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External mounted Polar Scope?

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#1 k5apl

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Posted 21 March 2009 - 08:37 AM

Has anybody attached a Polar Scope to their mount externally
ie. not the 'screw in' type that is designed for the mount?

My mount has an encoder that covers the hole for the polar
scope, so I need a way to mount the polar scope like a
finder on the mount body. Any suggestions?

Thanks,

Wes

#2 Eddgie

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Posted 21 March 2009 - 10:54 AM

Celestron (and maybe Meade) used to sell 10x50 Right Angle finders with an alignment reticule built in. They had a little illuminator that you turned on to illuminate the reticule when you wanted to polar align, and a little cardboard wheel to tell you where Polaris should be for the month, day, time.

And when it wasn't being used as a polar finder, it worked as the Right Angle finder.

Expensive, but might be a good way to go if you can find one. I don't know if they are produced new anymore, so that means you would have to look in the used market.

Option 2 would be to use something like the Celesron CGE Polar Finder. This comes with a bracket to mount on top of the RA Axis. It lifts the finder clear of the RA worm gear housing. To use it, you have to rotate the mount so that the Dec axis is horizontal to the ground and you can sight over the top. You didn't say what kind of mount, and perhaps this would require some kind of fabrication (the top of the CGE RA axle housing is flat, and if your mount is curved on top, you might not be able to attach it without some provision to adapt it..).

So, depending one the mount and scope types, there are two options here, but neither is cheap. One might require some kind of mount modification, and the other might be hard to find (Though I do see them sell used from time to time).

Oh, And this. Just use a telrad. You can use a planetarium program to determine the "Sight Picture" for Polaris for the date and time, then just point the mount at Polaris and use the Telrad rings and estimate the position. This will get you SURPRISINGLY close. For most "Go-To" mounts, this will get you more than close enough. If you are imaging, you will likely still need to drift align, but this will be more than good enough to get you in the party. I used this method for years when I used mounts with manual digital setting circles. Always got me pretty darn close.

#3 Arbacia

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Posted 21 March 2009 - 11:01 AM

Celestron CGE has an accesory paraxial Polar finder to bo mounted on top of the main chassis of AR axis. However CGE really doesn't need such a finder for precise aligment. The hand controler has a routine for polar aligment that allows to have an off-polar axis deviation up to 10º. The routine involves a 2+4 stars alignment, then sincronization with last star and then mechanical centering of such a star in the FOV operating the Alt and Az bolts of the mount.

What is your mount?

Patricio

#4 k5apl

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Posted 21 March 2009 - 02:27 PM

Hi Patricio
I have an A-P 600E mount. The DSC encoder covers the hole
for the A-P polar finder. I'll look into the CGE finder as
an option.

Thanks,
Wes

#5 k5apl

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Posted 21 March 2009 - 02:30 PM

Thanks Eddgie
I will consider the Telrad and look at the Celestron finder. And, do some looking for the Meade finder too. All
great ideas. Mount is an A-P 600E With DSC encoders.
Thanks,
Wes

#6 Doug Sanqunetti

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Posted 21 March 2009 - 06:25 PM

Mountain Instruments sells an external holder that uses a dovetail mount attached to the scope body. It uses the Losmandy polar alignment scope. Here is a link: http://www.mountaini...olarfinder.html

It's not cheap but it looks like it might work.

Best Regards, Doug

#7 jsiska

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Posted 21 March 2009 - 06:50 PM

JMI also sells an external polar alignment scope.

http://www.jimsmobil...olar_scopes.htm

Jim

#8 John Carruthers

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Posted 23 March 2009 - 04:17 AM


Astro Engineering (UK) sell the 'Polarmate'
http://www.astro-eng...oriesforce.html
it's more for wedges but can be easily adapted.
jc

#9 Tom and Beth

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Posted 23 March 2009 - 09:31 AM

Thanks Eddgie
I will consider the Telrad and look at the Celestron finder. And, do some looking for the Meade finder too. All
great ideas. Mount is an A-P 600E With DSC encoders.
Thanks,
Wes


Hi Wes,

On my older AP1200, the encoder unscrews which allows one to use the PASILL (Polar Finder). Once alinged, it's a simple matter to re-install the encoder. Perhaps yours does too?

<edit> BTW, mosy over to the AP web sites, technical support, Technical Support - Vintage Products. You can download a manual for your mount from there. You can also talk to Howard for technical information about your mount. AP customer support is top notch. It is quite possible you can use the Losmandy/AP Polar Finder in your mount by unscrewing the encoder.

#10 k5apl

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Posted 23 March 2009 - 12:16 PM

Thanks Doug for Mountain Inst link.
Thanks Jim for JMI link
Thanks JC for your UK link.
Thanks Tom for A-P info.

I downloaded the manual for the mount but not tried to remove the encoder yet. I'll try it and see if it is the
same as your AP1200 mount. Probably is. If I run into trouble or need more info, I'll call A-P.

I appreciate all of your responses.

Wes






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