BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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I am getting a fair amount of conflicing information here.
I have been told by people I trust, that a 10:1 ratio is adaquate, by others no less than 100:1, and Nasa / JPL is suggesting a whopping 500:1 ratio.
For cost, I had assumed a 5 ton concrete pier could hold 1/2 ton worth of scope / mount / counterweights. The pier would be heavier than this but I was not really able to ad the rebar weight very effectively.
Any additional thoughts on this? next month I pour the pier.
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Richard B. Drumm
Pooh-Bah
Reged: 07/14/05
Posts: 1486
Loc: Albemarle Co. Virginia
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What scope is going in there? How much does the scope + mount weigh?
You might need an engineer if it's a really big scope, like a 30"...
Rich
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AKA Richard Drumm The Astronomy Bum
Orion Atlas 10 (10" Newt on an equatorial mount)
Celestron 15x70 SkyMaster Binocs
Coronado Ha PST
President, Charlottesville Astronomical Society
IOTA member
38° 10' 57"N, 78° 23' 09"W
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Well, I am looking at the entire setup comming in at around 1000lbs. 100:1 seems to be what most professional observatories shoot for. In a re-thinking of my peir construction I think I can get it near 50:1 and still afford it. 10:1 generaly is said to meet bare minimum code for the load, but of course that is not a good idea for a sensative astronomical instrument.
My new idea which has been used quite a bit by large privately owned amature observatories is to create a cinder block chimney / structure and pour the concrete into that.
This is prefered on the DYI side, because there is virtually no risk of form failure. And it makes it much easier to create a bigger base thus easier to create a higher mess index.
Funny, I had went away from the Chinmey pour idea, but now that it is getting crunch time, the benefits and ease are certainly winning me over here. It increases the size of my pier up into the observatory to 32" so the inner concrete and rebar structure can still be 24" x 24"....
I think I now have a plan to get this done, the remote nature of the observatory makes it tough to get anybody out there to do any sort of engineering and/or contract work. I so far have a perfect track record of being stood up by various contractors to do work out there. At this point, I certainly don't want anybody out there that is going to bring up any permit issues with the project. 
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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100:1 seems excessive. I've got about 300 lbs of mount + scopes mounted on a 7700 lb pier. That's roughly 25:1, and if anything, I'd guess that's overkill. Kicking the concrete pier produces -no- visible vibration, even at a 4000mm focal length. (I've got a 50" steel pipe on top of the concrete; kicking the pipe produces 6 or 8 arc-seconds of movement which dampens in about 3/4 of a second.)
I'll admit that I don't image, so perhaps my idea of overkill wouldn't match someone's who's into astrophotography, but I still can't imagine a 100:1 pier.
-- Jeff.
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Wow, I had given up on this thread.
Thanks for posting in on this....
Well, My pier is not going to weigh 100,000lbs...
I am going to be around 50,000 so close to 50:1. I think I have a plan all set, two pours though.  If I follow the example I found of a working system using the same idea.
I found a website that detailed nearly what I am thinking, Russle Crowel(sp?) becuase I can't find his website again now. a pretty famous astro-imager. I think he went for 100:1, I think it's a 20" RC, and those are pretty darn heavy. My 30" EQ setup will be real light for the aperture size.
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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Russell Croman, perhaps?
http://www.rc-astro.com/equipment/observatory/index.htm
-- Jeff.
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Thanks again for all your information and help. That is the website, see how he poured into a cinderblock form? Cheapest and safest DYI way to do it for sure. Virtually no risk of form failure as that is a staggering amount of weight / pressure created by the volume of conrete in there with it's long vertical rise. My setup is nearly identical.
I'm feeling pretty alone on this one. My observatory is a little beyond the scope of even most higher end imagers and amature astronomers.
Edited by BluewaterObserva (03/14/07 11:35 AM)
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 12501
Loc: Always Dark skies of Belfair W...
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Quote:
Thanks again for all your information and help. That is the website, see how he poured into a cinderblock form? Cheapest and safest DYI way to do it for sure. Virtually no risk of form failure as that is a staggering amount of weight / pressure created by the volume of conrete in there with it's long vertical rise. My setup is nearly identical.
I'm feeling pretty alone on this one. My observatory is a little beyond the scope of even most higher end imagers and amature astronomers.
Indeed it is John. I'm definately on your side. You're my hero....  Git your happy down there, lay some block, and pour some cement... 
Rob( An..don't make me pull over...)
GOMOC
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http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group. www.goldmtobservingcenter.com
www.vimeo.com/6014031
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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I actually considered the cinderblock form as well. In the end I went with the sewer pipe form because I just couldn't come to terms with putting a square post into a round building. 
