What diameter for pier

[waz1642]

What diameter for a pier which is 2m high?

I was thinks of 200mm or 250mm

http://www.ebay.co.uk/itm/Spiral-Pipe-Ducting-Galvanized-Steel-Spiral-3-0m-Hydroponics-Ventilation/221751751339?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140107083358%26meid%3D7e2fca2dd6ee4f71acabd8a74d25e4d7%26pid%3D100011%26rk%3D1%26rkt%3D2%26sd%3D321703720104

[Bizibilder]

The stiffness of a tube increases with its diameter - so 250mm diameter would appear to be the better tube.  The wall thickness has little effect (within reason!).  However 250mm is quite a big tube and you may find that it will get in the way if the scope is getting near the zenith - its just a case of compromise, if the 200mm is better in that respect it may also be stiff enough to do the job.  If you want you can find the maths on the web.

[waz1642]

I could use 250mm then step down to 200mm for the top 1m

[Davey-T]

Are you planning on filling it with concrete?  2 meters seems a bit high unless you've got a long refractor.

Dave

[waz1642]

The walls of the observatory are 2.30m high

[Davey-T]

The walls of the observatory are 2.30m high

This is why people make them with drop down sides plus you rarely want to view / image horizontally.

Dave

[waz1642]

The garage is 2,30 high

[waz1642]

Elevation (°)

25

 

Wall distance from telescope center to wall (cm)

130

 

Height of telescope centerline above Floor (cm)

170

 

Wall height form centerline of telescope (cm)

61

 

Total wall height (cm)

231

 

[waz1642]

By the way I'm going to have a raised floor

[Davey-T]

The garage is 2,30 high

I see your problem

DSave

[wxsatuser]

My pier is 200mm brown drain pipe.

With the top adjustable plate being approx two thirds the height of the obsy walls, which are approx 78inches.

Even on tiptoe I cannot see over the obsy walls.

For me this puts the scope, I'm 6foot tall, at just about head level on an HEQ5.

I deliberately built my obsy so I could'nt see below 20degrees looking East, lots of LP here.

The only thing, when pointing south the mount goes on its side I'm restricted to about 30degrees and above.

The only pic I have of it.