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Leveling your mount, yes or no

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#1 Sacred Heart

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Posted 08 May 2021 - 09:39 PM

This is just a general question relating to goto motorized mounts.   Some say level does not matter for polar aligning or pointing.  I can see if the front leg of the pier / tripod is high or low but not the east or west leg.   How does the altitude and azimuth adjustment compensate for that??

 

I try to level all of my mounts,  as true as i can.

 

Just asking,  Joe



#2 jdupton

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Posted 08 May 2021 - 09:53 PM

Joe,

 

   You will find your answers in the following thread:

 

CN Thread: "Leveling a mount doesn't matter."

https://www.cloudynights.com/topic/768221-leveling-a-mount-doesnt-matter/

 

   I mostly agree with you. There are reasons to level the mount as it makes attaining polar alignment a little easier with less need for iterative movements. There is no need to go crazy with it though.

 

 

John



#3 martym

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Posted 08 May 2021 - 10:01 PM

Better to level, not difficult.



#4 Sacred Heart

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Posted 08 May 2021 - 10:13 PM

Joe,

 

   You will find your answers in the following thread:

 

CN Thread: "Leveling a mount doesn't matter."

https://www.cloudynights.com/topic/768221-leveling-a-mount-doesnt-matter/

 

   I mostly agree with you. There are reasons to level the mount as it makes attaining polar alignment a little easier with less need for iterative movements. There is no need to go crazy with it though.

 

 

John

 

 

Better to level, not difficult.

I'm with you guys,  I will level it,  not that time consuming or hard.  I don't spend all day doing it either,  get it as close as my eyes and level lets me.  One has a circle bubble level the other mount I use a contractors T level.  All are on the mount base.

                           Thanks,   Joe


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#5 rhart426

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Posted 08 May 2021 - 10:44 PM

After you have a mount get blown over with the telescope still attached, leveling the mount starts to look attractive for other reasons.


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#6 TOMDEY

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Posted 08 May 2021 - 10:48 PM

Most setups based on two (or more) star sightings are smart enough to back-solve for the non-level of your mount and correct for that so it's transparent to you, the user. For those of a mathematical bent, it relates to a nautical mile being equivalent to an arc-minute around the earth's curvature. So if, for example, you have your pier leaning NE by a degree... that's like being located sixty miles to the NE of your observatory. Nearly all algorithms take that into account --- so you don't need to fret over the arcane technicalities. And the iterative head-tweaks to attain level are almost entirely immune from nonlinearities because the adjustment errors are cosinusoidal --- so even being a whopping 5 degrees off level to start with still predicts a 99.6% correct 1st tweak because 1-cos(5o) = 0.996. Stuff like that keeps us from getting into trouble, even being lackadaisical/slipshod in setting up and using our mounts will still work like a charm.

 

I analyzed all this stuff decades ago in a white-paper entitled "Mathematical Reduction of Systematic Errors in Telescope Pointing". Couple pages of that stuff >>> Glad I don't have to derive all that again!    Tom

Attached Thumbnails

  • 123 couple of pages from Tom's white-paper on telescope pointing.jpg

Edited by TOMDEY, 08 May 2021 - 10:50 PM.

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#7 Brainebula

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Posted 09 May 2021 - 12:08 AM

I sure would love to see pp 1 to 25 too!



#8 NGC 2419

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Posted 09 May 2021 - 12:27 AM

After you have a mount get blown over with the telescope still attached, leveling the mount starts to look attractive for other reasons.


Unless it is ridiculously out of level, being level is probably the least of your worries when it's windy. Balance and cross section have way more influence on stability in the wind.

#9 robbieg147

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Posted 09 May 2021 - 04:54 AM

I would put it the other way is there any reason not to spend a couple of minutes levelling your mount when you are going to spend hours taking subs?



#10 NGC 2419

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Posted 09 May 2021 - 06:11 AM

I would put it the other way is there any reason not to spend a couple of minutes levelling your mount when you are going to spend hours taking subs?


