Pier

On Fri, 11 Jul 2003 20:56:05 GMT, "Michael Barlow"
wrote:

Everything I read tells me everything I want to know about buying a pier
and bolting it to the floor of my observatory. But I wont have a floor,
just dirt, and I don't want to buy a pier. So, what should I do? My plans
were to dig 4 foot down (frost line) and plant a 10 inch Sono-tube + 4 foot
above ground. Fill it with cement topped off with 4 J bolts to bolt the
mount to. 10 inches seems awfully big!

I'm going to be setting a Meade 127mm F/5 refractor on this with a heavy
mount (30ish lb.) and an OM-1 for astrophotography. What's the best size
for a pier with that in mind, 6", 8", 10"? and what perameters should I be
considering?

There's no reason at all to buy a pier- none of the commercial models offer
anything you can't easily provide yourself, and some have things like level
adjustments that you absolutely want to avoid. Your decision not to put in a
floor is also a good one, and will increase your performance both mechanically
and thermally.

My pier is 6" well casing (6.5" OD) filled with oiled sand. It is rock solid
with a 12" LX200 and a lot of additional equipment on it. Cement by itself can
support some interesting vibrations, so I think your instinct to use 10"
sonotube is good. Be sure to put some rebar in there, and I'd suggest a fiber
reinforced concrete. You could save some concrete by putting a 6" sonotube in
the center of the 10", and pouring only in the outer area. Then fill the inside
with sand, possible oiled, to help further damp vibrations.

The foundation is even more important. I'm down only about 3 feet, above the
frost line but sitting on solid rock. So I only have about an 18" round
foundation at the bottom, maybe 6" high. If you can't get down to rock, consider
a 3 to 4 foot square foundation at the bottom of your hole. With a permanent
polar alignment, you don't want the angle of your pier drifting by even a few
arcseconds.

Are you building a platform floor around the pier? If not, consider it. This
will be much more comfortable to work on than the ground. It only requires a few
hours to put one in, but you need to plan on your pier being 12-18 inches higher
if you do that.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Mon, 14 Jul 2003 08:56:42 -0400, "Ray Porter" wrote:

I'm facing this same decision but I'm leaning towards one of the commercial
piers. I have to allow for the possibility that the pier might have to be
relocated at a later date so a concrete pier isn't an option.

Most of the cost and difficulty in the pier- commercial or otherwise, is in the
footing, and that isn't going to be movable anyway.


I've been
leaning towards something from Ken Dauzat or Le Sueur Astro-Pier. If I
decided to do my own, what would I need? I'll be mounting an 8" SCT but I
want to allow for something larger in the future.

You can either go with a big pipe or a concrete pier. Both are pretty simple to
make. The pipe requires machining a cap or flange for attachment of the wedge.
With concrete, you can simply set some J-bolts. Michael's approach with a 10"
sonotube is likely to support anything he's ever going to put in his backyard!
If you make one like that, and ever move, just turn it into a birdbath. Worst
case, it wouldn't cost much to have someone bring in a demo hammer and knock it
off at ground level.


Also, I'm having a hard time deciding how high to make the pier. I plan to
build a roll-off roof observatory around the pier sometime in the next year.
The floor will be a minimum of 6" above the ground and may be higher since
our property slopes somewhat. I'm relatively comfortable viewing with my
tripod legs fully retracted (about 30"). Another factor affecting pier
height is, of course, the height of the observatory walls. How high do
folks generally make the walls of their home-grown observatories? I'm 5'8"
so 6' walls would pretty much block any neighborhood lights but would that
obstruct too much sky?

I set up my LX200 on the tripod and picked a height that seemed comfortable. It
wasn't a real big issue for me since I seldom use the scope visually. Then I
added that height to my planned floor height, and set the pier. I put my walls
at about 6 feet. I have no lights to block, but I wanted as good a wind break as
possible. At 6 feet, I start occluding the scope at an elevation of about 20
degrees, although I can normally view down to about 15. That is fine with me,
since the seeing is horrible that low anyway. If you need 6' walls to block
lights, be sure to carefully calculate the horizons that will create. If you
like the scope a little lower, you may end up cutting off too much sky.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Hi Chris,
How high is your pier above the floor of your observatory? I have no view
to the west due to high trees. The south is also blocked by trees below
about 30 degrees. East and north anything below 30 degrees or so is shot
due to light domes from neighboring cities.


