Date   

Re: Pier questoin

 

fair enough, so to whomever has that expertise, I looking for and answer that is "good enough", or as we said in the old days "good enough for gummit work"

or even just guidelines for "idiots"

Steve H
 
*This e-mail was made with 100% recycled (and recyclable) electrons.
No trees were destroyed and no animals were harmed.
Though the ozone may have been damaged.



From: "chris1011@... [ap-gto]"
To: ap-gto@...
Sent: Friday, December 16, 2016 11:04 AM
Subject: Re: [ap-gto] Re: Pier questoin

 
Someone with Finite Elements and time on their hands can probably best answer that question.

Rolando



-----Original Message-----
From: shoff535@... [ap-gto]
To: ap-gto
Sent: Thu, Dec 15, 2016 7:52 pm
Subject: Re: [ap-gto] Re: Pier questoin



Rolando,
Thank you for the explanation of the usage/purpose of the gussets.  One question comes to mind would be how wide would they be relative to the height/diameter of the pier, I suppose also it depends on whether the pier material is aluminum or steel.  You already stated that typically they would be 1/2 the length, but how wide optimally should they be at the base (or is that a really critical dimension).

Thanks,
Steve H




Re: DIY Dolly for AP Eagle Pier

Joseph Bianco
 

Gary,


I have been using the JMI Wheeley Bars to move my MACH1GTO and Eagle Pier in and out of my garage so I can image from the driveway.  I keep my imaging scope TV85 and guiding scope AT66 on the mount in the garage until the weather gets too cold in the Chicago, IL area (below 32 deg F),  The Mach1 has the RAPAS and most nights I can polar align, get on the image, focus, and start guiding in 30-45 min (If I don't do something stupid do to a brain freeze).


Joseph


Re: Pier questoin

Roland Christen
 

Someone with Finite Elements and time on their hands can probably best answer that question.

Rolando



-----Original Message-----
From: shoff535@... [ap-gto]
To: ap-gto
Sent: Thu, Dec 15, 2016 7:52 pm
Subject: Re: [ap-gto] Re: Pier questoin



Rolando,
Thank you for the explanation of the usage/purpose of the gussets.  One question comes to mind would be how wide would they be relative to the height/diameter of the pier, I suppose also it depends on whether the pier material is aluminum or steel.  You already stated that typically they would be 1/2 the length, but how wide optimally should they be at the base (or is that a really critical dimension).

Thanks,
Steve H


Top plate and control box attachment questions

Dale Hooper
 

I'm preparing to order an A-P 1100GTO within the next couple of months, so I hope you'll forgive me if these are obvious newbie questions.  I've tried to get some info from the archives before posting.

My first question I think I've determined an answer for.  I'll be using the mount with a Celestron 14" Edge HD.  I'm planning on purchasing the DOVELM162 to attach the Edge HD to the mount.  I've seen a few statements from people that this works with the non-standard size dovetail on the Celestrons.  Additional comments would be welcome.

My main questions are about attaching the mount to my pier top plate and attaching the GTOCP4 to the mount or top plate.  My top plate is 14" x 14" x 1" aluminum.  I originally had a Milburn wedge on it (for a Meade LX200) so it has a center hole and the three threaded holes normally found on a Meade tripod.  The mount I am replacing is a Losmandy Titan, so I have what they call an MAL currently attached to the top plate using the center hole and the Titan is attached on top of the MAL.

So, I am trying to determine it there is something fairly equivalent to the MAL.  I've looked at the 119FSA-FP, but that doesn't appear to have a center hole.  Is there something for attaching to the top plate which has a center hole?  If not, I'm sure that I can take my top plate into a local machinist.

Lastly, I can tell that the GTOCP4 is normally attached, vertically, directly to the back of the mount, but is it possible (and are cables long enough) so that I could instead attach it to the back of my top plate?  I've seen the Q6281KIT control box extensions, but I suspect it may be a bit unwieldy to extend it out several inches so it would be past the edge of the top plate.

I will certainly appreciate any help - this looks like a great group.

Clear skies,
Dale.



Re: Pier question

Christopher Erickson
 

All metals and metalloids (like aluminum) have different thermal expansion coefficients.
 
Important in mount and lens cell designs but not very important in pier designs, IMHO.
 
 
Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 



From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, December 15, 2016 4:07 PM
To: ap-gto@...
Subject: RE: [ap-gto] Re: Pier question

With all the discussion about piers, I personally don't recall anything about the thermal movement of aluminum.

 

Steve W.

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, December 15, 2016 7:53 PM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Pier questoin

 

 

Rolando,
Thank you for the explanation of the usage/purpose of the gussets.  One question comes to mind would be how wide would they be relative to the height/diameter of the pier, I suppose also it depends on whether the pier material is aluminum or steel.  You already stated that typically they would be 1/2 the length, but how wide optimally should they be at the base (or is that a really critical dimension).

Thanks,
Steve H


Re: Pier questoin

Christopher Erickson
 

A tapered hexagonal steel pier is a great choice.  No need to fill it with anything and it will have excellent thermal characteristics.  That is my usual recommendation to people who ask.
 
An X-pier is another possibility.  Excellent thermal characteristics and no ringing.
 
IMHO, filling steel tubes with sand (oiled or otherwise) does nothing except making the thermals worse and probably promoting corrosion.  Filling them with concrete makes the steel redundant.
 
FEA (Finite Element Analysis) modeling really comes out in favor of tapered steel piers and X-piers.
 
Massive concrete piers can have a lot of thermal inertia.  Making them hollow will help.
 
I hope this helps.
 
 
Christopher Erickson
Consulting Engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 



From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, December 15, 2016 6:10 AM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Pier questoin

The old Zeiss concept of making the pier a variable diameter from top to bottom will eliminate any resonances. A variable diameter pipe will not ring at any one frequency and will damp out quickly. You can make one by welding 4 pieces of trapezoid together, wide at bottom, narrower at the top. The other way is to use a single diameter tube and weld or attach 4 vanes from about 1/2 way down to the bottom. It will look like a rocket on the launch pad and these vanes will stiffen the pier greatly.

Rolando



-----Original Message-----
From: westergren@... [ap-gto]
To: ap-gto
Sent: Thu, Dec 15, 2016 7:30 am
Subject: [ap-gto] Re: Pier questoin



A very good treatise on pier design was written in 2005 by Dennis Persyk. It is available at Pier Design Fundamentals - How to . . .

I strongly recommend against filling a permanent pier with anything but air.  Dennis touches this subject but doesn't explain it completely.  There are two kinds of oscillation with a pier, especially a steel pipe version:

1. Ringing like a bell - this is of no concern, since it is a high frequency that won't affect the view, whether visual or imaging.  It can only be triggered by hitting the pier (like with a hammer) and won't be triggered by wind or simply touching the pier.  In other words, don't fret about it.

2. Fundamental bending of a cantilevered pier.,  This is of great concern for visual use of the scope.  It is the waving back and f orth of the scope/mount when you touch the scope to manually focus.  This can also be triggered by wind or simply walking on the concrete next to the pier.  Adding any mass inside the metal pier, like sand or concrete makes the fundamental frequency lower, causing the pier to wave back and forth for a longer time.  On a steel 8 inch x 1/4 inch wall pier 50 inches tall and an 8 inch refractor, this oscillation can go for 4 to 6 seconds without any added mass inside, just by manually focusing the scope.  Adding mass just makes it worse.  So DON"T ADD MASS inside your metal pier!

Diameter is the most important parameter to getting a good working pier.  However for a permanent observatory, with wind protection, imaging can be done with a less stiff pier as long as the mount isn't touched or moved by outside forces.

Don
 



Re: When Homing Limit switch for AP1100/1600 ready?

Lee
 

could you expand on what the CP4 adds to the horizon and meridian limits beyond what is available with APCC and the CP3

thanks


Re: Pier question

swiencek
 

With all the discussion about piers, I personally don't recall anything about the thermal movement of aluminum.

 

Steve W.

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, December 15, 2016 7:53 PM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Pier questoin

 

 

Rolando,
Thank you for the explanation of the usage/purpose of the gussets.  One question comes to mind would be how wide would they be relative to the height/diameter of the pier, I suppose also it depends on whether the pier material is aluminum or steel.  You already stated that typically they would be 1/2 the length, but how wide optimally should they be at the base (or is that a really critical dimension).

Thanks,
Steve H


Re: Pier questoin

 

Rolando,
Thank you for the explanation of the usage/purpose of the gussets.  One question comes to mind would be how wide would they be relative to the height/diameter of the pier, I suppose also it depends on whether the pier material is aluminum or steel.  You already stated that typically they would be 1/2 the length, but how wide optimally should they be at the base (or is that a really critical dimension).

Thanks,
Steve H


Re: DIY Dolly for AP Eagle Pier

swiencek
 

That seems the way to mount the PoleMaster on a Mach 1.

 

Steve

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Wednesday, December 14, 2016 8:03 PM
To: ap-gto@...
Subject: [ap-gto] DIY Dolly for AP Eagle Pier

 

 

I recently upgraded from an Orion Atlas EQ-G mount to an AP MACH1GTO mounted on an AP Eagle Pier.  I image from my driveway and store my mount in the garage.  When not in use, I remove the scope from the mount and I also remove the counterweights, but I keep the mount itself attached to the tripod for convenience.

 

It was no problem for me to move the Atlas tripod/mount by hand, but the Eagle Pier is very difficult for me with the MACH1GTO attached.  I tried a number of ways to lift it but I never found one that was comfortable. The Eagle Pier weighs slightly more than the Atlas, but more importantly, it is more awkward to carry because the tripod profile is much lower to the ground and there is no easy way for a tall guy like me to grab it without putting quite a bit of stress on my back.  I have learned from my Dob days that my use of a telescope is proportional to its ease of carry and setup, so I looked for a better way to move my Eagle Pier around.

 

One unique aspect of the Eagle Pier is the 6 inch vertical can which serves as the primary load bearing mechanism.  I thought I could create an inexpensive dolly which temporarily supports the can from the bottom during transit.  From Lowe's, I purchased their furniture dolly ($29) and a 2"x12"x8' piece of lumber.  As shown in the first picture, I attached the lumber to the dolly in layers so that it the top of it rises about 2 inches above the bottom of the Eagle Pier can.  When I want to move the pier, I simply tip the tripod back on two legs to lift it up a bit, slide the dolly underneath, and then lower the can on top of the dolly.  Just reverse the process to take the pier off of the dolly.  It is dead simple to build and to operate, and it is very sturdy and stable while rolling as long as I keep one hand on the pier to steady it and I move slowly. The dolly wheels are fairly large and it rolls well over rough surfaces. I don't sense that I am putting any undue stress on the mount and tripod, and in fact I think it will be less wear and tear on the mount in the long run than trying to carry it. 

 

Picture of Dolly

Picture of Pier on Dolly

 

Just thought I would share this in case any of you might find it useful.

 

Gary

 


Re: DIY Dolly for AP Eagle Pier

swiencek
 

Good idea. You never know. Could have large wheels for rough terrain.

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Wednesday, December 14, 2016 8:03 PM
To: ap-gto@...
Subject: [ap-gto] DIY Dolly for AP Eagle Pier

 

 

I recently upgraded from an Orion Atlas EQ-G mount to an AP MACH1GTO mounted on an AP Eagle Pier.  I image from my driveway and store my mount in the garage.  When not in use, I remove the scope from the mount and I also remove the counterweights, but I keep the mount itself attached to the tripod for convenience.

 

It was no problem for me to move the Atlas tripod/mount by hand, but the Eagle Pier is very difficult for me with the MACH1GTO attached.  I tried a number of ways to lift it but I never found one that was comfortable. The Eagle Pier weighs slightly more than the Atlas, but more importantly, it is more awkward to carry because the tripod profile is much lower to the ground and there is no easy way for a tall guy like me to grab it without putting quite a bit of stress on my back.  I have learned from my Dob days that my use of a telescope is proportional to its ease of carry and setup, so I looked for a better way to move my Eagle Pier around.

 

One unique aspect of the Eagle Pier is the 6 inch vertical can which serves as the primary load bearing mechanism.  I thought I could create an inexpensive dolly which temporarily supports the can from the bottom during transit.  From Lowe's, I purchased their furniture dolly ($29) and a 2"x12"x8' piece of lumber.  As shown in the first picture, I attached the lumber to the dolly in layers so that it the top of it rises about 2 inches above the bottom of the Eagle Pier can.  When I want to move the pier, I simply tip the tripod back on two legs to lift it up a bit, slide the dolly underneath, and then lower the can on top of the dolly.  Just reverse the process to take the pier off of the dolly.  It is dead simple to build and to operate, and it is very sturdy and stable while rolling as long as I keep one hand on the pier to steady it and I move slowly. The dolly wheels are fairly large and it rolls well over rough surfaces. I don't sense that I am putting any undue stress on the mount and tripod, and in fact I think it will be less wear and tear on the mount in the long run than trying to carry it. 

 

Picture of Dolly

Picture of Pier on Dolly

 

Just thought I would share this in case any of you might find it useful.

 

Gary

 


Re: Pickering's triangle with the 12" RHA

Roland Christen
 

Very very good image! A lot of faint stuff, and gorgeous colors.

