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zakkhogan

Why use a Pier ?

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1) You can't trip over the legs in the dark!

2) A pier can be made rock solid by setting it in concrete.

3) A tripod will be on the same surface you are standing on- hence sending vibrations to the scope.

4) Polar alignment needs checking/adjusting less often.

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There best used in a Obby, but people do have them covered up outside and set-up every time, +1 for what laser_jock99 typed 

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Pier in obsy means no setup.

Scope and everthing is already setup, just turn on power slide the roof back and away you go.

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Brilliant, ok next question . 

I just drawn an image of what my understanding is of how a wedge work,  is this correct?

post-23525-0-21616600-1390815503_thumb.j

Cheers 

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There is no need for levelling as the PA adjustments on the mount will correct for a platform that isn't level.  As long as it's roughly level you will have no problems.  Theoretically, PA can correct for any amount of angle but being roughly level (by eye is sufficient) makes PA slightly easier.

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I don't have an observatory but do have a pier in the garden. I keep the mount on it, polar aligned, and use 2 covers to keep it all dry. Best thing I did as it saves so much time.

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I don't have an observatory but do have a pier in the garden. I keep the mount on it, polar aligned, and use 2 covers to keep it all dry. Best thing I did as it saves so much time.

I have a garden pier as well as the obsy one. Set up time is much reduced this way.

DSCF8015_1024_zps1e3f71f6.jpg

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There is no need for levelling as the PA adjustments on the mount will correct for a platform that isn't level.  As long as it's roughly level you will have no problems.  Theoretically, PA can correct for any amount of angle but being roughly level (by eye is sufficient) makes PA slightly easier.

There is a new school of thought that suggests if you intend to use any of the PA assisting software (as in new handset firmware updates) then having a level mount is a good thing (since the software may assume this*). Otherwise - no mount levelling is necessary, indeed the 'wobbly bolt' method of mount levelling might make the pier less stable.

* I would like to have this confirmed?

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so if you were going to make a pier to use with a Nexstar 8SE - haw would you make a bit to replicate the top of the tripod to fix tot he top of the pier so the telescope can be bolted to it.

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so if you were going to make a pier to use with a Nexstar 8SE - haw would you make a bit to replicate the top of the tripod to fix tot he top of the pier so the telescope can be bolted to it.

Not sure if they can be had commercially, perhaps butcher a suitable tripod just for the head?  I machined my own to accept either a G11 or Meade Superwedge.

IMG_2006_zps0b088b58.jpg

ChrisH

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I will be using a wedge and not a EQ mount does that make a difference?

Not sure what you mean by that - a 'wedge' is typically what turns an alt-az mount into an eq (simplistically) - i.e. an angled plate at the top of the pier.

I know people that use a field tripod in their observatory, rather than a pier. I would  worry about it getting bumped and misaligned, and the space it takes up, but it's probably not as bad an idea as all that. And if you have the tripod already, you will save a wadge on the pier...

Callum

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when you say PA, you are referring to polar alignment?

Yes.

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The other advantage of a pier over a tripod is for long OTAs on German equatorial mounts.  You will get a collision between the scope and the tripod leg a lot sooner than you will with a pier.  This can allow you to track through and beyond the meridian without having to flip the mount as soon.

A wedge is normally used with fork-type mount (usually found on Meade/Celestron SCTs).  It is an angled plate that tips the base of the mount up so the forks point to the celestial pole, allowing what was an alt-az mount to track equatorially and without field rotation.  Not usually an issue for visual observing, but essential for imaging.

The main disadvantage of forks and wedges is that the mass of the scope is a long way from the base (which can lead to flexure / vibration in the fork arms) and also the wedge itself can be a major source of vibration depending on the design.

As others have said, a levelling plate on top of a pier is not a wedge, and nor it it really necessary.  You can polar align easily enough with a pier head that is not even remotely level, though being reasonably level will make it a lot easier since the alignment adjustments in Alt and Az will remain (largely) independent of each other with a level pier.

