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 | (show all)
Escher
Pooh-Bah
*****

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?


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

Reged: 10/06/07

Loc: Wells, Maine 04090
Re: Why not a cylindrical observatory? new [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


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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [Re: zawijava]
      #5053182 - 02/03/12 10:31 AM

working on it...

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

Reged: 05/24/06

Re: Why not a cylindrical observatory? new [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


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

Reged: 05/24/06

Re: Why not a cylindrical observatory? new [Re: dobsoscope]
      #5053197 - 02/03/12 10:36 AM

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

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


Reged: 11/23/10

Loc: HONG KONG
Re: Why not a cylindrical observatory? 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)


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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [Re: dobsoscope]
      #5053216 - 02/03/12 10:44 AM Attachment (112 downloads)

Yup... but much smaller

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

Reged: 05/24/06

Re: Why not a cylindrical observatory? new [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.

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


Reged: 11/23/10

Loc: HONG KONG
Re: Why not a cylindrical observatory? new [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)


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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [Re: MANDII]
      #5053249 - 02/03/12 11:03 AM

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

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

Reged: 10/06/07

Loc: Wells, Maine 04090
Re: Why not a cylindrical observatory? new [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


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

Reged: 05/24/06

Re: Why not a cylindrical observatory? new [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


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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [Re: dobsoscope]
      #5053281 - 02/03/12 11:24 AM Attachment (56 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)


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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [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..


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


Reged: 09/03/04

Loc: Three Rivers, MI U.S.A>
Re: Why not a cylindrical observatory? new [Re: Escher]
      #5053336 - 02/03/12 12:00 PM

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

Alan O.


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


Reged: 11/04/11

Loc: los angeles
Re: Why not a cylindrical observatory? new [Re: StarWrangler]
      #5053380 - 02/03/12 12:28 PM Attachment (79 downloads)

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

Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: Christopher 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.)


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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [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...


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

Reged: 12/31/08

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

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

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


Reged: 11/04/11

Loc: los angeles
Re: Why not a cylindrical observatory? new [Re: Goodchild]
      #5054284 - 02/03/12 10:52 PM Attachment (47 downloads)

Quote:

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


Oops, I left out a line in the sketch above the door which divides the top and bottom half of the structure. The bottom half is stationary, top half rotates.
Here's the revised sketch.


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


Reged: 01/07/04

Loc: Lyttelton, New Zealand
Re: Why not a cylindrical observatory? new [Re: Gastrol]
      #5054301 - 02/03/12 11:02 PM

Patrick Moore's Observatory was/is cylindrical- images here

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

Reged: 05/24/06

Re: Why not a cylindrical observatory? new [Re: Escher]
      #5054536 - 02/04/12 03:12 AM

and how would you seal between both octagons to prevent entrance of dust/insects/wind etc. inside the observatory?

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

Reged: 05/14/05

Loc: montana
Re: Why not a cylindrical observatory? new [Re: Gastrol]
      #5054670 - 02/04/12 08:37 AM

With that flat opening front; looks like it would collect snow & ice on it, in the colder climates; plus vulnerable to leaking.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5055232 - 02/04/12 02:22 PM

Quote:

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.)




I would think that this greatly depends if it is combined with elaborate wind (air flow) shutters under intelligent computer control that is also monitoring wind direction, speed, particulates, humidity and turbidity.

For observatories without wind shutters, any jutting square edge creates turbulence and becomes a point where wind energy is transferred to the observatory structure, usually creating vibrations with a number of different and often interfering harmonic periods. Depending on the effectiveness of the pier isolation, some of this "confused" energy can couple to the telescope mount and then on to the optics.

Also, rapid changes in air pressure in the observatory caused by turbulent air currents can directly couple to the optics of closed-tube telescopes (most refractors and most compound reflectors.) This can create interesting focus behavior in most commercial SCT's.

I hope this helps.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? *DELETED* new [Re: Christopher Erickson]
      #5055668 - 02/04/12 07:33 PM

Post deleted by BPO

Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5055712 - 02/04/12 07:59 PM

Unfortunately I've only been able to locate the following paper:

Some Airflow Properties of Telescope Enclosures Estimated from Water-Tunnel Tests

A search of Google should turn up others.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5055859 - 02/04/12 09:41 PM

Here is a better copy of the referenced document:

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1991PASP..103..597A&defaultprint=YES&filetype=.pdf

FWIW, it is a controversial document that has not been universally accepted.

There have been many professional observatories planned and built since that document was published that have not accepted their conclusions. Note that the TMT and the ELT are both being designed as hemispherical domes and not as cylinders.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5056068 - 02/05/12 12:01 AM

There are several that have been built (or are in the planning stages) since publication that do utilise cylindrical or semi-cylindrical enclosures, or propose to do so.

It's not a cut-and-dried issue.

To my knowledge, ESO et al have no regrets.


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

Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5056141 - 02/05/12 12:57 AM

My 2cent worth, If you're skills or money allow you to build a cylinder and not a hemisphere, then it's good to have a cylinder vs. not having an observatory

Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: Hilmi]
      #5056209 - 02/05/12 04:49 AM

As much as I love domed observatories I have to say that in most cases for amateurs, it is my opinion that low-mass roll-offs with good ventilation are more practical, more affordable, more reliable and more effective.

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


Reged: 08/20/05

Loc: London UK
Re: Why not a cylindrical observatory? new [Re: Escher]
      #5056279 - 02/05/12 06:20 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?


Have you built a dome or observatory "would be much easier to build [a cylindrical 'dome'], by several orders of magnitude" = mild exageration maybe

Quote:

As much as I love domed observatories I have to say that in most cases for amateurs, it is my opinion that low-mass roll-offs with good ventilation are more practical, more affordable, more reliable and more effective.


If you ignore the downsides - 1]little or no protection for user and instruments; 2] dew; 3] local light pollution If you need to be under-the-stars just step outside [your dome] and you have the best of both worlds

Post Extras: Print Post   Remind Me!   Notify Moderator  
skoop
sage


Reged: 03/13/10

Loc: 59° N
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5056287 - 02/05/12 06:34 AM

Kielder Observatory is really cool.
Do be honest, domes are a bit dorky looking.
Only thing I do not like about Kielder Observatory are the doors. Sliding doors will look way better. Something like Subaru has.

Quote:

square edge creates turbulence and becomes a point where wind energy is transferred to the observatory structure, usually creating vibrations with a number of different and often interfering harmonic periods.




Amateur observatories are relatively tiny structures. If square edges are so bad, why are we not living in mud and/or brick iglu


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: skoop]
      #5056950 - 02/05/12 01:53 PM

Quote:

Kielder Observatory is really cool.
Do be honest, domes are a bit dorky looking.
Only thing I do not like about Kielder Observatory are the doors. Sliding doors will look way better. Something like Subaru has.

Quote:

square edge creates turbulence and becomes a point where wind energy is transferred to the observatory structure, usually creating vibrations with a number of different and often interfering harmonic periods.




Amateur observatories are relatively tiny structures. If square edges are so bad, why are we not living in mud and/or brick iglu




LOL!

It is best to think of observatories as machines, not domiciles.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5057404 - 02/05/12 07:29 PM

That depends upon the owner and operator.

A large professional organisation such as ESO may consider its observatories to be machines, but the OP (and most others posting here) probably views their observatory as being part of their hobby.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5057466 - 02/05/12 08:23 PM

Quote:

That depends upon the owner and operator.

A large professional organisation such as ESO may consider its observatories to be machines, but the OP (and most others posting here) probably views their observatory as being part of their hobby.




Being part of a hobby is beside the point.

