BluewaterObserva
Postmaster
Reged: 05/18/04
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Re: Building a 24' Dome
[Re: frolinmod]
#5716732 - 03/06/13 04:04 PM
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I'm not to far away from you. Mine is a .8 meter under a 6 meter dome in the Zuni Mtn's, NM.
The weather is warming up, My wife and I and perhaps our well behaved little Beagle would love to see your setup down there. Once the snow melts I think there are some back roads that would make it a fairly short distance between us. Your welcome to come up here some time as well if interested.
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Tom Clark
professor emeritus
Reged: 11/14/07
Loc: North of Deming, NM
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Re: Building a 24' Dome
[Re: BluewaterObserva]
#5718336 - 03/07/13 12:28 PM
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PM sent.
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Tom Clark
professor emeritus
Reged: 11/14/07
Loc: North of Deming, NM
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Re: Building a 24' Dome
[Re: Tom Clark]
#5746125 - 03/20/13 08:12 PM Attachment (40 downloads)
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Haven't posted lately, as have been trying to figure out how to get our big sliding shutter to open and close properly. I hate to admit it, but getting the twin shutters to slide sideways was a lot easier to build and adjust…
The first motor I put on the dome was just too small. It would open the shutter a bit, but as soon as the open button was released the door would come crashing back down.
The door needed a more powerful motor that would hold the door in position. I ended up getting an electric winch gear motor, and taking it all apart, then building brackets so it could be mounted to the dome. It works, but seems to be too powerful and moves the door much faster than I would like.
Anybody know how to slow down an AC motor without doing it by gearing?
Edited by Tom Clark (03/20/13 10:51 PM)
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Tom Clark
professor emeritus
Reged: 11/14/07
Loc: North of Deming, NM
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Re: Building a 24' Dome
[Re: Tom Clark]
#5746140 - 03/20/13 08:15 PM Attachment (42 downloads)
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The door does go up and down, but I am still adjusting the support wheels to try to end up with a shutter that is trouble free. The simple truth is I just don't know what I am doing and could use a little help.
Building everything else on this project was actually quite easy, but solving this new problem is taking a bit of work.
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John Jarosz
Astro Gearhead
Reged: 04/25/04
Loc: Chicago area, IL
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Re: Building a 24' Dome
[Re: Tom Clark]
#5746323 - 03/20/13 09:21 PM
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If you use a worm drive then the weight of the shutter can't backdrive the motor after it's turned off. Worm drives have a high reduction which slows the output speed down AND gives you much more torque. It might be something to think about.
John
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John Jarosz
Astro Gearhead
Reged: 04/25/04
Loc: Chicago area, IL
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Re: Building a 24' Dome
[Re: John Jarosz]
#5746335 - 03/20/13 09:26 PM
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There are a zillion of them
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stmguy
super member
Reged: 10/11/12
Loc: Western NH
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Re: Building a 24' Dome
[Re: John Jarosz]
#5746944 - 03/21/13 06:35 AM
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You should be able to control the speed with a PWM control
http://www.ecrater.com/p/16370377/2000w-adjustable-controller-switch-ac?gps=1
this one is for 220 volts , not sure what you have for a motor
Norm
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Mike Lockwood
Vendor, Lockwood Custom Optics
Reged: 10/01/07
Loc: Usually in my optical shop
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Re: Building a 24' Dome
[Re: Tom Clark]
#5747499 - 03/21/13 12:27 PM
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Quote:
Anybody know how to slow down an AC motor without doing it by gearing?
There are a variety of solutions, but really you should know what type of AC motor it is before you choose a speed control method.
What other info do you have about the motor?
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Jeff B
Carpal Tunnel
Reged: 12/30/06
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Re: Building a 24' Dome
[Re: Tom Clark]
#5747548 - 03/21/13 12:45 PM
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Would it be possible to have a hanging weight with a rope snaked over pullies along the ID of the dome, like an elevator? The weight could be removed so you could rotate the dome and only attached when openning the shutter.
Just an idea.
Jeff
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Rustynuts
super member
Reged: 07/25/11
Loc: East Tennessee
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Re: Building a 24' Dome
[Re: Jeff B]
#5755049 - 03/24/13 09:48 PM
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Tom, what you need for controlling ac is a frequency inverter. they are industrial ac motor controllers. they worked like the drive correctors worked for the synchronous motors used in the older eq mounts. I am surprised that you decided to use a ac motor system because the only way to slow down a ac motor is to lower the frequency connected to it. Jon
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Tom Clark
professor emeritus
Reged: 11/14/07
Loc: North of Deming, NM
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Re: Building a 24' Dome
[Re: Rustynuts]
#5779147 - 04/05/13 08:57 AM Attachment (51 downloads)
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This is the first photo taken with the shutter all the way open. Mike Lockwood and Bob Noneman brought out the refigured and recoated 42" mirror, and also a used 90volt variable speed DC motor to use on the shutter. That solved all the existing problems. After a few adjustments to the rollers, they got the door working as it should. I had been fighting it for a couple of months, and it took them a couple of days…
It pays to have younger, sharper minded friends! Now we can get the 42" installed and ready to go. More photos to follow.
