Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Observatories

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | (show all)
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Pico Dome (it's that small)
      #5411733 - 09/09/12 02:21 PM Attachment (504 downloads)

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: Pico Dome (it's that small) new [Re: averen]
      #5411932 - 09/09/12 04:45 PM

A similar project:

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3024780/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1

Kevin does some amazing AP with this setup.

JimC


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Mirzam]
      #5412271 - 09/09/12 08:26 PM Attachment (186 downloads)

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: Pico Dome (it's that small) new [Re: averen]
      #5412362 - 09/09/12 09:30 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


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: Mirzam]
      #5412726 - 09/10/12 02:42 AM

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

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


Post Extras: Print Post   Remind Me!   Notify Moderator  
astrovienna
Carpal Tunnel


Reged: 12/04/06

Loc: The NoVa White Zone
Re: Pico Dome (it's that small) new [Re: Mirzam]
      #5413533 - 09/10/12 03:02 PM

Quote:

A similar project:

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3024780/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1

Kevin does some amazing AP with this setup.




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


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5413799 - 09/10/12 05:39 PM

Quote:

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

http://www.cloudynights.com/ubbthreads/showflat.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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: averen]
      #5414092 - 09/10/12 08:58 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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5414104 - 09/10/12 09:05 PM

Here's a robodome link:

http://www.homedome.com/store/product_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


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5416392 - 09/11/12 11:23 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


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: averen]
      #5418867 - 09/13/12 10:14 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


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5421224 - 09/14/12 04:23 PM

Quote:

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.

Quote:


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


Post Extras: Print Post   Remind Me!   Notify Moderator  
nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Pico Dome (it's that small) new [Re: averen]
      #5421350 - 09/14/12 06:02 PM Attachment (105 downloads)

Quote:

Quote:

I would strongly recommend you follow the guidelines given here by Nytecam for the ring beam rather than a layered ring. http://www.cloudynights.com/ubbthreads/showflat.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


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: nytecam]
      #5421701 - 09/14/12 10:38 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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Pico Dome (it's that small) new [Re: averen]
      #5421865 - 09/15/12 02:55 AM

Quote:

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!]

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: nytecam]
      #5422664 - 09/15/12 05:26 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.net/~jilldwr/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


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5428431 - 09/18/12 10:59 PM Attachment (100 downloads)

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

Edited by averen (09/18/12 11:05 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5429044 - 09/19/12 11:11 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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5434941 - 09/22/12 07:04 PM

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

-Rich


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mary B
Vendor - Echo Astronomy and Electronics
*****

Reged: 05/21/10

Loc: Minnesota
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5436698 - 09/23/12 06:25 PM

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

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Mary B]
      #5436845 - 09/23/12 07:43 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!



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


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

Edited by averen (09/23/12 07:52 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5449474 - 10/01/12 12:38 AM

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.



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.



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.



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


Post Extras: Print Post   Remind Me!   Notify Moderator  
nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Pico Dome (it's that small) new [Re: averen]
      #5449610 - 10/01/12 04:28 AM

Quote:

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.net/~jilldwr/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

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: nytecam]
      #5450252 - 10/01/12 02:32 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


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5451247 - 10/02/12 01:24 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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5459922 - 10/07/12 11:44 PM

I made a small amount of progress this weekend. I still need to cut the remainder of the bracing but figuring out how to cut those correctly is making my head hurt. I may just end up putting the dimensions of the dome in SketchUp and getting the measurements from there.

Here's the dome with the G11 inside. It's up on blocks to simulate the height that the dome will actually need to be at. It's still about 5" lower than it needs to be to put the RA axis at the middle of the dome. Since this will actually be on a pier I can make it shorter than my mount to keep things under the fence.



Someone mentioned about the sheet material only bending in a single direction. Because of this I'll be attaching the gores where the lines are in the image below and bending them up the arches.



The dome seems pretty sturdy as it is now. The main arches will hold my weight...and I'm not exactly a small guy!

Hopefully I'll figure out how to get the rest of the supports attached this week.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
seryddwr
Innocent Bystander
*****

Reged: 02/19/10

Loc: La-la land.
Re: Pico Dome (it's that small) new [Re: averen]
      #5461502 - 10/09/12 12:57 AM

Makes me want to build a femto dome! (Ha, just kidding) Though this idea ain't bad at all.

Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: seryddwr]
      #5462542 - 10/09/12 05:17 PM

any further progress on this one?

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5464139 - 10/10/12 05:00 PM

Nope...having 3 month old takes a lot of my time these days! I can generally only work on it on the weekends and we had company last weekend...and have company this weekend too. I might see if I can sneak some time in tomorrow or Friday. I think once I get the remaining uprights figured out I'll be able to start skinning.

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5480735 - 10/20/12 05:34 PM

Finally made a little more progress today! Very little unfortunately as we have plans for today, but hopefully I'll be able to work on it some more tomorrow as well.

I've decided to change gears a little and rather than doing a full frame I'm going to do a "mostly frameless" dome. Getting the frame pieces cut turned out to be very difficult because of the high rate of curvature on the small dome. I think for the size of dome it's just easier to go with a frameless design and use gores.

So that's what I'm doing. I'll leave the frame as is and will attach gores to the existing frame pieces and where there is no frame the gores will just get attached to other gores and the main arches.

So the progress for today was:
1 - figuring the above out.

2 - Beveling the pieces besides the main arches to about 20 degrees so that they'll accept the gores nicely.

3 - Creating a paper template for the gores using the website I mentioned at the beginning of this post


4 - Creating a masonite template:


Tomorrow I hope to use my router with a template bit to create a big mess...er, lots of gores using the masonite template I created above. To wrap each side of the dome I should need a total of 9 complete gores and 2 half gores. Each gore is 9.6" across at the widest point.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5482702 - 10/21/12 09:20 PM

I rough cut a whole bunch of gores today. This is enough to do one side. Each side will take 10 gores. This is 12 that are rough cut. These all came from a single sheet of 4'x8' masonite and I would have been able to get 13 out of it but I destroyed one when attempting the router.

I started to use the template and the router to cut them out...this was an epic fail. So I used the template to trace out the gores on the masonite, flipping the template over each time to get them better nested.

After I traced them out I used a skill saw to cut them into groups of 4 gores. And I took that more manageable size over to the bandsaw to cut the individual gores free.

Once they're all trimmed up I'll use a disk sander to get them to their final size and attach them to the dome.



I did a little testing with the template and found that if I pinned both of the edges of the bottom of the gore that I as able to successfully conform to the size of the dome in (roughly) both directions. I'm not sure how this will translate when multiple gores are attached but I plan to at least give it a shot.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5483442 - 10/22/12 11:16 AM

well done!

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5486246 - 10/23/12 11:20 PM

I attempted to attach some of the gores to the dome today...I'm coming to the realization that small domes are fairly difficult to build! The small size of the dome means that things curve faster which means that things need to be pretty accurate. I'm planning on fiberglassing the outside so gaps don't bother me too much, but getting the gores attached and lining up fairly closely is proving difficult. I think part of this might be because of the partial frame that I'm attaching the gores to on the top.

I'll have to do some more fighting to see if I can get the gores to fit. Otherwise I may end up going to plan B...which will be a tiny roll off roof. Unfortunately I don't have a lot of spare time these days to fight with getting the dome built.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5487139 - 10/24/12 03:00 PM

I think I have figured out a way to get the gores sized correctly. It will create some extra waste but I "think" it will get them fitting accurately. I'm going to give this a shot in the next couple of days and will post my results.

Hopefully this will work...I would much prefer to have a dome rather than RoR...especially after all the work that's already gone into the dome!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5504112 - 11/04/12 03:30 PM

Quote:

I think I have figured out a way to get the gores sized correctly.




Ya...that was wrong.

I've gone back to the frame design. And I'm positive I can get this to work! The semi-frameless design was not working. As the gores approached the uprights the angles got all crazy and I couldn't get things to work out. I even removed the uprights and planned on trimming everything to fit but this didn't work either. I think if I would have gone completely frameless this would have worked fine, but the "hybrid" method just did not work.

So...back to the frame. I managed to figure out how to cut the remaining frame elements...after I accepted the fact that they're not carrying any weight so they don't have to be perfect. The frame is just there to help the hard board contour to the dome shape.

Here's the current state of the frame:



After getting the frame constructed I then used some thick paper stapled to the frame to size the gores. This worked extremely well.



I was actually surprised by how close all the gores are to the same size. They're all within about 1/2" of each other so I can use the same template for all of them and just size each of the gores individually.

Here's a shot of one of the gores clamped on to the dome. I still have all 4 of the small ones to cut...I have a template cut for the small pieces but haven't cut any of them out yet. Since I ended up wasting a piece of hard board on the frameless gores I'll have to go pick up another sheet to make the small gores. Thankfully 1/8" hard board is only $8 a sheet!



Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5504545 - 11/04/12 08:50 PM

After my minor success today with getting everything figured out I just couldn't leave it alone. I worked a couple more hours out in the garage and have the dome nearly half way sheeted!

Here's a shot of the exterior. Each half has 4 gores. Here 3 of them are sheeted. The area opposite of the shutter should be fairly easy (I'm hoping...what could be difficult about a rectangle??)



The gores are held on with a couple of screws and a washer on the frame. At the top each gore has a couple of screws holding it in place as well.

Here's a shot of the interior of the gores:



I need to pickup another couple of piece of hard board tomorrow. Hopefully that will be enough for the rest of the dome structure.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: Mary B]
      #5507829 - 11/07/12 01:35 AM

The stainless is what gets eroded. Look at the screws.

