben)]

Howdy All

I once saw a YouTuber using a concrete birdbath that he tipped over so bath was used as ground base and the he attached mount to other end of birdbath.

He used as a temporary setup.
If memory serves me correctly I believe his channel is “ Dakota Starry Nights “

Best of luck

[LonelySpoon (Neville)]

Originally Posted by Astronut07

Howdy All

I once saw a YouTuber using a concrete birdbath that he tipped over so bath was used as ground base and the he attached mount to other end of birdbath.

Best of luck

Funnily enough, I used a 6" terracotta drainpipe with the flange up as my pier in Sydney. Filled it with concrete and stuck the mounting bolts in the top.

When we sold the house, I removed the metalwork and left it there as a birdbath.

Neville
LSO

[Leo.G (Leo)]

Originally Posted by joshman

oooh. I'm definitely paying attention to this. I'm about to embark on putting in a pier at some point in next few months, so I'm very keen to see everyone's ideas.


What's the final design and dimension for your pier? slightly pyramid shaped, with steel driven into undisturbed dirt radiating out underground?

Basically yes, I currently have a 600x600x600 hole dug, I'll slope the sides later and the steel rebar radiating outwards into the undisturbed dirt should give it a level of rigidity. I haven't looked at what stuff I have laying around, I know I have a heap of 19mm reo somewhere in my steel pile, I think they are 1200mm lengths and I'll likely cut them in half so there's less chance of getting unknown pipes or my electrical and fibre-optics running to my garden shed, that trench isn't too far from where I have the current hole, positioned to give some clearance over trees in other yards and to avoid the front street light which lights up parts of my backyard like a Friday night football game. The reo will all cross over in the slab, possibly like a frame for a tipi:


https://external-content.duckduckgo....d89&ipo=images


I'll also drive some vertical reo down to tie my 16mm (or 20mm I can't remember) stainless rod which will be the main mount points. I was going to weld and bolt the stainless rod in position but whether I can be stuffed pulling a welder out and trying to weld down in the hole, it's a whether dependant, whether I can be bothered but the hole has been dug right in the centre of my three pavers I currently use so I'm thinking not the place to be shuffling around in the dark. I either get it done or I don't take a telescope out.



My gear isn't overly heavy, an EQ5 PRO (modified) and my heaviest scope would be my 152mm Skywatcher refractor (often carries the Megrez as a spotter) or my 8" GSO f5 Newt but my primary scopes are my Megrez (original model) 80mm refractor and the GSO RC8 carbon. Both are quite light.

[doppler (Rick)]

Here's a couple of pic's of my pier setup. My ground is pretty hard so basically just a large fence post sized hole filled with a strong concrete mix. The pier is bolted to the concrete using concrete screws, stronger than dyna bolts but easily removed. I have a second concrete base further up the garden that gives me a good low western view for comet chasing. It is quick and easy to unbolt the pier and relocate it to the other base.
I do put a big load on it and have not had any issues apart from filling the tube with fine sand, the hollow tube would resonate when the dog barked.



Rick

[gb44 (Glenn)]

I like the anchoring with concrete screws rather than dynabolts. There are Xbolts that are concrete bolts that can take larger loads too.

Leo, what about building an insulated roll off box that can cover the pier, mount and possibly the telescope too? Tied down to the ground in case of storms using turnbuckles. Weatherproof to the ground level. Build-in room for a portable a/c unit that you switch on a few hours before using the scope in summer...

I'm looking at doing this. I had one years ago that I used for my 18inch newtonian and it was trouble free. I disguised it as a bird cage.

Cheers
GlennB

[Leo.G (Leo)]

Thanks Glenn!
I'm going to tie threaded stainless rod into the concrete so I won't need dynabolts or anything like that. I'll either weld up an angle bar drilled to take the rod and secure it with nuts and tie it all into some rebar driven in vertically or weld the angle to the rebar I'll make sure the 3 required studs are perfectly level (vertical) before and during pouring concrete.