Jump to content


Photo

Pico Dome (it's that small)

  • Please log in to reply
126 replies to this topic

#1 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 09 September 2012 - 01:21 PM

I've wanted to build an observatory for as long as I've been interested in astronomy...it always seems to be the holy grail! My wife and I bought a house a little over a year ago out "in the burbs" of Austin TX. So while it's not pitch black (or even remotely close) it's "dark enough."

I'm mostly an imager and from home I typically do narrowband because of the light pollution so I don't need to be in the dome. Plus the best spot for the observatory is near the front of our backyard and the HOA would have a fit about it rising over the fence line being that close to the front of the house.

So I've decided to make a VERY small dome. Essentially the bare minimum required to fit my equipment and give me a tiny bit of room to grow (very tiny). The diameter of the dome will be 5 feet (1.5 meters). And the entire structure will be around 6 feet (1.8 meters)tall. This keeps it just under the fence line and out of the HOA's control :-) The diameter of 5 feet was chosen for a couple of reasons. First, I'm planning on using a gore type construction with 1/8" masonite for the dome. At 5' I can build the entire dome from 2 pieces of masonite. I also plan on fiberglassing the exterior and possibly the interior of the dome as well. This will give it added strength as well as weather proof it. Second, at the smaller diameter I should be able to lift the dome off if needed by myself or with the help of one person. Since it will be unlikely that I'll be able to get into the dome (at least not comfortably) I'll need a way to do periodic maintenance and access the equipment.

I initially considered building a roll off roof as I could lay the scope on it's side and make the entire setup even smaller. But where I'm at is fairly windy so the added wind protection of a dome is a nice plus. And I like building things like this so the challenge of building the dome was a big part of the decision as well...one which I may regret later!

I'm also planning on automating the dome (eventually). Initially the azimuth will be automated but I'll likely forgo automating the shutter until a later time. I plan on building all the control hardware as well and writing an ASCOM driver for the dome controller. I believe there is already an Open Source Dome Controller out there so I may check that out as well.

Attached is an initial drawing that I have done with a G11 inside of the mount for reference. Everything is to scale to give you an idea how small the dome is.

Hopefully I'll get some pictures of the actual dome construction up fairly soon. I'm headed to the lumber store to pickup materials to start on the dome here shortly.

Jared

Attached Files



#2 Mirzam

Mirzam

    Skylab

  • *****
  • Posts: 4450
  • Joined: 01 Apr 2008
  • Loc: Lovettsville, VA

Posted 09 September 2012 - 03:45 PM

A similar project:

http://www.cloudynig...ll/fpart/1/vc/1

Kevin does some amazing AP with this setup.

JimC

#3 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 09 September 2012 - 07:26 PM

I considered a "Dog house" as well but like the roll off roof it still doesn't block as much wind. Which is the primary reason for the dome. I lose a lot of nights to imaging because of wind, hopefully the dome will help that! Plus it gets really dewy here and the dome should help to keep that under control as well.

I started on the lower ring for the dome. The center is 5' across. I'll cut a notch for the gores to rest in. Currently this is just rough cut and not glued up. I'll likely get to that later this week.

Jared

Attached Files



#4 Mirzam

Mirzam

    Skylab

  • *****
  • Posts: 4450
  • Joined: 01 Apr 2008
  • Loc: Lovettsville, VA

Posted 09 September 2012 - 08:30 PM

I can offer some advice on the lower ring. Make it much stronger than you think is necessary. I would laminate at least three layers of plywood like you have shown.

What will happen over time is that the ring will sag in between the wheels. Also be sure you use at least 6 wheels and even 8 would be better.

Sag will distort the slit opening and possibly cause leakage.

JimC

#5 dobsoscope

dobsoscope

    Messenger

  • *****
  • Posts: 412
  • Joined: 24 May 2006

Posted 10 September 2012 - 01:42 AM

I would strongly recommend you follow the guidelines given here by Nytecam for the ring beam rather than a layered ring.

http://www.cloudynig...wflat.php/Cat/1,2,3,4,5,8,9,10/Number/4783794/page/0/view/collapsed/sb/5/o/all/fpart/all/vc/1

#6 astrovienna

astrovienna

    Surveyor 1

  • -----
  • Posts: 1766
  • Joined: 04 Dec 2006
  • Loc: The NoVa White Zone

Posted 10 September 2012 - 02:02 PM

A similar project:

http://www.cloudynig...ll/fpart/1/vc/1

Kevin does some amazing AP with this setup.


