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Polar Align iPhone app


johnrt
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I'm on an app roll this morning, as I just posted about the Dark Sky meter app I thought I'd also do a quick post about the polar align app I've been using for a while.

George Varros has developed the app and very useful it is too, it uses the GPS in your phone to find your location and gives you an accurate position for the Polaris hour angle.

IMG_1957.png

You can also use your camera and the app will impose the display on to the screen so you can hold up the phone to your polar alignment scope and position polaris in a live view mode, however this is very tricky to do without some kind of holder to place your phone in.

I've been using this for a while and have found it a valuable little tool to have in my pocket, accurate and quick. I recommend you download it for yourself!

http://www.gvarros.c...lign_iphone.htm

Edited by johnrt
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I just set the RA setting circles to midnight on 1st November, then rotate the polar scope reticle until the Polaris marker is directly below the NCP (Polaris being directly above the NCP at that time, and the polarscope inverting the view). I usually do this during the day, and use some local vertical to make sure the two points are vertically aligned.

Doing it for the current time and date seems far more tricky and error-prone to me.

James

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Hi James,

I'm not sure about using setting circles, I don't use them or know how to use them. I simply use the position of polaris on the display to position in my polar scope and that does me for 10 minute + subs at 900mm focal length. I try to keep it as simple as I can.

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I just set the RA setting circles to midnight on 1st November, then rotate the polar scope reticle until the Polaris marker is directly below the NCP (Polaris being directly above the NCP at that time, and the polarscope inverting the view). I usually do this during the day, and use some local vertical to make sure the two points are vertically aligned.

Doing it for the current time and date seems far more tricky and error-prone to me.

James

So why do you use that particular date and time exactly James? :)

The app does look good, just wondering how accurate you can be to getting the exact Hour Angle just by eye.

The polar scope on my EQ3-2 doesn't have any markers or dial marks on it, unless the polar scope is more detailed on say an HEQ5 or EQ6?

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So why do you use that particular date and time exactly James? :)

Because Polaris should be due south of the North Celestial Pole on that date and time. Because the polar scope inverts its image, the Polaris marker should therefore be directly below the NCP marker when the RA circles are set to that time and date. So, to align the reticle in my polar scope I set that time and date on the setting circles, align the NCP marker with something like the edge of a door or building and turn the reticle so the Polaris marker is also aligned with the same reference vertical, below the NCP. Job done.

I prefer this method because it doesn't rely on estimating when the Polaris indicator is in the same relative position as appears on a diagram or image on-screen, which always struck me as quite error-prone.

I'd certainly say "use the method that works for you", but someone suggested this method some time back and I've always been very happy with it. My main goal at the time was to get accurate enough alignment of my EQ3-2 to keep a planetary image on my SPC900 sensor for half an hour to an hour at focal lengths exceeding four metres. It can certainly achieve that.

James

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Oh, it's fair to say that there's no substitute for drift aligning if you want real accuracy.

And case there's any doubt I should perhaps also point out that having set the alignment of the reticle in the manner above I start my observing session by rotating the RA axis so the setting circles read the current date and (GMT) time and adjust the alt and az adjusters to get Polaris in the correct position in the reticle.

James

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Yeah I think I can see how that works for you, so basically you're using a known exact date to position your reticule at the bottom, combined with the accuracy of a physical straight edge.

Hmm I think I might have to try this for myself the next clear night :)

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James I am with you on this. i find the setting circles more accurate because its so hard to positively align polaris using a clock face approach when you are couching down and perring up a polar scope in the dark. The HA method is also a method to use with the cr les but I find the HEQ5 RA circle is not relaible enough as it tends to stick when you are rotating the mount for the HA method.

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Great find - thanks for posting :cool:

What view setting should I use for an EQ6 polar scope?

Polar scopes give an upside down view too, so unless I'm mistaken, your view should be exactly the same as the picture in the first post above (Inverted I think). If it's the wrong way round, polaris will be bottom left when it should appear bottom right. My EQ3 mount should be the same as your EQ6 I should think and my view is like the picture above.

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Thanks johnrt. I have just download that Polar Align app. Down here in the southern hemisphere it is a struggle (at least for me) to track down Sigma Octans. The southern aspect from my house is the one direction where I have the worst light pollution and the southern pole star is only a dim wee thing.

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