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CarolG
scholastic sledgehammer
Reged: 10/16/06
Posts: 826
Loc: Oklahoma
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Well, I've about decided to get started with my observatory. I'm going with an Exploradome, but that is the only thing I know for sure. At first I thought I'd get the 10'6" round prefab setup, but after reading so much here, it seems that more space is always better. So I changed my mind and decided to go with the 10'x10' building. The prefab price for a square building is $4600. I decided I could build the building cheaper myself and just buy the dome and hardware. I want to put it on a deck and have an isolated deck within the deck for my scope. For now, I've opted not to have a pier. Now here's where I need your help. I'm a total novice when it comes to construction, and this is going to be a one woman project, so I know it will take a loooong time to finish. Now, where do I begin? I do know I will need a building permit, and I will have to show some basic plans to the city. After I get all the necessary permits, I will need to start with the deck. Do I go with a floating deck or dig holes and put in posts and concrete? This deck will be on an approximate 40 degree slope. I'd like to build either a 12'x14' or 12'x16' deck. What size joists should I use? Can I use 2x6's? 2x8's in the right lengths are hard to find at our local chain store. I have so many questions, I honestly don't know where to begin, but I think for now I just need to focus on the deck. I'm really excited about this project, but a little intimidated by it too, so I need all the  you can give!! I'm going to be gone for a couple of days, but I will be back as soon as I can. Thanks in advance for all the great advice I know you have to share!!
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Carol
Cor Caroli Observatory
NS11 XLT w/ HyperStar
TV85 w/FeatherTouch/DM4/SC on a Scopebuggy
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astrotrf
professor emeritus
Reged: 09/30/07
Posts: 695
Loc: Rodeo, NM
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Lowe's has an online deck designer (you have to register, so I didn't actually play with it), so you might want to start there. I presume that it will calculate sizing of structural members, etc.
For lumber, my advice would be to skip the chain stores and find a lumberyard. In fact, some lumberyards will have structural-design software and somebody who knows how to use it; they may be able to help you with the design on the spot.
You may want to hit amazon and buy a book on building a deck; that'll give you a good handle on how to go about it. You might even visit some of the do-it-yourself TV show web sites; they may sell videos of shows they've done on how to build a deck.
That 40-degree slope is going to complicate matters a great deal. That's going to mean one end of the deck will be *well* off the ground; you'll need to adequately brace the tall posts there.
A "floating deck" just means it's not attached to the house; it's not an alternative to posts and concrete, which are going to be necessary in any case. I would recommend NOT attaching the deck to the house unless you can get expert help for that piece of the construction job; it will have to be done properly so as to prevent water entry into your house's exterior wall.
There's a lot more to say about choices of structural lumber and decking material, using lag bolts and the proper nails or screws, etc. Do some of your own research to educate yourself, or ask a friend you have reason to believe actually *knows* the correct answers. The folks at the lumberyard will not always sell you the right thing.
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Terry (astrotrf)
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Rusty
Postmaster
Reged: 08/06/03
Posts: 17717
Loc: Brooker, FL
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First, having participated in the base construction of the Exploradome which was the subject of a recent comparo in Astronomy, I discovered an error in the wall plans, in that the load-bearing members of the transition section (from the walls to the dome itself) didn't line up with the load-bearing members of the walls. This was based on Exploradome's furnished plans, and I stumbled on the issue early enough so we could correct the plans.
Now, to address the no-pier issue...I think you may have a problem with the deck-within-a-deck on a 40° slope; my guess is that a pier - or at least a level concrete slab recessed into the ground would be a worthy consideration. I suspect the problem is that the upslope pillars would be shorter than the downslope side, and this would be difficult to make stable (but large enough lumber would do it). At the least, I'd level the ground where the inner deck would be installed, so that all pillars would be the same height, and if it were I, I'd go no less than 4x4s; 6x6s preferred, but at the lengths you'll need, the latter would be pretty heavy. Any lumber in contact with the ground should be pressured-treated, and rated for the application. Not all PT lumber is the same. I'd certainly recommend placing the deck-within-a-deck as close to the upslope end as possible, to keep the pillars short.
2x6 on 16" centers would do OK (but 2x8s would allow 24") centers with 3/4" plywood subfloor - if local bbuilding/zoning allows - 2x6s are marginal for this span. Note that the "cutout" for the deck-within-a-deck is going to require some extra support for the main deck, and this could get complex.
Since you're in Oklahoma ("Where the wind comes sweeping down the plain"), I'd completely discard any notion of a floating deck - sink posts. Referring back to that Astronomy comparo, the reviewer kept the Exploradome, and Tropical Storm Fay tested it with 60 mph winds, and no problem.
And here I'd give a plug for Backyard Observatories, owned by CN's own Dob Frog and Scott Horstman. They can furnish plans; those off-the-shelf are quite economical, and a set of custom plans, no doubt costing more, would be a VERY worthwhile investment. Not only would the issues with plans for the building and zoning department be minimized, you'd have a working set of plans to build without fear of the build-rip-it-out-try-again thing. Scott knows his stuff; I've seen several of his observatories, and worked with him on his own. He's good.
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N11GPS Fastar
TOA-130S
MK66 Std
Vintage C5
Megrez II 80mm ED Triplet APO
SolarMax 40
NJP Temma II
Sirius EQ-G
ST8XE/CFW-8(LRGBHa)/AO-7/DF-2/STV Dlx/ST237a/350D (Unmodded)/Mallincam Color Hyper Plus/DSI III Color/DSI II Pro
Two not-spoiled Golden Retrievers - Maggie and Casey
Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering. - Arthur C. Clarke
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RobVG
professor emeritus
Reged: 01/09/06
Posts: 737
Loc: Seattle Washington
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Quote:
Am I Ever Going to Need Your Help!!!
I don't know, will you? 
I built on a 3 to 1 slope. It's only 8'x8', but it might give you an idea how to do it.
Check out the link in my signature.
Rob
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C11 SGT(XLT)CG-5
Observatory (page 5)
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csa/montana
Wild Spirit
Reged: 05/14/05
Posts: 40155
Loc: montana
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CarolG. Congratulations! I so admire you tackling this project by yourself; except you are not really by yourself, you have all the great people here to help you along, & to provide encouragement!
My ROR is on a 10X10 floating floor; as it also is on a slope. It's been up for a year now, with no problems.
How about posting a picture of your Observatory site? That might help others to give you their best suggestions.
Best of luck CarolG, You Go, Girl! 
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Pentaxes; 5XW, 7XL, 10XW.
14mm Meade 4000 UWA
TV Panoptics; 22, 35
DreamCatcher Dobservatory, #2
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Mike Lewis
sage
Reged: 01/20/05
Posts: 384
Loc: Near Mulliken, Michigan USA
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Hi CarolG,
Congrats on getting started!!! You've gotten some good advice! You definitely need to sink your posts (to your local frost level at least) and 2x8's are the right choice.
Rusty's advice to talk to Scott and Diane is right on the mark!!!!You won't regret it!! I also have a deck book around here somewhere and would be glad to loan it to ya if you'd like. PM me if interested.
Most of all, do your homework and take your time!!!
Good luck and keep asking questions!!
Best skies
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Mike
.......................
Meade 7" Mak
Home built 8" Dob
120mm Sywatcher refractor
76mm Borg
Home built 12.5" Truss, F/5.6 Zambuto
PST
Dunham Hill Observatory
"Most people never look up, what a shame...."
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Rusty
Postmaster
Reged: 08/06/03
Posts: 17717
Loc: Brooker, FL
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Quote:
My ROR is on a 10X10 floating floor; as it also is on a slope. It's been up for a year now, with no problems.
The reason I suggest tying the deck into the ground is that the dome presents much more sail area than a ROR.
