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Polar Scope for Old CG-4 Mount

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#1 ericthemantis

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Posted 17 July 2019 - 04:32 PM

I've got an older CG-4 Mount (with the aluminum tripod) and the "discontinued" polar alignment scope #94221. Has anyone here found a suitable replacement? I learned I can unscrew the original backend of the mount with the 3 polar scope mounting screws to expose the threads that the newer polar alignment scopes use, but I have not found one that I am confident will fit.

 

I tried buying one on Amazon - Astromania Polar Alignment Scope for EQ-5, Black - for Both Northern and Southern Hemispheres Eyepiece Focus Adjustment to Achieve Sharp Focus on Reticle because it had pictures on it that look just like my CG-4 mount, so I thought i would be good to go. Turns out the diameter is too large for my mount. It measures 24mm. The tube inside my mount measures 20mm (or slightly under). Gonna have to return it since it obviously does not fit.

 

Picture from the Amazon product page.

Polar Scope EQ5.PNG



#2 zxx

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Posted 17 July 2019 - 06:21 PM

94223 should work.


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#3 ericthemantis

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Posted 17 July 2019 - 06:32 PM

94223 should work.

Not according to some amazon reviews. Does someone have a 94223 that could measure the diameter of the tube? It's gotta be 20mm (or a little less), and it needs inside threads that are about 24mm diameter to screw on to the mount. The scope I got, which looks similar to the 94223, has too large diameter a tube and the threads are on the tube itself.



#4 Jond105

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Posted 17 July 2019 - 06:40 PM

This is in stock. Not sure if it works the same or not though. 



#5 SuperSirLink

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Posted 17 July 2019 - 06:43 PM

CG-4 ... EQ3 ... EQ3-2

 

It's so confusing... I thought the CG-4s were all white...



#6 SuperSirLink

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Posted 17 July 2019 - 06:51 PM

Just found this... https://www.cloudyni...eq3-same-mount/

Maybe you have a CG-3, or maybe just an EQ3...  Might account for the difference...

 

I ordered this one for my CG-4 (white) https://www.bhphotov...inderscope.html

I can measure mine when it comes in on Friday...



#7 zxx

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Posted 17 July 2019 - 07:06 PM

Not according to some amazon reviews. Does someone have a 94223 that could measure the diameter of the tube? It's gotta be 20mm (or a little less), and it needs inside threads that are about 24mm diameter to screw on to the mount. The scope I got, which looks similar to the 94223, has too large diameter a tube and the threads are on the tube itself.

Yes the tube on my 94223 is just under 20mm and the inside threads are 24mm.


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#8 SuperSirLink

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Posted 17 July 2019 - 07:17 PM

Yeah I saw that Astromania one as well when I was looking for one... I don't think the EQ-5 is the same or compatible...  Try the 94223 from B&H, their returns are not bad if it too doesn't fit...


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#9 Jond105

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Posted 17 July 2019 - 07:21 PM

May I ask why the wanting of the polar scope though? If doing visual only, you’d be surprised at how much the little money could be saved for something else. 



#10 ericthemantis

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Posted 17 July 2019 - 07:23 PM

CG-4 ... EQ3 ... EQ3-2

 

It's so confusing... I thought the CG-4s were all white...

 

Just found this... https://www.cloudyni...eq3-same-mount/

Maybe you have a CG-3, or maybe just an EQ3...  Might account for the difference...

 

I ordered this one for my CG-4 (white) https://www.bhphotov...inderscope.html

I can measure mine when it comes in on Friday...

The newer ones are white. This one is old. Early to late 2000's would be my guess.



#11 ericthemantis

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Posted 17 July 2019 - 07:27 PM

Yes the tube on my 94223 is just under 20mm and the inside threads are 24mm.

Thanks for checking. I'll give it a shot.

May I ask why the wanting of the polar scope though? If doing visual only, you’d be surprised at how much the little money could be saved for something else. 

Have had the mount and C102-HD refractor on it for about 2 years now, but took the scope off and put my Skyguider Pro and camera on it. Just got a new tripod for the camera setup, so put the scope back on the rig, bought a dual axis motor kit, and am looking for a polar scope to do some tracked imaging with this setup. Eyeballing polaris through the empty axis get's me good enough to do some Moon and Planetary stuff I think, but I'd like to try for some longer exposure stuff. Hoping to get 10 sec exposures out of it, 30 seconds if I'm lucky.


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#12 zxx

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Posted 17 July 2019 - 07:36 PM

Thanks for checking. I'll give it a shot.

Have had the mount and C102-HD refractor on it for about 2 years now, but took the scope off and put my Skyguider Pro and camera on it. Just got a new tripod for the camera setup, so put the scope back on the rig, bought a dual axis motor kit, and am looking for a polar scope to do some tracked imaging with this setup. Eyeballing polaris through the empty axis get's me good enough to do some Moon and Planetary stuff I think, but I'd like to try for some longer exposure stuff. Hoping to get 10 sec exposures out of it, 30 seconds if I'm lucky.

You can add a guide port to the HC that came with the drive kit ,its easy to do all you need is an ST4 cable.

I get 4min exposures with my ED80 all night long with a total RMS under 1.00


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#13 ericthemantis

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Posted 17 July 2019 - 07:48 PM

You can add a guide port to the HC that came with the drive kit ,its easy to do all you need is an ST4 cable.

I get 4min exposures with my ED80 all night long with a total RMS under 1.00

Holy Crap! I just googled that and found a pdf showing the mod. Now if I get a guidescope I can use it for both my SGP and my newly motorized CG-4. Now I really want a polar scope for it :) (barring going to a Polemaster or something more expensive)



#14 zxx

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Posted 17 July 2019 - 07:59 PM

Holy Crap! I just googled that and found a pdf showing the mod. Now if I get a guidescope I can use it for both my SGP and my newly motorized CG-4. Now I really want a polar scope for it smile.gif (barring going to a Polemaster or something more expensive)

I would not bother with polemaster,or something more expensive, I guide DEC in one direction with the mount.

A polar scope is all you need because it helps to be out a tad when guiding DEC in one direction.

What is the FL of your 102 ?



#15 ericthemantis

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Posted 17 July 2019 - 08:18 PM

1000mm (F10). Originally bought for visual and to familiarize myself with GEM usage (got the scope, mount, tripod, and eyepiece for $95).

#16 zxx

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Posted 17 July 2019 - 08:18 PM

Here are a few I did starting out in the hobby with the CG-4. I don't spend a lot of time processing, do most of it in DSS

but the mount gets it done.

 

83R.jpg 175 stack-2 (2).jpg M42~1.jpg m45 40 s.jpg

 

 


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#17 zxx

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Posted 17 July 2019 - 08:24 PM

1000mm (F10). Originally bought for visual and to familiarize myself with GEM usage (got the scope, mount, tripod, and eyepiece for $95).

It's a refractor ? what's the weight ?  I use a 0x8 FR on my 80 ,gets me down to 480mm 


Edited by zxx, 17 July 2019 - 08:27 PM.


#18 SuperSirLink

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Posted 17 July 2019 - 09:13 PM

Beautiful zxx!!  I too am planning on adding the RA clock drive to do some entry level AP at some point...  Your shots show you can get really nice shots with lower level gear... Really nice! waytogo.gif


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#19 ericthemantis

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Posted 17 July 2019 - 09:14 PM

6 1/2 lbs. Achro. C102-HD. I think the Omni XLT 102 replaced it. Definitely not an astrograph, but I'm gonna see what I can get with it. I think the mount is rated for 15 lbs?

#20 zxx

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Posted 17 July 2019 - 09:24 PM

Beautiful zxx!!  I too am planning on adding the RA clock drive to do some entry level AP at some point...  Your shots show you can get really nice shots with lower level gear... Really nice! waytogo.gif

Hey thanks, yes the mount worked well for me. Adding the guide port made all the difference.



#21 zxx

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Posted 17 July 2019 - 09:40 PM

6 1/2 lbs. Achro. C102-HD. I think the Omni XLT 102 replaced it. Definitely not an astrograph, but I'm gonna see what I can get with it. I think the mount is rated for 15 lbs?

My rig is around 12lbs,scope,camera,guide scope and guide camera and finder scope. Your 102 will be a little more challenging,

a FR will help. I could keep about 97% of my lights with the ED80. Here is a pic of my 127mm f9.4 refractor I built.

I put it on the CG-4 one night not expecting much, hit start and walked inside. Got 50+ 4min lights on M51,had to trash 30%

of them but did get a satisfying result.

 

001~1.jpg

[attachment=1302740:m51-58-2-2~1.jpg

This image had no FR, 1200mm FL

Attached Thumbnails

  • m51-58-2-2~1.jpg

Edited by zxx, 17 July 2019 - 09:45 PM.

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#22 zxx

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Posted 17 July 2019 - 09:42 PM

The mount is rated at 20lbs.


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#23 ericthemantis

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Posted 17 July 2019 - 10:06 PM

Once I get the astromania one returned I'll give a 94223 a try. Looks like amazon just started doing free returns through Kohls, so that's dropped the shipping charge risk for trial orders.
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#24 zxx

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Posted 18 July 2019 - 10:14 AM

If you put a small scope like a Z61 or 70mm on the mount you would have a nice lightweight inexpensive setup.

A ED80 is about the max for the mount if you want to keep most of you exposures.


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#25 zxx

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Posted 19 July 2019 - 03:25 PM

Holy Crap! I just googled that and found a pdf showing the mod. Now if I get a guidescope I can use it for both my SGP and my newly motorized CG-4. Now I really want a polar scope for it smile.gif (barring going to a Polemaster or something more expensive)

If you do decide to add a guide port here is another mod I did that helped.

I did away with the cheesy gears on the DEC drive, made a steel plate and made it direct drive like the RA drive.

This helped a lot when calibrating with PHD2 

 

IMGP3676 (2).jpg

 

I also made a better bracket for the RA drive

 

IMGP3677 (2).jpg

 

I also tried other things like removing the bee wax grease and replaced with a lithium grease, but made no improvement.

I soon realized that an RMS under 1.00 was more then good enough for my ED80.




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