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About the 45-degree angle of some alt-az mounts...

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#1 dennilfloss

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Posted 20 March 2013 - 03:39 PM

Newb question here. :o

It just dawned on me that the latitude of my location (Ottawa, Canada) is 45.42 degrees. Does that mean I would have to use the altitude knob of, for example, an Astrotech Voyager mount with its altitude arm set to 45 degrees much less and basically have to do mostly azimuthal adjustments with the occasional minor altitude adjustment when tracking an object for visual use? Or am I seeing/guessing too much in a mere coincidence?

http://www.cloudynig...hp?item_id=1922

Thanks in advance. :)

Denis

#2 Gordon Rayner

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Posted 20 March 2013 - 03:58 PM

That is a coincidence which will not have the behavior for which you were hoping.

Add Stellarium dot org to your computer. They have optional coordinates of several types which one can choose. Watch the path of an object as you fast forward or backward. And/or read the altaz coordinates as they change rapidly during a fast forward/backward.

#3 dennilfloss

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Posted 20 March 2013 - 04:16 PM

Thanks for the input. :)

I should have concluded as much just from seeing celestial objects climb higher above the horizon with time and not stay at the same altitude. Got confused by a Sky & Telescope review of this mount at Astronomics mentioning what follows:

"Using the arm in an angled position also reduces the amount of declination drift for many observers when tracking celestial objects. Following objects across the sky becomes primarily a matter of turning the azimuth slow motion control, with only an occasional tweak of the altitude knob needed to keep an object centered in declination."



https://www.astronom...unt_p15058.aspx

Thought this might have the same effect as placing my wedgepod fork at the 45-degree setting when I had my Celestar 8 and the geared drive was enough to keep an object in the field of view. Now I realize the mount rotational axes remain horizontal and vertical in an alt-az mount rather than being inclined and that's why I'll have to use both knobs.

Already have Stellarium installed. :)

#4 Gordon Rayner

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Posted 20 March 2013 - 11:50 PM

That review is misleading. Will the reviewer please step forward to clarify/rewrite/ delete what seems to be either a misconception or poor writing?
Am I missing something?

Perhaps they thought that the azimuth axis could be tilted, instead of pointing at the Zenith.
Via lengthening one tripod leg, if one lives at a high lattitude? Low lattitude implies tripod tipover, when the center of gravity becomes outside a line connecting the tips of the two rear legs.

#5 Mark9473

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Posted 21 March 2013 - 03:59 AM

If the azimuth motion is at the bottom of the mount / top of the tripod then obviously this isn't going to work like Gordon said. But if you could rig up some rotation device at the top of the mount arm, and point the mount arm to Polaris, then you effectively have an equatorial mount.






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