Most of the cost and difficulty in the pier- commercial or otherwise, is
in the
footing, and that isn't going to be movable anyway.

Yep, but with a commercial pier (or a homemade steel pier bolted to
concrete) I can just unbolt the pier and cut off the bolts at ground level
then move the pier to whereever it needs to go. I hadn't really considered
the possibility of knocking down a concrete pier.

Thanks,

--
================================================== ==========
Ray Porter
Applications Analyst Programmer
Administrative Information Services, UNC-CH
Phone: (919) 966-5878
Fax: (919) 962-5840
Email:
Web: http://www.unc.edu/~dragon

Meddle not in the affairs of dragons
for thou art crunchy and taste good with ketchup

On Mon, 14 Jul 2003 11:17:01 -0400, "Ray Porter" wrote:

Hi Chris,
How high is your pier above the floor of your observatory?

The bottom of my Superwedge is 34.75 above the floor. Even though I was
concerned with imaging, I generally find the scope height pretty comfortable for
viewing. This is a 12" LX200, and I'm 6'1".


Yep, but with a commercial pier (or a homemade steel pier bolted to
concrete) I can just unbolt the pier and cut off the bolts at ground level
then move the pier to whereever it needs to go. I hadn't really considered
the possibility of knocking down a concrete pier.

Yes, it would be easier to remove a commercial pier. But you could make your own
and have it professionally removed for a lot less than the cost of the
commercial pier alone. And many of the commercial piers have adjustment doodads
for leveling that just seem like a real bad idea- added cost and reduced
stability in exchange for no gain. IMO it makes sense just to save a lot of
money on the pier and put it into some accessories.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

If I decide to do this myself, what sort of pipe do you recommend? I know
someone who might be able to weld a top plate/flange to the pipe but I don't
know anyone who could machine the top plate for actually attaching the
scope. I'll have to look around and see if there's anyone nearby. I do
know of a couple of places that sell pre-made mounting plates for piers.

Thanks,
Ray

"Chris L Peterson" wrote in message
...
On Mon, 14 Jul 2003 11:17:01 -0400, "Ray Porter"
wrote:

Hi Chris,
How high is your pier above the floor of your observatory?

The bottom of my Superwedge is 34.75 above the floor. Even though I was
concerned with imaging, I generally find the scope height pretty
comfortable for
viewing. This is a 12" LX200, and I'm 6'1".


Yep, but with a commercial pier (or a homemade steel pier bolted to
concrete) I can just unbolt the pier and cut off the bolts at ground
level
then move the pier to whereever it needs to go. I hadn't really
considered
the possibility of knocking down a concrete pier.

Yes, it would be easier to remove a commercial pier. But you could make
your own
and have it professionally removed for a lot less than the cost of the
commercial pier alone. And many of the commercial piers have adjustment
doodads
for leveling that just seem like a real bad idea- added cost and reduced
stability in exchange for no gain. IMO it makes sense just to save a lot
of
money on the pier and put it into some accessories.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Mon, 14 Jul 2003 11:58:48 -0400, "Ray Porter" wrote:

If I decide to do this myself, what sort of pipe do you recommend? I know
someone who might be able to weld a top plate/flange to the pipe but I don't
know anyone who could machine the top plate for actually attaching the
scope. I'll have to look around and see if there's anyone nearby. I do
know of a couple of places that sell pre-made mounting plates for piers.

I used standard 6" steel well casing, which is both common and inexpensive. I
bought an 8' section and set it first, only cutting it to height when I had it
in place. I chose this because I also use it on a portable pier, and the top
plate system I use is interchangeable. Otherwise, I probably would simply have
gone with a 10" concrete pier.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com