:roflmao: When I read "keep it below the fence," I knew exactly where Jared was coming from!

I'd love to have a dome to keep out the wind, Jared. But as anyone who's seen my doghouse-style obs could guess, I don't have dome building skills. Good luck, and feed us with pictures.

Kevin

#7 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 10 September 2012 - 04:39 PM

I would strongly recommend you follow the guidelines given here by Nytecam for the ring beam rather than a layered ring.

http://www.cloudynig...wflat.php/Cat/1,2,3,4,5,8,9,10/Number/4783794/page/0/view/collapsed/sb/5/o/all/fpart/all/vc/1


Thanks for that link. I like the idea of the box beam but I'm not sure if that's necessary for this size of dome. I may consider it though as it doesn't seem all that complex and it would be easy to implement that at this point since the rings are not glued together yet.

Jared

#8 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5595
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 10 September 2012 - 07:58 PM

I'd suggest one of the small shed conversions into ROR observatories for Arrow metal sheds folks have been doing. You'll have room to move around inside, and if the HOA peeks over the fence, it just looks like a garden shed.

Otherwise, you might as well get a robodome.

-Rich

#9 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5595
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 10 September 2012 - 08:05 PM

Here's a robodome link:

http://www.homedome....ct_robodome.htm

I'm trying to remember who here on CN recently built a metal shed ROR. He did a really good job on it.

-Rich

#10 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 11 September 2012 - 10:23 PM

I had looked at the Robodome but it's too small to to house my setup I need a minimum of 24" all the way around the RA axis and the Robodome is only 42" wide. 24" is pretty tight even. Plus it's well over what I want to pay for a dome.

Doing a RoR has it's benefits...it's definitely easier and faster to build but at the moment I'm still set on a dome.

Thanks,
Jared

#11 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5595
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 13 September 2012 - 09:14 AM

The dome has to be synchronized with the mount, you know.

The mini-ROR gives you room to work on the gear, and the synchronization collapses to park and open/close.

-Rich

#12 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 14 September 2012 - 03:23 PM

The dome has to be synchronized with the mount, you know.

Yes, I'm aware. I'm planning on motorizing the azimuth initially and will just use a manual shutter for the time being. Eventually, when time allows, I fully plan on motorizing the shutter as well which would give me a completely automated dome at that point. I'll be creating the software as well as the hardware to do this. I have experience with both of those things so it's not out of my wheelhouse.

The equipment to do this is still TBD but I will likely use an Arduino or AVR for control. I want it to be used through a PC but I also want it to be standalone as well so I can open the observatory in case the PC is powered down. I also plan on having at least one door in the base of the Obs. I may put in two smaller doors on opposing sides so that access is easier with I need to do maintenance.

The mini-ROR gives you room to work on the gear, and the synchronization collapses to park and open/close.


This is one of the main draws to the RoR to be honest. The dome will not give me a ton of room to work around the scope if something were to go wrong of if I needed to setup equipment. I had initially thought of hinging the dome since it will be fairly small. That way if I need to get into the obs I can simply unlock the dome and flip it over. I may still do this but that definitely complicates the design since domes aren't generally flipped over like that. It would require some way of locking the dome onto the base (which I will already have...but it will need to be stronger to withstand the lateral forces of the dome being on it's side and then upside down.

I have also considered making the dome lift off from the base after removing some clamps...but this scares me because if I drop it then I drop it directly on my gear! At least the hinged approach would provide a path for the dome and worst case I just destroy the dome!

