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G11 Polar Axis Correction-can you use a Camera?

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#1 WidowMaker


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Posted 23 June 2010 - 09:24 AM

Hey everyone.
I realize this is probably a dumb question but here recently the concrete my mount is sitting on shifted and I am no longer perfectly polar aligned (not sure I ever was 'perfectly' aligned!).

I know the Gemini has two built in Polar alignment tools where you can switch back and forth between two stars and correct the mounts alignment, but can you use a CCD camera, mainly my SBIG st2000xm, instead of an eyepiece or would the FOV create a problem?

Would it be any better or worse to use the crosshairs in MaximDl to do the Gemini polar correction than it would to use an eyepiece?

#2 gnowellsct


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Posted 23 June 2010 - 11:22 AM

You put a meridian star in the center of the fov. You press the correction. The scope moves AWAY from the star. That is how far your alignment is off. Using the altitude and azimuth knobs (NOT moving in Dec or RA) you put the star back in the center of the field of view. You can do it with a finder so long as the finder is accurately aligned enough to get the star in the field of view of the main scope and on your chip where it can be detected.

Otherwise, you'll be bumbling around looking for the star.

Greg N

#3 ZRX-Steve


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Posted 23 June 2010 - 12:11 PM

I use a Mallincam video camera on on G11 / Gemini with an 8" F/4 GSO Newt to a 9" Speco monitor exclusively. It has a crosshair feature that I turn on for the PAA and PAC polar alignment routines and it works flawlessly.

The scope is 800mm in F/L and the Mallincam is similar to a 8mm, 50 degree eyepiece in terms of FOV.

#4 WidowMaker


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Posted 23 June 2010 - 12:37 PM

Thanks a lot you all!
I figured there must be a way to use the CCD instead of trying to take it off for the Gemini PAA and PAC routine, never thought of the Finderscope.

Steve, how do you know which EP the Mallingcam is similar to in regards to FOV?

Im using the St2000xm on a Vixen R200ss with seems to be about the same as your 8" f/4 with the 800mm f/l. I am using the Baader MPCC if that changes anything.

Which EP would the ST2Kxm be similar to with my setup?

#5 blueman


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Posted 23 June 2010 - 12:47 PM

Use the Polar Align Corr in the alignment after you do a 3 star alignment. Have the mount go-to a star as near the meridian-equator as possible, center the star with the hand pad in Maxim so the star is on the cross hair.
GO to Align Mount, choose Polar Align Corr and it will move the star to the correct position. Now use the CED and RA screws to move the star back to the cross hair.
I find that it is best to now park the mount and turn it off and then turn it on and do another 3 star alignment. If the numbers given after the 2nd and 3rd alignment star are under 5, you are probably ready to go. If not repeat the procedure until you get as close to 0-0 as possible.

#6 WidowMaker


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Posted 23 June 2010 - 01:59 PM

Thanks Blueman. Kind of went over my head there.

What do you mean by 'if the numbers given after the 2nd or 3rd alignment are under 5...', what numbers are you talking about?
I assume you mean numbers on the hand control, but will they be telling me how close or far away I am from being aligned? If so, what can I expect to see, or what is it specifically im looking for there?

Also, when you say use the 'CED and RA screws', you do mean the altitude and azimuth adjustment knobs on the mount, right?


#7 Konihlav



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Posted 23 June 2010 - 03:46 PM

yes CED seems to be DEC - i.e. use altitude knob :)

blueman - thanks for great tip, I am a newbie user of G-11G and so far haven't tried to use any of the two PAA (polar alignment assist) methods. This seems to be easy to do. I should pay attention to the numbers shown after I sync on the alignment stars...

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