Why a concrete base 1m x 1m x 1m

[Alpollo]

4 minutes ago, Adam J said:

I am assuming that this has got to be with ultra long focal length scopes in mind because I dont seem to have vibration issues with my setup and I am just plonking it onto a patio that i suspect has not even been set onto hard core.

Indeed it may be a AP vs visual thing.

I've tried to image at 750mm on my wooden deck, I literally had to hold my breath, not kidding,  everything was making the scope move.

Even when I image at 75mm (50mm on a crop sensor) with a tripod on grass, I have to walk extremely gently or it will ruin the sub. I start the exposure, then moonwalk about 15' to 20' away to my awaiting coffee. Even a 12lbs dog running within 8' of my tripod will disturb it at 50mm.

This is why I say you should have your pier decoupled from the pad for maximum effectiveness. Mass aside, concrete is good at passing vibrations.

[iapa]

Thanks everyone.

I have decided  that a 1mx1mx1m is not where I am going right now.

Per a different topic, I have decided, on consulting a tame engineer, that several concrete slabs will be my base to support he pier.

The next topic - I would like to keep these separate as they cover different aspects of the subject - will be "which pier to choose". 

[Stub Mandrel]

Best story I ever heard was of a high-precision long-bed CNC machine tool installed at a former boat building yard using laser alignment to an accuracy that would make the most fastidious of imagers weep.

Once it was put into use, they found spurious errors occurring for extended periods. eventually a bright spark realised the time of the errors was shifting by about an hour a day - and they could only use the equipment when the tide was near the same state as when the machinery was set up...

 

As for imaging on grass, I once had Jupiter lined up on my laptop at an equivalent of about 3000mm f/l. Stepping within a foot of a tripod foot would make Jupiter move by about a diameter, so my advice is, if imaging on grass, start the timer then walk away!

[Alpollo]

There is a guy on youtube called "Astro Engineering" with some great videos that addresses the problem with "convetional" telescope piers.

IMO these are excellent videos and just what you are after. Everybody should have a look. You might be surprised how bad your pier is. I know it turned me off of a lot of designs.

Anti-vibration observatory piers Part 1

Anti-vibration observatory piers Part 2

Oscillatory vibration in telescope piers

 

 

 

[iapa]

9 minutes ago, Alpollo said:

There is a guy on youtube called "Astro Engineering" with some great videos that addresses the problem with "convetional" telescope piers.

IMO these are excellent videos and just what you are after. Everybody should have a look. You might be surprised how bad your pier is. I know it turned me off of a lot of designs.

Anti-vibration observatory piers Part 1

Anti-vibration observatory piers Part 2

Oscillatory vibration in telescope piers

 

 

 

Thnaks seen those, and I reference the product in my new topic "which pier to choose"

[iapa]

10 minutes ago, Stub Mandrel said:

Best story I ever heard was of a high-precision long-bed CNC machine tool installed at a former boat building yard using laser alignment to an accuracy that would make the most fastidious of imagers weep.

Once it was put into use, they found spurious errors occurring for extended periods. eventually a bright spark realised the time of the errors was shifting by about an hour a day - and they could only use the equipment when the tide was near the same state as when the machinery was set up...

 

As for imaging on grass, I once had Jupiter lined up on my laptop at an equivalent of about 3000mm f/l. Stepping within a foot of a tripod foot would make Jupiter move by about a diameter, so my advice is, if imaging on grass, start the timer then walk away!

that bedamned devil's eyeball gets us all at some time or another LOL

When on holiday, I am imaging on grass but all controlled remotely from 30m away to allow for such.

At home, on patio slabs - poorly laid - but again all managed from indoors.

Only timeI am near the mount is when polar aligning - and I stand still

[skybadger]

"Depth really isn't that critical for a pad, as much as area. If I was laying one I would make it a meter square but perhaps only 150cm thick on a good base of well tamped down hardcore.

We have the base for a summer house and the concrete is no more than 4" thick (over a sandy soil) and I would defy anyone to bother a scope set up on it with anything short of sledgehammer blows."

 

I don't think I can agree with this. I had a similar large thick concrete apron around the back of my garage which is where I bolted the observatory and the mount. I could easily see every truck that went past 60 yards away in teh scope vibrations and that was a sturdy, heavy welded tripod mount. 

I have a double pass liquid mirror ronchi tester in the garage and I can see every breath I take while standing 3 feet away in that because its on a common thick concrete floor.

Cheers

Mike

[Vox45]

We are talking about tons of concrete, laser aligned, double pass liquid mirror but at which point enough is enough ? wouldn't a big gust of wind have the same effect as walking 3m away ? What about seeing ? isn't guiding at the subpixel level enough to compensate for those vibration ?

I'm not trying to be a smarta** but I'm sincerly concerned that newcomers might be put off by the subatomic level of perfection we are implying one has to acheive to become an astrophotographer

[Davey-T]

The newest pier I made from three rectangular steel sections, not because of any master anti vibration plan but because I had most of it laying around but as a by product it doesn't ring if I hit it with a hammer, not something I tend to do while imaging though 

Dave

 

[tony210]

Hi-For what its worth  I have a similar base for my pier and live on an alluvial plain so movement will always occur - everything tends to move and slamming the observatory door affects my guiding - the main thing about a massive base in a permanent set up IMO is that polar alignment will be maintained a little longer though I suspect this will always alter over time- also large human beings treading near guiding mounts with long FL is a mistake - I get inside when I'm imaging - best wishes Tony

[Vox45]

 

5 minutes ago, Davey-T said:

The newest pier I made from three rectangular steel sections, not because of any master anti vibration plan but because I had most of it laying around but as a by product it doesn't ring if I hit it with a hammer, not something I tend to do while imaging though 

Dave

 

I like the "Steampunk" look of it very nice!

[iapa]

4 hours ago, Vox45 said:

We are talking about tons of concrete, laser aligned, double pass liquid mirror but at which point enough is enough ? wouldn't a big gust of wind have the same effect as walking 3m away ? What about seeing ? isn't guiding at the subpixel level enough to compensate for those vibration ?

I'm not trying to be a smarta** but I'm sincerly concerned that newcomers might be put off by the subatomic level of perfection we are implying one has to acheive to become an astrophotographer

I thought that was the minimum requirement

[Paul M]

 

On 08/03/2017 at 13:21, Vox45 said:

 

I'm not trying to be a smarta** but I'm sincerly concerned that newcomers might be put off by the subatomic level of perfection we are implying one has to acheive to become an astrophotographer

Haleluja!

I don't do imaging, partly because I just can't face the faff that is required to get anywhere with it (and the cost being a major detractor).

As for perfection, well I peaked some years ago (that doesn't mean I reached the summit!  ) and I'm well on the downslope of the "near enough is good enough" approach to life, and the Universe

[Peter Drew]

I could never see the rationale between digging out a ton of soil and then filling it in again with a ton of something else. My experience is that adequate footprint and pier dimensions are more important as well as isolating the base from the floor. I have large free standing telescopes that have not had problems in decades. 

[ollypenrice]

A quick aside but there is no such thing as 'crop factor' in AP. You don't get a longer focal length by having a smaller chip, more's the pity! When considering the damands on your mount your resolution is determined only by pixel size and focal length.

Olly

[spillage]

Just a thought. I need to put up a row of fence posts and will just buy a petrol auger for this. What if I dug a 1m x 1m x .30m hole and then bored down in each corner and wider hole the middle to sink my plastic pipe that will also be filled with concrete. This when filled would basically leave me a concrete table in the ground and reduce the amount of concrete I would have to use.

 

[laser_jock99]

On 09/03/2017 at 15:21, Peter Drew said:

I could never see the rationale between digging out a ton of soil and then filling it in again with a ton of something else. My experience is that adequate footprint and pier dimensions are more important as well as isolating the base from the floor.

Both good points- I wasn't planning on digging down much further than I already had.....

Having hand dug a level area from the hillside- my conrete pad was a mere 80x80x50cm. Basically a hole down the bedrock to keep the pier upright.

 

[Ouroboros]

Something I'm curious about ...... Whenever I look at photos of an observatory base under construction it looks as though people have left  in the timber form work surrounding the central block for the pier. If this true how can the pier base said to be truly isolated from the concrete pad? 

[saac]

On 06/03/2017 at 20:58, iapa said:

Sorry - @Knighty2112 @BXROneither are explaining WHY a cubic meter.

What is the specific empirical reason for this?

 

 

Iapa you are looking for something that does not exist - it is a rule of thumb, finger in the air that has been passed down via internet forum to internet forum.  The cubic m pier foundation is, in my humble opinion, one of the many lore in backyard astronomy that we all succumb from time to time.  I personally believe the cubic m is well over the top; my own pier foundation is more in the region 0.5 m^3 and I have never noticed any ill effects over the past 5 or so years. That said, I am no expert imager, indeed very far from that.  So although I think the 1m x 1x m x 1m pit is overkill, I also see a lot of sense in what Skipper Billy said, in effect digging a hole is easy and cheap and so is filing it with concrete.  Interestingly, most ready use concrete firms have 1m^3 as a minimum delivery; my recommendation is dig it until you are fed up with with digging then fill it with concrete; remember you are not tethering a Boeing 747.

As an after thought, it is amazing is it not that some folk can produce some of the most stunning images from a mobile setup (no pier, no 1m cube concrete base)? 

Jim

[JamesF]

On 07/03/2017 at 19:54, Alpollo said:

There is a guy on youtube called "Astro Engineering" with some great videos that addresses the problem with "convetional" telescope piers.

IMO these are excellent videos and just what you are after. Everybody should have a look. You might be surprised how bad your pier is. I know it turned me off of a lot of designs.

Anti-vibration observatory piers Part 1

Anti-vibration observatory piers Part 2

Oscillatory vibration in telescope piers

I've said it before some time ago, but I have a fair few issues with those videos from an engineering point of view.  I think they're marketing, plain and simple, and you should view them as you should any marketing material produced by someone who is trying to sell you something.

James

[bottletopburly]

My base 600x600x900 with 5x1000mm rebar , top of pier base 400mm dia to look pretty for the mrs? 

[Stub Mandrel]

"You might be surprised how bad your pier is."

The only test of a pier that matters is does it do the job it is meant for. The art in engineering is to design something as cheaply as possible to just do the job it was meant to do with sufficient margin of error to avoid accidents or premature failure.

The Watts Towers have foundations less than two feet deep, yet are 90 feet high and have survived earthquakes...

[iapa]

I bit the bullet, and with advice from youngest daughter went for 450 x 450 x 900

 

[saac]

32 minutes ago, Stub Mandrel said:

The only test of a pier that matters is does it do the job it is meant for. The art in engineering is to design something as cheaply as possible to just do the job it was meant to do with sufficient margin of error to avoid accidents or premature failure.

 

Effectively the definition of the professional engineer - someone who through application of engineering science has designed and is able to justify the characteristics of the design to meet the named constraints.

Jim

[saac]

48 minutes ago, iapa said:

I bit the bullet, and with advice from youngest daughter went for 450 x 450 x 900

 

 

Iapa, youngest daughters appear to be most persuasive when it come to pier design - mine negotiated the placing or her "meteorite" in the base of our pier. She said " it will be cool to think that there is a little bit of the heavens underfoot when we are observing "   Who was I to disagree, even though we both knew it wasn't a real meteorite  

Jim