Jared

#13 nytecam

nytecam

    Voyager 1

  • *****
  • Posts: 11512
  • Joined: 20 Aug 2005
  • Loc: London UK

Posted 14 September 2012 - 05:02 PM

I would strongly recommend you follow the guidelines given here by Nytecam for the ring beam rather than a layered ring. http://www.cloudynig...wflat.php/Cat/1,2,3,4,5,8,9,10/Number/4783794/page/0/view/collapsed/sb/5/o/all/fpart/all/vc/1


Thanks for that link. I like the idea of the box beam but I'm not sure if that's necessary for this size of dome. I may consider it though as it doesn't seem all that complex and it would be easy to implement that at this point since the rings are not glued together yet. Jared

A boxbeam is overkill for a 5ft dome - my 5'.6" DIY dome is strong and lightweight [walked it down garden on my back!] and brilliant for both me and my M12" SCT as link below. ;) Pico dome - very cool :lol:

Attached Files



#14 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 14 September 2012 - 09:38 PM

Very cool domes! What did you skin them with? I considered aluminum but assumed it would be too expensive. I guess tin sheets would do the job too.

#15 nytecam

nytecam

    Voyager 1

  • *****
  • Posts: 11512
  • Joined: 20 Aug 2005
  • Loc: London UK

Posted 15 September 2012 - 01:55 AM

Very cool domes! What did you skin them with? I considered aluminum but assumed it would be too expensive. I guess tin sheets would do the job too.

The big 10ft dome is frameless from 1/8" marine ply clad in 0.25mm ali Roneo plates as 'tiles' with ply boxbeam base ring and current 5'-6" picodome in 1mm sheet ali on lightweight ply frame and here on Youtube. If I was doing a picodome today I'd do this simplified wooden octagonal dome which can be rescaled to any size [and even a sphere!] :grin:

#16 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 15 September 2012 - 04:26 PM

I was initially planning on doing this frameless...I'm not really convinced one way or the other at the moment. Frameless does have the advantage of being a little less expensive and I would assume lighter weight...it also seems like it would be potentially faster to build. Although I would still need the inner pieces for the shutter. I was initially thinking of attaching the shutter ridges on the outside of the dome. They would add some additional structure but not as much as a frame. It also seems like there is less room for error when building a frameless dome.

The other option is something like this, which I'm also contemplating just scaling the outside to 6' or 5'6" rather than 8'.
http://users.csolve....lldwr/dome.html

My initial plan was to use 1/8" masonite on the exterior and use a parachute gore generator to create the cutting template. I was planning on keeping the gores "together" at the bottom to form a skirt. Using this method I would need 2 sheets of masonite to cover the dome and would have a single full seam in the back (and another in the front...but that's where the shutter would go).

I'm thinking of going the "framed" route at the moment. I like the idea of the octagonal dome but I think I would need to size it a little larger to accommodate the straight sides. I'll likely start cutting out the frame pieces tomorrow.

Jared

#17 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 18 September 2012 - 09:59 PM

I haven't been able to make a lot of progress, which is sad because we've had a nice cold front and it's finally under 120 (not an exaggeration!) in my garage.

I was able to get the rings glued together and I made a jig to trim them to size. I've also decided to go with a frame which will allow me to make the dome a little bigger.

Here's a quick shot of the jig I created...nothing fancy. I'll use a router to dimension the ring to it's final size. I'm also going to cut a couple of shallow channels in the bottom to run a couple of copper or aluminum wires to carry power for the shutter.

Jared

Attached Files



#18 dobsoscope

dobsoscope

    Messenger

  • *****
  • Posts: 412
  • Joined: 24 May 2006

Posted 19 September 2012 - 10:11 AM

If you skin with tin you have to prevent galvanic corrosion from happening at every point where you screw in the panels into the arcs.

With aluminium sheet you can use stainless steel screws with no problem.

Then you use something like SIKA MULTISEAL a.k.a FLASHBAND to go over the joints. I would suggest overlapping adjacent panels over each other the full thickness of the arcs and screwing once through both aluminium sheets into the wood.

Instead of the Flashband tape you may also seal with proprietary waterproofing products.

#19 Starhawk

Starhawk

    Space Ranger

  • *****
  • Posts: 5595
  • Joined: 16 Sep 2008
  • Loc: Tucson, Arizona

Posted 22 September 2012 - 06:04 PM

Aluminum with stainless is a strong galvanic couple. The aluminum will erode the stainless fasteners- this is why cadmium plated bolts exist.

