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Celestron 93781 Illuminated RACI Finder Scope

Celestron equipment
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#1 KevOxyland

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Posted 14 January 2021 - 04:45 AM

Hi, I'm fairly new here, but I've been a browser for a while. I thought I would post this for anybody struggling with this finder scope.

 

I have an Celestron Evolution 8 and it comes with the red dot finder, which as you probably know, does your back in after a while and is not the most accurate of devices smile.gif So I decide to change it and bought a Celestron 93781 Illuminated RACI Finder Scope. Anybody who has one of these will know what an absolute poor design the frame and control of this scope is. To the point it simply doesn't work for the most part. Here is a solution for you that will make the scope an absolute delight to use. It'll cost you a little bit, but it's so worth it.

 

1. Take the scope apart so you just have the scope itself and not the frame. Take off and ditch the crappy rubber ring too (what were they thinking).

2. Buy one of these...  (dovetail base)

 

https://www.amazon.c...0?ie=UTF8&psc=1

 

3. Buy one of these... (guiding scope ring kit)

 

https://www.amazon.c...C8WD0CHDAD1SW8S

 

Attach the dovetail base to your scope. Assemble the ring kit and place your finder scope in it, and slide it into the dovetail and make sure it's all tightened up.

 

ALL problems with the spring screw thing and any problems aligning will completley vanish. Once I did this, it took me less than a minute, and very easy to align during the day. It has a much broader aligning bandwidth, if you like, Why Celestron didnt use this approach in the first place, i will never know, but this approach turns it into an extremely high quality finder scope with no problems at all. I use a 3 point setup, so i still have my red dot finder for initial set up, which i do during the day on a distant object, then use the celestron for aligning the stars when it gets dark. So, so simple and has taken the pain of alignment away... quite literally smile.gif

 

Enjoy smile.gif

 

 


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#2 vkhastro1

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Posted 14 January 2021 - 06:05 AM

Welcome to CN on behalf of myself and our wonderful group of other CN members !

 

Excellent post.

 

I think the finderscope itself is very good optically and especially like the helicoid fine focus eyepiece.

 

A great alternative to the Orion type 9X50 RACI with fixed eyepiece and focus adjustable front objective. 
 

You are correct on the Celestron bracket - over engineered, heavy and totally useless.

I did a similar mounting bracket upgrade using a different option.

Kept the original Celestron bracket just in case I sell the Celestron RACI finder.


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#3 Noah4x4

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Posted 14 January 2021 - 06:09 AM

The Celestron RACI Finderscope works great once you realise that inside the fixed shiny cylinder (that itself has what appears to be a screwdriver slot that won’t turn) is a tiny adjustment screw requiring a hex  (Allen) head screwdriver. This is the missing third “leg”. Tighten this and the other thumbscrews will work fine and the original assembly lock tight.

It seems to take most folk a year to discover this screw as the supplied instructions are pathetic. You hence don’t need to replace the entire assembly, just find this hidden screw. I posted this guidance with illustrative photographs about a year ago but it has since sunk without trace.

 

EDIT

Found it. https://www.cloudyni...e#entry10701341


Edited by Noah4x4, 14 January 2021 - 07:35 AM.

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#4 KevOxyland

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Posted 14 January 2021 - 11:13 AM

Hi Hoah4x4, yes I saw your post and it was a light bulb moment... thanks :). I also knew about the Allen screw , inside the other shiny screw (it does actually turn)... with the spring... thing. I'm a designer myself, and if I came up with something like that, I think I'd be fired lol. there's too many parts that could go wrong... and so will.

 

Anyway, there were zero instructions that came with it, apart from a picture of where the batteries are, but I figured out how to use it pretty quickly after reading your post. I simply could not get on with it like that (I read a lot of posts that gave up with it). I almost sent it back, but figured I could modify it. I could not get enough movement from it to get it to convincingly line up easily and quickly. When I pretty much got it there, it shifted significantly for next time, and I seemed to spend more time messing with the hideous assembly combination than anything else. That rubber ring is dubious at the best of times. It didn't seem to fit properly. I pushed it in with a stick as suggested, but it seemed to slide it's way back out over time. I think that'll decay over time too.

 

With the new rig, it 'just works'. Easy to adjust, very quickly and stays firmly in place. It's a joy to use.

 

But thanks, appreciate the initial help.



#5 Noah4x4

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Posted 14 January 2021 - 12:40 PM

I don't disagree with the sentiment that its design could be improved. Step one is to include some proper instructions. However, once you have found the hidden Allen key screw it does work pretty well. It should not need a "lightbulb moment" which is the experience of most.

 

The Celestron rubber ring arrangement does mean that you only need to adjust one set of screws.  With two seperately adjustable scope rings I imagine that could be more difficult, but once correct it should then be more robust. However, having found the hidden Allen screw, mine has not required adjusting for 12 months, but before it was out of alignment before every session. 


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#6 KevOxyland

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Posted 14 January 2021 - 01:26 PM

*However, having found the hidden Allen screw, mine has not required adjusting for 12 months, but before it was out of alignment before every session.*

 

That's interesting. I do wonder if mine was faulty. It didn't 'look' to be at fault, and works perfect now, so I'm very happy with it. The two set of adjusters are fine. When you initially set it up, I centered the scope through the hoops and it wasn't far off. Then I simply let gravity do the work by loosening the top screw so it kind of rests on the two bottom ones and then adjust it accordingly. It sort of pivots on the front screws anyway (a bit like the rubber ring effect). It's kind of odd, because the two hoops sit exactly over the two grooves (where the rubber ring goes and the adjustment screws from the old Celestron rig) and the plastic tipped screws on the new rig sit right on in there perfectly.


 



#7 Noah4x4

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Posted 14 January 2021 - 01:44 PM

On delivery, the tiny Allen screw in mine was so unscrewed that even screwing in the two other thumb screws to their maximum left my RACI illuminated finderscope wobbly. When I did find this rather hidden Allen screw, I had to tighten it almost to its maximum. But having got this right it has stayed solid thereafter. 




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