The point I was trying to make is that when it comes to observatory reliability and design, it is most productive to view the observatory as a machine and not as a building. The differences may seem subtle but from an engineering perspective they can be significant. By definition buildings are static. Machines are dynamic.

I hope this helps.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5057486 - 02/05/12 08:34 PM

The discussion appeared to be mainly centred around the idea of amateur astronomers constructing cylindrical style enclosures rather than the more traditional domes.

Various studies by professionals indicate and conclude that the classic dome enclosure may not be the best design or choice for an observatory, with cylindrical or semi-cylindrical designs being more efficient in many ways.

Such structures have been employed very successfully by the likes of ESO et al, and there appear to be few valid reasons why amateurs would or should not also adopt the design instead of the traditional dome.

Whether or not the very expensive professional observatories should be considered to be "machines" is a little beside the point in this case, IMO.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5057501 - 02/05/12 08:47 PM

Quote:

The discussion appeared to be mainly centred around the idea of amateur astronomers constructing cylindrical style enclosures rather than the more traditional domes.

Various studies by professionals indicate and conclude that the classic dome enclosure may not be the best design or choice for an observatory, with cylindrical or semi-cylindrical designs being more efficient in many ways.

Such structures have been employed very successfully by the likes of ESO et al, and there appear to be few valid reasons why amateurs would or should not also adopt the design instead of the traditional dome.

Whether or not the very expensive professional observatories should be considered to be "machines" is a little beside the point in this case, IMO.




The professional observatories referenced all have intelligent, computer-controlled air flow shutters. Unless the amateur duplicates that feature, a direct comparison would be of limited value.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5057581 - 02/05/12 10:00 PM

Yes, that's the point: for the most part, direct comparisons between amateur and professional observatories is - dare I say it? - pointless.

However, the advantages and disadvantages of the basics of the enclosure designs being discussed generally apply to both professional and amateur users alike.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5057604 - 02/05/12 10:17 PM

Quote:

Yes, that's the point: for the most part, direct comparisons between amateur and professional observatories is - dare I say it? - pointless.

However, the advantages and disadvantages of the basics of the enclosure designs being discussed generally apply to both professional and amateur users alike.




I think that you have it exactly upside-down.

At any rate, let's agree to disagree and let it drop.


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

Reged: 03/06/07

Loc: Northumberland, UK
Re: Why not a cylindrical observatory? new [Re: Escher]
      #5057754 - 02/06/12 12:29 AM

Hi Christopher,

There are quite a few amateur observatories from way back that had rotating tops that were not domed.

I have been inside a small observatory with a flat top and it seemed to work fine. It was like Patrick Moore's flat top and the one in your sketch. A slight pitch would help avoid problems with water puddling and make it easier to clear snow.

The famous solar observer W M Baxter used a rectangular shed with a rectangular pitched roof that rotated. You can find pictures on the web. I suspect this would be a more water and snow proof arrangement than the flat top but he never needed to access the zenith.

If you have second thoughts a dome or dome-like top isn't that hard to make. Maurice Gavin's (nytecam) dome is simple, lightweight and durable.

Cheers,

Keith


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: Keith Howlett]
      #5057810 - 02/06/12 01:22 AM

Quote:

Hi Christopher,

There are quite a few amateur observatories from way back that had rotating tops that were not domed.

I have been inside a small observatory with a flat top and it seemed to work fine. It was like Patrick Moore's flat top and the one in your sketch. A slight pitch would help avoid problems with water puddling and make it easier to clear snow.

The famous solar observer W M Baxter used a rectangular shed with a rectangular pitched roof that rotated. You can find pictures on the web. I suspect this would be a more water and snow proof arrangement than the flat top but he never needed to access the zenith.

If you have second thoughts a dome or dome-like top isn't that hard to make. Maurice Gavin's (nytecam) dome is simple, lightweight and durable.

