Steel Pier Construction

[Astrokev]

4 minutes ago, adyj1 said:

And I'd go so far as to say I can't see why theoretically even a leaning pier of Pisa would have any affect on PA - I would expect it to only limit  the maximum travel in one direction, not adjustment travel for PA. 

However from SGL discussions I have observed so far,  I understand there to be  three EQ pier levelling Belief Systems; 

 

...and you then go on to list 4 points ?. “What did the Romans’ do for us” !

I too found it difficult to visualise at first that a non-level pier would not affect PA. The scientist in me was bothered by this, so in Heath-Robinson tradition I constructed a quick and dirty “model” out of scraps of card/paper and pencils to help get my head around it. After playing with this for a short while it became very clear to me that PA was unaffected by a non-level pier. 

That said, when I built my pier I tried to get it as level as I could because I’m a bit OCD and it would have niggled me if I didn’t! ?. 

[Ibbo!]

I think there is some confusion between PA and cone error.

[adyj1]

10 minutes ago, Astrokev said:

..and you then go on to list 4 points ?. “What did the Romans’ do for us” !

Oops - I did originally have 3... It must be the wine. Or the roads. ? (reference to Monty Python Romans quote for the uninitiated ?). 

I'll change the original post, so it makes sense... 

And chalk you up as a type 4 EQ Pier believer ☺ 

Ady

[Scott]

I don't believe leveling is in any way necessary to find polaris. However (there's always a however  ), taken to the extreme, if your pier is at an angle of 45 degrees, gravity, wind are more likely to induce a bouncing effect. When this is negligible, Iv'e no idea. 
The way I looked at it when building my pier was "it's just as easy to put it in level than not" so why do it any other way? 

[JamesF]

The mk2 Mesu 200 pier isn't even remotely level

James

[adyj1]

45 minutes ago, Scott said:

The way I looked at it when building my pier was "it's just as easy to put it in level than not" so why do it any other way? 

In my made-up order of beliefs, a type 3 would level roughly by eye and a type 4 would put the extra effort into using a spirit level... 

A radical type 3 would try 45 degrees just for kicks ? 

?

[JamesF]

Just now, adyj1 said:

A radical type 3 would try 45 degrees just for kicks ?

I very seriously considered having an angled top to my piers specifically to move the alt adjusters on Skywatcher and similar mounts into ranges that made them less likely to suffer from the loadings that cause bendy bolts.

James

[JamesF]

In fact, that's basically what an EQ wedge is, isn't it?

James

[LongJohn54]

5 minutes ago, adyj1 said:

In my made-up order of beliefs, a type 3 would level roughly by eye and a type 4 would put the extra effort into using a spirit level... 

A radical type 3 would try 45 degrees just for kicks ? 

?

Type 5? There's level and there's engineering level.  ?

 

[JamesF]

Does type 5 also account for any distortions to local "level" on account of nearby mountain ranges?

James

[adyj1]

1 hour ago, LongJohn54 said:

Type 5? There's level and there's engineering level

You're covered; Radical fundamentalist Type 1.

[adyj1]

1 hour ago, JamesF said:

I very seriously considered having an angled top to my piers specifically to move the alt adjusters on Skywatcher and similar mounts into ranges that made them less likely to suffer from the loadings that cause bendy bolts.

James

Orthodox Type 3 ☺ 

[Astrokev]

As I mentioned, I made sure the pier was vertical (for aesthetics). The level top is achieved by adjustment of the 4 bolts attaching a top aluminium plate to the pier. I used a spirit level to get this as accurate as this method allows. 

On a more practical note, having a level mount probably makes polar alignment quicker, since this allows adjustment of the position of Polaris, through the polar scope, in azimuth and altitude to be done completely independently. If the mount is not level, an adjustment of azimuth will also give a small shift in altitude, and vice versa, requiring continuous adjustment in both axes to complete PA. 

[Astrokev]

2 hours ago, Ibbo! said:

I think there is some confusion between PA and cone error.

Interesting. Why do you say that? 

 

[adyj1]

6 minutes ago, Astrokev said:

On a more practical note, having a level mount probably makes polar alignment quicker, since this allows adjustment of the position of Polaris, through the polar scope, in azimuth and altitude to be done completely independently. If the mount is not level, an adjustment of azimuth will also give a small shift in altitude, and vice versa, requiring continuous adjustment in both axes to complete PA. 

That is a good point, and a good reason to level an EQ mount - to more easily achieve PA. 

Well put. 

 

[Astrokev]

18 minutes ago, adyj1 said:

That is a good point, and a good reason to level an EQ mount - to more easily achieve PA. 

Well put. 

 

Yep, but I have no idea what belief type that is, maybe 6

[Ibbo!]

46 minutes ago, Astrokev said:

Interesting. Why do you say that? 

 

Regarding the meridian flip, if you have cone error the scope will not point in the same spot in the sky after the flip, but you are still polar aligned.I think thats why you do the 3rd goto alinment star on the other side of the mount so it can try to copenstae for that cone error.

 

My NJP tripod does not have any levelers and the polar scope on that is great (in fact on it's first trip to Keilder I had to put concrete flag under the north leg as the mount would not go high enough  - now machined to fix) its pier was checked with a level to be vertical but I did not bother to check the top for level.

 

[adyj1]

1 hour ago, Astrokev said:

Yep, but I have no idea what belief type that is, maybe 6

Well, the belief is to do whether you think you need a level pier for good polar alignment and tracking. If you are only aligning for ease not need, then I suggest type 3. Otherwise, type 1 or 2. (You have the advantage of being able to choose either belief without compromising your morals ?) 

[Swoop1]

14 hours ago, adyj1 said:

And I'd go so far as to say I can't see why theoretically even a leaning pier of Pisa would have any affect on PA - I would expect it to only limit  the maximum travel in one direction, not adjustment travel for PA. 

However from SGL discussions I have observed so far,  I understand there to be  four EQ pier levelling Belief Systems; 1. Pier levelling is critical in both axes,  2. Pier levelling East/West is critical, 3. Pier levelling is not critical in either axes, and 4. "I don't think belief 1 (or 2) should matter, but I'm going to do it anyway just in case they turn out to be right" ?

IMHO, each of these beliefs is respectful of the other (in the main ? ), but none can be easily convinced otherwise by theoretical argument. In other words, we all agree to differ. 

(Which is surprising, given we all believe in the scientific method, but nevertheless this has been my observation) 

For what it's worth... 

Ady

 

Don't forget the other 2 reasons for ensuring criticality in levelling a pier (or anything else for that matter)-

1) Significant other has an eye for level that would put Stanley Laser to shame and would keep bugging you that your pier isn't level.

2) You have an eye for level that would put Stanley Laser to shame and wouldn't be able to sleep or relax in the obsy until you knew it was perfect.

[spillage]

You definitely do not need your mount level and as polaris is a fixed point and the earth is round it technically will never be level. They only thing that having your mount level will help with is the adjustment of PA and this just helps a little. I can only guess that if you set up every session then PA would be quicker (by a few seconds) knowing the exact way polaris will move in the scope when making your adjustments.

At the same time I do not want to look at my mount and see that it's not level but I do have a permanent set up.

That being said if you have set your mount using a lazer level you might just need to invest in a seismic detector just in case you have some ground movement. You can then go back and readjust for this movement to keep things nice and as they should be..

[Astrokev]

10 hours ago, adyj1 said:

Well, the belief is to do whether you think you need a level pier for good polar alignment and tracking. If you are only aligning for ease not need, then I suggest type 3. Otherwise, type 1 or 2. (You have the advantage of being able to choose either belief without compromising your morals ?) 

I am a Type 3

[souls33k3r]

Great discussion and lots to think about. Cheers guys.

One question though, does the base plate of the the pier have to be flush with the concrete when putting it in? 

Also thinking about eliminating vibrations, i see some fins are placed around the pier. Do they have to be in a right angle triangle (figure 1) or can they be a right angle rectangle (figure 2)?

 

[ollypenrice]

Here's a levelling thought experiment: precisely polar align your mount on a perfectly level pier. Now run a tight fitting steel shaft through the RA axis and bolted at one end to the floor and at the other to the obsy wall. It will get in the way but this is a thought experiment! ) Your PA is now absolutely fixed by that shaft, agreed? Nothing can can move it. Now unbolt your pier from the floor and loosen the alt-az adjusters on the mount. You can point the pier wherever you like. It can slope forwards, backwards and sideways without in any way affecting your PA.

For the more practically minded, this is a very expensive Takahashi tripod for their equatorial mounts. Notice anything missing?

Olly

 

[adyj1]

5 minutes ago, ollypenrice said:

Here's a levelling thought experiment: precisely polar align your mount on a perfectly level pier. Now run a tight fitting steel shaft through the RA axis and bolted at one end to the floor and at the other to the obsy wall. It will get in the way but this is a thought experiment! ) Your PA is now absolutely fixed by that shaft, agreed? Nothing can can move it. Now unbolt your pier from the floor and loosen the alt-az adjusters on the mount. You can point the pier wherever you like. It can slope forwards, backwards and sideways without in any way affecting your PA

Olly, you type 3 evangelist, you... ? 

That's the best and easiest to understand description of it so far. ✅ 

( I didn't find the shaft got in the way much, but I think that's because I don't have an obsy ? ?) 

Ady 

[adyj1]

10 minutes ago, ollypenrice said:

For the more practically minded, this is a very expensive Takahashi tripod for their equatorial mounts. Notice anything missing?

I hate to be the bearer of bad news, but some tea leaf has had off with your OTA. ? 

I reckon it was a lucky escape, personally. If you've got a tripod where the legs don't adjust how are you going to sell it to a type 1/2???

(I'll get me coat ?) 

 

Ady