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## Re: leveling a tripod

 Subject: Re: leveling a tripod Paul Schlyter Sun, 30 Apr 2006 09:43:06 GMT sci.astro.amateur
 ```In article , Fred Scharmann wrote: > Since I am new to this all, you are probably right. > > All I know is that if I level my mount and do a polar alignment, chasing > something at 200X is one hell of a lot easier than if I am "almost" level > and do a polar alignment. Maybe the problem of semantics is occurring in > the definition of polar alignment. You and I may be talking about apples > and oranges. Since I am a beginner, my thoughts about polar alignment may > be incorrect and you being experienced, probably actually know what is meant > by polar alignment. > > Whatever the problem, I find your responses to my posts as negative and > non-constructive. If you know more than me, which is very, very possible, > teach me. Don't attack me! Why is leveling so unimportant to you? Because what matters is how well your polar axis is aligned. Nothing else - the levelling is in principle unimportant. How do you align your polar axis? Do you adjust your wedge to your latitude and then align the telescope azimuth to the north? If so, your method of polar alignment is dependent on your levelling, and the reason you find chasing something at 200x a hell more difficult when your scope is only "almost level" is not because it's not quite level, it's because your scope is then not polar aligned properly. Polar alignment only means your polar axis points to the celestial pole - nothing else. So how do you determine whether your scope is polar aligned or not? The traditional method is to turn on the scope drive, then let the scope follow a star near your local meridian. If the star appears to drift northwards or southwards, adjust the azimuth of your polar axis until that drift vanishes. Next, let the scope follow a star near +6 or -6 hours of local hour angle -- i.e. approximately in the east or west. If the star appears to drift northwards or southwards, adjust the inclination of your polar axis until the drift vanishes. Go back and forth between following a star near the meridian and approximately in the east or west, until you're satisfied with your polar axis alignment. This method takes some time, and is therefore most suitable for permanently mounted scopes, but it will give you the most accurate polar alignment. A faster method, which I use myself, is to learn the star field near the celestial pole, or get a good star map of that field, so you easily can see where the celestial pole is in that star field. Note that, due to precession, the celestial pole moves slowly - this should be marked on that chart if you want an accurate polar alignment. Next, set your scope to +90 deg declination and +6 (or -6) hours local hour angle. Look through your finder scope, adjust your polar axis so that the crosshairs of the finder scope points at the celestial pole. Next, turn your scope 12 hours in RA, look through your finderscope again. Most likely, the crosshairs will point somewhere else, and that's because your scope didn't point to precisely 90 deg declination in its mounting. Adjust the scope's declination until the crosshairs of the finder scope points to precisely the same position in the sky no matter how you turn the scope in RA. Now the scope points parallell to the mounting's polar axis, so all you have to do is to adjust its polar axis until the crosshair of the finder points right at the celestial pole. (This method cannot be used near the equator of the Earth). None of these two methods depends on any "levelling" of anything on the scope. Polar alignment is actually independent of levelling, although some methods of polar alignment can be dependent on levelling -- such methods don't give very accurate alignment though. -- ---------------------------------------------------------------- Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN e-mail: pausch at stockholm dot bostream dot se WWW: http://stjarnhimlen.se/ ```
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