Cheers,

Keith




I am not against cylindrical, hemispherically-domed, roll-off, clamshell, turret, garden, tent or any other kind of observatory. In fact I love all kinds of observatories and that is part of why I became a professional engineer. And although I believe that roll-offs are generally the best kind of observatory for most amateurs, I chose instead to build my own personal observatory as a 4 meter fiberglassed geodesic dome.

My only desire has been to share objective information about observatory design and how different approaches compare from the perspective of a professional engineer. If I list some of the negatives of any particular observatory design, it does not mean I summarily dislike that design or am exclusively in love with a different design. The profound variety of observatory designs that exist is testament to the fact that there is a vast number of ways to skin this particular cat!

I wonder what I keep doing wrong to keep giving people the wrong impression about my intentions.



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


Reged: 08/20/05

Loc: London UK
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5057870 - 02/06/12 03:23 AM

Quote:

I wonder what I keep doing wrong to keep giving people the wrong impression about my intentions


As you are, as stated, a professional engineer and I'm a [professional] architect our opinions in this amateur forum are not gospel as many choose to explore their own design route and construction skills with quite different expectations in the final result.


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

Reged: 03/06/07

Loc: Northumberland, UK
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5057872 - 02/06/12 03:25 AM

Hi Chris,

Sorry for the confusion, I was replying to the OP who is also called Christopher.

I was interested to read your posts.

Best Wishes,

Keith


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5057883 - 02/06/12 05:03 AM

There are quite a few professional scientists and engineers working within the fields that encompass the design of telescope enclosures. Their papers and other writings make for very interesting reading. The one thing they almost all agree upon is that nobody knows everything about it.

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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5058254 - 02/06/12 11:29 AM Attachment (36 downloads)

Sorry guys - too many Chris' around here!

All good points - as to my original question - I'm having more basic hurdles to clear in regard to this project than I had anticipated. Namely, a suitable location that won't requre a large investment of $$$.

I had planned on using my garage, then thought about a separate building, now back to the garage again...

In regard to my orignal query - for me, the cylindrical Obs. will be much easier to accomplish in a short period of time, with less manual work (i.e. not cutting many triangles and building a dome, v.s. cutting rectangles and attaching to a frame.). That was my reasoning behind the question.

The discussion about airflow and turbulence is interesting.

Actually, I just had a thought in that regard - but its a bit on the obscure side, and much to complex for an amateur obs..

Wouldn't the best shape actually be an airfoil, but instead of an airfoil designed to generate lift, it would have the top and bottom surfaces a mirror image of each other... essentially trying to minimize the effect of the breakup of the boundary layer.

YOu would create a very large airfoil shape, which would then be able to rotate and be adjusted to be perfectly in line with the wind stream. This would surround the observatory, which would also rotate, independently...

This is taking things to the extreme of course - but that should allow for a relatively laminar flow over the outside of the observatory at all times, since the airfoil would always be pointing into the wind..

Rough sketch time:


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

Reged: 04/01/08

Loc: Lovettsville, VA
Re: Why not a cylindrical observatory? new [Re: Escher]
      #5058342 - 02/06/12 12:11 PM

Thinking a bit more about the cylinder style, how will you attach the roof to the cylinder? You will still need a ring, or in the case of a beveled cylinder, an ellipse. The latter especially would not be very easy to construct.

By the way, your airfoil idea would cause major problems when the wind direction shifts, unless its movement was independent of the slit position. I see no point really.

JimC


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

Reged: 08/30/07

Loc: Fenton, MI
Re: Why not a cylindrical observatory? new [Re: Mirzam]
      #5058398 - 02/06/12 12:40 PM

Quote:


By the way, your airfoil idea would cause major problems when the wind direction shifts, unless its movement was independent of the slit position.




Yes - as I mentioned previously, the airfoil and the "observatory" would rotate independently of each other, the airfoil continually pointing into the wind, and the observatory (dome, roof, etc.) tracking whatever it chooses..

