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Re: Pier design and sand
Joe Zeglinski
Hi,
I have been thinking about putting a temporary pier in the ground, to see how the back yard observing spot works out. I don't want to commit to heavy steel posts and concrete bunker footing. I was thinking of using one of those very thick walled, 10" diameter, street water main/sanitation pipes, and simply bury it 3 or 4 feet deep (3 feet above ground), and fill the inside back in with earth (perhaps only to ground level). I am hoping that the perhaps 1/2", (or thicker), PVC walls won't ring as much as steel, and will be solid enough for an AP900 system. I think these street pipes should be temperature stable and should not warp or vibrate, in normal city street use, so it might have advantages as pier material. Advantages include being easier to construct, (even remove to adjust for height), and can eventually be moved to a better spot, or removed entirely. Opinions please. Joe
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Re: Pier design and sand
Joe Zeglinski
Hi,
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If the Petrie dish has value, then it is far simpler to attach a mic to the side of a pier, and plug the mic output into your laptop audio port. The waveform can be captured and displayed, and displayed at greater convenience in better detail, in any music editing program - even the rink dink Sound tools in the Windoze Accessories folder. Using better sound recording programs, you can measure the amplitudes and frequencies, and even get the Fourier Transform to identify the dominant frequencies and power. Then one can apply dampening techniques like sand, or perhaps bolting on step rings at sections of the pier to change the modes, and perhaps cancel them. One other side benefit might be to discover if there are any other sources (traffic, walking on observatory floor, etc) ground vibrations, or stepper motor frequencies being coupled from an operating mount into the pier, and being amplified by the steel pier. The nice thing about the above approach is that these WAV files can be graphed and saved, to be shared with others in the group in perhaps the FILES section. Then, any visitor can get the geometries of the pier used, with the resulting recorded waveform, for download, or even live online playback using RealPlayer etc., to compare everyone's pier dampening technique. If you like the Petrie dish approach, capture the mic output and simply play it back using the RealPlayer or any PC CD playback program - it will show the same waves as the water in the Petrie dish. Joe
----- Original Message -----
From: "William R. Mattil" <wrmattil@...> To: <ap-gto@...> Sent: Wednesday, October 31, 2007 10:49 AM Subject: Re: [ap-gto] Re: Pier design and sand Murray Hammick wrote:Having been following this thread, I could say with any confidence whichA few years ago I was in New Mexico visiting Andy Homeyer and he
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Re: Pier design and sand
Jeff Young <jey@...>
Murray --
I went through all these arguments when I built my pier. Each side seemed to have logic (and expertise) in their favor. Finally, I just experimented. I have a 10" diameter, 50" tall steel pier. Empty, a solid kick to the pier would produce 20 arc-second vibrations in the eyepiece that damped in about 1 second. Filled with oiled sand, the amplitude dropped to about 15 arc-seconds while the dampening time stayed the same. The results were hardly scientific, but they were fairly well repeatable. The results were enough on the plus side of the ledger that I left the sand in, but I'd be hard pressed to say it makes much of a difference. -- Jeff. ________________________________ From: ap-gto@... [mailto:ap-gto@...] On Behalf Of Murray Hammick Sent: Wednesday, October 31, 2007 1:47 PM To: ap-gto@... Subject: Re: [ap-gto] Re: Pier design and sand Having been following this thread, I could say with any confidence which side has won the day. How about a very simple experiment. Does someone have the equipment/instrumentation to monitor vibrational energy, damping etc in a simple steel tube and measure it with and without a dry sand or a sand/oil mix ? MPH r1300rs <cardiofuse@... <mailto:cardiofuse%40mac.com> > wrote: Just a comment about the sand issue. I tend to disagree about the sand in the tube; although I believe both wood and sand accomplish similar things-they both absorb energy and act as a dampeng agent to the system to resist resonance and its inherent fundamental frequency and thus will cease any oscillations quicker-sort of like applying electrical or viscous resistance to the system. Generally, sand is a very good vibration control material since it has the ability to absorb a huge amount of energy without saturating and is able to provide high mass which will lower the resonant frequency of a decoupled vibration control system. Additionally, it can help create substantial resistive mass which will address horizontal displacement. Sand is quite efficient in converting mechanical energy (vibration) into thermal energy (heat). It can be viewed as a reservoir to absorb and dissipate the unwanted stored energy trapped in the component. This is just my opinion to interject.
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Re: Pier design and sand
William R. Mattil <wrmattil@...>
Murray Hammick wrote:
Having been following this thread, I could say with any confidence which side has won the day.A few years ago I was in New Mexico visiting Andy Homeyer and he described how he dampened his piers and it made sense. He drilled a hole near the top and mounted the mount, OTA and what not. Additionally he then mounted a small petri dish to the side of the pier and filled with water. Striking the side of the pier would then cause ripples in the water in said petri dish that could be easily observed. He then timed the duration of the ripples and started adding sand and retesting until he reached a minimum. What he did was essentially "tune" the system for maximum damping. You can all decide for yourselves if it makes any real difference. But I thought that it was a very well thought out approach and makes sense. Regards Bill -- William R. Mattil : http://www.celestial-images.com
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Re: Pier design and sand
Woodwind
Having been following this thread, I could not say with any confidence which side has won the day.
How about a very simple experiment. Does someone have the equipment/instrumentation to monitor vibrational energy, damping etc in a simple steel tube and measure it with and without a dry sand or a sand/oil mix ? MPH r1300rs <cardiofuse@...> wrote: Just a comment about the sand issue. I tend to disagree about the sand in the tube; although I believe both wood and sand accomplish similar things-they both absorb energy and act as a dampeng agent to the system to resist resonance and its inherent fundamental frequency and thus will cease any oscillations quicker-sort of like applying electrical or viscous resistance to the system. Generally, sand is a very good vibration control material since it has the ability to absorb a huge amount of energy without saturating and is able to provide high mass which will lower the resonant frequency of a decoupled vibration control system. Additionally, it can help create substantial resistive mass which will address horizontal displacement. Sand is quite efficient in converting mechanical energy (vibration) into thermal energy (heat). It can be viewed as a reservoir to absorb and dissipate the unwanted stored energy trapped in the component. This is just my opinion to interject.
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Re: Pier design and sand
Woodwind
Having been following this thread, I could say with any confidence which side has won the day.
How about a very simple experiment. Does someone have the equipment/instrumentation to monitor vibrational energy, damping etc in a simple steel tube and measure it with and without a dry sand or a sand/oil mix ? MPH r1300rs <cardiofuse@...> wrote: Just a comment about the sand issue. I tend to disagree about the sand in the tube; although I believe both wood and sand accomplish similar things-they both absorb energy and act as a dampeng agent to the system to resist resonance and its inherent fundamental frequency and thus will cease any oscillations quicker-sort of like applying electrical or viscous resistance to the system. Generally, sand is a very good vibration control material since it has the ability to absorb a huge amount of energy without saturating and is able to provide high mass which will lower the resonant frequency of a decoupled vibration control system. Additionally, it can help create substantial resistive mass which will address horizontal displacement. Sand is quite efficient in converting mechanical energy (vibration) into thermal energy (heat). It can be viewed as a reservoir to absorb and dissipate the unwanted stored energy trapped in the component. This is just my opinion to interject.
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Re: Pier design and sand
r1300rs
Just a comment about the sand issue.
I tend to disagree about the sand in the tube; although I believe both wood and sand accomplish similar things-they both absorb energy and act as a dampeng agent to the system to resist resonance and its inherent fundamental frequency and thus will cease any oscillations quicker-sort of like applying electrical or viscous resistance to the system. Generally, sand is a very good vibration control material since it has the ability to absorb a huge amount of energy without saturating and is able to provide high mass which will lower the resonant frequency of a decoupled vibration control system. Additionally, it can help create substantial resistive mass which will address horizontal displacement. Sand is quite efficient in converting mechanical energy (vibration) into thermal energy (heat). It can be viewed as a reservoir to absorb and dissipate the unwanted stored energy trapped in the component. This is just my opinion to interject.
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Re: Power Supply for Mach1GTo
Dean S
Good question Larry, I am also using the Lacey 18 volt converter. But from
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what I have seen, Roland says 16 is recommended but really no problem until 22-24 volts. I suspect in cold weather our 18 volt is fine but maybe we need to lower that during warmer weather? Dean
----- Original Message -----
From: "Larry Phillips" <llp41astro@...> To: <ap-gto@...> Sent: Tuesday, October 30, 2007 8:20 PM Subject: [ap-gto] Power Supply for Mach1GTo I am new to owning an AP mount and expect to have one soon. In
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AP1200 on Pier-Tech?
Jim S.
Hi,
I'm confused as to how one mates an AP1200 to the various Pier-Tech piers. Can one bolt an SPA onto the Pier-Tech Top Plate? Or does one need an FSA and an RPA? Or do both of those options work, just pick one? Thanks, JS
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Re: Pier design
Rick Thurmond
Ever since Larry told me about that trick, I've done it in each of my
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piers. It works great. The pier is totally dead after that. Rick
On Oct 30, 2007, at 7:38 48AM, Dean S wrote:
My MI-250 portable pier has wood discs wedged tightly into each end
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Power Supply for Mach1GTo
Larry Phillips
I am new to owning an AP mount and expect to have one soon. In
preparation for that, are there any recommendations for a DC power supply that is appropriate for the Mach1? That is, 11.5 to 16 volts DC filters and regulated with 110 V AC input? I have an 18 V power supply now that I have been using with a Gemini system but this appears to be too high a voltage. Larry
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Re: AP1200 on Permanent Pier sans Observatory
Joe Zeglinski
Jim,
When you get all set up, you will end up with a harness of bundled cables, wrapped up in split coil sleeves, or something. If you do remove the CP3, I would put a small plastic bag (or Saranwrap), to seal the AP cable connector ends (if they re part of a harness bundle) - otherwise, you could bring the AP cables in as well. That just adds time at both ends, which defeats the purpose of an observatory. Later, all you will need is to plug everything back in, if it was unplugged. Anyway, you might have a "semi heated "observatory, (when not in use), so moisture shouldn't be a problem. When you close down at dawn, just "turn on the furnace". That will keep your "OTA optics" dry as well. Only if you keep the observatory unheated, will you to take need moisture counter measures. As for the temperature rod heater ... it doesn't matter if a boat burns down, there are lots of replacements. OTA's are also plentiful. But, an AP mount takes time to remake ... like a fine wine ... years in fact if you are on ..... THE LIST. Just be careful. Joe
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Re: AP1200 on Permanent Pier sans Observatory
Jim S.
Hi Joseph,
Definitely the Hand Paddle comes in, and I was given the same advice by someone at AP with respect to the CP3. I guess there are two approaches. One school seems to argue that a tight seal with a moisture-removing agent is the way to go, and the other seems to argue the more air flow the better. Though perhaps I'm misreading/misrepresenting one or both of those camps. A quick web search revealed these convenient, rechargeable, "indicating", desiccant containers: http://www.multisorb.com/products/desiccants/cartridges/drican_html A bunch of those underneath that TeleGizmos cover might work well. Alternatively, a friend of mine recommended a low temperature electronic-rod heater that he uses for due prevention on his 35ft boat, available at most marine stores. I appreciate everyone's help on this. I think the "dry it out, and seal it tight with desiccant/heater inside" method is how I'm going to proceed. And, of course, I'll bring the CP3 and the HP inside. I imagine the same advice ("bring 'em in") holds for power supplies and cables, although redoing all of the cables each time I set up is about the least fun part of this hobby for me. Definitely need an observatory. Or an apprentice. Darth Sumthin'-or-nuther. :) JS --- In ap-gto@..., "Joseph Zeglinski" <J.Zeglinski@...> wrote: remove the CP3 controller, and bring it inside. The concern was for condensationgetting into the electronics, causing corrosion.
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Re: AP1200 on Permanent Pier sans Observatory
Joe Zeglinski
Hi,
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One thing that Marj once recommended to me was to at least remove the CP3 controller, and bring it inside. The concern was for condensation getting into the electronics, causing corrosion. Air pollution and dew make a good battery acid solution. It's quite easy to do if you have replaced the set screws holding it to the mount, with the optional thumb screws that came with the mount, in a small envelope (unless it got pitched with the packing peanuts). It would have been nice if the CP3 controller were designed to be mounted using "ball bearing spring latches". That way, a simple press of a lever - or just a tug on the CP3, if it is held in place by additional "ball bearings in spring sockets" - would release the unit to slide off the mount, without the hassles of possibly losing the small thumb screws. I mean, you ARE going to take the Hand Pad indoors for the same reason, so why not the controller as well. I say "additional", in case there should be a problem with the springs approach, and you need to use the old screw retainer method. Still, I wonder if condensation affects the servo motors as well - the rest is just stainless steel and aluminum. At least protecting the CP and hand pad is easy. Joe
----- Original Message -----
From: "Murray Hammick" <mphammick@...> To: <ap-gto@...> Sent: Tuesday, October 30, 2007 12:21 PM Subject: Re: [ap-gto] AP1200 on Permanent Pier sans Observatory There is a often bit of misunderstanding about condensation etc. and
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Re: Pier design
dmwmpd <westergren@...>
Hi Niels,
Yes the amplitude will be slightly less for an impact, but will be the same for a force applied. A force deflection of the mount depends on the stiffness of the pier tube, not the mass. In any event, once the oscillation starts, it takes about the same amount cycles (and time) to settle out. The simple fact is adding mass without structure change is bad for piers. It's not a disaster, and it the pier is very stiff, you might not notice the difference. But the taller and thinner the steel tube pier, the more important it is to avoid succombing to the old wives tale about filling with sand. Regards, Don --- In ap-gto@..., "N. Foldager" <nf@...> wrote: the withcantelevered oscillation. The sand just goes back and forth same asthe pier. The added mass lowers the frequency, which is the changeincreasing the period (length of each oscilation). With no ofin damping, the sand filled pier will oscillate the same number masscycles, which will take longer.OK. is increased? (for same impact)
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Re: AP1200 on Permanent Pier sans Observatory
Woodwind
There is a often bit of misunderstanding about condensation etc. and equipment. The military has this sort of problem and uses environmental covers and spray treatments for a wide range of equipment that is left outside for long periods with few problems.
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If you have a good seal around the cover (such as a velcro and neoprene collar around the pier) the mount can heat and cool all it likes - but there will be little change in the amount of water inside the cover per-se. What is in the bag to start with is what you tend to end up with. You might move it around by allowing the equipment to get very hot and then cold - thermal stability will help reduce ingress of water into the equipment itself. If you want to help reduce humidity levels simply remove the cover for an hour or two on sunny or breezy and dry day and replace whilst everything is still relatively warm/dry and no condensation has formed. There are also a lot of good water repellent compounds around these days and many are tuned for specifics such as cabling, seals, electronics etc. Many of these would in any case be good for a mount in the normal course of events - if you are going to get moisture into a joint etc - unless you treat it, its going to start getting in there during a dingle night's viewing let alone a season outside. All the other methods mentioned such as silica-gel etc are going to assist. But the best thing is to wipe off any moisture you can after use (or even blow it down with a hair dryer to warm the surfaces and remove water in those tiny cracks etc), make a good seal around the pier and give it a good airing when you can between use. Murray Rick Thurmond <yahoogroups@...> wrote: I haven't seen condensation inside yet, but a bag of dessicant sitting on the base of the mount might be a good idea. I think hardware stores sell them to dry musty closets. Some of them might be rechargeable in the oven. Rick
On Oct 29, 2007, at 2:46 20PM, Jim S. wrote:
> Thanks Ian. And thanks much Rick for your help here and off-line as > well! > > Ok, you both have me seriously wanting to install a permanent pier for > my new AP1200. But an observatory is out of the question with the > Aesthetics Committee. So, I worry about protecting the mount from the > elements, even with something like the Telegizmo 356/24/7 cover. > > Isn't condensation an issue with any cover like this? In my climate, > we can easily have >30deg swings between day and night, with the > relative humidity going from nearly nonexistent to dripping wet, > respectively. It doesn't get terribly cold here though. It's VERY > rare for the low to dip below 30degF on the coldest nights. > > Anyone else have their AP1200 mounted permanently, sans observatory? > How do you protect it (and the pier), and how do you mitigate > condensation if at all? > > Thanks, > JS > > --- In ap-gto@..., "Ian Underhill" <astro1ds@...> wrote: > > > > But I would have to say in the long run you should > > consider what Rick said. Having your setup ready and aligned every > > night just makes life sooo much easier and more enjoyable. I still > > can't believe I went for a year before learning that lesson. Hope > > this helps. > > > > Ian > > > > > > --- In ap-gto@..., Rick Thurmond <yahoogroups@> wrote: > > > > > > Jim, > > > I'm also observatory-less at present, at least compared to my last > > > place where I had an Astro-Haven dome. But I would never go pier- > > > less. I have a Astro-Pier from LeSeur bolted to a few hundred > > pounds > > > of concrete in the one spot in my yard where I can see the whole > > sky. > > >
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Re: AP1200 on Permanent Pier sans Observatory
Joe Zeglinski
... somehow, I wouldn't feel right about doing that indignity to an AP mount.
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:-) Joe
----- Original Message -----
From: "Dean S" <dean@...> To: <ap-gto@...> Sent: Tuesday, October 30, 2007 8:25 AM Subject: Re: [ap-gto] Re: AP1200 on Permanent Pier sans Observatory I still like the one that looks like an outhouse, including the half moon on
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Re: Pier design
Dean S
My MI-250 portable pier has wood discs wedged tightly into each end (about
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4") and this acts as dampeners and does a good job, without increasing weight. Dean
----- Original Message -----
From: "N. Foldager" <nf@...> To: <ap-gto@...> Sent: Tuesday, October 30, 2007 9:18 AM Subject: Re: [ap-gto] Re: Pier design
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Re: Pier design
N. Foldager
Hi Don,
Filling the pier with sand doesn't dissipate any energy during theOK. But don't you agree that the amplitude will be smaller when the mass is increased? (for same impact) Best regards, Niels
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Re: AP1200 on Permanent Pier sans Observatory
Dean S
I still like the one that looks like an outhouse, including the half moon on
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the door. Just open the door and it rolls away from the scope. Should fit right in behind any modern home :))) http://www.noomoon.com/noomainastroOH.htm
----- Original Message -----
From: "Joseph Zeglinski" <J.Zeglinski@...> To: <ap-gto@...> Sent: Monday, October 29, 2007 11:52 PM Subject: [ap-gto] Re: AP1200 on Permanent Pier sans Observatory Hi Jim,view of my garden. The best spot, in the far corner of the yard, is surroundedby a few small trees, and one of them is the neighbour's.by a university, have a look at:http://home.moravian.edu/users/phys/mejjg01/interests/apparatus_pages/telescope_enclosure.htm an aluminum Greek column (e.g. Home Depot, hollow decorative porch posts), ontop of which will be my AP900. When not in use, a similar, very slightlywider, Greek column upper half will be dropped down over the mount, mated to theAs far as security is concerned, except for the neighbours, intruders willthink it is just "yard sculpture".for heat and condensation control. The lower and upper column sections will bekey locked at the join, for security.well!
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