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Celestron RACI finder on C8 prevents swinging OTA on fork

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#1 randallpatrickc

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Posted 17 October 2021 - 02:22 PM

Hi - newbie here;

trying to replace the standard 6x30 finder with the RACI but one of the screws that clamp the diagonal doesn’t clear the forks. I could get around this if the finder OTA would rotate in its rings but I don’t want too force it. Does it rotate pls?

I could always shorten the screw I suppose

Help!

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Edited by randallpatrickc, 17 October 2021 - 02:23 PM.


#2 Chris Johnson

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Posted 17 October 2021 - 05:02 PM

Can you/ post a picture of the complete scope and mount. Something doesn’t look right. What mount are you using?
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#3 Rich V.

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Posted 17 October 2021 - 05:06 PM

If you spin the forks 180° around, you won't have the finder buried down inside of the forks in the first place, if I'm seeing your setup correctly. The finder should end up on the top of the scope away from the fork, not the bottom.  A better, wider view of the whole fork/scope setup would be a help.


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#4 Napp

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Posted 17 October 2021 - 05:06 PM

If I am actually understanding your question, the finder does rotate within its rings.  Just loosen the screws that secure the finder OTA and turn it to where you want it.  Then retighten.  You will have to realign the finder to the scope afterwards.  However, I agree with above.  Why are you in this position?


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#5 randallpatrickc

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Posted 17 October 2021 - 06:58 PM

I am a complete beginner so apologies!

I thought that I would have to rotate the tube through the forks and one of the screws stopped me doing that.

here’s a pic.

Are you saying that I’ll never have to swing the tube through the forks so the finder always stays on top?

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  • IMG_5434.jpg


#6 randallpatrickc

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Posted 17 October 2021 - 07:02 PM

So the finder never has to pass through the forks?

(penny might be dropping)

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#7 randallpatrickc

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Posted 17 October 2021 - 07:05 PM

Also, is there a manual for the RACI somewhere? Will I ever have to focus it? I see the eyepiece screws in and out.

Thanks for the info on rotating it - I see the “O ring” seems stiff.



#8 CassGuy47

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Posted 17 October 2021 - 07:13 PM

I wish you had a wider view of your scope.  I've owned fork mounted SCT's for about 40 years, and if you use the scope correctly, the problem you are experiencing can't happen.  I've attached an Internet capture of a 8" fork mounted Celestron with a RACI finder.  If a picture is worth 1,000 words, this photo should save a lot of writing.  As you can see, the fork mount rotates on the RA axis, and the optical tube is never under the forks.

 

I hope this helps!

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  • Fork Mounted SCT with RACI Finder.jpg

Edited by CassGuy47, 17 October 2021 - 07:18 PM.

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#9 Rich V.

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Posted 17 October 2021 - 07:46 PM

Randall, the photo above (#8) and your photo in post #5 are how your scope will be oriented most of the time when you're viewing; finder side up.  Your second photo (#6) is the worst case scenario pointing to the north celestial pole or North Star.  On an EQ fork, that's the most difficult eyepiece position, aimed at the NCP,  as the eyepiece is down into the fork and difficult to look through.  Fortunately, aside from very near the pole, most of the sky will not be that difficult to view.

 

Note in the photo above of the black SCT, the manual RA control knob is on the tripod base side of the fork, where you can reach it easily, not flipped over to the top side.

 

You'll get the hang of it with a little practice.  Get an adjustable chair to sit on and you can get comfortable at most of the viewing angles.

 

Rich



#10 Napp

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Posted 17 October 2021 - 07:50 PM

Contact your local astronomy club.  Ask if you can take the scope to a club outreach or observing event and have a club member give you some hands on help.  Using a scope on a wedge is not inherently intuitive.  I had an sct on a wedge one time. It did not take long for me to ditch the wedge.  Unless you are planning to do long exposure astrophotography you do not need the wedge.  If you just want to do visual observing remove the wedge and just use the mount in the alt-az configuration.  Your eyepiece won’t end up in such an awkward position.



#11 whizbang

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Posted 17 October 2021 - 11:20 PM

Unless you want to use the setting circles to find objects, you would never polar align, and yes, the finder stays on top.

 

If you are going to polar align and use the fine RA control for "tracking" and the setting circles for locating, then, your current finder will bump the forks.

 

Quite frankly, a polar aligned orange tube is real awkward to use.  I recommend against it.  Do it a couple times so you get the idea.  But, then go back to Alt-Az with the finder on top.


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#12 B 26354

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Posted 29 November 2021 - 04:24 PM

Unless you want to use the setting circles to find objects, you would never polar align, and yes, the finder stays on top.

 

If you are going to polar align and use the fine RA control for "tracking" and the setting circles for locating, then, your current finder will bump the forks.

 

Quite frankly, a polar aligned orange tube is real awkward to use.  I recommend against it.  Do it a couple times so you get the idea.  But, then go back to Alt-Az with the finder on top.

???

 

In the 44 years I've owned it, the only time I've ever used my C8 in alt-az mode was when I was photographing Space Shuttle landings with it, at Edwards Air Force Base. I've never had the slightest problem using the fork mount in EQ mode, which of course -- having a clock-drive and setting circles -- is its intended purpose.

 

I've also never heard anyone recommend not polar-aligning a wedge-mounted SCT. Without doing so, the mount won't track accurately enough to keep objects in the eyepiece's FOV... which again, is the whole point to having an EQ-mounted telescope, whether it happens to have setting circles or not.

 

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