Image a weather vane - that continually turns into the wind - but scale the central shaft up and put the observatory in it... The actually mechanics of the airfoil pointing would be very simple. An encoder mounted on a weathervane to register the wind direction, then fed into a control system for the airfoil rotation...

It may very well be pointless - but I thought it was an interesting idea nonetheless... Sometimes Engineers do things just to see if they can...

As to attaching the roof to the cylinder - see my previous post and drawing about the 2X12 octagons for the track.. just use one for the top and cover it... As to an angled roof - not sure if I would go that route or not... I'm thinking of some sort of hybrid with a pitch to the top... but I have several thoughts...


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


Reged: 04/26/08

Re: Why not a cylindrical observatory? new [Re: Escher]
      #5058437 - 02/06/12 01:02 PM

"....It may very well be pointless - but I thought it was an interesting idea nonetheless... Sometimes Engineers do things just to see if they can..."

Another thing engineers do is analysis paralyis. I was one once, and sometimes getting results from a group means chosing one idea and running with it, when any of the other ideas might work as well.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: Escher]
      #5058610 - 02/06/12 02:19 PM

Quote:

Quote:


By the way, your airfoil idea would cause major problems when the wind direction shifts, unless its movement was independent of the slit position.




Yes - as I mentioned previously, the airfoil and the "observatory" would rotate independently of each other, the airfoil continually pointing into the wind, and the observatory (dome, roof, etc.) tracking whatever it chooses..

Image a weather vane - that continually turns into the wind - but scale the central shaft up and put the observatory in it... The actually mechanics of the airfoil pointing would be very simple. An encoder mounted on a weathervane to register the wind direction, then fed into a control system for the airfoil rotation...

It may very well be pointless - but I thought it was an interesting idea nonetheless... Sometimes Engineers do things just to see if they can...

As to attaching the roof to the cylinder - see my previous post and drawing about the 2X12 octagons for the track.. just use one for the top and cover it... As to an angled roof - not sure if I would go that route or not... I'm thinking of some sort of hybrid with a pitch to the top... but I have several thoughts...




Unfettered brainstorming is one of the most fun things in the world to an engineer!

If anybody were to ever ask me about the best features of an observatory (no amateur ever has) I would list the following:

1. Intelligent thermal management.
* No big heat sources inside of the observatory.
* Minimize *all* heat sources inside of the observatory.
* Every watt of electricity used in the observatory is a watt of heat generated in the observatory.
* Ability to be pre-cooled to the predicted night temperature.
* Low mass structure.
* Active air flow shutters and high-efficiency (squirrel cage) fans.
* Ability to react rapidly to changes in air temperature.
* Avoid placing observatory on top of a hot existing structure.
* Avoid placing observatory near other hot structures.
* Having a partitioned or separate, heavily insulated control room can really help with heat issues.
* Heavy concrete pads act as heat capacitors that are always out of heat-phase with the environment.
* Hollow concrete piers can be just as rigid as solid piers and with a great deal less concrete and thermal mass (concentric sonotubes.)
* Seeing is cumulative. City dwellers benefit just as much from effective thermal management as do country dwellers. Don't needlessly throw away any.
2. High reliability with failsafe features.
* Make sure that you can always close your roof/shutter, regardless of mains power.
* If operated remotely or robotically, make sure that the roof/shutter will close itself upon mains loss or communication loss.
* Avoid any observatory design that requires the telescope to be in a certain position before the roof/shutter can be safely closed.
3. Observatories are (dynamic) machines, not (static) buildings.
* Choose fastening systems based on movement, shear, vibration, unexpected vector forces, corrosion and wear factors.
* Stainless steel machine and wood screws and Nylock nuts are your friend. Nails generally are not.
* Motor soft start modules can really extend the life of moving parts and guideways.
* The less moving parts, generally the better.
4. Observatory designs with 2D and 3D curves and arcs are considerably more difficult to construct from basic residential building materials.

