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Polar alignment and leveling the tripod question

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#1 archer1960

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Posted 22 December 2012 - 07:49 PM

I had always been under the impression that leveling a tripod (and therefore the mount) was *necessary* for good tracking. Now I saw a post on another forum that said all leveling did was to make polar alignment easier, but that once an alignment was achieved, tracking accuracy was not dependent on the mount being level, only on the quality of the alignment.

Which is correct? It seems intuitive to me that the mount would need to be level to track properly, but I've been known to be wrong before...

Note that I'm not asking about guiding, nor am I referring to the accuracy of a goto, only about simply tracking an object in RA once I have it where I want it in the FOV.

#2 andysea

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Posted 22 December 2012 - 08:18 PM

Leveling the mount isn't really necessary unless you drift align. In which case you must be as accurately level as possible so that the adjustments in AZ and ALT won't affect each other.
If you use a polar scope you don't need to be level at all. You just want your RA axis to be lined up with the celestial pole that's all.
That's a general rule, however the particular design of some polar scopes might need the mount to be level. I just don't know.
With my Tak mount I could have the tripod on a slope, polar align with the polarscope, and everything will work fine. Same for the AP which uses the Losmandy polarscope - The new AP right angle polar scope is a whole different story.
I don't see how tracking would be affected by the mount not being level. Unless the tripod was so far off that the center of gravity of the setup was off enough to throw the whole system off but at the point the mount would probably tip over.

#3 archer1960

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Posted 22 December 2012 - 08:27 PM

Thanks for the comments. I use a polar scope on my LXD-55, but I've replaced the original tripod with an old Meade standard field tripod that is incredibly sturdy, but which does not have height-adjustable legs, so leveling is a pain (I use carpenter's wedges under each leg) and I'm trying to figure out if I can get by without it.

#4 andysea

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Posted 22 December 2012 - 08:31 PM

I am not familiar with he LXD55 polar scope but most likely you will just need to be close to level for maximum stability but not for polar aligning.
That's my 2c anyway:)

Andy

#5 Hikari

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Posted 22 December 2012 - 08:32 PM

+1

All that matters is the RA axis is aligned to the poles. What the relative position of the mount is is irrelevant--you can have it upsidedown if you want to.

#6 archer1960

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Posted 22 December 2012 - 08:35 PM

Thanks! I'm talking only an inch or less difference in leg height off of being level, so tipping over is no danger (at least no more than if it were perfectly level).

#7 andysea

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Posted 22 December 2012 - 11:57 PM

Yeah you will be fine. Just remember to level the mount if you want to drift align.

#8 TxStars

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Posted 24 December 2012 - 04:43 AM

The mount does not need to be leveled for polar alignment or drift aligning.
It is all comes down to practice.
After you use your equipment enough you will be able to polar align durring the day with only the sun. :smirk:

#9 roscoe

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Posted 24 December 2012 - 08:08 AM

I agree, not important. As long as your RA axis is pointed true North, you're aligned. The little bubble levels installed on many mounts aren't all that accurate, and seem to be placed there so they look more 'techno', which makes those of us with OCD happy, and so makers can charge an extra $20 for their product......
Surveyors, who take the concept of level to a whole nother dimension, don't ever level their tripods, depending on the transit mount for that.
Russ

#10 astroRoy

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Posted 24 December 2012 - 08:22 AM

Myself, I find that cone error is far more important to eliminate than anything else. Gotos are far more accurate when going from the west side to the east side or visa versa. Having said that, I do believe that a level mount helps in that regard as well. The more accurate the starting point, the easier everything else will be. Not to take away from what others have said, Many mounts have built-in bubble levels, and if yours doesn't, bubble levels are cheap and easy to use. Why not start as accurately as possible.? It certainly helps with initial alignment.

Roy

#11 andysea

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Posted 24 December 2012 - 08:57 AM

The mount does not need to be leveled for polar alignment or drift aligning.
It is all comes down to practice.
After you use your equipment enough you will be able to polar align durring the day with only the sun. :smirk:


How do you accurately drift align if the mount is not level? I always thought that with a non leveled mount any adjustment in AZ would undesirably affect Alt and vice versa.

Andy

#12 rmollise

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Posted 24 December 2012 - 09:40 AM

Leveling is not necessary for polar alignment or for good tracking. It has no effect on the latter, and while it can make some polar alignment methods easier to do, it is most assuredly not necessary. ;)

#13 rmollise

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Posted 24 December 2012 - 09:42 AM


How do you accurately drift align if the mount is not level? I always thought that with a non leveled mount any adjustment in AZ would undesirably affect Alt and vice versa.

Andy


If you are not level, you might have to do a couple of additional iterations while drifting (check the Meridian star one last time after you have done the horizon star), but that is it.

#14 archer1960

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Posted 24 December 2012 - 10:37 AM


...

Many mounts have built-in bubble levels, and if yours doesn't, bubble levels are cheap and easy to use. Why not start as accurately as possible.? It certainly helps with initial alignment.

Roy


I just use a 6" spirit level to level my rig, but leveling my tripod with non-adjustable legs is a royal PITA, and if I don't have to, it will probably faster overall. I'll just be trading off time not spent leveling for some extra time needed for a polar alignment of a non-level tripod.

#15 psandelle

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Posted 24 December 2012 - 11:30 AM

I find that when I hang pictures from my mount, leveling makes them look better...er, wait - forget that.

My darksite is a trailhead parking lot which slopes quite a bit; the reason I level is I like things to be as reproducible as possible. I'm a creature of habit, and if the cables are in the same place and the OTA is at the same spot on the dovetail and the mount is leveled the same way, etc., I can set up quicker and with less thinking. Less thinking is good for me. Zero thinking would be best, but that's gonna have to wait for the observatory.

I'd say if your tripod is a PITA (royal, or otherwise), then don't sweat it.

Paul

#16 andysea

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Posted 24 December 2012 - 12:33 PM

[/quote]
If you are not level, you might have to do a couple of additional iterations while drifting (check the Meridian star one last time after you have done the horizon star), but that is it. [/quote]

Ah that's good to know if I ever want to drift align since my Tak tripod is not adjustable:)






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