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Equipment Discussions >> Observatories

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Escher
scholastic sledgehammer

Reged: 08/30/07

Loc: Fenton, MI

Why not a cylindrical observatory?
#5053164 - 02/03/12 10:19 AM

Just wondering - why not use a cylindrical shape instead of a dome? Other than the fact that domes are cool...

Just giving this a brief amount of thought, a cylinder (actually a segmented cylinder obviously) would be much easier to build, by several orders of magnitude. It could be capped by simple plywood with some support ribs. It could still be rotated on a track, and adding the viewing slot would be easier as you could just remove part of one of the segments, not cut though a bunch of tria's in a dome...

Thoughts?

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zawijava
scholastic sledgehammer

Reged: 10/06/07

Loc: Wells, Maine 04090

Re: Why not a cylindrical observatory? new

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[Re: Escher]
#5053174 - 02/03/12 10:27 AM

Quote:

Just wondering - why not use a cylindrical shape instead of a dome? Other than the fact that domes are cool...

Just giving this a brief amount of thought, a cylinder (actually a segmented cylinder obviously) would be much easier to build, by several orders of magnitude. It could be capped by simple plywood with some support ribs. It could still be rotated on a track, and adding the viewing slot would be easier as you could just remove part of one of the segments, not cut though a bunch of tria's in a dome...

Thoughts?

Having a hard time picturing what you're thinking

...probably just me, but can you give it another try or perhaps a simple drawing? thanks! -Tim

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Escher
scholastic sledgehammer

Reged: 08/30/07

Loc: Fenton, MI

Re: Why not a cylindrical observatory? new

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[Re: zawijava]
#5053182 - 02/03/12 10:31 AM

working on it...

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dobsoscope
sage

Reged: 05/24/06

Re: Why not a cylindrical observatory? new

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[Re: zawijava]
#5053186 - 02/03/12 10:33 AM

i guess you're referring to something like this?

http://www.rainydaymagazine.com/RDM2011/RainyDayScience/NEAF/Observatories/UrbanObservatoryBig.jpg

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dobsoscope
sage

Reged: 05/24/06

Re: Why not a cylindrical observatory? new

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[Re: dobsoscope]
#5053197 - 02/03/12 10:36 AM

http://astroprofspage.com/wp-content/uploads/2007/08/vlt_esopia00065sites.jpg

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MANDII
professor emeritus

Reged: 11/23/10

Loc: HONG KONG

Re: Why not a cylindrical observatory? new

new

[Re: Escher]
#5053215 - 02/03/12 10:43 AM

yap ! this is a good question to ask about . Why not cylindrical ? and why not triangular ? Square ? I think any shape of oject can be rotated once it's put on a round track . You know there is a plate above the rotational track. And the dome of any shape can be mounted on this plate to achieve it's rotational view in 360 degree . So , firstly the rotating view problem is solved by the track,not by the shape of a dome . Then come th e the second question , it should be how big the view that this shape can obtained for a telsceope . 3rd question is how rigid /sturdy this shape can have when it is against the strong wind . 4thly how big this shape can provide the room among same amount of material being used . 5thly how much ennoying street light can be blocked by a certain shape of dome .

Among all factors , people think the spherical dome is the best shape , not the trainagula , cylindrical or others . Of course , that depands on your own needs .

Edited by MANDII (02/03/12 10:47 AM)

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Escher
scholastic sledgehammer

Reged: 08/30/07

Loc: Fenton, MI

Re: Why not a cylindrical observatory? new

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[Re: dobsoscope]
#5053216 - 02/03/12 10:44 AM Attachment (104 downloads)

Yup... but much smaller

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dobsoscope
sage

Reged: 05/24/06

Re: Why not a cylindrical observatory? new

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[Re: MANDII]
#5053218 - 02/03/12 10:45 AM

There is always the headache in making the transition from a whatever shape 'dome' to a circular track.

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MANDII
professor emeritus

Reged: 11/23/10

Loc: HONG KONG

Re: Why not a cylindrical observatory? new

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[Re: dobsoscope]
#5053237 - 02/03/12 10:55 AM

well once we are going to build a Obs , headache cannot be avoided . All we need is just taking some useful drugs .

And here I am just talking in more generally , and let us think more about the question of 'SHAPE" , specific technical problem , should be specificly seeing to it .

Edited by MANDII (02/03/12 10:57 AM)

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Escher
scholastic sledgehammer

Reged: 08/30/07

Loc: Fenton, MI

Re: Why not a cylindrical observatory? new

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[Re: MANDII]
#5053249 - 02/03/12 11:03 AM

..at least it eliminates the need for the complex dome shape and that building nightmare...

