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Atlas polar finder scope - please help

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#1 mewmartigan

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Posted 16 June 2009 - 12:58 PM

Hi All,

I have an Atlas EQ-G that I use with the EQMOD software and Starry Night Pro 4.5

I am sitting here thinking about the polar alignment routine and the more I think about it the more confused I get. According to the instructions:

Point the mount at Polaris, look through the polar finder scope and turn the RA axis until Casseopia and the Big Dipper are approximately where they are in the sky. Since Polaris isn't exactly at the CNP, it rotates around the "x" shown in the scope. I then adjust the RA and Dec knobs until Polaris is in the circle shown on the reticle.

Now it was my understanding that once I set the Declination, I wouldn't have to set it again unless I move a significant distance....I will always be on my back deck.

So, I set the polar alignment as per the procedure in the manual...now if I look through the polar scope 4 hours later and move the RA axis to line up with where Casseopia is now, I would have to adjust the RA and Dec levers again to get polaris back in the circle.......??????? :question:

So can someone explain to me how to do a proper polar alignment? I don't see how it works if the circle on the reticle for polaris rotates such a large amount around the actual NCP.

By the way, my polar scope is aligned because I can rotate the RA axis around and the crosshair in the center doesn't move.

Thanks for helping to clear the confusion!

#2 John Carruthers

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Posted 16 June 2009 - 01:03 PM

If I understand you correctly then you should be adjusting the mount alt/az not the RA/dec to get Polaris in the circle and once set then yes, it should stay there as the hour angle advances.

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#3 neptun2

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Posted 16 June 2009 - 01:45 PM

As you have already understood polaris is not at the NCP but close to it and rotates around the NCP. When you match the constellations in polar scope to the actual situation on the site you already know where polaris should be at this time and date. When you put polaris into the circle using the azimuth and altitude adjustment bolts you make your mount to point to the NCP. After this the movement of polaris around NCP is irrelevant because your mount is already pointing at the NCP and this will not change unless you move the tripod or touch the azimuth and/or altitude adjustment bolts.

#4 mewmartigan

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Posted 16 June 2009 - 01:45 PM

Hi Guys,

Thanks for the replies, I think it's coming together. Is there an accurate way to turn the RA axis to line up Casseopia and the Big Dipper? It seems like being off by a small amount in the eyeball estimate of where the constellations are could make a big difference in the alignment...

#5 astro_baby

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Posted 16 June 2009 - 01:47 PM

1/ Point the mount North with the scope sitting over the mounts counterweights. And centred.

2/ Look in the polarscope and rotate the scope through RA until the Big Dipper and Cassiopea are showing to the coirrect positions (or use polar finder to locate the position of polaris).

3/ Lock the RA in that position.

4/ Use the altitude and azimuth adjusters to get Polaris into the small target circle.

5/ Job done.
Now just use the RA and DEC to move the scope around.

If you want a more comprehensive guide that uses the scopes own polar alignment setting circles you could take a look at one I wrote here

http://www.adur-astr...HEQ5/HEQ5-1.htm

Hope thats some help to you.

#6 mewmartigan

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Posted 16 June 2009 - 02:01 PM

Hi John, yes, I did mean alt/az adjustments, sorry for the confusion :)

astro_baby, your webpage is very helpful and I will definitely use it. I am not by my mount now but I could swear up and down that I do not have the date/time scale. The silver ring where it should be is just a blank silver ring. I don't know if this is something Orion changed but I bought mine in Sept. 08.

#7 Ramses

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Posted 16 June 2009 - 04:32 PM

One easy way to find out where to line up polaris on the reticle is to use EQMOD. There is a function built in to show you where on the circle that surrounds the NCP to place polaris in the polar alignment scope.

When you connect your scope, click on "Setup" on the EQMOD window. On the expanded portion of the window click on the small box that displays polaris hour angle in the section marked "Site Information". This will bring up a window displaying the position for polaris as seen through the polar scope. You simply adjust the alt/az adjustment screws to place polaris on the circle in the indicated position.

#8 mewmartigan

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Posted 16 June 2009 - 04:50 PM

Hi Ramses,

Thanks for pointing that out, I didn't even know EQMOD had that!! I think there are still plenty of things I can learn about EQMOD.

On another note, I checked my mount and it definitely doesn't have the date stamp around the polar scope...the silver ring is blank. It this correct for an ATLAS EQ-G? I am going to email Orion but if somebody else has a blank silver ring then maybe that is the norm??

#9 Ramses

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Posted 16 June 2009 - 05:19 PM

Mine doesn't have it either. I'm not sure why Orion doesn't print it on the ring.

I learn new things about EQMOD all the time. It's an amazing piece of software!

#10 DanB

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Posted 16 June 2009 - 10:44 PM

Hi,

I use Polarfinder software. Recommend you download it, its very helpful. You can use it to find polar transit times or use it to guestimate a rough polar align.. I use it like this a lot.
Check it out, its free. Click on "Dr Jason Dale excellent polarfinder software".. Its a really simple little prog.
Dan

http://www.madpc.net/Links/links.html

#11 John Carruthers

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Posted 17 June 2009 - 02:04 AM

Sorry if I was teaching you to suck eggs :-)
Alan has a handy polar 'how to' here

#12 mewmartigan

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Posted 17 June 2009 - 07:28 AM

Hi Guys,

Thanks for the links. Between all the links I have read and the two programs (PolarFinder and EQMOD) I think I am good to go! :)

#13 Charlie Hein

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Posted 17 June 2009 - 07:36 AM

On another note, I checked my mount and it definitely doesn't have the date stamp around the polar scope...the silver ring is blank. It this correct for an ATLAS EQ-G? I am going to email Orion but if somebody else has a blank silver ring then maybe that is the norm??


It's normal - you really don't need the date/time scales to get a pretty good polar alignment using the polar scope. From my experience if you want to get better than you can get with a careful polar alignment using the polar scope you should probably drift align. FWIW, I hadn't *needed* to drift my Atlas at all once I carefully lined up with the polar scope. I'd done it just to stay in practice but it wasn't necessary to get good pictures.

#14 mewmartigan

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Posted 17 June 2009 - 09:30 AM

Hi Charlie,

I am glad to hear that it's normal (i.e. nothing missing from my mount!) but at the same time I wonder why Orion decided not to stamp it in there....?

#15 Charlie Hein

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Posted 17 June 2009 - 06:42 PM

My guess is because it isn't really needed in order to use the polar scope - probably saves them a couple of bucks per unit and that's huge when you're talking about mass production.

#16 Applal

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Posted 17 June 2009 - 09:59 PM

Don't forget to check the alignment of the polar scope to the RA axis. If this isn't very close, you might get the error you saw over time.
You can use Polaris as a suitable target to get this right, and the manual is pretty clear on how to do this.
Good Luck!






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