Rolando

-----Original Message-----
From: mj.astro@... [ap-gto]
To: ap-gto
Sent: Thu, Dec 15, 2016 11:29 am
Subject: [ap-gto] Pickering's triangle with the 12" RHA

Hi all,

I would like to share my latest image done with my Riccardi-Honders from my yard 29 km from Paris.
The target is the famous Pickering's triangle in Cygnus. One thing : no accentuation in this image, only curves and levels in PS CS1.


12" Riccardi Honders astrograph
AP1600 GTO mount and SBIG STL6303e camera.
Ha 26x10min and OIII 33x10min.

Link to the full version :

Hoping you enjoy with,

Best,

Marc



Re: Pickering's triangle with the 12" RHA

Worsel
 

Marc

Wonderful image.  Thank you for sharing!

Joyeux Noel

Bryan


Pickering's triangle with the 12" RHA

marc jousset
 

Hi all,


I would like to share my latest image done with my Riccardi-Honders from my yard 29 km from Paris.

The target is the famous Pickering's triangle in Cygnus. One thing : no accentuation in this image, only curves and levels in PS CS1.


http://www.astrosurf.com/jousset/forums/ngc6974_rha_160830_forums.jpg


12" Riccardi Honders astrograph

AP1600 GTO mount and SBIG STL6303e camera.

Ha 26x10min and OIII 33x10min.


Link to the full version :

http://www.astrosurf.com/jousset/images/deepsky/nebuleuses/rha/ngc6974_rha_160830_f.jpg


Hoping you enjoy with,


Best,


Marc


Re: AP future

Roland Christen
 

:^))

Rolando



-----Original Message-----
From: Fritz Two fritztwo@... [ap-gto]
To: ap-gto
Sent: Thu, Dec 15, 2016 10:19 am
Subject: [ap-gto] Re: AP future



AP Future:

Well, I haven't posted anything to Cloudy Nites in AP's defense, but I did just send out 35 Xmas cards containing the following lines.  I'm doing my bit :)

"My mount [AP1100 AEL] and astrograph are about as big as I can go.  Indeed the mount was bought to last the rest of my life and half way into my next. It is absolutely exquisite; the way a set of fine china or a diamond ring is to a woman! "

So that's my two cents :)

fritz kleinhans




Wed Dec 14, 2016 2:46 pm (PST) . Posted by:

uncarollo2

Hello Astro-Folks,


Recently there has been a thread on Cloudy Nights regarding the future of Astro-Physics Inc, and whether we are here for the long run. Here are two of the posts:

blah, blah, blah

And Roland responds:

- - - - - - -
The mount production pretty much runs itself with almost no input from myself. If I were to retire today (which I am not doing btw) it would make zero difference in the future of our mountings. I do spend the majority of my time in the optical shop with making the lenses and mirrors. I have a great crew that makes the mechanical parts and helps with the assembly of all the bits and pieces. I also spend a fair amount of time developing ways to make optics in a more deterministic way that requires less of the old school techniques and uses more advanced processes that can be done by people other than myself. So, I am passing down my knowledge as time passes, and you will eventually see AP scopes being offered with optics by other top world class opticians. And yes, we are also very much making plans to develop new leadership of this company in the business end of AP.

Roland (Rolando) Christen
Astro-Physics Inc.




Re: Pier questoin

Joe Zeglinski
 

Rolando,
Thanks for the terrific added pier idea.
 
    I really like the “old ZEISS concept” you mentioned, of using a CONICAL pier.
In effect,  the gradual widening of the tube is very much like having a “continuous gusset plate” attached to a tube – but it is on all sides, enveloping the pier, and all the way top to bottom, with a much wider footprint to further stabilize its stance from any sway as heavy equipment changes position.
 
    It is also the same design used for super tall street lighting standards. The aluminum poles are not quite tubular, but conical, gradually narrowing to the top.
 
    As I recall seeing old pictures of (likely post Korean War era) photos of military target, or early space program rocketry,  tracking radar dishes. They too had a conical pier to support it. I think I still have the photo of an ad somewhere, perhaps in my stash of avionics magazines.
 
    Conical pier was a good idea,  combining the strength of the triangle instead of effectively a vertical slab.  Perhaps the reason it died was because tubular piers were considered sufficient for our hobby, so we fight these minor stability problems again. Likewise, it might be more difficult and costly to manufacture.
 