Of course this list could go on for another couple of pages but these seem to me to be some of the issues that are the most often overlooked.

I hope this helps.


Post Extras: Print Post   Remind Me!   Notify Moderator  
John Carruthers
Skiprat
*****

Reged: 02/02/07

Loc: Kent, UK
Re: Why not a cylindrical observatory? new [Re: Hilmi]
      #5060441 - 02/07/12 02:02 PM

if you live in an arid area have a flat topped cylinder/cube/whatever yes, otherwise put some fall on it (1:12) to shed rain.

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

Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Why not a cylindrical observatory? new [Re: John Carruthers]
      #5060477 - 02/07/12 02:23 PM

A bit of a slope is not a bad idea even in an arid area. Sometimes in arid areas, when it rains, it really does rain.

Look up tropical storm/cyclone Gonu online to see what it's like when you get rain in an arid country.


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


Reged: 08/26/05

Loc: Auckland New Zealand
Re: Why not a cylindrical observatory? new [Re: Hilmi]
      #5060657 - 02/07/12 04:18 PM

What about inside one of these? Put the whole tank on rails - rotate the whole thing. Don't know how you'd do the slit but...

http://www.tanks.co.nz/product_info_tank.php?products_id=32


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

Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: Why not a cylindrical observatory? new [Re: gavinm]
      #5061303 - 02/07/12 11:06 PM

Your not the first to consider it, we have here in Oman dome topped tanks. I dropped the idea when I found out they had a thick layer of insulation that's also part of the structural strength of the building.

Cutting one is easy, I have a Rage III circular saw, cuts nice and clean and fast.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mi 3 (CH)
member


Reged: 01/24/12

Loc: Riga, Latvia
Re: Why not a cylindrical observatory? new [Re: Hilmi]
      #5062332 - 02/08/12 02:17 PM

Today i've had nothing special to do and absolutelly any wish to build my pier or astroshair.
And i've try to make few models of dome with unusual, not semispheric, shape.
Look what i get:





Building a frame from welded square profile i can make that type of dome up to meters.
Tomorrow i'll fix wef moments.

Edited by Mi 3 (CH) (02/09/12 07:24 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
altair1956
sage
*****

Reged: 07/05/09

Loc: Light polluted central Mass
Re: Why not a cylindrical observatory? new [Re: Mi 3 (CH)]
      #5066083 - 02/10/12 07:33 PM

The astronomy group I belong to has a cylinder top observatory as our main building. It was built in 1915 and is 2 stories. It houses an 8" Alvin Clark. It has been very durable, though the roof being flat does need regular maintenance to keep from leaking. There is a standard size door opening on the wall and a rolling slit on the top. No idea of the thermal characteristics, but the views with the scope have always been good. Here's a link to our website with some pictures of the building:
http://theskyscrapers.org/content5938.html
Steve


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mi 3 (CH)
member


Reged: 01/24/12

Loc: Riga, Latvia
Re: Why not a cylindrical observatory? new [Re: altair1956]
      #5066725 - 02/11/12 07:38 AM

New model with "door":







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

Reged: 02/02/10

Loc: sebastopol, california
Re: Why not a cylindrical observatory? new [Re: Mi 3 (CH)]
      #5067040 - 02/11/12 11:32 AM

yeah, i agree with erickson's list of considerations. and i'd suggest they lead to one conclusion. once you plug in all the thermal and operation issues, a dome or anything that rotates simply doesn't make sense without the single overriding criterion of thermal shelter in extremely cold conditions.

yes, domes or modified cylinders are used on the "big boy" observatories. but part of that is an engineering solution for a really big mobile structure.

i can't look at the models here without feeling that the modified cylinder is fundamentally an *esthetic* and conceptual solution to the shelter problem in a small instrument observatory. and that usually means the practical operation and maintenance issues, not to mention the management of thermal discharge through the "chimney", are going to be more of a hassle than you anticipate.

whatever you do, good luck.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: Mi 3 (CH)]
      #5067506 - 02/11/12 04:56 PM

Nice work!