I got a concrete truck in to fill the 4' x 4' x 4' block at the bottom of the pipe:
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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... and then we filled the pipe by hand that afternoon:
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Looks like it came out really well. So your slewing a full bore Meade 16" LX200 with a 100mm Refractor piggy backed scope and lots of imaging equipment? Using the AP1200 EQ mount?
Of course my building is square. I still plan to use a 6' tall 24" flanged pipe up to the actual eq mount once inside the structure.
Edited by BluewaterObserva (03/14/07 05:31 PM)
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 12501
Loc: Always Dark skies of Belfair W...
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I only dream of a dome like that for LBM...  at GOMOC
Rob
Gold Mtn Observing Center
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http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group. www.goldmtobservingcenter.com
www.vimeo.com/6014031
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Well you know.. If I had to do it all over again, I would probably go Dob and Roll Off Roof. It's been a wild ride for sure getting this up and running.
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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Quote:
Looks like it came out really well. So your slewing a full bore Meade 16" LX200 with a 100mm Refractor piggy backed scope and lots of imaging equipment? Using the AP1200 EQ mount?
Yep (except for the imaging part -- I'm purely visual for now).
Quote:
Of course my building is square. I still plan to use a 6' tall 24" flanged pipe up to the actual pier once inside the structure.
Dang, that's one big dome.
Here's a quick shot of my rig:
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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Nice setup....
6 meter dome, 30" Newtonian EQ astrograph with a 6" refractor, and lots of heavy imaging stuff to eventually. the EQ mount is rated at 1 ton payload, it came with 450lbs of counterweight.
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 12501
Loc: Always Dark skies of Belfair W...
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Quote:
Well you know.. If I had to do it all over again, I would probably go Dob and Roll Off Roof. It's been a wild ride for sure getting this up and running.
Yeah, but John, if everything worth being proud of was easy to attain then we'd be overly proud.....
Your gig is the bomb..
When do we get some pix of the inside????? 
Don't feel to bad.... I'm just a logger right now, and a landscaper...and a weeder...and tired.
Rob
GOMOC
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http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group. www.goldmtobservingcenter.com
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 12501
Loc: Always Dark skies of Belfair W...
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Quote:
Nice setup....
6 meter dome, 30" Newtonian EQ astrograph with a 6" refractor, and lots of heavy imaging stuff to eventually. the EQ mount is rated at 1 ton payload, it came with 450lbs of counterweight.
 Pix.. John.. pix.
I don't know if my monitor can hold that much image data..
Rob
GOMOC
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http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group. www.goldmtobservingcenter.com
www.vimeo.com/6014031
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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Quote:
Pix.. John.. pix.
Indeed. Especially of that mount....
-- Jeff.
--------------------
Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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BluewaterObserva
Postmaster
Reged: 05/18/04
Posts: 5748
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The inside isn't very polished rigth now, walls are painted flat black and the floor is just the deck. The dome rises impressively large from the floor though. From July 4th weekend of last year up to Thanksgiving day weekend of last year it was all I could do to get the 10' high 32' x 24' deck built, the structure / dome done. Nothing of this project really existed before July 4th weekend.
Keep in mind my observatory is 550 miles from where I live right now, also keep in mind it is in the middle of nowhere, 100+ mile round trip for building materials. And everything had to be painted at minimum, in the desert southwest even at 8000' they don't really use treated wood, just construction pine and paint. Myself and my observatory partener who is a 5'4" and petite lady built this thing to where it stands now in that time. Getting closer...
I still only have teaser pics, but more should be comming soon now that work can resume. The OTA needs a few more hours work, I still don't have the cradle to hold it done that probably still has 8 to 16 hours of work to be done on it. I still have not figured out how to retro fit the stepper driven mount with the new DC Servo stuff with built in encoders either. I wish I could just find a cheapo stepper controler that I knew would / could work, but I suspect the exisitng RA stepper is in bad shape, I think that may have been why the mount was replaced.
I've posted this pic of the mount on here way to often. Notice the look of terror on my face, it was all two of us could do to get just the mount with no conterweights up on and bolted to the work bench so we could assemble it, by the time the pic was taken I had jelly arms and even the shaft alone was heavy. The mount is amazingly smooth in it's motions. If you point the shaft up in the air and let it go, the mount will pendulum back and forth in RA for like 15min with the drives not installed. 16" Byers gear on the RA and 14" on the dec, 3.5" bore / shaft size in both axis. The mount can appear weled in the pic here, but is actually completely bolted together. I mean, is seems like it will slew my pultry 500lbs of scope around like it was nothing in all honesty. The mount came from a University just north of Baltimore. I paid $2K even for it.
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 4491
Loc: Ireland
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Sweet. Love the color of those Byers gears.
Have you looked into the AWR stepper controllers? I'm afraid they're not likely to qualify as cheap, but I imagine they'd work....
http://www.awrtech.co.uk/awr_cat.htm#MICROSTEP
-- Jeff.
--------------------
Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-125 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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