Yes, because it is unnecessary and makes no difference once you are polar aligned.
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#11 Jarno

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Posted 09 May 2021 - 06:12 AM

Leveling a mount has precisely zero effect on the goto and tracking accuracy of a GEM. Consider this thought experiment: you have a mount that's perfectly polar aligned and with the tripod perfectly level. Now you place the RA axis in a clamp and remove the floor so that the tripod can swing freely in the east-west and north-south directions. Will that change anything? No, because the mount head is still aligned with the motion of the sky. Conclusion: once you have done the polar alignment and the mounts coordinate system is aligned with the celestial coordinate system, the orientation of the tripod underneath the mount head is no longer a factor. You could have the mount suspended upside down from the ceiling and it'll still work. Of course having the tripod level will make it slightly easier to polar align but that's all. I approximately level my tripod for convenience's sake but don't fuss about it.

 

Of course the above only applies to a GEM or fork-mounted scopes on a wedge. An alt-az mount will most definitely benefit from being level.

 

Jarno


Edited by Jarno, 09 May 2021 - 06:13 AM.

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#12 Sacred Heart

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Posted 09 May 2021 - 06:32 AM

After you have a mount get blown over with the telescope still attached, leveling the mount starts to look attractive for other reasons.

Ouch!!!  I bet that hurt.   Joe



#13 Sacred Heart

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Posted 09 May 2021 - 06:52 AM

Most setups based on two (or more) star sightings are smart enough to back-solve for the non-level of your mount and correct for that so it's transparent to you, the user. For those of a mathematical bent, it relates to a nautical mile being equivalent to an arc-minute around the earth's curvature. So if, for example, you have your pier leaning NE by a degree... that's like being located sixty miles to the NE of your observatory. Nearly all algorithms take that into account --- so you don't need to fret over the arcane technicalities. And the iterative head-tweaks to attain level are almost entirely immune from nonlinearities because the adjustment errors are cosinusoidal --- so even being a whopping 5 degrees off level to start with still predicts a 99.6% correct 1st tweak because 1-cos(5o) = 0.996. Stuff like that keeps us from getting into trouble, even being lackadaisical/slipshod in setting up and using our mounts will still work like a charm.

 

I analyzed all this stuff decades ago in a white-paper entitled "Mathematical Reduction of Systematic Errors in Telescope Pointing". Couple pages of that stuff >>> Glad I don't have to derive all that again!    Tom

 

 

Leveling a mount has precisely zero effect on the goto and tracking accuracy of a GEM. Consider this thought experiment: you have a mount that's perfectly polar aligned and with the tripod perfectly level. Now you place the RA axis in a clamp and remove the floor so that the tripod can swing freely in the east-west and north-south directions. Will that change anything? No, because the mount head is still aligned with the motion of the sky. Conclusion: once you have done the polar alignment and the mounts coordinate system is aligned with the celestial coordinate system, the orientation of the tripod underneath the mount head is no longer a factor. You could have the mount suspended upside down from the ceiling and it'll still work. Of course having the tripod level will make it slightly easier to polar align but that's all. I approximately level my tripod for convenience's sake but don't fuss about it.

 

Of course the above only applies to a GEM or fork-mounted scopes on a wedge. An alt-az mount will most definitely benefit from being level.

 

Jarno

 

 

Yes, because it is unnecessary and makes no difference once you are polar aligned.

Tom, Jarno and NGC 2419,   This may be true,  and I will try it with my ME  being I just shortened my pier.  I cannot be out too far, I have only about 15 degrees of east west movement to pull it back in.   But even if it works I will level the mount,  I just feel better with it level.  

 

Just one more question for you guys,  with the tripod not level,  and your mount knowing its limits for when to flip during a go to, horizontal is not horizontal anymore.  It is 90 degrees plus how much you are out of level and would that not affect your balance as a total unit for stability or possibly slewing / tracking into itself??

 

             Joe


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#14 TOMDEY

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Posted 09 May 2021 - 09:24 AM

I sure would love to see pp 1 to 25 too!

