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Equipment Discussions >> Observatories

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Keith Howlett
Pooh-Bah
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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


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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.



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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.


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Keith Howlett
Pooh-Bah
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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


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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.

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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:


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Mirzam
Post Laureate
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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


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Escher
Pooh-Bah
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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...


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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.


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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.


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John Carruthers
Skiprat
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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.

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Hilmi
Post Laureate
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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.


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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


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Hilmi
Post Laureate
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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.


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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)


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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


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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":







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drollere
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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.


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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!

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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.


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