-Rich

Quote:

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




Post Extras: Print Post   Remind Me!   Notify Moderator  
Mary B
Vendor - Echo Astronomy and Electronics
*****

Reged: 05/21/10

Loc: Minnesota
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5508622 - 11/07/12 04:03 PM

Just serviced my 43 foot vertical that is all aluminum/stainless. No corrosion I can see. The stainless hose clamps look like new yet. All the screws look new too.

Post Extras: Print Post   Remind Me!   Notify Moderator  
CMacD
super member


Reged: 01/23/12

Loc: Ontario, Canada
Re: Pico Dome (it's that small) new [Re: Mary B]
      #5509713 - 11/08/12 10:51 AM

Quote:

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




I am at the point of skinning my trailer in aluminum and decided to research this topic. Funny - when I look at the theory it would seem to suggest that aluminum and stainless are not the best match. In practice, however, it seems that many people use them. And to my surprise the aluminum boat and plane people say that they work great together. Apparently the water test is really the true test of robustness as the water normally leads to the galvanic reaction. Needless to say I have started to skin the trailer with aluminum held down with stainless screws. I guess I will find out


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5510212 - 11/08/12 04:29 PM

well done!!

Quote:

After my minor success today with getting everything figured out I just couldn't leave it alone. I worked a couple more hours out in the garage and have the dome nearly half way sheeted!

Here's a shot of the exterior. Each half has 4 gores. Here 3 of them are sheeted. The area opposite of the shutter should be fairly easy (I'm hoping...what could be difficult about a rectangle??)



The gores are held on with a couple of screws and a washer on the frame. At the top each gore has a couple of screws holding it in place as well.

Here's a shot of the interior of the gores:



I need to pickup another couple of piece of hard board tomorrow. Hopefully that will be enough for the rest of the dome structure.

Jared




Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5513313 - 11/10/12 03:18 PM

Had a couple of hours to work on the dome this morning! I managed to get all the gores sized and attached. So hopefully the hard part of the building is done! From here I need to seal all the gores and sand the ridges between the gores. I'll also fiberglass the exterior of the dome and the main uprights to make it more waterproof.

Here's how I sized the gores. This method worked fairly well. As I mentioned above I used a paper template to create the initial sizes. That template was over sized just slightly to allow the gores to be individually sized. So this is starting with the rough cut gores.

Step 1: Clamp the gore to the dome. Make sure that it's a good vertical fit.



Step 2: Mark the inner position of the supports:



Step 3: Well, not really a step just showing the inner positions of the supports...



Step 4: Marked positions 3/8" out from the inner line:


Step 5: Played "Connect the dots" to approximate the curve.



I then cut out the outter lines on the band saw and cleaned things up on the disc sander. This worked very well! On a couple of the gores I had to make a couple of small tweaks with the disc sander. For these areas I would mark where there was interference and just slowly remove material until the gore fit nicely.

Each gore took around 10-15 minutes to size and fit...so not too bad!

Finally, I was left with this!



I have found that the lower ring has warped a little bit due to the high humidity that we've had lately and the fact that it's been on sawhorses for that time. So for the time being I have it setting on the garage floor. Hopefully the ring will unwarp. It's not horrible, at the worst position it's probably arouns 1/8" off from flat.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5514743 - 11/11/12 04:29 PM Attachment (61 downloads)

I've been contemplating Shutter sizes lately. I'm planning on having a lift out bottom piece that will need to be manually removed to go below 30-35ish degrees. Along with the moving shutter piece on rails and probably sliding on teflon pads. I had contemplated bearings but I want to keep it as low profile as possible. So teflon sliding on aluminum seems like a better alternative.

I've been plugging numbers into a Google Docs spreadsheet and came up with the following shutter piece sizes:
Bottom Lift out Shutter: 19" (30 degrees)
Main Shutter: 47"
Back Size: 47"
Zenith Opening: 9.5" 15 degrees past zenith.

I may end up making the lift out portion a little larger. Probably around 35-38 degrees. I'm going to have some overlap between the main shutter and the bottom shutter as well as the main shutter and the back piece. Making the bottom shutter a little longer would allow me a little more leeway with respect to the main shutter sizing.

Since this is an imaging only dome I don't really foresee myself going below 35 degrees very often. The bad thing is that when I do need to remove the bottom shutter piece that I won't be able to automatically close the dome because the bottom shutter will be missing. Thankfully the "good" direction for going low is East so if I do end up needing to track lower it will be at the beginning of the night and I can likely re-install the bottom piece before heading to bed.

Attached is half a pie chart showing the shutter sizing.
Blue: Bottom Shutter
Red: Main Shutter
Orange: Back piece

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5609438 - 01/06/13 11:16 PM

Sorry it's been so long since I've had an update...but I haven't had any time to actually work on the dome either so there hasn't been any progress to show.

Today I was able to find some time and get things ready to fiberglass. I plan on filling gaps tomorrow and then this weekend I should be able to actually get some real work done on the dome! After the dome is fiberglassed I'll be able to size the shutter and move on to the building.

Today I setup the dome and made sure that i would have adequate room for the mount and telescope.



Thankfully I have about 6" of space in every direction, which is what I was hoping for. This is with the center of the mount a little higher than I initially wanted as well but because of the height that the dome needs to be this will have to be the case. I may try and get the RA center to be closer to the horizon of the dome but it should be fine as is if I'm unable to accomplish that.

After getting the measurements for the pier height (which I plan to dig and pour in the next couple of weeks) I dropped the dome and set it on blocks so that it will be ready for fiberglass.



Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
Al8236
Pooh-Bah
*****

Reged: 08/18/10

Loc: 48.9173N 122.1390W
Re: Pico Dome (it's that small) new [Re: averen]
      #5609915 - 01/07/13 10:46 AM

Jared,
What are you planing for a rain skirt around the bottom of the dome?
If you are planing a solid skirt you might add that before fiberglassing to get a good seal. I added my skirt later and had some problems getting a good seal, wish I had put it on first!


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Al8236]
      #5610517 - 01/07/13 04:17 PM

Al,
I was planning on putting on the skirt later but I will be fiberglassing it to the dome. I'll fiberglass the main dome structure now (and not paint). Then when I have it mounted on the structure I will attach the skirt and fiberglass it to the dome.

That's at least the plan for now.

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
CharlesW
scholastic sledgehammer


Reged: 11/02/12

Loc: Chula Vista & Indio, CA
Re: Pico Dome (it's that small) new [Re: averen]
      #5611252 - 01/08/13 12:32 AM

I appreciate that you have been working on this for a while now and I'm a Johnny-Come-Lately to the conversation but, any chance you could dig down a couple of feet below grade to install the lower part of the observatory? You would have a structure that was almost full height but still below the fence.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Al8236
Pooh-Bah
*****

Reged: 08/18/10

Loc: 48.9173N 122.1390W
Re: Pico Dome (it's that small) new [Re: averen]
      #5611359 - 01/08/13 03:59 AM

Jared,
That will work! I was just concerned that perhaps you hadn't thought to the next step
It's looking good!


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Al8236]
      #5612964 - 01/08/13 11:58 PM

Quote:


I appreciate that you have been working on this for a while now and I'm a Johnny-Come-Lately to the conversation but, any chance you could dig down a couple of feet below grade to install the lower part of the observatory? You would have a structure that was almost full height but still below the fence.




If I were going to use a larger dome this would be needed. But as it is I can get the scope where it needs to be inside of the smaller dome without having to dig down. Plus going below grade adds other issues like the need to keep out ground water.

Quote:


That will work! I was just concerned that perhaps you hadn't thought to the next step
It's looking good!




Since this is taking me so long I think I'm planning like 10 steps ahead! I worked out the schematics for the rotation/shutter control earlier today. The shutter is going to be a little different than I had initially though. Since I didn't add any provisions for a power ring on the dome I was planning on only opening/closing the shutter when the dome was parked. But I've decided to use the parked "power feed" to the dome more as a "charging point". So I'll have a small 12V sealed lead acid battery that rides on the dome and provides power to open/close the shutter when the dome isn't parked. This is mainly needed for emergency issues.

This will require 2 microprocessors with the ability to communicate wirelessly...which isn't a big deal. Also the microprocessor that will be installed on the rotating portion of the dome will control my light box. So I figured since this was going to be in place anyways I might as well add in the shutter piece and have the ability to control the shutter from other positions besides park.

I also ordered all the hardware for the dome controller and that should be here in a couple of days...so even if I can't build the actual dome i can work on the hardware/software aspect of the dome control.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5619896 - 01/12/13 10:06 PM

My wife was kind enough to allow me some time to dedicate to the dome today...so I tried to make the most out of it!

First I skinned the back of the dome. This was a somewhat important decision as it somewhat sets the size of the shutter in stone.



Next I flipped the dome over and started the fiberglass work on the bottom of the ring. Tomorrow, after the bottom is dried, I'll trim the excess fiberglass off and flip the dome back over to fiberglass the outside.




Here's the ring all wetted out. This is 4oz fiberglass with West Systems epoxy.



So hopefully tomorrow I'll be able to get started on fiberglassing the exterior of the dome. I'll start by "taping" the seams and filleting some of the area and then I'll go all over the dome with the 4oz fiberglass. I hope I have enough epoxy...I only picked up a quart!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5632382 - 01/19/13 10:47 PM

So I've made quite a bit of progress in the last couple of days. I actually thought I had posted an update...maybe I started to and forgot.

So here's how the dome currently sits:


I know it looks ugly...but it's actually quite smooth in person. All of the seams have been sealed and fillets have been constructed where the ring meets the gores.

Next I get to finally start working on the lower and moving shutter! The dome will stay looking about like this until it's ready to go onto the building. At that point I'll fiberglass the gores as well as the skirt and then paint the dome.