Post Extras: Print Post   Remind Me!   Notify Moderator  
BPO
sage


Reged: 02/23/10

Loc: South Island, NZ
Re: Why not a cylindrical observatory? new [Re: drollere]
      #5067526 - 02/11/12 05:09 PM

Isn't any enclosure with an opening that is quite small relative to the volume always going to have plume issues?

Hemispherical domes are no better or worse than other shapes in that regard it would seem, without the system of vents, fans and AC employed by large observatories in an attempt to manage and minimise the effects of of such issues.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Christopher EricksonModerator
Carpal Tunnel
*****

Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: Why not a cylindrical observatory? new [Re: drollere]
      #5067926 - 02/11/12 10:06 PM

Quote:

yeah, i agree with erickson's list of considerations. and i'd suggest they lead to one conclusion. once you plug in all the thermal and operation issues, a dome or anything that rotates simply doesn't make sense without the single overriding criterion of thermal shelter in extremely cold conditions.

yes, domes or modified cylinders are used on the "big boy" observatories. but part of that is an engineering solution for a really big mobile structure.

i can't look at the models here without feeling that the modified cylinder is fundamentally an *esthetic* and conceptual solution to the shelter problem in a small instrument observatory. and that usually means the practical operation and maintenance issues, not to mention the management of thermal discharge through the "chimney", are going to be more of a hassle than you anticipate.

whatever you do, good luck.




Just for general information, adding some square louvers and/or a squirrel-cage fan is fairly easy and inexpensive to do to just about any observatory.

Of course the best solution is to generate as little heat as possible in the observatory in the first place.


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

Reged: 09/03/05

Loc: NSW, Australia
Re: Why not a cylindrical observatory? new [Re: BPO]
      #5664942 - 02/06/13 10:33 AM

Mi 3, your design is identical to this one made by Shevill Mathers details on his page.

http://www.apstas.com/astrotas/mathers/smathers.htm


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

Reged: 07/11/03

Loc: Smithfield, RI
Re: Why not a cylindrical observatory? new [Re: netwolf]
      #5664958 - 02/06/13 10:43 AM Attachment (33 downloads)

May I present to you...Seagrave Memorial Observatory, North Scituate, RI. Home of an 8" Alvan Clark refractor.

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

Reged: 07/11/03

Loc: Smithfield, RI
Re: Why not a cylindrical observatory? new [Re: RobertED]
      #5664960 - 02/06/13 10:44 AM Attachment (33 downloads)

Closer view of circular dome.....

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

Reged: 07/11/03

Loc: Smithfield, RI
Re: Why not a cylindrical observatory? new [Re: RobertED]
      #5664962 - 02/06/13 10:45 AM Attachment (28 downloads)

...and a third....

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

Reged: 05/24/06

Re: Why not a cylindrical observatory? new [Re: RobertED]
      #5665026 - 02/06/13 11:23 AM

Just make sure you do not escort anyone out of the second level door !

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

Reged: 07/11/03

Loc: Smithfield, RI
Re: Why not a cylindrical observatory? new [Re: dobsoscope]
      #5665087 - 02/06/13 11:57 AM

They used to have a nice staircase to escort folks down during the "Halley's Comet Crunch"....but have since been removed to keep it looking as it did originally .

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


Reged: 11/02/12

Loc: Chula Vista & Indio, CA
Re: Why not a cylindrical observatory? new [Re: RobertED]
      #5666156 - 02/06/13 10:25 PM

Maybe I'm over simplifying this but it seems to me that early astronomers adopted a hemispherical dome because they needed an enormous roof structure, unsupported in the middle. Subsequent observatory designers probably stuck to tradition. If the architect of the Palomar Observatoy had access to modern lightweight construction materials, that structure might look quite different. Even with my extremely modest construction skills, it would seem to me to be vastly easier to build a small backyard cylinder.