Heh --- pp. 28-42 and three appendices are also engaging!

Here's page 17 where I was just picking up a head of steam deriving my equn #8 etc. My greatest fear was that the inherently non-linear relationships would not be sufficiently-linearizable to allow reliable damped least-square convergence. I took on the project for credit at school, so considerations like that matter, where the entire thesis would collapse to naught if the math got intractably out of hand or beyond my (or anyone else's) ability to handle the arcane complexities. But it all worked out and I earned that degree. I later went on to immerse on some of the Mt. Hopkins Six-Shooter analysis that was running in parallel with mine (and without my knowing it!) and even later the similar software that percolates in the Leica Laser Tracker routines. So we collaborated. The lesson in all this is that somewhere, somebodies are deriving all the math that percolates in our canned software and firmware. I also worked geodesy, astrometry, and GPS. Sure glad I decided to get the math degree!    Tom

 

Therefore --- leveling the mount doesn't matter much.    Tom

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  • 123 page 17 from Tom's white-paper on telescope pointing.jpg

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#15 TOMDEY

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Posted 09 May 2021 - 09:44 AM

Tom, Jarno and NGC 2419,   This may be true,  and I will try it with my ME  being I just shortened my pier.  I cannot be out too far, I have only about 15 degrees of east west movement to pull it back in.   But even if it works I will level the mount,  I just feel better with it level.  

 

Just one more question for you guys,  with the tripod not level,  and your mount knowing its limits for when to flip during a go to, horizontal is not horizontal anymore.  It is 90 degrees plus how much you are out of level and would that not affect your balance as a total unit for stability or possibly slewing / tracking into itself??

 

             Joe

Hi Joe!

 

Leveled is not necessary --- but best practice, regardless, and most everyone establishes that first, before doing anything else.

 

The non-plumb condition should not affect dead-reckoning GoTo or balance at all. The optimal ~when to flip~ toggle would be affected a bit, but there is (should be) plenty of safety margin built into that routine aka you won't be close to crashing anything. The flip-time is advanced or retarded from nominal by no more than four minutes per degree of E-W leaning of the pier.    Tom


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#16 NGC 2419

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Posted 09 May 2021 - 09:56 AM

...
Just one more question for you guys, with the tripod not level, and your mount knowing its limits for when to flip during a go to, horizontal is not horizontal anymore. It is 90 degrees plus how much you are out of level and would that not affect your balance as a total unit for stability or possibly slewing / tracking into itself??

Joe


I think one of the problems with these threads is that nobody ever talks about degree of levelness.

I don't go out and setup my tripod 10° askew on purpose, I eyeball it. It is pretty easy to judge if something is within a degree or so of level.

The poster above suggested that your telescope could be blown over if it was out of level, which is absurd as long you at least eyeball it when you set it up. If a degree or so from level is enough that your scope blows over in the wind, then it was just too windy and you were asking for trouble to begin with.

So to answer your question, no, having my tripod not perfectly level has never interfered with my slewing, tracking, balance, or stability. Nor has it ever caused my mount to get tipped over by the wind.
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#17 Sacred Heart

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Posted 09 May 2021 - 10:43 AM

Hi Joe!

 

Leveled is not necessary --- but best practice, regardless, and most everyone establishes that first, before doing anything else.

 

The non-plumb condition should not affect dead-reckoning GoTo or balance at all. The optimal ~when to flip~ toggle would be affected a bit, but there is (should be) plenty of safety margin built into that routine aka you won't be close to crashing anything. The flip-time is advanced or retarded from nominal by no more than four minutes per degree of E-W leaning of the pier.    Tom

 

 

I think one of the problems with these threads is that nobody ever talks about degree of levelness.

I don't go out and setup my tripod 10° askew on purpose, I eyeball it. It is pretty easy to judge if something is within a degree or so of level.

The poster above suggested that your telescope could be blown over if it was out of level, which is absurd as long you at least eyeball it when you set it up. If a degree or so from level is enough that your scope blows over in the wind, then it was just too windy and you were asking for trouble to begin with.