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zawijava
scholastic sledgehammer

Reged: 10/06/07

Loc: Wells, Maine 04090

Re: Why not a cylindrical observatory? new

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[Re: Escher]
#5053276 - 02/03/12 11:20 AM

Quote:

..at least it eliminates the need for the complex dome shape and that building nightmare...

thanks for the sketches! My first thought, being from Maine, would be the "snow load" considerations for both the flat top dome and the flat top warm room area. -Tim

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dobsoscope
sage

Reged: 05/24/06

Re: Why not a cylindrical observatory? new

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[Re: Escher]
#5053277 - 02/03/12 11:21 AM

how about these

http://www.inhabitat.com/wp-content/uploads/kielder1.jpg
http://stargazerslounge.com/diy-observatories/76752-daves-diy-observatory-chapter-4-a.html
http://www.google.com.mt/search?q=kielder+observatory&hl=mt&prmd=imvns&source=lnms&tbm=isch&ei=BwksT-bRGMep4gT1gY2cDg&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CBEQ_AUoAQ&biw=1280&bih=656&sei=YQksT4-kDbOM4gTr6a22Dg

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Escher
scholastic sledgehammer

Reged: 08/30/07

Loc: Fenton, MI

Re: Why not a cylindrical observatory? new

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[Re: dobsoscope]
#5053281 - 02/03/12 11:24 AM Attachment (53 downloads)

I like your second link...

Here is a simple solution for the track... Using an octagon of 2X12 or similar pieces, you can inscribe a circular track.... Instead of trying to make a perfectly circular piece.

I would use two courses rotated a bit so that their seams are not inline - to give additional strength.. Then put rollers on the bottom of the octagon shaped "cylinder" to rotate it...

Edited by Escher (02/03/12 11:39 AM)

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Escher
scholastic sledgehammer

Reged: 08/30/07

Loc: Fenton, MI

Re: Why not a cylindrical observatory? new

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[Re: zawijava]
#5053287 - 02/03/12 11:31 AM

Quote:

Quote:

..at least it eliminates the need for the complex dome shape and that building nightmare...

thanks for the sketches! My first thought, being from Maine, would be the "snow load" considerations for both the flat top dome and the flat top warm room area. -Tim

I thought about that as well... I'd likely put some peak to the warm room area... still working on what to do for the top of the obs. area..

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StarWrangler
scholastic sledgehammer

Reged: 09/03/04

Loc: Three Rivers, MI U.S.A>

Re: Why not a cylindrical observatory? new

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[Re: Escher]
#5053336 - 02/03/12 12:00 PM

What about the old Lowell Observatory
http://en.wikipedia.org/wiki/Lowell_Observatory

Alan O.

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Gastrol
scholastic sledgehammer

Reged: 11/04/11

Loc: los angeles

Re: Why not a cylindrical observatory? new

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[Re: StarWrangler]
#5053380 - 02/03/12 12:28 PM Attachment (72 downloads)

I like simple cylindrical shapes. Here's my little sketch.

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Chris Erickson
Carpal Tunnel

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii

Re: Why not a cylindrical observatory? new

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[Re: Escher]
#5053390 - 02/03/12 12:34 PM

Historically the most important reason for building a dome is for wind management. It theoretically provides the best air flow over the observatory for minimizing wind forces on the telescope itself and for smooth heat stripping (rapid thermal equalization).

The shape of the ground and "ground scatter" (other objects) under and around an observatory can also greatly influence that air flow. The Subaru observatory here in Hawaii is cylindrical because after extensive wind tunnel tests, they felt that design (combined with an elaborate series of wind shutters) was the best design for handling the way the wind flowed over and around their chosen location at the summit of Mauna Kea. Possibly the most important feature of the Subaru Observatory is the fact that they open up specific pairs of wind shutters that allow wind to flow under the telescope and around the mount as part of their wind energy mitigation.

In general I would say that cylindrical observatories will not be as good as hemispherical domes for wind management for amateur observatories. And the nuisance of dealing with a multitude of curves and arcs in construction mostly remain.

One final note is that dome shutters that pull up and over are best for wind management. Split shutters that open laterally create their own wind turbulence and vibration problems.

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BPO
sage

Reged: 02/23/10

Loc: South Island, NZ

Re: Why not a cylindrical observatory? new

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[Re: Chris Erickson]
#5053696 - 02/03/12 03:39 PM

Stashed away somewhere I have some papers written about wind tunnel testing of enclosure designs which demonstrated fairly conclusively that the most efficient (or least inefficient) aerodynamic shape is a flat-sided cylinder with either a flat or sloping top, such as used by the VLT, JCMT, Subaru, et al.

Due mainly to uplift factors, the classic hemispherical dome shape was either second or third best choice. (I will try to find links to those papers.)

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Escher
scholastic sledgehammer

Reged: 08/30/07

Loc: Fenton, MI

Re: Why not a cylindrical observatory? new

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[Re: Gastrol]
#5053710 - 02/03/12 03:45 PM

Quote:

I like simple cylindrical shapes. Here's my little sketch.

I like this a lot...

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Goodchild
scholastic sledgehammer

Reged: 12/31/08

Re: Why not a cylindrical observatory? [Re: Escher]
#5054275 - 02/03/12 10:46 PM

Gastrol, wouldn't the whole building have to rotate based on your design?

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