    I was always thinking of visiting a city scrap yard, to search for a mangled lighting standard, and saw off the bottom 4-feet – a perfect conical pier, with a heavy base plate, already drilled with its 3/4 inch (?), bolt holes. The pole walls must also be about 3/4” thick as well. We could probably ask someone at our City Works dept. where do they dispose of their broken poles, after a road accident. The dept. may even give  a heads up, after the next accident clean-up, so you can rush over. Might be able to get one for the cost of scrap, or free, since all we need is the bottom  4 feet off the original aluminum 50-footer. Likely only the upper section was bent over, with our section still in perfect shape.
 
Joe Z.
 

From: chris1011@... [ap-gto]
Sent: Thursday, December 15, 2016 11:10 AM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Pier questoin
 


The old Zeiss concept of making the pier a variable diameter from top to bottom will eliminate any resonances. A variable diameter pipe will not ring at any one frequency and will damp out quickly. You can make one by welding 4 pieces of trapezoid together, wide at bottom, narrower at the top. The other way is to use a single diameter tube and weld or attach 4 vanes from about 1/2 way down to the bottom. It will look like a rocket on the launch pad and these vanes will stiffen the pier greatly.

Rolando
 
 
 
-----Original Message-----
From: westergren@... [ap-gto]
To: ap-gto
Sent: Thu, Dec 15, 2016 7:30 am
Subject: [ap-gto] Re: Pier questoin



A very good treatise on pier design was written in 2005 by Dennis Persyk. It is available at Pier Design Fundamentals - How to . . .

I strongly recommend against filling a permanent pier with anything but air.  Dennis touches this subject but doesn't explain it completely.  There are two kinds of oscillation with a pier, especially a steel pipe version:

1. Ringing like a bell - this is of no concern, since it is a high frequency that won't affect the view, whether visual or imaging.  It can only be triggered by hitting the pier (like with a hammer) and won't be triggered by wind or simply touching the pier.  In other words, don't fret about it.

2. Fundamental bending of a cantilevered pier.,  This is of great concern for visual use of the scope.  It is the waving back and f orth of the scope/mount when you touch the scope to manually focus.  This can also be triggered by wind or simply walking on the concrete next to the pier.  Adding any mass inside the metal pier, like sand or concrete makes the fundamental frequency lower, causing the pier to wave back and forth for a longer time.  On a steel 8 inch x 1/4 inch wall pier 50 inches tall and an 8 inch refractor, this oscillation can go for 4 to 6 seconds without any added mass inside, just by manually focusing the scope.  Adding mass just makes it worse.  So DON"T ADD MASS inside your metal pier!

Diameter is the most important parameter to getting a good working pier.  However for a permanent observatory, with wind protection, imaging can be done with a less stiff pier as long as the mount isn't touched or moved by outside forces.

Don
 



Re: AP future

Fritz K
 

AP Future:

Well, I haven't posted anything to Cloudy Nites in AP's defense, but I did just send out 35 Xmas cards containing the following lines.  I'm doing my bit :)

"My mount [AP1100 AEL] and astrograph are about as big as I can go.  Indeed the mount was bought to last the rest of my life and half way into my next. It is absolutely exquisite; the way a set of fine china or a diamond ring is to a woman! "

So that's my two cents :)

fritz kleinhans




Wed Dec 14, 2016 2:46 pm (PST) . Posted by:

uncarollo2

Hello Astro-Folks,


Recently there has been a thread on Cloudy Nights regarding the future of Astro-Physics Inc, and whether we are here for the long run. Here are two of the posts:

blah, blah, blah

And Roland responds:

- - - - - - -
The mount production pretty much runs itself with almost no input from myself. If I were to retire today (which I am not doing btw) it would make zero difference in the future of our mountings. I do spend the majority of my time in the optical shop with making the lenses and mirrors. I have a great crew that makes the mechanical parts and helps with the assembly of all the bits and pieces. I also spend a fair amount of time developing ways to make optics in a more deterministic way that requires less of the old school techniques and uses more advanced processes that can be done by people other than myself. So, I am passing down my knowledge as time passes, and you will eventually see AP scopes being offered with optics by other top world class opticians. And yes, we are also very much making plans to develop new leadership of this company in the business end of AP.

Roland (Rolando) Christen
Astro-Physics Inc.


Re: Pier questoin

Stuart Heggie <stuart.j.heggie@...>
 

Rolando, the gussets I described for my AP900 pier are exactly what you described. Looks like a rocket on the pad. And even at a mere 6" diameter I have never had cause to complain. 

Stuart

On Thu, Dec 15, 2016 at 11:11 AM chris1011@... [ap-gto] <ap-gto@...> wrote:


















































The old Zeiss concept of making the pier a variable diameter from top to bottom will eliminate any resonances. A variable diameter pipe will not ring at any one frequency and will damp out quickly. You can make one by welding 4 pieces of trapezoid together, wide at bottom, narrower at the top. The other way is to use a single diameter tube and weld or attach 4 vanes from about 1/2 way down to the bottom. It will look like a rocket on the launch pad and these vanes will stiffen the pier greatly.





Rolando













































-----Original Message-----




From: westergren@... [ap-gto] <ap-gto@...>




To: ap-gto <ap-gto@...>





Sent: Thu, Dec 15, 2016 7:30 am




Subject: [ap-gto] Re: Pier questoin






































A very good treatise on pier design was written in 2005 by Dennis Persyk. It is available at Pier Design Fundamentals - How to . . .









I strongly recommend against filling a permanent pier with anything but air.  Dennis touches this subject but doesn't explain it completely.  There are two kinds of oscillation with a pier, especially a steel pipe version:









1. Ringing like a bell - this is of no concern, since it is a high frequency that won't affect the view, whether visual or imaging.  It can only be triggered by hitting the pier (like with a hammer) and won't be triggered by wind or simply touching the pier.  In other words, don't fret about it.









2. Fundamental bending of a cantilevered pier.,  This is of great concern for visual use of the scope.  It is the waving back and f

orth of the scope/mount when you touch the scope to manually focus.  This can also be triggered by wind or simply walking on the concrete next to the pier.  Adding any mass inside the metal pier, like sand or concrete makes the fundamental frequency lower, causing the pier to wave back and forth for a longer time.  On a steel 8 inch x 1/4 inch wall pier 50 inches tall and an 8 inch refractor, this oscillation can go for 4 to 6 seconds without any added mass inside, just by manually focusing the scope.  Adding mass just makes it worse.  So DON"T ADD MASS inside your metal pier!











Diameter is the most important parameter to getting a good working pier.  However for a permanent observatory, with wind protection, imaging can be done with a less stiff pier as long as the mount isn't touched or moved by outside forces.









Don
















 

























































































































Re: Pier questoin

Roland Christen
 

The old Zeiss concept of making the pier a variable diameter from top to bottom will eliminate any resonances. A variable diameter pipe will not ring at any one frequency and will damp out quickly. You can make one by welding 4 pieces of trapezoid together, wide at bottom, narrower at the top. The other way is to use a single diameter tube and weld or attach 4 vanes from about 1/2 way down to the bottom. It will look like a rocket on the launch pad and these vanes will stiffen the pier greatly.

Rolando



-----Original Message-----
From: westergren@... [ap-gto]
To: ap-gto
Sent: Thu, Dec 15, 2016 7:30 am
Subject: [ap-gto] Re: Pier questoin



A very good treatise on pier design was written in 2005 by Dennis Persyk. It is available at Pier Design Fundamentals - How to . . .

I strongly recommend against filling a permanent pier with anything but air.  Dennis touches this subject but doesn't explain it completely.  There are two kinds of oscillation with a pier, especially a steel pipe version:

1. Ringing like a bell - this is of no concern, since it is a high frequency that won't affect the view, whether visual or imaging.  It can only be triggered by hitting the pier (like with a hammer) and won't be triggered by wind or simply touching the pier.  In other words, don't fret about it.

2. Fundamental bending of a cantilevered pier.,  This is of great concern for visual use of the scope.  It is the waving back and f orth of the scope/mount when you touch the scope to manually focus.  This can also be triggered by wind or simply walking on the concrete next to the pier.  Adding any mass inside the metal pier, like sand or concrete makes the fundamental frequency lower, causing the pier to wave back and forth for a longer time.  On a steel 8 inch x 1/4 inch wall pier 50 inches tall and an 8 inch refractor, this oscillation can go for 4 to 6 seconds without any added mass inside, just by manually focusing the scope.  Adding mass just makes it worse.  So DON"T ADD MASS inside your metal pier!

Diameter is the most important parameter to getting a good working pier.  However for a permanent observatory, with wind protection, imaging can be done with a less stiff pier as long as the mount isn't touched or moved by outside forces.

Don
 



Re: DIY Dolly for AP Eagle Pier

Gabe Shaughnessy
 

That's a unique solution for a common problem!  I have a similar setup - Mach1 on an Eagle Pier and got a used scopebuggy to make it mobile.  If you don't have an observatory, having the mount on wheels is the next best thing.  

Gabe