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Equipment Discussions >> Mounts

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James Cunningham
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Reged: 08/07/10

Loc: Maryland
Polar scope alignment new
      #4436235 - 03/08/11 10:14 PM

If you can center Polaris in your finder scope and main scope, will it be the same in a polar scope?

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Peter in Reno
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Reged: 07/15/08

Loc: Reno, NV
Re: Polar scope alignment new [Re: James Cunningham]
      #4436273 - 03/08/11 10:28 PM

If you are talking about polar alignment, you want your mount to be pointing to North Celestial Pole, not Polaris. Polaris is about a degree off from true North Celestial Pole. So centering Polaris with finder scope or main scope is not a good idea. Polar scope in mount is a better instrument to line up your mount to true North Celestial Pole.

Good reading material: http://en.wikipedia.org/wiki/Celestial_pole

Peter


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James Cunningham
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Reged: 08/07/10

Loc: Maryland
Re: Polar scope alignment new [Re: Peter in Reno]
      #4436407 - 03/08/11 11:34 PM

So is true north east of Polaris, north of Polaris, south of Polaris or West of Polaris by that one degree?

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Peter in Reno
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Re: Polar scope alignment new [Re: James Cunningham]
      #4436418 - 03/08/11 11:40 PM

I am not exactly sure but if you have a planetarium software, it should tell you. Polaris is always rotating around true NCP because of earth's rotation and orbit around the sun so it depends of time of the year where Polaris is currently at.

Peter


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Peter in Reno
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Re: Polar scope alignment new [Re: Peter in Reno]
      #4436445 - 03/08/11 11:55 PM

Hi Jimmy,

This neat Polar Finder might help you understand better how to find exactly where Polaris is relative to NCP. Just enter your Longitude and it will display what it would look like through a polar scope.

http://myastroimages.com/Polar_FinderScope_by_Jason_Dale/

Click on "Small download (polar204.zip) only 49K." link. Unzip the file and run "PolarFinder".

Peter


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jrcrillyAdministrator
Refractor wienie no more
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Reged: 04/30/03

Loc: NE Ohio
Re: Polar scope alignment new [Re: James Cunningham]
      #4436458 - 03/08/11 11:59 PM

Quote:

So is true north east of Polaris, north of Polaris, south of Polaris or West of Polaris by that one degree?




All are true within any 24 hour period.


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James Cunningham
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Reged: 08/07/10

Loc: Maryland
Re: Polar scope alignment new [Re: Peter in Reno]
      #4436464 - 03/09/11 12:01 AM

Thank you. So, if I get Polaris through the polar scope and move the crosshair just a little bit in the direction of true north, I am better polar aligned.

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Peter in Reno
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Re: Polar scope alignment new [Re: James Cunningham]
      #4436996 - 03/09/11 09:37 AM

Simply screw the polar scope into the mount. Adjust mount's Latitude and Azimuth until Polaris looks exactly like the PolarFinder software. When you rotate the RA axis, Polaris should remain the same distance from the center of crosshairs. In other words the crosshairs should rotate while RA axis is rotating but Polaris should remain at the same spot and same distance from center crosshairs. Once there, that means the center of crosshairs is pointing to true NCP.

Peter


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Steve OK
scholastic sledgehammer


Reged: 09/22/07

Loc: OKC, OK
Re: Polar scope alignment new [Re: James Cunningham]
      #4437025 - 03/09/11 09:52 AM Attachment (25 downloads)

The North Celestial Pole is nearly on the line between Polaris and Kochab (Beta Ursae Minoris), just under 1° from Polaris. If you can easily remove the polar scope from the mount, take a look at the Moon with it. The moon is close to 0.5° across in the sky, so the NCP would be about "two moons" away from Polaris.

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rdandrea
Carpal Tunnel
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Reged: 06/13/10

Loc: Colorado, USA DM59ra
Re: Polar scope alignment new [Re: jrcrilly]
      #4437111 - 03/09/11 10:32 AM

Quote:

Quote:

So is true north east of Polaris, north of Polaris, south of Polaris or West of Polaris by that one degree?




All are true within any 24 hour period.




Actually, any way you go from the North Pole is south.

So true north is north of Polaris


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John Carruthers
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Reged: 02/02/07

Loc: Kent, UK
Re: Polar scope alignment new [Re: James Cunningham]
      #4439061 - 03/10/11 03:33 AM

Hi Jimmy, just to add to the muddy waters, make sure your polar scope is concentric with your mount's polar axis first. I may be already but if it's mis aligned you will be fighting it forever more, see;
http://galacticfool.com/polar-align-eq-mount/

or
http://www.awrtech.co.uk/oddtopic.htm#POLARSCOPE

If you use a planetarium programme to find the time of the highest or lowest point of Polaris you can set north on that, then 6 hours later when it's 'beside' the pole you can set the altitude.


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avarakin
Carpal Tunnel
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Reged: 07/13/09

Loc: Parsippany NJ, USA
Re: Polar scope alignment [Re: John Carruthers]
      #4440968 - 03/10/11 08:33 PM

I agree with Steve OK - the best polar alignment is done using Kokab method - no need for messing with programs, entering time of day ,figuring out if you need to use ST or DT , just look at where Kokab is and make a correction.
Works like a charm

Alex


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