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Project Galileo
professor emeritus
Reged: 11/14/07
Loc: Jefferson County, Colorado
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Re: Building a 24' Dome
[Re: Tom Clark]
#5779450 - 04/05/13 11:43 AM
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Congrats on getting over the speed bump. Your progress is beautiful. I can imaging the buzz and excitement around there while you install the guts of your observatory.
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dmdouglass
professor emeritus
Reged: 12/23/07
Loc: Tempe, AZ
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Re: Building a 24' Dome
[Re: Project Galileo]
#5779692 - 04/05/13 01:59 PM
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Seeing the pitcture (above) with the group standing in front, gives a whole new perspective to the size of that building. And..... probably to the size of the scope that is being configured inside.
Wow !!!!
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BluewaterObserva
Postmaster
Reged: 05/18/04
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Re: Building a 24' Dome
[Re: dmdouglass]
#5779948 - 04/05/13 03:42 PM
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I am getting excited looking at it.....
I still get warm and fuzzies thinking about the first time I got stars to focus on my .8 meter.
If you have a 1st light gathering, my astronomer wife and I would love to be there for it.
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csa/montana
Den Mama
Reged: 05/14/05
Loc: montana
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Re: Building a 24' Dome
[Re: Tom Clark]
#5780882 - 04/05/13 11:30 PM
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That is most impressive! A really beautiful Dome; Congratulations! 
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Tom Clark
professor emeritus
Reged: 11/14/07
Loc: North of Deming, NM
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Re: Building a 24' Dome
[Re: csa/montana]
#5781417 - 04/06/13 10:20 AM Attachment (37 downloads)
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4/5/13 A date that will be remembered for awhile. After 8 hours of hard labor, (not counting the last 6 months) the pieces of the 42 were moved from the garage to the dome, resembled, hoisted into the air, the newly refigured and recoated optics installed, a rough collimation, we had first light at 10:48 PM. We observed a few objects for an hour, and then went to bed exhausted.
Present were the dome slaves Mike Lockwood, Bob Noneman, Steve Coe, Jeannie Clark, and myself.
More later…
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BluewaterObserva
Postmaster
Reged: 05/18/04
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Re: Building a 24' Dome
[Re: Tom Clark]
#5782011 - 04/06/13 02:45 PM
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Thanks for the report... Gives me tingles and I'm not usually easily tingled. It will be interesting getting your impressions of the refigured / recoated optics
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Tom Clark
professor emeritus
Reged: 11/14/07
Loc: North of Deming, NM
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Re: Building a 24' Dome
[Re: BluewaterObserva]
#5791980 - 04/11/13 09:24 AM Attachment (29 downloads)
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Thanks to everyone who has followed this thread and posted positive comments to encourage us to get the job done. As anyone who owns an observatory knows, they are never finished - you will keep on tinkering forever. However, this project is basically finished.
The scope is working far better than it ever did before. Mike Lockwood is a perfectionist who wants me to change out my old sling for a cable sling, so that is on the list of projects to do. The skies here in the New Mexico desert have such wonderful transparency compared to what we used to call our 'underwater observing' back in Florida that our observing will be like starting over. However, for now it is time to take a rest from the construction frenzy and rest a bit.
We had a small first light party 4/6. Present were Jeannie and I, Mike Lockwood and Bob Noneman, Steve Coe, and Lon Shelton. Lon helped me so much with the dome construction. The night was not good as the SQM was only 21.3. (A storm was blowing in from the west. Best night so far has been 21.9.) Still, the observing was the best the old 42 has ever provided. We will be inviting many friends over in the near future and will write some observing reports.
We have new neighbors moving in here at the New Mexico Astronomy Village to help build out the neighborhood. If you are getting ready to retire to better skies, look us up.
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csa/montana
Den Mama
Reged: 05/14/05
Loc: montana
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Re: Building a 24' Dome
[Re: Tom Clark]
#5793231 - 04/11/13 08:51 PM
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Got to say, I think many of us have followed your thread with great interest 7 anticipation for your first light! A huge congratulations on a beautiful job, well done!
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Mary B
Vendor - Echo Astronomy and Electronics
Reged: 05/21/10
Loc: Minnesota
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Re: Building a 24' Dome
[Re: csa/montana]
#5794835 - 04/12/13 04:19 PM
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Great project and observatory, wish it was in my backyard!
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