I've made a lot of progress on the electronics as well. The motors and almost all components arrived late last week. I ended up burning up one of the Arduino boards that I'll be using as a controller (actually just burned up the voltage regulator). I have the PCB design done for the controller that will control the shutter and my lightbox. I also have all of the software for that controller completed as well.

The rotation controller software is mostly complete as well and I will start on the PCB design for that controller later in the week.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
1965healy
The Snarkster
*****

Reged: 06/23/07

Loc: San Antonio, TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5632498 - 01/20/13 12:29 AM

Not ugly just a diamond in the rough! You've really made a ton of progress on a lot of fronts. Take your time tho, we've had clear skies the last few nights here in Central Texas and as you get closer to completion you're gonna draw clouds this way.

Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: 1965healy]
      #5633571 - 01/20/13 05:06 PM

So the gores are only held down at three points along their length? (top bottom and central bolt)

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5633759 - 01/20/13 06:44 PM

Quote:

So the gores are only held down at three points along their length? (top bottom and central bolt)




That's how they were attached to the frame. The glass and epoxy is really what keeps everything together.

But yes. Only those fasteners on each gore. Although there are more along the top than just one.
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5634359 - 01/21/13 05:19 AM

thanks, then you could I assume have done away with the ribs. I am skinning mine with aluminium sheeting which gets nailed/screwed down onto 1 inch thick ribs.

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5635726 - 01/21/13 09:12 PM

Quote:

thanks, then you could I assume have done away with the ribs. I am skinning mine with aluminium sheeting which gets nailed/screwed down onto 1 inch thick ribs.




Yes, and I had initially considered building a frameless dome. But this turned out to be easier for me to build. Plus removing the ribs now would be considerably more difficult!

I made a ton more progress this weekend! I had today off and I spent a good portion of it working on the dome...with the exception of about 4 hours when I met to pickup my new 12" dob :-) (that will not even get close to fitting in the dome)

First I drilled and countersunk the rails for the shutter to ride on. The shutter will ride on teflon pads on these rails. The rails are 1.5" wide. The shutter will be held on by by pieces of wood or aluminum on the bottom of the rail.



I also made and fitted the lower shutter. It's not 100% done. There will also be some pieces that go on the outside of the uprights to fully seal the lower shutter. Here's the shutter in place:



And here is a shot of the shutter removed:



The lower shutter will not be automated in any fashion whatsoever. It will be held in place with 4 bolts running into the uprights. If I ever decide to image that low I will manually remove the shutter. It's doubtful that it will ever come out...with the exception of passing equipment in and out of the dome.


Other than the physical dome work I've been breadboarding the controller and making sure that everything will work there. I managed to burn up the voltage regulator on one of my microprocessors. Apparently it wasn't rated for 12V...so I've ordered a couple more voltage regulators and I'll get that fixed once they get here.

I can't recall if I've mentioned how the dome controller will work...so here goes.

The dome controller will consist of 2 microprocessors (AVRs, I'm using Arduinos). One unit will be physically attached to the computer. The other unit will be in the top of the dome.

They will each be responsible for the following pieces:

Computer attached unit

  • Rotation
  • Forwarding communication to dome unit
  • Finding rotation home
  • Calculating dome rotation position


Dome unit

  • Opening/Closing the shutter
  • Controlling my flat field


The dome unit has a TON of safety code in it for the shutter. Obviously I have to rely on some sort of wireless communication between the two controllers so there is a lot of communication built in that just makes sure that the communication is valid. And if the unit that controls the shutter doesn't hear from the rotation unit for a certain amount of time it will automatically close the shutter.

Anyways I'm really looking forward to getting some more work done on the dome. I hope to etch one of the PCBs sometime this week.

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: averen]
      #5636737 - 01/22/13 11:54 AM

This is pretty cool. Making the templates from paper attached to the dome was definitely the right way to go. Do you have a plan for a roller track? The more circular it is, the better. However, with a dome this small, I am wondering if it could touch the track in only three places (which would give it a lot of resistance to out-of-round conditions).

-Rich


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5636751 - 01/22/13 12:02 PM

[quoteDo you have a plan for a roller track? The more circular it is, the better. However, with a dome this small, I am wondering if it could touch the track in only three places (which would give it a lot of resistance to out-of-round conditions).




I have an idea in my head :-) I actually attached the track this weekend, it's in the photos above. And as you mentioned the shutter will have 3 contact points with the track to keep binding to a minimum. Although I'm pretty confident that the arches are very round. At the moment I'm contemplating using some angle aluminum for the front and back of the shutter and a flat piece in the center. Attached to these aluminum pieces will be some teflon pads to slide on the aluminum guides.

I'm still trying to work out the actual shutter mechanism for opening/closing the shutter. I'm thinking I my make a curved rack and pinion gear to move the shutter up and down.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5646585 - 01/27/13 06:11 PM

I didn't get a lot done this weekend. I helped a friend pour his pier for his observatory. We used around 1 ton of concrete for his base and pier. Gives me some practice for when I'm ready to pour mine. He'll also be helping me pour mine so that was some additional incentive to help him :-) He rented a 2 bag concrete mixer...money WELL spent! I'll be doing the same when I go to pour my pier. I may try and dig next weekend and then do the pour the following weekend. I can at least use the pier while I'm still building :-)

I managed to mess up my back unloading some extra bags that he gave me when I got home. So for the majority of today I've been limping around.

I did manage to get a little work done. I built the dome rotation sensor and verified it's functional with the board.



The hardest part was stretching the rubber around the exterior of the wheel!

There are 16 holes around the wheel, a "tick" will be triggered at each change so that's 32 ticks per rotation. This will give the dome movement a resolution of around 1/2 degree.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5647267 - 01/28/13 12:43 AM

I managed to get a little more done this evening.

The dome controller is almost finished! This controller is in charge of rotation as well as communicating with the other controller. As it is much simpler than the other controller I just used a prototyping shield for the Arduino rather than etching a circuit board.

If you click through there are notes on different items in the image.

Dome Rotation Controller

I also tested the entire system. That Wondermotor has some torque! It literally jumps to life on start up...It gave my wife, dog and I a startle when it started up the first time. After that I made sure I had a hold of it!


Test Setup

So that's one controller down...one to go. I was surprised I didn't have to fix anything on it and that I didn't blow it or my computer up! My electronics skills aren't all that great. I prefer the software side!

Jared

Edited by averen (01/28/13 12:44 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Pico Dome (it's that small) new [Re: averen]
      #5647396 - 01/28/13 04:03 AM

A couple of thoughts - based on my experiences in automating the dome on my Astro Society's observatory.

The jump when the motor starts may damage the dome or the motor supports. I am using a PWM output to allow the dome power to be applied and removed smoothly. It also slows the dome down as it approaches the target position. I started with a relay to set the direction and a MOSFET to control the power but after burning out a few mosfets I fitted a Poholu DC motor controller that's rated to handle 15A. We are using what looks like the same size of motor.

The other thing is that I an using an electronic compass module to get the dome position, a Sparkfun breakout board. This is bolted to the dome. It should be easy to fit this to your dome Arduino running it off the 3V3 supply and the I2C data lines.

Chris


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: cn register 5]
      #5647715 - 01/28/13 09:58 AM

Quote:


I am using a PWM output to allow the dome power to be applied and removed smoothly.





I will be running PWM on the motor as well. But for testing I just had it full on/off. I haven't implemented the ramp up/down but I'll be doing that this evening. I actually considered using an RC speed control for the motor as well. They're fairly inexpensive and very easy to control with an Arduino. I may still go this direction. I made the mosfet "socketed" so pulling it out is trivial. I will have a large heat sink on it if I keep the mosfet.

Quote:


The other thing is that I an using an electronic compass module to get the dome position, a Sparkfun breakout board. This is bolted to the dome. It should be easy to fit this to your dome Arduino running it off the 3V3 supply and the I2C data lines.





On my setup this would need to be on the shutter controller. So it would make it more complicated. I think for the time being I'll stick with the rotation encoder. If I have issues with that then I will check out the electronic compass. Thanks for the heads up!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5648155 - 01/28/13 01:18 PM

Chris
Were you using any type of flyback diode across the motor when you burned up the Mosfets?

Thank
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Pico Dome (it's that small) new [Re: averen]
      #5648597 - 01/28/13 04:11 PM

I had a diode across the power supply, the MOSFETs had an internal diode and there was a surge suppressor across the motor terminals. The supressor didn't survive either.

The MOSFET was OK for a while but once I got more ambitious about PWM motor speed control it failed within an hour or two. No idea why.

One thing you will find with PWM control is that you will have a singing dome. The B flat two octaves above middle C I think


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: cn register 5]
      #5648629 - 01/28/13 04:26 PM

Quote:


The MOSFET was OK for a while but once I got more ambitious about PWM motor speed control it failed within an hour or two. No idea why.





Probably not a big enough/fast enough diode? High frequency PWM can cause a HUGE spike when the motor (now an inductor) is turned off. Since PWM pulses the motor constantly the collapsing electromagnetic grows very large to a point when the diode can no longer keep up and eventually...poof! This can happen when any coil is pulsed fast enough.

I believe it's also common to put in a resistor with the diode when using PWM so that you consume the spike from the motor. If you have no resistor then you're using the coil in the motor as a resistor to consume the spike. If the spike is large enough and your frequency is fast enough you might not have adequate time to consume your spike and it will just keep growing and growing each time your magnetic field collapses (motor is turned off...and in PWM land that happens a LOT)

I think I'll learn from your experience and calculate out what diode and resistor I will need...I was just going to hope and guess...maybe I'll just order a controller. Also last night I was doing PWM and noticed that the Mosfet was actually shocking me a little when I touched it to see if it was hot. Just the back EMF that I wasn't capturing from the motor. I shut it down before I did any damage.