-Rich

#20 Mary B

Mary B

    Vendor - Echo Astronomy and Electronics

  • *****
  • Vendors
  • Posts: 3070
  • Joined: 21 May 2010
  • Loc: Minnesota

Posted 23 September 2012 - 05:25 PM

Amateur radio antennas are typically aluminum with stainless fasteners. I have never noticed any corrosion when taken down for cleaning/tune up.

#21 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 23 September 2012 - 06:43 PM

I finally made some progress today and got the dome ring to it's final dimensions! I have yet to cut any additional channels for shutter power but I will probably do that in the next couple of days. I doubt I'll have the shutter automated initially but I at least want to have the frame work in there and ready to do when that does come around...much easier to do now rather than later!

I didn't have enough plunge on my router bit to make it through the 1.5" of plywood (mainly because of the 3/4" of added height because of the MDF I used for the circle cutter). So I ended up having to use my jig saw to remove the excess and then used a flush trim bit to get everything evened up.

Here's a shot of the ring about half way though the cutting using the jig I quickly threw together...it worked very well too!

Posted Image

And here's a shot of the finished ring cut to it's final size.
Posted Image

I may end up getting some Formica and lining the bottom of ring with it to provide a smoother surface for the rollers...I don't know if this is really required or not or if I should just get some softer wheels. The plywood is kind of smooth...but it's not all that great. And there is some unevenness in it as well.

I'll probably pickup a couple more sheets of plywood tomorrow and get the template created for the dome forms so that I can cut them out fairly quickly and use a router to dimension them to the proper size.

Jared

#22 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 30 September 2012 - 11:38 PM

Finally had some time to work on the dome this weekend! I got the main supports and the ribs all cut out. Now I just need to size the ribs accordingly.

Here are the ribs being cut...what a mess! I even had my shop vac hooked up to the router but it couldn't keep up apparently. I cut out 8 ribs and 4 other supports with the router...it got a good workout.

Posted Image

After about 2 ribs I realized I was doing more work than I needed to do. I started by cutting the outside radius then I moved to cut the inside radius (also cutting the rib free). After 2 ribs like that I decided that I would just keep the radius the same and use the for the inside as well. This meant that I would really only need to do 1 cut per rib which would set it free from the sheet. Below on the left is the rib where I was making multiple cuts...the two on the right, which next better, are using the same radius.

Posted Image

I also cut out the main arches as well. This time I cut them with the router rather than rough cutting them with the jigsaw. This worked out much better. Here's a shot of the arches mocked up on the ring.

Posted Image

Hopefully I'll be able to get the ribs cut to size and the frame of the dome built this week so I can start to skin it this weekend.

Jared

#23 nytecam

nytecam

    Voyager 1

  • *****
  • Posts: 11512
  • Joined: 20 Aug 2005
  • Loc: London UK

Posted 01 October 2012 - 03:28 AM

The other option is something like this, which I'm also contemplating just scaling the outside to 6' or 5'6" rather than 8'.
http://users.csolve....lldwr/dome.html My initial plan was to use 1/8" masonite on the exterior and use a parachute gore generator to create the cutting template.

These plans show the gores curved to a partial sphere but this is not possible with sheet material which will only bend in one plane eg cylindrical - unless deformed to the spherical shape via a 'steam mould' or whatever etc :(

#24 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 576
  • Joined: 20 Jan 2009
  • Loc: Austin TX

Posted 01 October 2012 - 01:32 PM

To cut out the gores I'm planning on using some thick paper and tracing between the ribs. Then adding on 3/8 to the sides and 1.5" to the bottom. Hopefully that will mimic the bending of the sheet material.

Thanks,
Jared

#25 dobsoscope

dobsoscope

    Messenger

  • *****
  • Posts: 412
  • Joined: 24 May 2006

Posted 02 October 2012 - 12:24 AM

Neither the thick paper itself will bend between the ribs. The ribs face different azimuths so their short edges are not in line with each other.

If the ribs were parallel then the gores would meet at a butt joint.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics