Pier design

[Lysithea]

Hi! 

Going to be building an observatory with roll-on roll-off roof over the coming months. Just in the process of finalising the pier design and could do with some help. I have a 10" Newtownian on a HEQ5, and was planning to put in a concrete pillar. However, I'd really like to upgrade to a much larger scope in the near-ish future -- I have vague daydreams about research-grade scopes, CCDs and various other equipment. The pillar will be over-engineered to carry up to 1000kg to cover any eventuality -- but what about mounting plates?

I had initially imagined 4 bolts set in the concrete pillar, and then the mounting plate on top. I think this would be fine for the HEQ5 but probably not for much larger. I'm assuming that if I upgraded to a 16" scope (which might be the case in the next year or so) + proportionally larger mount, then 4 bolts would be nowhere near enough? Is there a good design to ensure that a bigger telescope remains vibration proof? If I put in perhaps 8 or 12 bolts, would this be enough to hold heavier equipment? If so, would there be any problems for my current setup in the mean time, e.g., would the plate have to be of such a wide diameter that it would get in the way of the telescope skirt? 

I'd love to be in a position where all I have to do is replace the mounting plate whenever I upgrade equipment (I'm trying to make the current observatory design suitable for the next 10 years), and never touch the pillar -- but I don't have much experience here. Does anyone have any advice? Sorry for all the questions and apologies if this doesn't make sense. 

Note: I don't have a specific telescope in mind for an upgrade, I just want to be able to be flexible.

[mwayne]

1000 kg? I gotta admit, you think big!! Just my hipshot guess, your building is going to be 7 by 7 meters with 2.5 meter tall walls?

[Stu Todd]

1000 kg... You won't get to 100kg unless you have government backing...

If you are wanting to do research, it isn't so much the size of scope but more the quality of filters used, camera pixel size, spectrograph resolution etc etc. To this end, an EQ6 to big Losmandy will suffice for nearly every conceivable pro/am scientific interest.

Of course the larger the scope, the fainter the subject obtainable but you will find it is generally the brighter stuff the pros want data on as they're busy looking at really faint stuff with their 1000 Kg scopes.

Stu 

[DannyLee]

4 big bolts M10 or bigger, set into solid concrete at a wide spacing will hold anything. That is all they use to hold down the columns that support large warehouse type buildings. the key will be the thickness of the plate that carries the mount. too thin and it will flex...

Dan

[Skipper Billy]

On 8/10/2016 at 22:12, DannyLee said:

4 big bolts M10 or bigger, set into solid concrete at a wide spacing will hold anything. That is all they use to hold down the columns that support large warehouse type buildings. the key will be the thickness of the plate that carries the mount. too thin and it will flex...

Dan

Agreed it will hold it - but will it be flex free ?? I think not - depending on the free length it will wobble like a wobbly thing! Warehouse building supports are in compression and the bolts are only to prevent lateral movement.

8 x 14mm bolts with as little as possible free length will be much less prone to flex.

[Skipper Billy]

https://www.flickr.com/photos/113316085@N05/albums/72157663274320360

 

[DannyLee]

Hi Billy,

Not strictly true that, they (warehouse columns) also have to resist lateral wind loads, but I suppose the more bolts the merrier, specially with the winds you get where you are.  Must say though, what do you intend to hold up that needs 8x14 mm bolts ?

I am looking at building a pier for my about to be acquired HEQ5 I doubt if there will be a bolt near it. I prefer a steel truss type construction myself with welded joints like I did for my EQ3 bedded in a bag of instant set post concrete.

Cheers 

Dan

Dan