Post Extras: Print Post   Remind Me!   Notify Moderator  
mikey cee
Postmaster
*****

Reged: 01/18/07

Loc: bellevue ne.
Re: Why not a cylindrical observatory? new [Re: CharlesW]
      #5666203 - 02/06/13 10:58 PM

The biggest problem I would have with a cylindrical observatory is the viewing circle. Any desk, chair, accessories cart or cabinet is always smack dab in the way. I'd be forever stumbling over or backing into something in the road. Mike

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

Reged: 07/11/03

Loc: Smithfield, RI
Re: Why not a cylindrical observatory? new [Re: mikey cee]
      #5666493 - 02/07/13 06:00 AM

I'm even thinking, if memory serves me, that the clubmembers have to occasionally clear heavy snow off the flat roof surface!!(re: Seagrave Obs.).....

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

Reged: 09/03/10

Loc: A Land Down Under
Re: Why not a cylindrical observatory? new [Re: Christopher Erickson]
      #5667916 - 02/07/13 09:43 PM

It does help Those are some very good pointers for any observatory cylindrical or not!

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

Reged: 09/03/10

Loc: A Land Down Under
Re: Why not a cylindrical observatory? new [Re: CharlesW]
      #5667921 - 02/07/13 09:47 PM

Yes. I believe the housing for the GMT will essentially be a cylinder

Post Extras: Print Post   Remind Me!   Notify Moderator  
SkipW
sage


Reged: 02/03/11

Loc: Oklahoma, USA
Re: Why not a cylindrical observatory? new [Re: timwetherell]
      #5668182 - 02/08/13 12:23 AM Attachment (19 downloads)

Here's the "Grain Bin Dome" at the National Solar Observatory in Sunspot, NM. It's the earliest instrument shelter at the facility, built from a modified mail-ordered Sears & Roebuck Corrugated Grain Bin.

Post Extras: Print Post   Remind Me!   Notify Moderator  
SkipW
sage


Reged: 02/03/11

Loc: Oklahoma, USA
Re: Why not a cylindrical observatory? new [Re: SkipW]
      #5668188 - 02/08/13 12:27 AM Attachment (12 downloads)

Drive mechanism for the Grain Bin Dome at NSO.

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

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Why not a cylindrical observatory? new [Re: SkipW]
      #5670656 - 02/09/13 12:34 PM

There's a certain degree of beauty the cylinders lack. Consider a square building with either a peaked roof with a shutter or a single slope roof where the whole thing rotated. It could set on the ground and just be a rotatable building.

-Rich


Post Extras: Print Post   Remind Me!   Notify Moderator  
rimcrazy
sage


Reged: 03/03/12

Loc: Overgaard, AZ
Re: Why not a cylindrical observatory? new [Re: Starhawk]
      #5671938 - 02/10/13 08:05 AM

Here in Arizona two of the most historically famous observatories are cylinders.

The Clark dome houses the Clark refactor that Percival Lowell used in founding the Lowell Observatory.



And Clyde Tombaugh used the telescope in this building to discover Pluto.



I would say that there are a few pretty famous cylindrical observatories around.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Kaizu
sage


Reged: 08/17/07

Loc: Finland
Re: Why not a cylindrical observatory? new [Re: Escher]
      #5672043 - 02/10/13 09:48 AM

Quote:

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...




I built mine almost as by your sketch. Click the first image and you see how I built it. The "dome" is made of aluminium sheets which are fixed and sealed on a wooden sceleton. The Cityobservatory has resisted wind, rain and snow few yeas. Inside there is a 10" TAL250K or a 10" Newton astrograph.

Kaizu


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


Extra information
10 registered and 15 anonymous users are browsing this forum.

Moderator:  Christopher Erickson, Joe C, Mr Greybush 

Print Thread

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


Thread views: 4834

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics