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Adjusting Celestron 9 x 50 RACI Finderscope

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#1 Noah4x4

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Posted 23 July 2020 - 04:42 AM

I have recently read a number of posts moaning that the expensive Celestron 9 x 50 RACI Finderscope "wobbles loose" or otherwise isn't fit for purpose. I disagree as I find it to be a fantastic bit of kit, yet can be frustrating if you don't know the knack of adjusting it, but will agree that the supplied instructions are hopeless (as usual). So, I thought I might post some helpful guidance.

 

Fitting the Finderscope is easy. Just replace the original Star Pointer using the same screws and OTA holes. But the knack to success is knowing how to use the barrel screw adjuster that my screwdriver is pointing at (see image below). Confusingly,  it has what appears to be two grooves cut into the barrel (as if for a slot screwdriver). You do NOT turn this shiny barrel unless the barrel unit has itself become loose. That simply locks the screw barrel adjuster assembly into the body of the unit, but it confuses everybody. Instead....

 

Look inside the shiny metal barrel and rotating inside there is a grub screw (and spring) with a STAR headed screwdriver slot. This is what you adjust, but it confuses most people as it isn't obvious that the adjustment takes place inside the shiny barrel.

 

Firstly, make sure that the rubber ring is seated properly in the forward ring. This creates a pivot so you can then adjust your aim using the rear ring. Start by aiming your OTA at a distant static object (distant telegraph mast by day or Polaris at night) and get that absolutely centre using a cross hair reticle eyepiece, doughnut technique or whatever you favour.

 

You then insert the STAR headed screwdriver down into the barrel and turn the grub screw until your view through the Finderscope is slightly below and left of the object.

 

You then TIGHTEN the other two thumb screws on that same concentric circle until you pull the target centre, checking that both it and OTA are centred.

 

If these thumbscrews remain too loose, tighten the grub screw another turn, then TIGHTEN the two thumbscrews  again. If you have to loosen the thumbscrews to centre the object then the grub screw is probably too loose (and hence the "wobble"). Eventually you will get all three screws snug tight and you should then not need any further adjustment for a considerable length of time. Where folk fail with this is that they turn the shiny barrel assembly tight not realising that the crucial adjustment is the STAR headed grub screw inside the barrel. 

 

 

RACI.jpg


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#2 PolyWogg

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Posted 23 July 2020 - 08:40 AM

I don't have the finder, might never have that type of finder, but if I do, I would *NEVER* figure that out. You deserve a prize for post of the month.

 

P.


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#3 Noah4x4

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Posted 23 July 2020 - 09:52 AM

I don't have the finder, might never have that type of finder, but if I do, I would *NEVER* figure that out. You deserve a prize for post of the month.

 

P.

It took me about a year to figure it out!

 

It's simply not intuitive, and the two slots in the shiny barrel that suggest "put a wide blade screwdriver in these" are confusing. Frankly, I dismantled it in my quest to resolve the wobble problem before spotting the grub screw with the STAR screwdriver hole hidden deep inside the shiny barrel. Once that grub screw is sufficiently tight, it is easy to tighten the thumb screws to pull the target into the Finderscope centre where it locks firm.



#4 skaiser

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Posted 23 July 2020 - 12:26 PM

Ahh

way to go noah.

i always wondered about that 3rd “adjustment “ screw on the finder.

i realized it was for helping to center but thought it was a fixed screw with no adjustments since they didn’t put a knob on it like the other 2.

never got curious enough to really look closely at it.

Now I can actually tweak in all 3 directions, instead of having a loose screw sometimes to get it centered properly.

take care

steve



#5 Raiders

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Posted 23 July 2020 - 12:40 PM

I have the standard Celestron straight finderscope. I’m having trouble focusing. I end up turning the barrel but scope comes apart two pieces. Anyone know the process to focus the straight finderscope.
Thanks

Edited by Raiders, 23 July 2020 - 12:41 PM.


#6 Noah4x4

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Posted 23 July 2020 - 06:15 PM

Ahh

way to go noah.

i always wondered about that 3rd “adjustment “ screw on the finder.

i realized it was for helping to center but thought it was a fixed screw with no adjustments since they didn’t put a knob on it like the other 2.

never got curious enough to really look closely at it.

Now I can actually tweak in all 3 directions, instead of having a loose screw sometimes to get it centered properly.

take care

steve

Skaiser, I feel we have grown up almost as blood brothers regards other solutions . So glad my tip has worked for you.

 

It's so simple if you know how! 



#7 Noah4x4

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Posted 23 July 2020 - 06:50 PM

I have the standard Celestron straight finderscope. I’m having trouble focusing. I end up turning the barrel but scope comes apart two pieces. Anyone know the process to focus the straight finderscope.
Thanks

I assume you mean the original red dot Finderscope?

 

I don't understand your question as its alignment is simply dependent on its adjustment screws. The real pain is its a straight through tool, which is terrible if you suffer from sciatica. The 9 x 50 RACI finderscope is vastly superior. 



#8 Raiders

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Posted 23 July 2020 - 08:57 PM

No red dot
I have the 9x50 straight finderscope
No right angle

#9 Orion68

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Posted 23 July 2020 - 10:28 PM

I also have the 9x50 RACI and went through the same frustrating learning curve. Thanks to the OP for the very helpful tip. CN should be required reading for anyone using this finder!



#10 Michael_Swanson

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Posted 23 July 2020 - 10:39 PM

I have the standard Celestron straight finderscope. I’m having trouble focusing. I end up turning the barrel but scope comes apart two pieces. Anyone know the process to focus the straight finderscope.
Thanks

It is correct to back off the locking ring behind the cell holding the front lens and then turn that cell to focus.  Then you tighten the locking ring.  It should come into focus well before the front cell comes off.

 

Best regards,
Mike Swanson
https://www.NexStarSite.com


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#11 drmedjools

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Posted 24 July 2020 - 01:34 PM

Thanks Noah a Million!

 

I just checked and on my 'USA' delivered Celestron that the grub screw is an 'Allen' wrench (hexagon) screw instead of a Torx/STAR.

 

But you solved the problem with the other C14 I'm trying to upgrade for another group of people.  The RACI scope came out of the box totally mis-set so that I could get it to align!  Now I know why.  This screw in a screw was not properly set from the factory.  Maybe it will work now that it can be adjusted.

 

Dr.  Medjools



#12 Noah4x4

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Posted 24 July 2020 - 03:17 PM

Thanks Noah a Million!

 

I just checked and on my 'USA' delivered Celestron that the grub screw is an 'Allen' wrench (hexagon) screw instead of a Torx/STAR.

 

But you solved the problem with the other C14 I'm trying to upgrade for another group of people.  The RACI scope came out of the box totally mis-set so that I could get it to align!  Now I know why.  This screw in a screw was not properly set from the factory.  Maybe it will work now that it can be adjusted.

 

Dr.  Medjools

It could well require a hex Allen key. To me, it's just a dark hole deep inside a shiny barrel in my dimly lit observatory. But given Celestron don't supply an Allen key, (or clear instructions) I tried various of my STAR precision screwdrivers and the second one did fit. A mere half a turn convinced me I had the solution to why I could never get the device tight enough. Now it's locked robustly. 



#13 skaiser

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Posted 27 July 2020 - 08:22 PM

Hi Noah

Yes , the scope adventure continues.

Hope you are staying well.

 OK I have way too much time on my hands waiting for clouds to clear to image comets, galaxies, stars, anything.....

So being curious, I just had to find out for sure on the RACI 3rd "grub" screw.

I setup my lighting and imaging station to "see" what was really in there.

First I had to clean out many years of debris that was hiding the true screw head.

screw debris1
screw debris2

Then after cleaning, scrubbing, I finally had a clear view in the hole.

I have photo proof that it is a HEX wrench, specifically a 3mm .

Hex head

 

 Mystery solved.

Looks like another cloudy night....

Take care all

Steve


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#14 Orion68

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Posted 30 July 2020 - 07:11 PM

Thanks for confirming this in case I need to tweak my finder. Once these finders are dialed in they are quite nice.



#15 charlesgeiger

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Posted 04 December 2020 - 01:10 AM

I have a new 9X50 RACI Celestron illuminated Finder.  I made a post regarding it and a fellow is measuring for me the thread pitch of the shiny outer cylinder.  I too found that the interior screw is a allen head and I see that from above it may be a 3mm allen.  As well as tightening the outer shiny cylinder with a flat screw driver, I did tighten the inside allen screw as reasonably tight as I could get it.  I then tightened the two other ball tip screws enough.  The finder still seems to be loose upon slight pressure against the cylinder with spring loaded pin.  I was thinking to replace the whole cylinder with a nylon or delrin screw of about 1" length so it would not collide with the base or the scope.  As stated, the outside cylinder appears to have a rather odd thread pitch so don't know if this will work.  But I suppose the hole could be drilled and re tapped to fit something standard.  Let me know if any of you have done this.

Thank you,

Charlie



#16 Noah4x4

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Posted 04 December 2020 - 04:16 AM

I have a new 9X50 RACI Celestron illuminated Finder.  I made a post regarding it and a fellow is measuring for me the thread pitch of the shiny outer cylinder.  I too found that the interior screw is a allen head and I see that from above it may be a 3mm allen.  As well as tightening the outer shiny cylinder with a flat screw driver, I did tighten the inside allen screw as reasonably tight as I could get it.  I then tightened the two other ball tip screws enough.  The finder still seems to be loose upon slight pressure against the cylinder with spring loaded pin.  I was thinking to replace the whole cylinder with a nylon or delrin screw of about 1" length so it would not collide with the base or the scope.  As stated, the outside cylinder appears to have a rather odd thread pitch so don't know if this will work.  But I suppose the hole could be drilled and re tapped to fit something standard.  Let me know if any of you have done this.

Thank you,

Charlie

If new, get it replaced under warranty. Don't attempt DIY.

 

I posted this thread after a year of frustration thinking the outer sleeve with two wide screwdriver slots was the sole adjustment. Me finding the inner Allen key screw was a Eureka moment for many CN'ers as the later posts testify. However, once you can adjust in all  three planes, the device works fine.

 

However, one other thought. Is the Finderscope rubber ring correctly positioned? If not, this will cause wobble. It fits into a single location and you might investigate. Beyond that, if the Allen Key screw won't adjust/hold, get the entire device replaced under warranty. Celestron are very obliging with replacing rare DOA devices.



#17 Gary0359

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Posted 20 February 2021 - 08:21 AM

...and Celestron expect us to work all that out. I’ve had one of these finderscopes for a couple of years, and even now I have learned a bit more from your post. It’s actually a nice bit of kit but frustrating without the knowledge given here. Thanks.

 

What is it with equipment not coming with instructions anymore ? It’s not like it isn’t expensive stuff. I recently purchased the ZWO ADC adapter (£124) and that is exactly the same, absolutely no guidance.

 

Gary



#18 Gary0359

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Posted 20 February 2021 - 08:24 AM

I have the standard Celestron straight finderscope. I’m having trouble focusing. I end up turning the barrel but scope comes apart two pieces. Anyone know the process to focus the straight finderscope.
Thanks.

On the diagonal version its the at the end of the finderscope eyepiece, is it not the same with the straight through version ?



#19 BradBB

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Posted 20 February 2021 - 04:10 PM

I have also been fighting this RACI finder since summer. After finding this thread, I tried again today. The inner hex head does not seem to be independent of the outer barrel. If I turn one, the whole chrome barrel rotates. With the barrel turned all the way tight, the adjustment thumb screws are still barely tight.



#20 Noah4x4

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Posted 20 February 2021 - 04:27 PM

I have also been fighting this RACI finder since summer. After finding this thread, I tried again today. The inner hex head does not seem to be independent of the outer barrel. If I turn one, the whole chrome barrel rotates. With the barrel turned all the way tight, the adjustment thumb screws are still barely tight.


That might explain why the chrome barrel has what appears to be a screwdriver slot.

Mine has always been locked tight and I have deliberately never applied enough force to loosen it. I didn't immediately find the inner hex screw, and that seems to be most folks initial experience, thinking that only the other two thumb screws are adjustable. But maybe yours has been loosened and you need to tighten the chrome barrel until it locks tight before adjusting the inner hex screw? As I said, my chrome barrel doesn't move, only the hex screw.

#21 BradBB

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Posted 22 February 2021 - 11:32 AM

I gave this another try after I discovered last night that the finder was not even close to alignment. After getting it aligned on Procyon, the two adjusting thumb screws were at almost no tension. This morning I removed the chrome barrel screw to see if I could free up the inner hex head screw. In the vice with breakfree oil applied, I got the hex screw to release. I took it apart for inspection. The spring, adjusting pin, and the screw are all in good condition. I set up the scope in the yard and sighted on a street sign about 400 meters distant, the farthest I can see in my neighborhood. I tried setting the hex screw as deep as possible, trying to get the most tension on the two adjusting thumb screws. This may not end up being the best combination, but it is all trial and error. Using my 10 mm eyepiece in the C8, I achieved alignment with somewhat light tension on the adjusting screws. Just to note, there is very little adjustment in the chrome barrel hex screw; it is only a few mm in length. After achieving alignment I removed the finderscope and immediately reinstalled it. I tried to keep the same direction of pressure on its mount. The finderscope was then off by about 2 meters at that 400 m distance. I realigned it and watched in the eyepiece as I loosened and then tightened the mount screws. It moves a good bit, moving the alignment up to over 2 m at that distance. My conclusions are: 1) there is enough play in the mounting system that a significant realignment will be necessary each time I set up the scope. I have to remove the finderscope to fit the OTA in its case. 2) I am not sure if my screw settings are optimal, with maximum initial spring tension. It may be that it will be better to start off with lower spring tension and use the adjusting thumb screws to duplicate the tighter spring tension. You people with domes and permanent setups do not have the same issues as we mobile astronomers!


Edited by BradBB, 22 February 2021 - 11:34 AM.

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#22 BradBB

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Posted 22 February 2021 - 04:01 PM

After allowing my brain to digest my last attempt at aligning the Celestron RACI, I had an insight. In my case, the spring loaded pin does not seem to push the scope far enough to the right. When I back off the thumb screws to achieve alignment, they become too loose. It just occurred to me that the dovetail base that attaches to the OTA has slots, rather than round holes, for the mounting screws. I believe their purpose is to allow some adjustability in alignment. It is raining now, but next time I am going to slightly rotate the dovetail bracket clockwise. Worth a try!



#23 Lasko

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Posted 22 February 2021 - 07:15 PM

After allowing my brain to digest my last attempt at aligning the Celestron RACI, I had an insight. In my case, the spring loaded pin does not seem to push the scope far enough to the right. When I back off the thumb screws to achieve alignment, they become too loose. It just occurred to me that the dovetail base that attaches to the OTA has slots, rather than round holes, for the mounting screws. I believe their purpose is to allow some adjustability in alignment. It is raining now, but next time I am going to slightly rotate the dovetail bracket clockwise. Worth a try!

The whole system is a bit clunky, and I figured out early on that once you remove the finder from the OTA bracket all bets are off.  Also noticed last time out that you can "adjust" it quite a lot by changing the tension of the screws holding the finder bracket onto the OTA bracket.  This makes it impossible to retain alignment after you've removed the finder from the OTA, and depending on how tight or loose you make it, could put it out of the adjustable range. 

 

The whole thing is a balance in getting the brackets aligned to where the tensioner can be pressing on the finder tube enough to hold it in place when aligned with the scope.  I don't think the screw holding the spring in the tensioner is intended as an adjustment by itself, it is just retaining the spring.  If you loosen it you just reduce pressure from the spring, and if you can't align it without loosening it one of the brackets is probably misaligned.

 

The other thing I noticed is that if the finder is pushed too far back in the finder bracket, the tensioner doesn't line up with the ridge on the tube that seems made for it.  It pops over the side of it and you end up with less overall adjustment than you should.

 

The finder itself is great, and really accurate if you can get everything lined up.  Seems like they should be able to do better with the mounting system.



#24 Lasko

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Posted 22 February 2021 - 07:19 PM

With the barrel turned all the way tight, the adjustment thumb screws are still barely tight.

Also was going to comment on this but forgot.  Since it is a spring tension system, I've come to the conclusion that the adjustment screws will never be tight, and should not be.  As long as it is being held in place by the two adjustments and spring pressure from the tensioner, that is the best you can do.



#25 BradBB

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Posted 22 February 2021 - 09:24 PM

Alas, when I say mine are not tight they often are not touching at all.


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