So to answer your question, no, having my tripod not perfectly level has never interfered with my slewing, tracking, balance, or stability. Nor has it ever caused my mount to get tipped over by the wind.

Tom and NGC2419,  Yes, if you are within a few degrees,  just about anyone can eyeball level - I think,  you will be fine. As long as you PA every time you move the mount.   You should not be say 5" out of level, that's crazy.

Like I said,  I was just asking,  I know it is a common sense thing.

 

Thanks for all of your answers,   Joe


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#18 teashea

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Posted 09 May 2021 - 08:47 PM

I think it is a good idea.



#19 chanrobi

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Posted 10 May 2021 - 12:02 AM

Ouch!!!  I bet that hurt.   Joe

Hurts more when you realize had nothing to do with levelling



#20 skybsd

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Posted 10 May 2021 - 12:40 AM

This is just a general question relating to goto motorized mounts.   Some say level does not matter for polar aligning or pointing.  I can see if the front leg of the pier / tripod is high or low but not the east or west leg.   How does the altitude and azimuth adjustment compensate for that??

 

I try to level all of my mounts,  as true as i can.

 

Just asking,  Joe

I personally take the time to level the tripods / mounts (GEM + Alt-Az)  for all portable and / or travel set ups.., 

 

skybsd 


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#21 MikeECha

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Posted 10 May 2021 - 06:11 AM

This is just a general question relating to goto motorized mounts.   Some say level does not matter for polar aligning or pointing.  I can see if the front leg of the pier / tripod is high or low but not the east or west leg.   How does the altitude and azimuth adjustment compensate for that??

 

I try to level all of my mounts,  as true as i can.

 

Just asking,  Joe

As a general statement, leveled tripod does not matter for a GEM but it helps speed up your PA. The better the tripod mount base level is, the lesser the influence an adjustment in one axis has on the other axis and therefore smaller numbers of iterations to good PA. And in a smaller degree of importance, the load is better balanced on the tripod. 


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#22 rhart426

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Posted 10 May 2021 - 07:45 AM

Guys, an unlevel system, which is implied to be unbalanced over the center of gravity of the tripod, is going to be less stable than one that is level and balanced, per physics.

 

Will it cause your system to fall over all on its own?  Of course not.  But what if you get a freak unforecasted windstorm, or maybe somebody trips and falls into it the wrong way?

 

My intended point was that, after having my rig fall over once, I pay a lot more attention to making it as stable as possible, including keeping it as close to level as possible.  It's a small part of the equation, but not a negligible one.  I certainly don't think it warranted the tone in some of the replies.


Edited by rhart426, 10 May 2021 - 07:48 AM.

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#23 Jarno

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Posted 11 May 2021 - 06:49 AM

I certainly don't think it warranted the tone in some of the replies.

Welcome to the internet, the place where there'll always be someone who's overreacting...

 

Anyway, if the wind is powerful enough to flip over your rig if it's 5 degrees off horizontal then having it perfectly level isn't going to help either. For all intents and purposes, "eyeball level" will be good enough.

 

Jarno


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#24 Wildetelescope

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Posted 11 May 2021 - 08:54 AM

As a general statement, leveled tripod does not matter for a GEM but it helps speed up your PA. The better the tripod mount base level is, the lesser the influence an adjustment in one axis has on the other axis and therefore smaller numbers of iterations to good PA. And in a smaller degree of importance, the load is better balanced on the tripod. 

This.  It just makes things easier. No need to obsess about it, but making sure your tripod is generally level takes very little effort and makes what follows easier.  Is it strictly necessary, no, but it certainly makes polar alignment less time consuming, so why not?  

 

JMD


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#25 davidmalanick

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Posted 11 May 2021 - 02:18 PM

What else, but leveling your mount, is there to do while waiting for it to get dark?  Double checking everything, + attached to +, - attached to -, wires connected correctly, computer connecting to everything and level the mount.  Takes less then a minute and just makes it easier to adjust PA.


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