Quote:


One thing you will find with PWM control is that you will have a singing dome. The B flat two octaves above middle C I think




This depends on the frequencey of the PWM. If you're in the audible range you'll be able to hear it :-) Maybe I can switch PWM frequency fast enough to play the "Flight of the Bumblebee" or something as the dome is rotating :-)

The default PWM frequency on the Arduino is either (around) 500Hz or 1000Hz depending on the pin used. Both are in the audible range. The only one that is inaudible is 31kHz and I believe that's barely audible, definitely on the upper range of human hearing...neighborhood dogs and young kids would hate you.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5650057 - 01/29/13 11:02 AM

After looking through what I would need for flyback protection I have decided to buy the Pololu controllers:
http://www.pololu.com/catalog/product/1376

The motors should pull around 3A so a 15A controller will be more than adequate.

They have reverse as well as ramp up and ramp down. This means the shield I made can be completely replaced by this controller...I just need a way to attach the XBee and I should be good.

Thanks for the heads up on these controllers!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Pico Dome (it's that small) new [Re: averen]
      #5650663 - 01/29/13 04:18 PM

I got the high power motor driver, this one
http://www.pololu.com/catalog/product/758
it may be overkill but I was fed up with killing mosfets.

I didn't need the USB input as I was connecting to the existing Arduino using the existing code and ports.

It will be interesting if the XBee can be connected to through the serial port on the board.

Chris


Post Extras: Print Post   Remind Me!   Notify Moderator  
csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Pico Dome (it's that small) new [Re: cn register 5]
      #5650681 - 01/29/13 04:24 PM

Keep us posted!

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: cn register 5]
      #5650691 - 01/29/13 04:28 PM

Quote:

I got the high power motor driver, this one
http://www.pololu.com/catalog/product/758
it may be overkill but I was fed up with killing mosfets.





No such thing as overkill!

Quote:


I didn't need the USB input as I was connecting to the existing Arduino using the existing code and ports.





I don't really need USB either. But it will make setting up the unit much easier...I think. The board supports automatic ramp up/down which will make my life a little easier.

Quote:


It will be interesting if the XBee can be connected to through the serial port on the board.




The XBee will not be connected directly to this board...although I had contemplated that for my other controller to be honest. Both use 3.3V logic so I would think that the XBee would mate nicely to this board. I will likely try this "just because"

In my setup the rotation unit will be connected directly to a motor and use an XBee to communicate with another arduino which will open and close the shutter as well as control a light box.

So the rotation unit will be connected to the PC via the hardware serial. Then it will have a software serial to communicate with the Shutter/Lightbox via XBee and another Software Serial to communicate with the rotation motor controller. I had considered just using the RC Servo output but a serial connection makes me feel more comfortable.

I haven't been able to find an Arduino library for this controller yet...so I guess I'll be writing that too...should be easy enough.

Thanks again,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: cn register 5]
      #5657944 - 02/02/13 11:22 AM

Quote:

I got the high power motor driver, this one
http://www.pololu.com/catalog/product/758
it may be overkill but I was fed up with killing mosfets.





Thanks again for suggesting the Pololu controllers! They're nothing short of awesome! I picked up the "Controller" versions rather than the "Driver" version. The driver has more basic control...generally all that's needed for our purposes. But I'm lazy and as such wanted to automatic ramp up/down that the controller version offers.

Depending on your dome setup I'm pretty positive that you could get away with just using a couple of the Pololu Controllers to control your rotation and shutter. The controller has the ability to do ramp up/down as well as the ability to have limit switches for each direction (what I'll be using to trigger when the shutter reaches the end during open/close).

You can also daisy chain multiple of the controller versions together when using a serial connection. I wrote a quick and dirty Arduino library that supports daisy chaining.

The only thing I don't like about them is that the serial connection pinout does not conform to the very standard FTDI layout. So I can't directly use an FTDI cable to connect to the board. This really isn't a huge deal as I won't be controlling them this way, but it would have been a nice plus for anyone that wants to control them via a serial FTDI cable.

Quote:


It will be interesting if the XBee can be connected to through the serial port on the board.





This does work nicely. With the BEC on the controller in 3.3V mode I powered the XBee and controller off of the same battery. Then I just ran the RX from the XBee to TX on the Pololu controller and did the same for the TX/RX lines. I then wrote an Arduino sketch that used the Pololu library that I created and assigned it a software serial port and easily controlled the motor from another arduino directly through the XBee.

I didn't attempt this directly with my PC as I didn't feel like writing something that would handle binary serial. I already had that library for the Arduino so it literally took less than 5 minutes to test this.

Hope that helps anyone considering these controllers for dome control!

Also they have another controller that can even take an encoder as input, so you could use that to get your dome position.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5664523 - 02/06/13 12:16 AM

Software keeps chugging along! We had company this last weekend and I also planted a tree (good hole digging experience!) so I didn't get too much done on the dome. I hope to dig the hole for the pier and finish the shutter this weekend, I'm also trying to find a pier plate so I can pour concrete weekend of the 16th...lofty goals I know.

I feel that the controllers for the dome control are nearing completion. The only piece I have left is the ASCOM driver and that should be a piece of cake thanks to WCF and C#!

There's quite a bit of software and hardware involved since I have 2 controllers in the dome. Software wise I have written:

  • Controller software for Shutter/Lightbox controller
  • Controller software for rotation controller (also the relay to the Shutter/Lightbox controller)
  • Dome Server (seen below) which brings the functionality of the controllers together
  • Custom flatbox for Sequence Generator Pro.


All that's left is the ASCOM Dome controller which will interface with the Dome Server. And I'm sure a lot more things once I actually test everything together! I'm pretty confident that the Shutter/Lightbox controller is complete and functions well. I've been testing it for stability for the last 48 hours without a single glitch and have done a TON of other testing with that controller.

Here's a screenshot of the Dome Server and the control panel from SGP showing the light box control:


DomeDuino Server and SGPro

Couple of things to note on the above image:
- Brightness is for the lightbox. This was set in SG Pro and then the Dome Server updates via the device, so this is a real value.
- Shutter is closed...the Pololu controller has the ability to use a couple of the inputs as kill/limit switches. I'll use a reed switch for these and the motor controller will handle stopping the motor (I was glad the controller could do this...it kind of scared me!)
-The "Relay" portion is used to send serial commands directly to the controllers. The rotation controller is directly attached to the computer but the >RS; command is actually a command used on the Shutter/Lightbox controller to get the battery status. The >R designates that the rotation controller should pass the command to the shutter/lightbox and echo back the result.

Unfortunately there's not much else to show at this point unless I post some code...and I have a feeling that most don't want to look at that!

Hopefully this weekend I'll have a much more interesting update! However this is a pretty huge milestone for me...just not a lot of tangible stuff to post. Plus the actual structure is more fun!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5671451 - 02/09/13 09:25 PM

Finally got the shutter construction done! (mostly...)

First I cut the arches with my router then attached them to some bracing. After that I cut out 6 PTFE pads and countersunk them to act as the slides. Working with the PTFE was a breeze...that stuff was extremely easy to work with!

Here is the shutter in place. The shutter overlaps the lower shutter by about 1.5".


2013-02-09 16.43.07

Once the frame was completed I sheeted it with 1/8" board.


2013-02-09 17.46.20

The shutter slides VERY nicely on the PTFE. I'm worried that the shutter might be a little heavy to close so I may need to add a counterweight or a spring to help getting the shutter moving. It's not that heavy but when open all of the weight of the shutter is towards the back. When closed the shutter doesn't go as far down as when open so I don't think opening it will be an issue.

The shutter also goes a good deal past zenith, not a ton but it should be more than adequate to track through. I could have actually moved the shutter back a little bit more if I would have planned this better.


2013-02-09 17.47.04

So now I need to figure how how I'm actually going to mechanize the shutter. I'm considering a bike chain attached to the top of the shutter and a small sprocket to engage the chain.

Hopefully I'll get something figured out. I think I'll be digging the hole for the pier tomorrow!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5671845 - 02/10/13 05:54 AM

Well done ! I have divided my slit into 5 portions. 1 part fold down flap, 2 parts sliding shutter, 2 parts fixed at the back.

How strong did you find working with the pocket hole jigs? I notice pocket holes in the ribs to bottom ring joints. Did you use the same idea to fix the ribs to the two main central arches forming the slit?


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5673202 - 02/10/13 10:27 PM

Got a little more work done today! I'll be pouring the pier next weekend (weather permitting). So this weekend I dug a large hole for the pier to go into. The footing will be 3'x3' and 2' deep. I still need to measure for the height of the pier...it won't be very tall.



I should also be picking up my mounting plate from the metal folks tomorrow.

And I fixed a couple of small issues with the controllers communicating back and forth. I keep adding in things that are nice to have but not really mandatory. Namely battery/temp status from both the controllers. Here the shutter controller is hooked up but the rotation motor controller is disconnected. Thus the "junk" values. Values coming from the shutter controller are valid though. Plus the "Azimuth" value is coming from the actual encoder as well.




Quote:

Well done ! I have divided my slit into 5 portions. 1 part fold down flap, 2 parts sliding shutter, 2 parts fixed at the back.




Any pictures of your dome?

Quote:


How strong did you find working with the pocket hole jigs? I notice pocket holes in the ribs to bottom ring joints. Did you use the same idea to fix the ribs to the two main central arches forming the slit?




They work fairly well. The real restriction on them is the material (plywood) in hardwood they hold extremely well. But with the amount of ribs there are a fair amount of screws. So they do their job!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5684018 - 02/16/13 06:27 PM

What a busy week! It's amazing how much prep work has to be done before pouring concrete. First I looked all over town for a 10" sonotube. I couldn't find any. So I had to use a 12" tube. This isn't horrible but it will mean that I won't be able to track as far past zenith in certain areas or my camera will hit the pier! Then I made multiple runs to pickup all the concrete (800lbs each time...times 3). Finally I put the rebar together last night and rented a 2 bag concrete mixer.

A couple of weeks ago I helped a friend pour his pier, which was nice practice, and it meant that he would help me pour mine. We started after he arrived around 9:30 this morning. After moving all 35 bags of concrete out from the garage to to where the pier would be located we were ready to get started. I had previously built the support for the sonotube but decided I better measure for the total height before we started pouring...good thing too as I had placed the mark for the height above the support 2x4 (it was supposed to go below) so that meant that the pier was 3.5" taller than it needed to be! We poured the "dead man" and while that was setting up I fixed the sonotube and support.

It was somewhat dry today so we decided that 15 minutes was enough time to let the dead man setup before pouring the pier. The concrete actually seemed somewhat rigid after 15 minutes ... but that was a big mistake! We poured the entire pier and as we were tamping it the seal from the sonotube broke and concrete started pouring out the bottom! Not good! We shoveled out what we could and then removed the sonotube completely. Then we shoveled out the rest of the overflow and replaced the sonotube. This time we waited an hour before pouring the pier and the lower concrete held!

Here's a shot of the pier as it drys.


Concrete Pier

So next up I'll start framing out the building. I need to figure out the total height of the building before I start building walls. I should be able to get that completed tomorrow and then I'll start on the floor. The walls will likely be pretty short (around 3' tall) The concrete pier is only 21" tall. On top of that there will be the steel plate (seen in the above picture) and attached to that plate will be a Losmandy MA adapter. Bringing the total height to 27".

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
palmer570
super member
*****

Reged: 09/04/12

Loc: Scranton, Pennsylvania
Re: Pico Dome (it's that small) new [Re: averen]
      #5684581 - 02/17/13 02:23 AM

What do you estimate the cost of the dome to be?
How much does it weigh?

Was considering doing something similar but a smaller dome and came across this maker of Plastic Domes .


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: palmer570]
      #5684835 - 02/17/13 09:30 AM

Quote:

What do you estimate the cost of the dome to be?
How much does it weigh?





So far just the dome has probably cost me around $200 to build. I estimate it's weight to be around 100lbs.

Quote:


Was considering doing something similar but a smaller dome and came across this maker of Plastic Domes .




I had looked at those as an option but I haven't been able to find a 6' dome. Most of the plastic ones seem to top out at 4'. Although you may be able to contact them and see if they can go larger.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
palmer570
super member
*****

Reged: 09/04/12

Loc: Scranton, Pennsylvania
Re: Pico Dome (it's that small) new [Re: averen]
      #5685162 - 02/17/13 12:52 PM

From what I saw on the website they can make up to 8' domes but have to inquire about price. I think up to 4' is in stock and over is made to order.

I emailed them to see if they can tint the plastic or how they recomend painting it. Also inquired about how to go about cutting the opening, if they can do it or if I can get my dads coworker to throw it on the CNC.

However I think for my original plan to mount something semi-temporary on top of my RV I'm going to make something like a pentagonal pyramid that the sides fold flat to the roof deck to be locked down.

Edit: Would be like your Pico dome but with flat triangle panels instead of curved.

Edited by palmer570 (02/17/13 01:32 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: palmer570]
      #5693744 - 02/21/13 11:05 PM

I pulled the sonotube off...I'm pleased with how it looks!



This weekend I hope to fill a couple of small voids in the concrete and paint it as well.

I also plan to start on the building. I think I can probably have the entire frame completed this weekend. It's a small building. Only 6'x6'x3'. The height is approximate. I haven't measured so that's only an estimate. But I'm probably pretty close.



Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
MikeCMP
super member


Reged: 07/12/11

Loc: Chardon OH
Re: Pico Dome (it's that small) new [Re: averen]
      #5693752 - 02/21/13 11:11 PM

That looks pretty good, you are getting close to being done!

How are you getting power in there?

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: MikeCMP]
      #5694052 - 02/22/13 05:52 AM

At this stage think also on 1) how to shed off water from the obs building (ie.) rainwater flowing down the dome and 2) how to prevent the dome from flying off in strong winds!

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: MikeCMP]
      #5698935 - 02/24/13 09:14 PM

Quote:


How are you getting power in there?





Initially I'm going to use an extension cord. Eventually I will trench in a more permanent line.


This was a very busy weekend! Lots of site prep and building. On Saturday I started building the building. I had to pull the dome out of the garage and temporarily set it up on some saw horses to make sure that the dome was placed on the center of the mount (not the same as the center of the pier!) I didn't take any pictures of that...it was a little windy having the dome up on sawhorses made me pretty nervous.




I got the decking finished and started on the actual building structure.




As you can see the wall height is pretty low! I'm hoping I don't need to get in there all that much. But even if I do the dome will hinge up allowing me better access to the equipment. The bottom of the dome will be up another 6 inches from the top of the frame.



Next weekend I hope to have the building completed and the dome mounted (or mountable) on the building.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
palmer570
super member
*****

Reged: 09/04/12

Loc: Scranton, Pennsylvania
Re: Pico Dome (it's that small) new [Re: averen]
      #5702840 - 02/27/13 02:29 AM

Looking good!

Post Extras: Print Post   Remind Me!   Notify Moderator  
astrodog73
super member


Reged: 02/22/13

Loc: Australia
Re: Pico Dome (it's that small) new [Re: palmer570]
      #5702906 - 02/27/13 05:20 AM

Looking great - I feel for you, I have a three month old (and a three year old) - makes it hard to find time for this sort of stuff!

When I did my obs, I installed a caravan/trailer power inlet socket in the wall, I just plug a lead into this when I need power....


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: astrodog73]
      #5708721 - 03/02/13 12:29 PM

How big is the gap around the pier? It looks a little tight.

-Rich


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5709778 - 03/03/13 12:04 AM

Quote:

How big is the gap around the pier? It looks a little tight.

-Rich




The gap is 3/8"

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: averen]
      #5710279 - 03/03/13 10:17 AM

That should be more than any day-to-day shifting. The real board floor is a nice upgrade to the usual plywood.

-Rich


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5711665 - 03/03/13 10:38 PM

My dad was in town to visit on Saturday so I put him to work. We mocked up the dome on the supports to make sure that it would stay below the fence and that there was adequate room inside for the scopes to clear the frame:



Today I started on the base "ring" (octagon) for the dome. I still have one missing wheel. Which will be for the rotation motor:



Then I moved the dome onto the ring and tested the rotation (by hand). Thankfully it seems very smooth and quiet! This week I'll work on getting the rotation motor hooked up to the dome and get some



I should be able to put in some weeknights now that the sawing and hammering is dwindling down. My son's room shares a wall with the garage and I don't think my wife would appreciate if I woke him up (he turns 8months old on Tuesday.)

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
astrodog73
super member


Reged: 02/22/13

Loc: Australia
Re: Pico Dome (it's that small) new [Re: averen]
      #5711716 - 03/03/13 11:13 PM

Dads love a project when visiting don't they!
Its coming along nicely....


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: astrodog73]
      #5713593 - 03/04/13 11:20 PM

Quote:

Dads love a project when visiting don't they!
Its coming along nicely....




We'll it's partly my dad's fault...

Here he is with his previous setup before they moved from San Antonio. He still has the BRC-250 and TOA-150, but he's now more of a mobile observer and has an NJP.

When they moved he actually offered me this dome, but I didn't have any place to put it at the time. I should have just said yes and stored it. He ended up donating it to a school in San Antonio, still a worthy location for it.




Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
dmdouglass
professor emeritus


Reged: 12/23/07

Loc: Tempe, AZ
Re: Pico Dome (it's that small) new [Re: averen]
      #5714762 - 03/05/13 04:02 PM

Like Father -- Like Son !!

Now just how cool is that ??
You've got to love it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
astrodog73
super member


Reged: 02/22/13

Loc: Australia
Re: Pico Dome (it's that small) new [Re: dmdouglass]
      #5714957 - 03/05/13 05:40 PM

I think that is the biggest GEM I've seen - or is your Dad really small??

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dmdouglass]
      #5715432 - 03/05/13 09:44 PM

Quote:

Like Father -- Like Son !!

Now just how cool is that ??
You've got to love it.




For the past couple of years we generally do a father/son astronomy trip to the Texas Star Party. Makes for a nice 4 nights just to get away and unwind too! I hope to continue the tradition with my son when he's old enough to appreciate it and enjoy it. My dad been into astronomy since I can remember but I didn't really start getting interested in it until about 6 years ago.

Quote:

I think that is the biggest GEM I've seen - or is your Dad really small??




Ya, it's not the latter...both my dad and I are 6'2" and neither of us is exactly skinny. The mount is an AP1200...so it's big...but not HUGE. It's smaller than a Paramount. I think the counterweight extension along with the angle makes the mount look considerably larger than it is.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5724845 - 03/10/13 10:28 PM

I started out this weekend by saying if I got the dome rotating under it's own power that it would be a success...thankfully that happened!

First I started by making some rotation guides. I used 5/16" bolts with Pex (tubing that is commonly used for water in homes) acting as the bearing surface. The block is attached to the base frame with a very long bolt. The block is also attached to the caster frame so it's nice and rigid! There are 4 of these in total.



Once I was certain that the dome was not going to rotate off of the casters I then started on the motor mount. I even went so far as to create a scale model in SketchUp as I was worried about motor placement. Unfortunately I realized that my initial idea that I had created in sketchup wasn't going to work...but I think my final solution is actually better.



Initially I had used a smaller hinge (only on the back piece of aluminum). This was too weak to resist leverage that the wheel was putting on the hinge and caused the back of the motor to contact the bottom of the dome! Needless to say this didn't work! The 3" hinge works much better and is considerably stronger. The spring on the left is actually going over another piece of Pex that makes the entire assembly slide up and down very smoothly.

Once this was done I though I was in the clear...wrong. The wheel kept slipping on the motor shaft. So I made a very ugly aluminum piece to capture the cut outs on the motor shaft.



And finally we have the video proof that this thing is rotating!

http://www.flickr.com/photos/averen1/8547344512/

There seems to be some additional drag when rotating counter clockwise. I'm not exactly sure what is causing this...

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
dmdouglass
professor emeritus


Reged: 12/23/07

Loc: Tempe, AZ
Re: Pico Dome (it's that small) new [Re: averen]
      #5724907 - 03/10/13 11:07 PM

Very cool !!
You have worked very hard on this project, and done well.
We are all proud of you.

Now.... to get it mounted.... and something inside !!


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dmdouglass]
      #5769972 - 04/01/13 12:40 AM

Had a busy weekend working on the shutter. I decided to go with a cable shutter to keep as much of the zenith clear as possible. Overall I'm pretty happy with how the shutter works! I need to figure out a way to make the cable wind up nicely every time and I need to add some tensioners as well.

Here's a shot doing the initial cable runs, before the motor was installed. The motor is installed at the back of the dome (but I have no pictures that are this wide with the motor...



The cables stay within arcs of the dome so as not to interfere with the telescope. The cable on top connects to the shutter. The cable on bottom runs back to the motor.



The motor is mounted on the back of the dome and it's mounted low. You can see the rotation guide at the bottom for reference. Unfortunately the cables don't always wind up as nicely as this. I need to figure out a way to make them wind more reliably. However for the most part when they overlap it's not a problem. But they did bind after playing around with opening and closing the shutter once...and since the motor has enough power to rip the shutter apart I would prefer to avoid that from happening!



Speaking of the motor power I was initially worried that it wouldn't be enough to open and close the shutter. But because of the small winding bar it has more than adequate power. It's probably too powerful.

I still need to install the limit switches for the shutter. I'll do that sometime in the week. I also managed to let the magic smoke out of one of the motor controllers so I'll be ordering another one of those :-/

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5799500 - 04/14/13 09:41 PM

Sorry for the lack of photos...I'll try and get some up soonish!

The shutter is now complete with both limit switches installed and it works very nicely! I notched out the removable shutter to make room for the pulleys so it's back in place too.

Next up is the building "flange" (not really sure what to call this...the piece that goes from square to circle). I know how I'm going to do it I just need to get it done. Maybe some interior painting will happen too.

I haven't bee focusing as much on the dome because I'm headed to the Texas Star party in about 4 weeks and have other projects that need to finish up before I head out.

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
1965healy
The Snarkster
*****

Reged: 06/23/07

Loc: San Antonio, TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5799761 - 04/15/13 01:06 AM

Could you use a coarsely threaded rod instead of a smooth one to act as a guide for the cables to spool/wrap on? Or a larger diameter rod? The larger the diameter the fewer wraps and the less tendency for the cable to jam/bind. It could also run slower since each rev accomplishes more take up of the cable. Just spitballing, I'm an audio engineer, I'm not a mechanical engineer.

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: 1965healy]
      #6072415 - 09/10/13 12:14 AM

Wow, last post in April...it's been too long!

So a couple of weeks ago I decided that the dome would be completed before this project was 1 year old! And looking at my photo stream on flickr the project turned 1 year old today. So "Happy Birthday Dome" you've taken entirely too long to build! I'm not completely done yet...but I'm darn close.

Somewhere in this thread I had mentioned contemplating making the dome a "walk in" dome but decided to leave well enough along and just have the tiny door. That has changed.



The walk through is probably one of the better decisions I've made with this dome. It's held in place by a couple of latches (commonly used to secure windows). The majority of the force is taken by a couple of oak blocks attached to the uprights.



After I had cut the dome and flange that took me so long to build I started priming them both. You can see that the flange has been primed in the background as well.



After the dome and flange were primed I started on the building. I had actually built the building once before but since it sat outside for so long with no structure, and the frame was not pressure treated, it began to rot. So I removed all the non-pressure treated wood and started anew.



And yes, that's the door that I was planning on crawling through. I'm very glad I made this "walk in".

Finally with the building done and the flange in place it was time to paint the flange and dome (the building is painted in the picture above). As we were discussing the logistics of carrying the dome out it began to rain. We quickly covered the flange and waited about 15 minutes for it to pass then we carried out the dome and painted the flange and dome. After which we moved the dome onto the structure.



Here's a shot with the walk through open. There are 3 pieces which must be removed, plus the door opened and shutter retracted. If you click through the pieces are annotated.



In normal operation this is what the dome will look like. The lower shutter will be installed unless I need to get below 35 degrees.



And for a sense of scale here's a bad shot of me and my son standing in the opening. Needless to say this is an imaging only dome :-)



At this point I think the dome is about 99% done. The rotation and shutter work well. I need to make a couple of minor improvements to the shutter limit switches and fix an area where the dome skirt rubs on the flange. But other than that it's pretty much done.

I'm hoping to get first light this coming weekend. Where I'm sure I'll find some other issues about dome slaving or something.

This has been a pretty fun project and it's a real sense of pride knowing that I made 100% of the dome as well as the motor controllers and everything that runs it! I can't wait to get some use out of it!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Pico Dome (it's that small) new [Re: averen]
      #6072599 - 09/10/13 04:56 AM

Nice work - small has a new meaning in that photo - enjoy the ride and keep us posted with you future imaging :-)

Post Extras: Print Post   Remind Me!   Notify Moderator  
Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pico Dome (it's that small) new [Re: nytecam]
      #6072702 - 09/10/13 07:10 AM

Nice job Jared!

One question - what holds the dome down to the rest of the building when not in use? I didn't see anything in your photos and Id be concerned that a big windstorm could pull it off.

-Dan


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Midnight Dan]
      #6074255 - 09/11/13 12:50 AM

Quote:


One question - what holds the dome down to the rest of the building when not in use? I didn't see anything in your photos and Id be concerned that a big windstorm could pull it off.





Dan,
The guides are pictured below. The washer on top keeps the dome on. I'm actually reworking these at the moment. Although these are likely sufficient. Large winds generally push the dome down, not up. The day after I put the dome on the building we had 20+ MPH winds and some 40 MPH gusts. I was out there for some of it and the dome didn't even seem to notice.



Post Extras: Print Post   Remind Me!   Notify Moderator  
Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pico Dome (it's that small) new [Re: averen]
      #6074495 - 09/11/13 07:13 AM

While a dome does inherently shed wind load better than other type of roofs, if you have a serious wind storm, the dome can be lifted off the building quite forcefully. 20 mph with 40 mph gusts is just a windy day, not a wind storm.

Those washers on the guides won't hold it. Especially since you mentioned you only have 4 of them. That means if it begins to lift, it will do so on one side first and only contact one of the washers at a time.

Right now, your dome's only defense against wind is it's shape and the fact that it takes a lot of wind to create the needed upward lift on a dome shape. But, once an edge starts to lift, even a little, the wind will get under that edge and the upward force will increase dramatically and almost instantly. Just my 2 cents, but I'd use some kind of clamping mechanism, maybe toggle clamps, to secure the dome to the rest of the building when you're not using it.

You put so much effort into that dome, and have done such a beautiful job, it would be a shame to see it in shambles after a good storm!

-Dan


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Midnight Dan]
      #6074706 - 09/11/13 09:57 AM

Quote:

While a dome does inherently shed wind load better than other type of roofs, if you have a serious wind storm, the dome can be lifted off the building quite forcefully. 20 mph with 40 mph gusts is just a windy day, not a wind storm.

Those washers on the guides won't hold it. Especially since you mentioned you only have 4 of them. That means if it begins to lift, it will do so on one side first and only contact one of the washers at a time.





All 4 washers will always be over the dome ring. Even if the dome is pushed to one side it will still be under all 4 washers. That is unless either the building or the actual dome inner ring begins to bend, then I have other problems! Thankfully about 40mph is about as high of wind as we usually get here. I do agree that the washer solution isn't 100% adequate. Which is why I'm redoing the hold downs. I'll be using some angle iron that will overlap more of the ring.

Quote:


Right now, your dome's only defense against wind is it's shape and the fact that it takes a lot of wind to create the needed upward lift on a dome shape. But, once an edge starts to lift, even a little, the wind will get under that edge and the upward force will increase dramatically and almost instantly. Just my 2 cents, but I'd use some kind of clamping mechanism, maybe toggle clamps, to secure the dome to the rest of the building when you're not using it.





I do have provisions in there to clamp the dome to the building. There are 8 areas that I can quickly attach the dome with clamps if things get really bad. I do like your idea about toggle clamps. I can probably fairly easily provided I can find some adjustable clamps that are long enough. I don't think that should be an issue though.

Really my main concern is hail. We generally get a bad hail storm about once every 10 years. I'm not sure how the dome would fair in a hail storm...probably not too well.

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: averen]
      #6074996 - 09/11/13 12:28 PM

I had thought you were going to fiberglass the whole thing. Fiberglass cloth is pretty cheap and can result in a very tough structure. You can find it at US Composites in large formats. You'll have real strength if you can do a layup stack with 0° plain weave alternating with 45° woven fabric with a stack like so: 0°, 45°, 45°, 0°, and repeat in blocks of 4. Note, the more complex weaves like satins are more conformable, but you would have to keep track of which side is up, because the fabric has a bias when woven that way the plain weaves don't. But you could make a really tough dome with a little more heft. Assume a density of .08 lb/ in^3 to calculate weight before you overload your supports and drive mechanism.

-Rich


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #6081288 - 09/14/13 11:37 PM

What a week! I'm getting close...I can feel it!

Unfortunately the week started out with me blowing up one of the motor controllers. I had decided to move away from the "tick" wheel and use a digital tilt compensated compass to get my heading. I was being hasty and didn't unplug the battery while I was removing the controller...$40 lesson learned. The controller is still usable for something else, but the voltage regulator was blown (which I need to power my Arduino).

The compass was an interesting experiment but wasn't as accurate or precise as I had hoped, even after calibration I could only get repeatable results within 3 degrees. So I removed the compass and added an additional optical encoder to the "tick" wheel. Now the tick wheel is running full quadrature encoding and is directional. Previously it would just count ticks and my controller would be responsible for knowing the direction based on which way it told it to get there. This was generally ok but the single encoder was prone to noise and could count up randomly at times. The additional encoder prevents this, or at least makes it less likely. Plus it has the added benefit of giving the rotation double the resolution! The tick wheel now has a resolution of 15 minutes of arc (.25 degree), however I don't need that level of accuracy and I'm not going to program a PID into the rotation mechanism to get it either. I can repeatedly get under 1 degree of accuracy and that's all I really need!

So the dome is rotating and the shutter is opening. Both controllers are installed in their permanent locations. I still need to add a home switch (I'm thinking Hall effect sensor) and add some power contacts to charge the shutter battery. If anyone has suggestions on this I would love to see them!

Other than that things are pretty much done. I'm sure I'll need a couple more tweaks to the software but not a lot.

Oh and did I mention I made a remote control to open/close the shutter and rotate the dome? It's been a huge time saver and it makes me feel pretty cool click a couple of buttons as I'm walking out to the dome and watch it open!

Hopeful to have first light in a week!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
astrodog73
super member


Reged: 02/22/13

Loc: Australia
Re: Pico Dome (it's that small) new [Re: averen]
      #6081326 - 09/15/13 12:06 AM

Looks great Jared - a fine job....
I just use some long M10 bolts to hold my ROR obs roof down, just a hole through track and roof frame, bolt slips up and bolts the roof down.... I use 3 for day-to-day use, and have holes for a few more if a good low-pressure cell is on the way....


Post Extras: Print Post   Remind Me!   Notify Moderator  
cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Pico Dome (it's that small) new [Re: astrodog73]
      #6081482 - 09/15/13 03:38 AM

I gave up on encoders because of the noise issues, even with a quadrature encoder.

Interesting that the compass gave you problems. Isn't 3 degrees good enough? I tried this and had no trouble. This is using a home made compass module with a digital compass, a PicAxe and a small transmitter to send the compass X,Y,Z vector.

The compass is mounted level and I get the direction from the XY vector. There is a load of code to calibrate the compass position, both for the module gain and offset, and set a number of calibration positions to interpolate between. I set the gain and offset but have not needed to use the position calibration. The result is that the dome moves accurately enough that the scope can see out. That's no trouble after a lot of research, developing software and testing of course

For dome power I'd be tempted to look at using a battery with solar charging.

Chris


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: cn register 5]
      #6081919 - 09/15/13 11:47 AM

Quote:

I gave up on encoders because of the noise issues, even with a quadrature encoder.





With shielded cable I have a very minimum amount of noise. It was rarely problematic with the single encoder and now with the dual encoders it's been completely (thus far) eliminated.

Quote:


Interesting that the compass gave you problems. Isn't 3 degrees good enough?





To be honest I don't know. But I didn't feel comfortable with the amount that it ranged even when sitting still. Plus my dome is small and likely not very "magnetic friendly" with the motors and such. Truth is the farthest I can get the compass from either motor at any given time is about 3'. Which is likely close enough to affect the field measurement.

Quote:


For dome power I'd be tempted to look at using a battery with solar charging.





I have considered this. But the panel must be attached to the dome in my case (the shutter battery rotates with the dome. I don't really want to drill any holes in my dome at the moment :-/ I guess I could have a panel attached to the building but I would still need to transfer power up to the dome some how. I have a couple of ideas but nothing that I'm 100% sure of at the moment.

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: astrodog73]
      #6081941 - 09/15/13 12:00 PM

Quote:

Looks great Jared - a fine job....
I just use some long M10 bolts to hold my ROR obs roof down, just a hole through track and roof frame, bolt slips up and bolts the roof down.... I use 3 for day-to-day use, and have holes for a few more if a good low-pressure cell is on the way....




I contemplated something similar. As it is now I use some beefy C-Clamps that attach to the dome ring and then to the building. These are attached at the wheels of the dome so it's a nice hard point as well. If things look like they're going to get "really bad" I have some blocks that I will use to slightly elevate the dome off of the wheels and then the blocks allow me to put considerably more pressure on the C-clamps without worrying about denting the wheel surface. I can add up to 8 of those if needed.

For daily use I have no clamps in place other than the guides which also act to keep the dome affixed to the building.

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #6082962 - 09/15/13 10:47 PM

Well the shutter is done and fully functional! Below are some screen grabs from my security camera marking the first time I ever completely opened and closed the shutter without being in or nearby the power supply The security camera will be used to monitor things while I'm inside the house. It will sit one the south end of the mount (where it's currently at)

I still have some work to do on the rotation. I found a couple of weeks ago that it's rubbing in one spot so I need to move one of the guides about 1/2" forward to stop that. I've removed the guide and will fix this tomorrow. Then I need to get a "home" switch (looking like it will be a reed switch) and I need to get a couple of contact points to relay up the power for the shutter battery charger when the dome is parked. Finally I need to finish my calibration routine which will count the total ticks based on the home switch.

So here are some pics from the security cam in my dome. Yes, these are with IR on. I can easily turn it off though...which was one of the main selling features of this particular camera!

Shutter Open:


Shutter Motor/Windlass. Also to the right up on the dome is the shutter controller, if you click through there are annotations on the image:


Motor Controller and Rotation Power Supply (also annotated):


Shutter Closed:


Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #6087794 - 09/18/13 11:23 AM

I fixed the rotation guide and installed the home button. After some minor modifications to my calibration code I as able to quickly calibrate the rotation steps of the dome.

Here's a video of the shutter and rotation. The volume is fairly loud. You'll want to turn your speakers down. I need to fix the popping sound coming from the shutter but it's just the spring holding the tension quickly moving against the cable:

http://www.flickr.com/photos/averen1/9794932986/

I'm pretty much "go" for first light. I also tested out my ASCOM driver and verified that it was still functional. All commands in the video above are actually done through the ASCOM driver.

I need to finish the power "relay" to charge the shutter battery and then the dome should be all done. Although I'm sure I'll still find some things to work on! Like a weather alert station that is integrated with the dome controller.

The forecast for this weekend isn't looking to great at the moment but we desperately need the rain so I won't complain!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
MHamburg
scholastic sledgehammer
*****

Reged: 06/21/06

Loc: Brooklyn, NY/Berkshires, MA
Re: Pico Dome (it's that small) new [Re: averen]
      #6088384 - 09/18/13 04:29 PM

Jared,
That video is awesome!! In fact, your engineering is very impressive.
Michael


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: MHamburg]
      #6094396 - 09/22/13 01:17 AM

First light is happening as I type!



I'm using the AT106 tonight. Eventually it will house the AP130 but I wanted to have a little extra clearance "just in case". And the 130 should actually be more forgiving when it comes to dome slaving as the FOV is narrower, but less forgiving when it comes to clearance (although when I built the dome I was expecting around 5-6 inches all the way around with the 130)

It's been a little rough but things started evening out around 10:00 or so. I fought with POTH for a little while and eventually gave up. I'm currently using the ASCOM Dome Control hub which is working extremely well. I've had network problems and the dome PC just got a new OS yesterday so I was bound to forget something, unfortunately that something was setting the gain/offset values for the CCD. Thankfully I realized that after only 1 20 minute frame...

I've found that my wifi network doesn't really get the job done out there, it's fine if the laptop is about 3 feet higher, but that's not where it goes in the dome! I have a separate router just to get signal out to the dome but apparently it's not close enough. Thankfully I happened to have some unused powerline networking equipment that is working like a champ! Faster speeds than my WiFi could support too so I think I'll just leave the Powerline equipment in there until I can run some cat 6 out there.

Getting the mount polar aligned was not fun...lots of contorting around. Although I'm getting very good about getting in and out through that tiny door. I spent about 2 hours today sitting on the floor dodging the counterweight shaft or the scope while I was setting up the dome geometry parameters. I put the scope in a lot of different positions to verify that the slaving was correct. It's pretty much spot on!

Now I just need to start planning some targets in anticipation of the new moon!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
astrodog73
super member


Reged: 02/22/13

Loc: Australia
Re: Pico Dome (it's that small) new [Re: averen]
      #6095664 - 09/22/13 07:59 PM

Congrats Jared - you've done a fine job.... leave a few photons for the rest of us now!

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: astrodog73]
      #6274664 - 12/27/13 12:00 AM

Well the dome has been up and running for a few months now. So far it has been pretty reliable. I've made a couple of changes though.

1 - I've added a digital compass that rides with the dome this helps to keep the dome on track. I found that my tick wheel was skipping occasionally however I think I have this fixed as well. The compass will sync the dome ever 10 seconds. Unfortunately the compass is only accurate to about 2 degrees, so it does tend to float some.

2 - Flange leak. The flange has leaked since I put it out there. However the leak is pretty small and by the door so I've been lazy about fixing it. We had over 9" of rain in 2 days and there was only a couple of cups by the door and no where near gear. And since the floor is pressure treated and planks it just flows out, so I haven't had a lot of motivation to fix it. It's actually where the "walk through" is at. Over the Christmas vacation I've set out to fix it. Here it is mid way through the process. At this point it has a layer of fiberglass and resin on it. It will get painted tomorrow.



I designed shutter controller to also handle a lightbox that will be mounted on the inside of the dome. I plan on getting that setup in the next month or two.

I'm also building a weather station. I have the Cloud, Temp and Humidity sensors complete. I just need to finish up the rain sensor and get it setup by the dome. It will be hardwired to the dome controller and will close the shutter if things go bad. Worst case it loses power (which means the dome controller loses power) and the shutter will close itself after it recognizes this case.

Anyways, just wanted to post a little update since it's been a while. Shortly after I got everything out there and the dome completed we had a ton of rain over the next month! So it's been slow going acquiring data but I've had a handful of nights that I've been able to image. I don't want it to run completely automated without the weather station. Weather here in Central TX is to unpredictable!

Thanks,
Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #6275963 - 12/27/13 07:14 PM

Well the base still looks ugly. Hopefully I'll be able to paint tomorrow after the flange completely hardens. It's nice a smooth so the filler has done it's job, but it just looks horrible because there are multiple layers and even different types.

Today I built up an overlap on the removable piece such that I can get some weather stripping in there and provide a water tight seal. Here's a shot of the fiberglass layup. The removable section is on the left and the flange is on the right. Looking at the picture above this is the section over the open part of the door.

The electric tape and masonite are just there to act as a mold, to bring the flange up about 1/8". This will allow some space for weather stripping to provide a tight seal.



Everything should be hardened by tomorrow morning. I'll sand it down and smooth everything out then trim to shape and get everything painted and looking pretty.

Previous to pulling everything apart we had lots of cloudy nights. Since I've started this project it's been clear and stable for the last 3 nights in a row (not to night though)....figures.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: Pico Dome (it's that small) new [Re: averen]
      #6275968 - 12/27/13 07:19 PM

Thanks for the update!

I'd like more specifics about the digital compass and it's use to control dome positioning. Seems like a great idea!

JimC


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Mirzam]
      #6276161 - 12/27/13 09:38 PM

Quote:

I'd like more specifics about the digital compass and it's use to control dome positioning. Seems like a great idea!




Jim,
The compass is not all that fancy. It's a 3 axis, tilt compensated compass...this one:
http://www.adafruit.com/products/1120

Keep in mind that I built my own dome controller so I'm not sure if this is something you could do with a commercial dome controller without some additional ingenuity. But none the less this is what I did.

My dome consists of 2 separate but integrated controllers. The rotation controller and the shutter controller. The rotation controller is stationary and the shutter controller rides with the dome and is constantly powered by a 12V battery which is charged when the dome is parked. The rotation position is controlled by the rotation controller but the controller is stationary so it wouldn't be a good place for the compass :-) So I wired up the compass to the shutter controller and since the rotation controller already talks to the shutter controller I just added a new command to get the current azimuth position from the compass. The rotation controller then syncs to this position.

Currently the position is synced every second while the dome is stationary. The stationary part is important because I still rely on the tick wheel for the actual rotation. If i synced while rotating this could cause me to overshoot my position and keep rotating until I actually got to it. The tick wheel doesn't need to worry about overshoot as I can be guaranteed to receive every tick. But since this isn't the case with the compass I just left the tick wheel in place mainly to serve as a "best guess" for the rotation.

In all honesty the compass is somewhat of a hack and while it works it's not something that I want to have to rely on. I will likely remove the compass syncing from the rotation controller once I get the tick wheel more reliable (it's wood and it swelled causing extra friction which causes it to slide occasionally rather than rotate). Because of the friction my dome looks like a decaying sine wave when it's going to a specific position since it will overshoot then get synced, then overshoot, then get synced...but each overshoot is generally less and less so it eventually gets to the correct location after a few of the slave timers have gone by.

This might sound bad and unworkable but the error is really only about 5-10 degrees on the largest slews. And in normal slaving operation it works just fine as it's only moving 2-3 degrees at a time.

When I send a manual azimuth sync to the dome controller it syncs the compass as well. So there are essentially 2 different syncs that happen. A manual sync as mentioned above and a sync that updates the rotation controller position with that of the compass.

So that's the digital compass story. I believe someone (Chris R?) made a dome controller for his club/friend that relied solely on the digital compass for the azimuth. I had considered this but didn't think a 2 degree window of error would be adequate. Now that I've imaged with the dome for a while and have even gone to an OAG 2 degrees should have been more than adequate. I just don't know if I want to rewrite that portion of the dome controller! Maybe in the summer months when it's more galaxy season since I don't have a good focal length for that!

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #6279003 - 12/29/13 11:52 AM

So after everything dried I removed the molding pieces and trimmed everything to size and feathered it in.



Then I painted and installed some weather stripping to make a seal against the removable piece.



To do this work I had to remove the dome skirt. I ended up shortening the skirt by a good amount to allow clearance. But There is still a nice sized overlap. I will likely use some garage door weather stripping and create a nice seal between the dome and the flange. I'm not too concerned about sealing this off for "visitors" as the flooring has lots of gaps. I'm more concerned about sealing dust and blown debris out.



I think this is the only time that I've ever HOPED for rain so that I can see how well things are sealed up now...

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
Raginar
Post Laureate
*****

Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Pico Dome (it's that small) new [Re: averen]
      #6279086 - 12/29/13 12:34 PM

Looks nice Jared.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Midnight Dan
Postmaster
*****

Reged: 01/23/08

Loc: Hilton, NY, Yellow Zone (Bortl...
Re: Pico Dome (it's that small) new [Re: Raginar]
      #6279142 - 12/29/13 12:59 PM

Looks good! Your garden hose should be able to simulate rain. That's how I tested my SkyShed POD for leaks.

-Dan


Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Midnight Dan]
      #6279164 - 12/29/13 01:13 PM

Quote:

Looks good! Your garden hose should be able to simulate rain. That's how I tested my SkyShed POD for leaks.

-Dan




I considered that. I'm pretty certain it will be leak free, or at least it will leak less than previously which wasn't all that bad. I'll just wait until we get the real deal. I know the dome doesn't leak and that's the part protecting the spendy stuff :-) if the flange has a leak it's not a big deal as it won't get to the gear.

We had 9" in 2 days a couple of months back. Water definitely got into the obs but it wasn't much and it wouldn't have gotten any equipment wet. As long as this solution keeps things "more dry" I'll be happy! Plus I want to make sure the paint has completely hardened, which it probably has but I'm going to try and give it a couple more days.

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: Pico Dome (it's that small) new [Re: averen]
      #6279228 - 12/29/13 01:48 PM

Jared, you've certainly done a great job on your dome, congratulations!

Post Extras: Print Post   Remind Me!   Notify Moderator  
SpaceConqueror3
super member


Reged: 09/19/13

Loc: Phinney Ridge, Seattle, WA
Re: Pico Dome (it's that small) new [Re: csa/montana]
      #6279532 - 12/29/13 04:49 PM

That is awesome. I wish I had those kind of craftman skills.

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: SpaceConqueror3]
      #6279644 - 12/29/13 05:56 PM

Quote:

That is awesome. I wish I had those kind of craftman skills.




Honestly not a lot of skills involved. Just a willingness to try is generally all that's needed and a willingness to redo work if need be! I usually start with an idea of how to do something and based on the success/failure of that I change plans.

For instance I used expanding foam to initially create the large fillets. Probably not the best idea as it's mostly air and when it got cold the bubbles decreased in size and much of the foam collapsed as it hardened. Thus the bondo :-/ What you don't see is that I initially created a fillet around the entire dome but it was extremely difficult to work in that narrow area so I ripped all the foam off and sanded it down.

I did work at a body shop through college so that definitely helped with the bondo and I used to build composite RC planes so that helped with the fiberglass work. Nothing someone couldn't quickly pickup from reading some forums though. Composites are actually pretty easy to work with but they seem overly complex...not so if you're just doing structural work like this and don't care about saving weight.

No need to be afraid of failure...I've got lots of bondo, fiberglass and sandpaper :-)

Jared


Post Extras: Print Post   Remind Me!   Notify Moderator  
SpaceConqueror3
super member


Reged: 09/19/13

Loc: Phinney Ridge, Seattle, WA
Re: Pico Dome (it's that small) new [Re: averen]
      #6279667 - 12/29/13 06:05 PM

I like your reassurances but car repair for me revolves around getting my new tag properly placed on my license plate. : )

Post Extras: Print Post   Remind Me!   Notify Moderator  
averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: SpaceConqueror3]
      #6279670 - 12/29/13 06:08 PM

Quote:

I like your reassurances but car repair for me revolves around getting my new tag properly placed on my license plate. : )




Here in TX they're on the interior bottom left corner of the windshield. My wife used to have a CX-7 that had a fairly steep windshield which required a contortionist to remove and reapply those things!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | (show all)


Extra information
3 registered and 5 anonymous users are browsing this forum.

Moderator:  Christopher Erickson, Mitchell Duke 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 19174

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics