Anti-vibration observatory piers (Part 1, Piers: The good the bad and the Rat Box)

Anti-vibration observatory piers (Part 1, Piers: The good the bad and the Rat Box)
Ralph Bell talks to Robert J Dalby of Astro Engineering.
Guest star: Basil the Rat
Produced by The Astronomy and Nature Centre.
Produced by DB Video Services for Astronomy and Nature TV

[@lawrence5254]

One of my favorite videos on KZbin on pier construction. You helped me when I made my pier and because of this video, my pier works better than perfect. Thank YOU so much!!!!!!!!!!!!!!!

[@mesample1705]

I liked this explanation, and you're spot on regarding mount head level importance to polar alignment and accurate star alignment. The problem still remains, that in 2021, several astronomy computer applications require those three alignments to function correctly. To my knowledge, that star model is not synced between all the applications. Without the star map, they assume the mount is level.

[@ant_hart]

I’m confused! ‘A sophisticated machine’ ...it’s a standard pier just with extra supports welded on...it’s literally 7 pieces of steel. Just fill it with sand or concrete ...it’s the same effect. I’d love to see several images taken with exactly the same setups but with the only change being the pier and try to tell the difference. I’d be happy to be proved wrong.

[@fredmercury1314]

If you can afford the type of equipment that would reveal those errors in your images, you could afford the pier he's selling to avoid seeing them. If I'm spending £30k on astro equipment why wouldn't I just buy the £1k pier?

[@jonasj611]

I really really believe what he says only from observing the way he does it sometimes forgetting what he just said and going back catching those words again. One of my only few subscriptions.

[@neiltonks]

It sounds like a 15 minute commercial for his own pier. There are many many videos on KZbin that show homemade ones and they are quite happy with the results.

[@nighttrain1236]

Without trying to sound unkind, there isn't really much to these devices other than using a wide and heavy steel tube to maximise stiffness. You could probably make their one even better by filling it with concrete. What would be more sophisticated is to deploy FEA to avoid resonance with the kind of applied loads these piers see, such as, for example, the tiny vibrations from motor-assisted worm-gears, which probably cause the most problems in terms of seeing. But there are also issues of vibrations from the ground being transmitted to the telescope, such as from traffic. Stiffness isn't always your friend. Mass needs to be dampened.

[@fredmercury1314]

Only because they don't know any better...

[@montygiavelli8125]

Wood dampens vibration, some of the very expensive tripods are made from wood. What about a wooden pier that is dried and sealed so no moisture can get inside. Maybe an 8x8 pressure treated post or plywood pieces glued together to make an 10x10" square post and bolted to concrete in the ground. Laminated plywood is very strong. Great videos, thanks, really got me thinking. Monty

[@skaruts]

"I think you know where you stick your rat" :) lol Excelent work there. I'll probably never use one of these, but at least I know the its intricacies, in case I ever change my mind someday.

[@FyreMunky69]

As a Autocad Draftsman...I Whole heartedly agree with your policy of not giving out too much info I also agree with your breakdown of the original pier you showed and how it wouldnt excise vibration during an observing session...an Astrophotographer might notice the vibration when processing his images just to find out he wasted his night so when I move to Lake Tahoe to have my observatory built...what is your company website so i can order a pier from you Great video !..extremely informative !

[@fredmercury1314]

5:39 Is that pier better or worse than any of the £100 tripods (that cost £250 to buy) that people are using? Because if it's better and cheaper than a tripod, then it's not a bad pier.

[@kingdom777866]

Okay I get your point.. but everything has a certain amount of vibration, but what Lengths do we have to go to, to eliminate ALL vibration ? I notice you never mentioned anything about concrete piers, I would imagine this would be ideal, again it depends on how far you want to take it.. you can’t blame folks making there own piers given the cost of them, besides look at how many are quite happy with there home made piers !

[@kippyjohnson]

Lovely video! Awesome info!

[@DurkoppFordertechnic]

I thought if the top is not accurately levelled up, the pole star is going to drift off the polar alignment as it transits? Even if the mount is aligned with the pole star.

[@RocketPlanet]

Hi Vincent. No , the leveling of any part of the mount plays no part in improving or diminishing the accuracy of polar alignment once achieved. The critical datum is aligning the centre of the RA rotational axis of the mount as precisely as possible with the rotational axis of the Earth. There are no other considerations. The phrase 'precisely as possible' hides rather a lot of considerations in fact, but they do not impact on the validity of the previous statement. The pier can be bolted on the wall, subject to the wall's strength, and the pier top can be canted at any crazy-house angle - all that matters for PA is that the RA axis' centre of rotation is aligned with the centre of the Earth's axis of rotation. This is normally achieved by pointing the RA axis as precisely as we can at the calculated North or South point of rotation as projected on to the celestial sphere (depending on which hemisphere we are in). The mounts standard of level (and its always interesting to hear how folk are going to achieve and measure this initially) has a role to play when aligning equatorial mounts in the field, where time is short and we are prepared to accept approximations for the general good of achieving a task specific standard of PA but is otherwise irrelevant in the critical path outlined above. For more information please see my longer reply to Curtis Reynolds above. I hope this helps. Thanks for posting. KR RJD A&NTV

[@woody5109]

I built my pier using an 8”x8” pressure treated wood post. I also have a “rats cage” on the top and have zero vibration, absolutely zero. I know because I have a frequency tester, I tested vibratory compactors for years, I completely disagree with you on the rats cage as a stability problem area.

[@antandshell]

Seven people who have "Rat cages' disliked the truth lol.

[@Mrpaulgs]

No evidence presented for the claims made - it's just what some guy who sounds like an authority says. How do you balance your mount if it's not level?

[@fredmercury1314]

8:19 I've always seen the bolt thing as one of the dumbest ideas. It's pretty obvious that you've just compromised the integrity of the pier, and I'm just some guy on the internet. I've even seen a Planewave installation of a huge reflector mounted in the same way; on some big bolts. Crazy.

[@thevirologist6036]

side-by-side comparison and maybe I'd believe the claims.

[@nitehawk86]

5:58 brilliant!

[@Mrpaulgs]

Yeah if you can't provide evidence why something is bad just make fun of it! This is a logical falicy in action. Casts doubt on the entire presentation.

[@linberg9519]

Interesting!

[@CURTIS-W5CER]

I don't disagree with the "rat box" commentary, but....if you're not leveled, don't you drift off target?....even with a perfect polar alignment.

[@RocketPlanet]

Hi Curtis and thanks for your question. No the level of the pier is irrelevant once the rotational centre the RA axis is aligned with the north celestial pole. But read on as there's a bit more detail lurking behind that statement. It doesn't matter what angle the pier or its top plate are positioned at once correct polar alignment (PA) is achieved. However, instructions supplied with telescope mounts that require PA seem, at first glance, to deny this fact. The reason why it is tactically useful to level, to an albeit approximate standard, the tripod top prior to fastening the head in position is that it will make the process of achieving a useful standard of PA easier and therefore quicker. An important consideration when setting up equipment in the field. A level tripod top, and therefore more or less square, level and perpendicular N/S latitude and azimuth E/W axes, makes homing in on good PA easier if you are not dialing in a large North or South error every time you move the mount head East or West and vise versa - as you do in the case of an out of level head. But the picture is quite different for a permanent installation. We are not constrained by time and the need to accept approximations and given that the installation is to be permanent the additional time required to achieve good PA always becomes utterly trivial measured against the operational lifetime of the pier. So to in anyway compromise the rigidity and stiffness of the pier - for its entire lifetime - in the cause something that adds 10 minutes to achieve a standard of PA comparable with what was achieved on the 'level' tripod - is clearly folly. Indeed, you would never want to fly in a plane or drive a car built employing this kind of flawed logic. You'll note that I put inverted commas on that word level in the last but one sentence. You might ask yourself what someone really means when they say that the tripod head or pier top should be levelled. In most cases the manufacturer of the tripod has glued a little 10 to 15mm diameter bubble level into the top casting. A blind man's guess is probably better than this at gauging approximate level. And a good seven inch DIY spirit level won't be much better either as there just isn't a wide enough base-line anywhere on the pier or tripod to get a good (enough) level to ensure that there will not be axis errors dialled in by adjusting the opposite axis. So the best pier installation strategy is to place rigidity and stiffness above, well above, any considerations of ease of achieving a high standard of PA - because it will not be level to the impossibly high standard it needs to be (to achieve single axis adjustment unhindered by cross axis error) anyway. Realising that every head is out of level, to a high standard, no matter what you do, and therefore might as well be out of level to a much wider standard actually liberates you to concentrate on what matters; and that's achieving a suitable (task specific) standard of PA with the stiffest and most rigid pier/tripod mount you can manage. The 'rat box' and other similar devices that compromise the function of the pier but promise the inexperienced purchaser (or copyist - as the rat-box has been copied hundreds if not thousands of times by well-intentioned home builders) ease of installation offer no useful contribution to the mission as I have stated it above. I hope this helps and thanks for the chance to explain this. KR RJD A&NTV

[@CURTIS-W5CER]

Awesome. Thanks for the very thorough explanation.

[@fordpwrXR8]

excellent....Im an amateur lol