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N11GPS Fastar
TOA-130S
MK66 Std
Vintage C5
Megrez II 80mm ED Triplet APO
SolarMax 40
NJP Temma II
Sirius EQ-G
ST8XE/CFW-8(LRGBHa)/AO-7/DF-2/STV Dlx/ST237a/350D (Unmodded)/Mallincam Color Hyper Plus/DSI III Color/DSI II Pro
Two not-spoiled Golden Retrievers - Maggie and Casey
Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering. - Arthur C. Clarke
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Scott K
Pooh-Bah
Reged: 09/13/07
Posts: 1407
Loc: Dallas, TX & Eufaula, OK
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Quote:
Now, to address the no-pier issue...I think you may have a problem with the deck-within-a-deck on a 40° slope; my guess is that a pier - or at least a level concrete slab recessed into the ground would be a worthy consideration.
Since you're in Oklahoma ("Where the wind comes sweeping down the plain"), I'd completely discard any notion of a floating deck - sink posts.
I'm going to agree with Rusty 100% here - if I had to build my observatory again, this is precisely how I'd do it.
You really should build a concrete pier - or at least a footer onto which you can mount a pier. You'll want this for stability.
The great thing about building a deck is that it's much, much easier to level, and you can build it above grade, and seal the structure on it from water much more easily than with a concrete foundation.
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Bob Griffiths
Postmaster
Reged: 10/10/05
Posts: 6556
Loc: Frederick Maryland
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Well Carol...Congratulations... my ED will mark its 1st light ...2nd anniversary this Thursday...
Got a question... on the deck...how high off the ground is it...?
The floor of my observatory straddles a huge tree stump ($2,800 buck quote just to cut down tree...ended up costing me $800 and let the tree trimmer have the wood).. anyhow way to expensive to have the stump removed...so I built my "deck" seven foot off the ground...built it 12x10 feet 10x10 with a solid floor and a 2x10 section of regular decking...made a nice place to place flower boxes etc.. I used 2x12 boards for my joists...placed them on 12 " centers .. way overkill but I'm a Tm Allen type and consider overkill to be the only way to build something.. ... used 6x6 posts in the ground ...
Solved the pier problem by building a small 4x4 foot little deck 5 foot tall directly under the observatory... used 3/4 inch plywood for the decking and put in 3 layers (2.25 inches think of plywood..)...I then placed an Antares portable pier on the "lower" deck...sandbagged it in place and of course isolated it from the obs... this was intended to be a temporary solution until I figured a way to get rid of the stump... well after 2 years of use I no longer consider it temporary..it works just fine...
I do not image BUT this pier set up is more then stable enough to hold an 11' SCT..much better then the tripod ever was...
BTW... The standard rate around here for Carpenters to do "side jobs" on the weekends is to charge you double the
material price... My sons actually built my deck and building for me in one day..materials for the deck/building and lower deck was just under $1000... so I estimate that you could find a carpenter to build everything for you for $1000..plus materials..
I did NOT need a building permit as anything up to 100 square foot did not require any ...so you may not need one...?
I did use the plans for the building...and I had no problems like those mentioned by Rusty...the weight of the Dome itself and the transition panels is under 200 pounds...and does not put a lot of "load" on the supporting structure..
There is an Exploradome Yahoo group which is pretty active... JOIN IT...
Bob G.
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CPC1100
Nexstar 8i + GPS & Rays Brackets
Denk S1 power switch
Orion 100 mm Refractor
Meade LXD 55 ...AR-5 127 mm Refractor
Exploradome Observatory S.I.E. (Smiling Irish Eyes)
Gerbring Heated Motorcycle clothing in the winter
39*21'03" N
77*28'12" W
The sky over my head....
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rsbfoto
sage
Reged: 06/10/06
Posts: 341
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Quote:
... For now, I've opted not to have a pier. ...
Hi Carol,
You already got tons of advice.
The only thing that makes me wonder and shiver is the sentence you write and I quoted above.
¿ Are you 100% sure ? 
One day you surely will want to put a pier into your observatory and adding it later into an existing building make things from my point of view very very annoying. Once you moved into the observatory ...
Just think about the changes which will have to be done.
Just think about digging out the hole inside the finished building. From my side I nearly would prefer to build a separate new Observatory on another spot starting with the hole for the pier.
OK, it is your decision but ...
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regards Rainer
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BluewaterObserva
Post Laureate
Reged: 05/18/04
Posts: 4968
Loc: Zuni Mtns, NM
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Without a pier? It's way better to do a gravel floor and cement tile or other wise type of tile floor. You can isolate the one tile in the middle for the scope to sit on. Pretty elegant simple solution that bears looking into.
You can use the gravel to level the erea as well. Pretty good no shaking, no pier solution.
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csa/montana
Wild Spirit
Reged: 05/14/05
Posts: 40155
Loc: montana
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Quote:
You really should build a concrete pier - or at least a footer onto which you can mount a pier. You'll want this for stability.
CarolG: Here's how I did mine for my Dob: Used the bottom of a 50'gal drum; later removed some of the framing around it, built new framing down to the ground around the drum, & poured more completely around the drum. Maybe not the best way, but a girl's gotta do, what a girl's gotta do 
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Pentaxes; 5XW, 7XL, 10XW.
14mm Meade 4000 UWA
TV Panoptics; 22, 35
DreamCatcher Dobservatory, #2
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csa/montana
Wild Spirit
Reged: 05/14/05
Posts: 40155
Loc: montana
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floor:
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Pentaxes; 5XW, 7XL, 10XW.
14mm Meade 4000 UWA
TV Panoptics; 22, 35
DreamCatcher Dobservatory, #2
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Scott K
Pooh-Bah
Reged: 09/13/07
Posts: 1407
Loc: Dallas, TX & Eufaula, OK
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Quote:
One day you surely will want to put a pier into your observatory and adding it later into an existing building make things from my point of view very very annoying. Once you moved into the observatory ...
Let me just add that doing it right the first time is really important. Read my horrible, horrible thread entitled "how not to build a pier footer", and just look at what I went through trying to fix mistakes I made early on. I can tell you that I've spent nearly as much trying to fix my dome's foundation as I spent pouring the stupid thing in the first place. Doing things the right way will, no doubt, increase your cost and effort a bit. This is regrettable. It will, however, be much much cheaper and much less trouble in the long run than trying to fix something that's almost, but not quite, right.
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Bob Griffiths
Postmaster
Reged: 10/10/05
Posts: 6556
Loc: Frederick Maryland
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As a visual observer I really did not need to anchor my scope to the Rock of Gibraltar so I opted for a portable pier placed on a solid footing under my observatory floor. which I explained in my earlier post in this thread ..works great ..stable, isolated yada yada yada
BUT to me the MAJOR advantage is that it opens up a heck of a lot of walking room inside the observatory ..no more tripod legs to trip over etc... no more having to place your observation chair off to one side because a darn tripod leg is dab smack in the way of the chair... and even if you have to pick up the chair and move it to observe in the opposite side of the sky you no not have to watch out for the chair hitting a tripod leg etc...
Take everyone's advice and at least pour a concrete base for a pier like Caro/Montana did....The entire idea behind my observatory is to have my "stuff" all in one place, always ready to use, scope aligned 24/7, and get me out of the cold winter breezes...why skimp and place a 3 legged tripod that you have to avoid...
Bob G
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CPC1100
Nexstar 8i + GPS & Rays Brackets
Denk S1 power switch
Orion 100 mm Refractor
Meade LXD 55 ...AR-5 127 mm Refractor
Exploradome Observatory S.I.E. (Smiling Irish Eyes)
Gerbring Heated Motorcycle clothing in the winter
39*21'03" N
77*28'12" W
The sky over my head....
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CarolG
scholastic sledgehammer
Reged: 10/16/06
Posts: 826
Loc: Oklahoma
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Thanks everyone for your advice. I'll write more tomorrow when I'm not so exhausted. I have pictures of the slope, but I don't know if you can tell much from them, but I will post them tomorrow. About a year ago I ordered Scott's (BYO) plans, and they are very helpful. Now to tell you a little bit about what I learned this morning as I was staking out the obs outline. First, the deck is all wrong, I think. I think a 10' x 16' deck would be better. There's too much wasted space with a 12x14 or 12x16. I want to have a little "porch" in front (about 4') and a 2' extension to the building in the back-similar to the ED 'bays'. If I place the long side of the deck from the top of the hill down, the elevation on the high end is about 36". The reason for the deck within the deck is because I don't have a pier-my Nexstar 11 is on a tripod. However, you have me rethinking the pier issue. I laid out a 42" square for the tripod, and it didn't leave much room inside. That's why I am considering adding a 'bay'. Digging a pier or post holes, for that matter, is going to be a challenge since the hill is mostly rock. I had a hard time getting the stakes in the ground-kept hitting rocks. My husband is a good source for advice, since he has done quite a bit of building, but he thinks this project is a waste of time and money. His advice so far is to put up my dark sky panels and lug everything outside, but in all fairness, I think he will help if I really need it. I could hire it done, but part of the fun is the journey to the destination. Well, I will write more tomorrow and post some pics. I will have lots and lots of questions as time goes by. Again, thanks for your help.
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Carol
Cor Caroli Observatory
NS11 XLT w/ HyperStar
TV85 w/FeatherTouch/DM4/SC on a Scopebuggy
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Scott K
Pooh-Bah
Reged: 09/13/07
Posts: 1407
Loc: Dallas, TX & Eufaula, OK
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What part of Oklahoma are you in, by the way?
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CarolG
scholastic sledgehammer
Reged: 10/16/06
Posts: 826
Loc: Oklahoma
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Scott, I've read your entire saga of 'How not to build a pier' and it looks like you've been dealing with some pretty major problems. I just read about your leaks, and it seems your problems never end. Good luck!! But, to answer your question, I'm in southern OK not too far from the Red River.
I've been thinking about the pier issue, and I think I'll go with the pier and ditch the tripod. But before I get ahead of myself, here's some pics showing the site. We have 2 very wooded acres, and I had 3 choices, well 2 really, for sites. The only open site with a nice southern exposure is right in the middle of the front yard, so that was out. Next is the flat roof of the garage, and I seriously considered that, for about 2 seconds. I knew I'd have to put a hole in the roof to build a pier, and I didn't want to do that. So that left this site. Lots of trees, but actually I've got more open sky there than I do here in the city. Plus, I can actually see stars there, so I can't complain much. As funds allow, I will eventually take out some more trees. (My son and I have already cut down 15). Anyway, here's a pic looking west. I'm standing about a third of the way down the hill.
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Carol
Cor Caroli Observatory
NS11 XLT w/ HyperStar
TV85 w/FeatherTouch/DM4/SC on a Scopebuggy
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CarolG
scholastic sledgehammer
Reged: 10/16/06
Posts: 826
Loc: Oklahoma
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Here's one on top of the hill looking north onto the golf course.
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Carol
Cor Caroli Observatory
NS11 XLT w/ HyperStar
TV85 w/FeatherTouch/DM4/SC on a Scopebuggy
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CarolG
scholastic sledgehammer
Reged: 10/16/06
Posts: 826
Loc: Oklahoma
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Here's one looking east. I've roughly staked it out with the 10x10 building outline in the bottom left corner and the tripod site inside that. The outer borders on the top and right sides of the pic are the outlines of the deck, which I will alter.
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Carol
Cor Caroli Observatory
NS11 XLT w/ HyperStar
TV85 w/FeatherTouch/DM4/SC on a Scopebuggy
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