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Wedge Angle and Latitude

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#1 deansjc

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Posted 10 February 2019 - 07:36 PM

This is a basic question.  Having just built an equatorial wedge - styled after the Celestron brand - I am stumped as to what angle to set the wedge to.  My latitude is 43 degrees North.

 

(Reading manuals for both of Celestron's and Meade's fine wedges has not advanced the cause, as I am unsure as to whether their wedge-mounted scales manage the (rather simple) calculation already.  I have read in some placed that they do, others that they do not.)

 

So, trusting that this image illustrates the angle(s) in question (where x+y=90 degrees) what is the the value of x and y?

 

                                                         /

                                                        /

                                                       /

North <<<<<<<<<<<<   ____x___/_y_________

 

(For greater clarity, the same angle is seen in the Celestron wedge manual with a slight clockwise rotation of the image.)

 

Thank you CN members!

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#2 Jim Waters

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Posted 10 February 2019 - 08:02 PM

X+Y = 180

 

Really don't understand the problem.  Set your wedge to 43 degrees.

https://www.google.c...055924009904437

 

https://www.sears.co...FCABEgIH1PD_BwE

 

https://www.amazon.c...aps,182&sr=8-17



#3 Garyth64

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Posted 10 February 2019 - 08:07 PM

If your latitude is 43 degrees, then Polaris is 43 degrees above the horizon.  The part of your wedge should point to the celestial equator  That angle is 47 degrees.

 

As Jim said x + y = 180, not 90.

 

In your drawing, y = 47 degrees, x = 133 degrees.   133 - 90 = 43.

 

When you put your scope on it with the forks, then you have your polar axis, and it should point to Polaris.

 

 

degrees.jpg

 

-picture worth a thousand words.  (maybe)  smile.gif


Edited by Garyth64, 10 February 2019 - 08:35 PM.

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#4 deansjc

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Posted 10 February 2019 - 08:37 PM

Indeed, a picture is worth a thousand words.  Thank you Gary.  

 

Yes of course, x+y = 180 and not 90.  A  complete blunder on my part blush.gif

 

Thanks also Jim, but the question was which angle was 43 degrees, and by deduction, which was 47 degrees.  If you look on various boards, you see both - and of course only one is correct.

 

'Cheers.


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#5 msl615

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Posted 10 February 2019 - 09:17 PM

The confusion comes from the wedge angle you would need to build (on the right in the above well drawn image), which would be 47 degrees, to brace up the mount in order for it to be pointing at 43 degrees above the horizon  to the left. 

 

Let's expand the issue where 43 and 47 are not so close to each other.

 

I live at 65 degrees north in Fairbanks.  Polaris is 65 degrees above the horizon. To build a wedge on the backside of a mount, it would need to be 90-65 = 25 degrees.  Using the above drawing, I would need to build a wedge on the right side that is 25 degrees, in order to push the mount 25 degree to the left, which in this case, would put it at 65 degrees above the horizon.

 

 I have  GEM mounted on a permanent pier and polar aligned. Looking at it from the side, it is pointed up 65 degrees above horizontal towards polaris...but on the other size, it is only 25 degrees above horizontal.

 

Maybe think of a right triangle sitting on the table in front of you, with one arm to the right on the table and the other pointed straight up.  To tilt the upper arm 25 degrees to the left (and reach my 65 degrees north, the table arm on the right would need to move up 25 degrees.

 

I hope this helps.

 

Mike



#6 Earthbound1

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Posted 10 February 2019 - 10:42 PM

Since you built this, does it have a bubble level on it's base? That way you'll be able to get as close as you can to perfect alignment with polaris if you're in the Northern hemisphere.

Edited by Earthbound1, 10 February 2019 - 10:46 PM.


#7 deansjc

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Posted 10 February 2019 - 11:02 PM

Thank you for the additional comments.

 

Mike, yes being located close to 45 degrees North does illustrate the approach further.  In your scenario, you present a much higher latitude but the angle depicted originally as "x" is that latitude, and the "build-up" of the wedge as you describe it is 90 degrees less Fairbanks' 25 degrees for 65 degrees. That is the "y" value.  

 

As to a bubble level, yes.  One will be either in or on the base of the wedge.  

 

I will likely post my finished product when it's dressed up a bit.  It includes azimuth adjustment of +/- 5 degrees which should be sufficient for fine tuning, and an adjustable altitude range from 35 degrees to 60 degrees.  I was a fun build.  Now to practise using Mike Swanson's many alignment tips.  I don't think there is any path clearing required here, just practise.


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