Refining the alignment using drift (whether manual or software assisted) would work fine on a non-level pier, though you might need a few more iterations as an Alt adjustment will slightly throw out Az and vice versa.  I don't know about the smarter routines in handsets and software though.  Certainly the first step of initial polarscope alignment method in EQMOD relies on a level mount as you drop polaris from the central crosshair to the outer ring of the polarscope reticule to find the 'six o'clock' position, which would not work if the pier or tripod is significantly off-level.

Edited by IanL
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Not sure what you mean by that - a 'wedge' is typically what turns an alt-az mount into an eq (simplistically) - i.e. an angled plate at the top of the pier.

I know people that use a field tripod in their observatory, rather than a pier. I would  worry about it getting bumped and misaligned, and the space it takes up, but it's probably not as bad an idea as all that. And if you have the tripod already, you will save a wadge on the pier...

Callum

What i mean is, that a wedge will only adjust left, right, up and down, there is now way of adjusting one side higher than the other.

I dont understand why you wouldnt need a level platform. 

Lets go extreme here.  If i was to put a pier in my garden that looked like the leaning tower of pisa i woundnt be able to polar align due to the angle of the pier\wedge system?

 i fail to understand how you can polar align if the pier\wedge system is level?  

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There is a new school of thought that suggests if you intend to use any of the PA assisting software (as in new handset firmware updates) then having a level mount is a good thing (since the software may assume this*). Otherwise - no mount levelling is necessary, indeed the 'wobbly bolt' method of mount levelling might make the pier less stable.

* I would like to have this confirmed?

When I put my pier in last summer I used AlignMaster, but couldn't get PA  as good as I wanted, and read somewhere that AlignMaster likes a level mount. So I used the PHD method instead and got a more refined PA that way.

Pier is not in an obsy, just has a plastic trade paint bucket on top then a Scopecoat.

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What i mean is, that a wedge will only adjust left, right, up and down, there is now way of adjusting one side higher than the other.

I dont understand why you wouldnt need a level platform. 

Lets go extreme here.  If i was to put a pier in my garden that looked like the leaning tower of pisa i woundnt be able to polar align due to the angle of the pier\wedge system?

 i fail to understand how you can polar align if the pier\wedge system is level?  

If your pier adapter is 100% level when you put your mount on you adjust the horizontal/vertical with the att/lat bolts.  This is to center the axis of your mount to polaris (well just off polaris). They will do the same adjustments if your pier adapter is not 100% level, as long as the adjustment range is enough. So of course when we say not level we don't mean so far out the pier was mounted vertically instead of horizontal.

If you point your mount south  though not even a 100% level pier can adjust for that!

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Why don't you need a level base? Think of it like this; an imaginary and magic steel bar bar passes right through the polar axis of your mount holding it in perfect polar alignment withoutt any need for anything else to support it. This bar is just suspended by magic in the right place. No tripod, no pier, just a magic bar floating in a set position and holding your mount perfectly aligned. (I want one!!!) Now you can rotate your mount around this bar but whatever you do it must remain perfectly polar aligned. So polar alignment is not predicated on where the rest of the mount is pointing, it is predicated on whether or not the mounts polar axis is pointing at the pole.

Olly

Edit; the best mounts to align, in my view, are Takahashi and these don't have adjustable legs. The bubble level is on the RA housing. Its only purpose, as on a conventional GEM mount, it to set the polar scope reticle to vertical, noon/North at the top.

Edited by ollypenrice
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Just to add that I have a Pulsar observatory and had a tripod first of all.  Now I have a pier and after several months I still marvel at the amount of extra space I have.  Still have moments when I 'step around' the missing tripod legs.

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so if you were going to make a pier to use with a Nexstar 8SE - haw would you make a bit to replicate the top of the tripod to fix tot he top of the pier so the telescope can be bolted to it.

I came across this and thought it may be usefull to you?

http://www.bencooper.karoo.net/AstronomyMountsWedge.html

Edited by zakkhogan

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