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Celestron C11 XLT 9x50 finderscope alignment?

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#1 Oscar Szentirmai

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Posted 20 January 2020 - 09:06 AM

I have recently acquired a used 2015 C11.

 

I am struggling to align the scope with the finderscope? Its almost impossible to get the finder to point to where the OTA is pointing, as the nylon thumbscrews reach their limit, and i am still off?

 

I tried to manually force the whole finderscope to point to where i want by loosening the bracket thumbscrews and tightening them back while holding the body of the finderscope in my other hand, which helped a little, but I am still a little off?

 

Any advice would be most appreciated! I must be doing something wrong?

 

I do not want to buy a newer finderscope, as I'm broke after all the gear I bought since xmas!

 

grin.gif



#2 pyrasanth

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Posted 20 January 2020 - 09:27 AM

Are you aligning the finder-scope with an object at infinity like the moon?

 

Center the "infinity object" with a low powered eyepiece in the telescope main optics then align the finder with that view. There should really be issue getting the finder to align-so can't see at this point what the issue might be- perhaps a picture of the finder & bracket would help.


Edited by pyrasanth, 20 January 2020 - 09:28 AM.


#3 Second Time Around

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Posted 20 January 2020 - 09:40 AM

Could it be that that the shoe of the finder bracket (the bit that's attached to the telescope tube) is out of alignment?

If so, loosen off the screw or screws here and move the finder and bracket by hand so that the finder image roughly corresponds to the view through the telescope. Still holding the finder and bracket in your hand tighten the screw or screws on the shoe so it doesn't move. Then do a normal alignment of the finder.

This is something I had to do on a secondhand scope I bought.
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#4 Oscar Szentirmai

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Posted 20 January 2020 - 09:42 AM

Are you aligning the finder-scope with an object at infinity like the moon?

 

Center the "infinity object" with a low powered eyepiece in the telescope main optics then align the finder with that view. There should really be issue getting the finder to align-so can't see at this point what the issue might be- perhaps a picture of the finder & bracket would help.

Yesterday night the sky in London was just dense cloud. I pointed at a tower light, probably about 5 miles away. It was a very strong bright red light, just above the horizon.

The cross hairs in the finderscope would move close to it, but always a small distance off it.

Unfortunately there was nothing usable in the sky.



#5 Oscar Szentirmai

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Posted 20 January 2020 - 09:43 AM

Could it be that that the shoe of the finder bracket (the bit that's attached to the telescope tube) is out of alignment?

If so, loosen off the screw or screws here and move the finder and bracket by hand so that the finder image roughly corresponds to the view through the telescope. Still holding the finder and bracket in your hand tighten the screw or screws on the shoe so it doesn't move. Then do a normal alignment of the finder.

This is something I had to do on a secondhand scope I bought.

i'll try that tonight. Thanks

By the way, I hate the finderscope!   confused1.gif

I know that the red dot finder on the Nexstar 8SE receives a lot of hate, but i found that one MUCH MUCH easier to use.


Edited by Oscar Szentirmai, 20 January 2020 - 09:46 AM.


#6 charlesgeiger

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Posted 20 January 2020 - 07:35 PM

You might check and see if the finder is properly installed in the bracket.  Someone else mentioned this subject recently.  Make sure the finder with its "O-ring" are mated properly in the finder bracket.  If it is not installed properly (the O-ring) needs to be near the bottom of the finder and then you push it in from the top down.  Just something to check.  If the O-ring is to high in the finder bracket the finder will slop around within the bracket and will lead to incorrect seating so that it will not be parallel with the optical path of the main telescope.

I hope it is a simple solution for you.  Let us know.

charlie


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#7 Oscar Szentirmai

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Posted 20 January 2020 - 07:43 PM

You might check and see if the finder is properly installed in the bracket.  Someone else mentioned this subject recently.  Make sure the finder with its "O-ring" are mated properly in the finder bracket.  If it is not installed properly (the O-ring) needs to be near the bottom of the finder and then you push it in from the top down.  Just something to check.  If the O-ring is to high in the finder bracket the finder will slop around within the bracket and will lead to incorrect seating so that it will not be parallel with the optical path of the main telescope.

I hope it is a simple solution for you.  Let us know.

charlie

Can I just check this with you, as the instructions in the manual were hopeless for the uninformed, like me.

 

The finder bracket has TWO rings.

 

The finder slides into it backwards (as in, the finder enters the front ring first, then into the back ring).

 

The PROXIMAL ring (the one closer to the back of the OTA) has the adjustment thumbscrews, and they screw DIRECTLY onto the body of the finder, in the grooved slot.

 

The DISTAL ring (the one closer to the front of the OTA) should have the rubber O-ring squeezed into it from the DISTAL end, and it gets squeezed under it's front (leading) edge?

 

Is that how it should be?

 

Thanks


Edited by Oscar Szentirmai, 20 January 2020 - 07:45 PM.


#8 macdonjh

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Posted 20 January 2020 - 08:35 PM

I tried all the things suggested so far, and on one scope it still wasn't enough.  I ended up adding a few sheets of paper to one "corner" of the finder bracket's shoe to act as a shim.  That finally did it.



#9 charlesgeiger

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Posted 20 January 2020 - 08:41 PM

I am not sure about this arrangement.  The scopes I have had with O-rings have the adjustment screws at the upper end of the finder holder on the top ring.  The O-ring usually is in the lower tube ring on the holder.  As you say, you push the finder down through to cinch up with the lower ring (O-ring on lower end).  Somebody else might chime in here.  

Is it possible that the finder base is mounted backwards on the main tube?

Again, I hope this will all resolve quickly for you.

Charlie



#10 techmgr

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Posted 20 January 2020 - 11:40 PM

Found this from the C-11 manual:

 

To install the finderscope:
1. Attach the bracket to the optical tube. To do this, place the curved portion of the bracket with the slot over the two holes in the rear cell. bracket should be oriented so that the rings that hold the finder are over the telescope tube, not the rear cell (see Fig 2-11). screws in by hand and tighten fully with an Allen wrench.
2. Partially thread-in thumbscrews that hold the finder in place inside the bracket. Tighten the screws until the nylon heads are flush with the inner diameter of the bracket ring. Do NOT thread them in completely or they will interfere with the placement of the finder. (Having the screws in place when the finder is installed will be easier than trying to insert the screws after the finder has been installed.)
3. Slide the rubber O-ring over the back of the finder (it will NOT fit over the objective end of the finder). It may need to be stretched a little. Once on the main body of the finder, slide it up about one inch from the end of the finder.
4. Rotate the finder until one cross hair is parallel to the R.A. axis and the other is parallel to the DEC axis.
5. Slide the eyepiece end of the finder into the front of the bracket.
6. Slightly tighten the three nylon tipped thumbscrews on the front ring of the bracket to hold the finder in place.
7. Once on, push the finder back until the O-ring is snug inside the back ring of the finder bracket.
8. Hand tighten the three nylon tipped thumbscrews until snug.

 

So it seems the o-ring needs to be in the back ring, not the front ring.  Perhaps you have the bracket on backwards?


Edited by techmgr, 20 January 2020 - 11:43 PM.


#11 Oscar Szentirmai

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Posted 21 January 2020 - 05:05 AM

I tried all the things suggested so far, and on one scope it still wasn't enough.  I ended up adding a few sheets of paper to one "corner" of the finder bracket's shoe to act as a shim.  That finally did it.

 

 

I am not sure about this arrangement.  The scopes I have had with O-rings have the adjustment screws at the upper end of the finder holder on the top ring.  The O-ring usually is in the lower tube ring on the holder.  As you say, you push the finder down through to cinch up with the lower ring (O-ring on lower end).  Somebody else might chime in here.  

Is it possible that the finder base is mounted backwards on the main tube?

Again, I hope this will all resolve quickly for you.

Charlie

 

Found this from the C-11 manual:

 

To install the finderscope:
1. Attach the bracket to the optical tube. To do this, place the curved portion of the bracket with the slot over the two holes in the rear cell. bracket should be oriented so that the rings that hold the finder are over the telescope tube, not the rear cell (see Fig 2-11). screws in by hand and tighten fully with an Allen wrench.
2. Partially thread-in thumbscrews that hold the finder in place inside the bracket. Tighten the screws until the nylon heads are flush with the inner diameter of the bracket ring. Do NOT thread them in completely or they will interfere with the placement of the finder. (Having the screws in place when the finder is installed will be easier than trying to insert the screws after the finder has been installed.)
3. Slide the rubber O-ring over the back of the finder (it will NOT fit over the objective end of the finder). It may need to be stretched a little. Once on the main body of the finder, slide it up about one inch from the end of the finder.
4. Rotate the finder until one cross hair is parallel to the R.A. axis and the other is parallel to the DEC axis.
5. Slide the eyepiece end of the finder into the front of the bracket.
6. Slightly tighten the three nylon tipped thumbscrews on the front ring of the bracket to hold the finder in place.
7. Once on, push the finder back until the O-ring is snug inside the back ring of the finder bracket.
8. Hand tighten the three nylon tipped thumbscrews until snug.

 

So it seems the o-ring needs to be in the back ring, not the front ring.  Perhaps you have the bracket on backwards?

Thank you all for your reply

 

In my case, there were no screws to tighten BY HAND, I just removed TWO Philips screws, and attached the bracket! Certainly not Allen screws

 

Please have a look at the pics, which will explain my setup and orientation. Must be something wrong?

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#12 mclewis1

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Posted 21 January 2020 - 09:08 AM

Oscar,

 

A C11 ... oh boy.

 

Ok, with your finder setup. Take the whole finder assembly off of the scope and look at that shoe (the bracket attached to the scope). It looks to me like that bracket is not lined up well, and it looks like there isn't a lot of movement available, so you may have to play with this a bit.

 

Loosen the two bolts (phillips head screws) you have used to attach it. Line up the bracket visually, just try and get the bracket as straight as you can visually. Keep it as straight to the scope as possible and then snug those two bolts back down. (These were the original bolts in that position, right? ... and they are not new bolts added?)

 

Loosen the two big thumb type mounting bolts on the bottom of your finder scope assembly. Position them so they are roughly equal (notice in your photos that you've got one in a very different position than the other ... understandable as you've been trying to align things). Tighten your finder setup in place. Roughly center the finder scope using the 3 alignment bolts.

 

Now go out and use those three alignment bolts to align the finder with your big C11.


Edited by mclewis1, 21 January 2020 - 09:13 AM.

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#13 Oscar Szentirmai

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Posted 21 January 2020 - 09:17 AM

(These were the original bolts in that position, right? ... and they are not new bolts added?)

 

Yes, those 2 philips screws were already there in the rear cell. Manual says ALLEN bolts, and initially tighten with hand, but not in my case

 

(notice in your photos that you've got one in a very different position than the other ... understandable as you've been trying to align things). Tighten your finder setup in place. Roughly center the finder scope using the 3 alignment bolts.

 

yes, I took that pic for that reason, as the finder carrier does not look like it slides onto the bracket symmetrically, no matter what I do

 

Now go out and use those three alignment bolts to align the finder with your big C11.

 

So, is my orientation of the rubber O-Ring correct?

 

Many thanks



#14 mclewis1

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Posted 21 January 2020 - 09:30 AM

So, is my orientation of the rubber O-Ring correct?

Sorry, don't know as I don't have one of these newer finder brackets (my old one has two sets of 3 alignment bolts,  and no O-ring). I'd assume that if it's all snug and the finder tube is roughly centered (as it appears to be) that it should be fine.

 

If you don't bother with those two thumb type bolts (and have backed them out) does the whole assembly slide onto the bracket on the scope and sit squarely? Yes it will be a bit loose and so you'll need to press lightly on one side to keep it lined up with the bracket. I'm curious if there's anything (flashing etc.) fouling the position on the bracket.

 

The piece with those two thumb type bolts is actually called a saddle and it slides over the dovetail bracket on the scope ... just like the mounting point on your C8SE did when you attached it to the mount.



#15 mclewis1

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Posted 21 January 2020 - 09:37 AM

Oh and one other thing when re aligning everything, and I hate to bring this up but in the interest of being complete ... 

 

Are you doubly certain you are aligning on the same object (that red light) and that there isn't another light that could be mistaken for it? The C11 has such a long focal length (a monsterous 2850mm or just over 9 feet) that because of the high magnification and small field of view it can be very easy to miss identify objects ... particularly terrestrial/land based ones.



#16 macdonjh

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Posted 21 January 2020 - 09:45 AM

This looks suspect to me:

 

post-21573-0-28418400-1579601069.jpg

 

The finder scope bracket looks crooked on the mounting shoe.  Perhaps fiddling with those two silver thumb screws until the finder scope mounting bracket is parallel with the shoe?  From some of the other photos posted it doesn't look like the mounting shoe has much adjustment available, so hopefully this will work.



#17 techmgr

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Posted 21 January 2020 - 10:12 AM

So, is my orientation of the rubber O-Ring correct?

 

Many thanks

According to the pictures you have posted, I would suggest that the finderscope bracket is on backwards.  The ring that accepts the o-ring should be towards the rear of the scope, not the front. The o-ring should be at the rear of the finderscope, and then fitted into the rear ring of the bracket.



#18 Oscar Szentirmai

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Posted 21 January 2020 - 03:31 PM

According to the pictures you have posted, I would suggest that the finderscope bracket is on backwards.  The ring that accepts the o-ring should be towards the rear of the scope, not the front. The o-ring should be at the rear of the finderscope, and then fitted into the rear ring of the bracket.

Are you sure?

 

According to this pic on FLO website, my orientation should be the correct one?

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#19 techmgr

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Posted 21 January 2020 - 05:48 PM

Well, after some more investigation, I can understand the confusion.  Your picture and the Celestron website show the adjustable ring as the rear ring.  I pulled this from an online C-11 manual showing the front ring as the adjustable one, and I think this is what mine looked like when new.  I don't use this now, and don't have it any longer to check for sure.  Anyway, it's possible that there is more than one finderscope and more than one bracket depending on how old the C-11 is.

 

 

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#20 kathyastro

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Posted 21 January 2020 - 05:56 PM

Anyway, it's possible that there is more than one finderscope and more than one bracket depending on how old the C-11 is.

Comparing your photo with the OP's photo, it is clear that they are referring to two completely different finders.

 

It shouldn't matter which ring is in front and which is behind.  Unless having it the wrong way around affects how the bracket sits on its mounting plate.  The OP's photo of that certainly looked suspect.
 


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#21 Steve C.

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Posted 21 January 2020 - 05:56 PM

One of the issues I've seen with the Celestron finder mounts is that the spring loaded knob on the adjustable ring may not go in far enough. I think that it can be adjusted with an Allen wrench (hex key).



#22 techmgr

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Posted 21 January 2020 - 06:26 PM

Comparing your photo with the OP's photo, it is clear that they are referring to two completely different finders.

 

It shouldn't matter which ring is in front and which is behind.  Unless having it the wrong way around affects how the bracket sits on its mounting plate.  The OP's photo of that certainly looked suspect.
 

I thought the same thing.



#23 charlesgeiger

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Posted 21 January 2020 - 07:15 PM

Again, the part of the bracket you mount onto the tube is correct.  However, the 'ring' bracket is supposed to be reversed.  The adjustment screws should be on the 'top' ring (ring facing front of your optical tube).  The picture is incorrect.  Give it a try.  I bet the ring bracket will fit better onto the base piece on your optical tube.  As noted, you put the O-ring on the eyepiece end of the finder itself about an inch onto the tube.  Then you stick the tube through the top ring (eyepiece end first) and push the tube down into the first ring so that the O-ring sets into the top of the bottom ring.  Finally, screw in or tighten the nylon adjusting screws in the top ring and approximately center.  Then you are ready for final adjustment or collimation with the main scope.  There should be no O-ring on the top ring period   It is worth a try (also, you can wrap some electricians tape around the finder tube as it enters the top ring so the adjustment screws bite into the tape rather than your finish). This is up to you regarding the tape.  Let us know how this works.  I am sure this is what is needed.

Charlie 



#24 JMP

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Posted 21 January 2020 - 08:16 PM

Hi Oscar;

 

Welcome to the world of telescopes! I have a finder just like yours. You've got it mostly right but there are two issues. The rubber "O" ring is not seated in the finder bracket, and the bracket is not quite seated in the base.

 

Take the finder and bracket off the scope. You'll see that the base has two "V" shaped notches, when the bracket is positioned correctly the thumb screws will mate with the notches.

 

The other issue is the "O" ring. The front ring is open to the front. Place the rubber ring about 1 or 1.5 inches behind the ribbed ring near the lens, then insert the finder from the front. The ring will push into the bracket and hold the front of the finder firmly. In your picture the ring is not seated so the finder is not centered.

 

You are close, but take it apart and you can see the issues. I would place the finder in the bracket first, then slide the bracket onto the mounting base. If all goes well, the finder should stay nearly aligned even if you need to remove the finder for storage.

 

Jeff Phillips

Eugene, Oregon


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#25 psyhiker

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Posted 23 January 2020 - 01:02 AM

I have this same finder scope and C11 and have the same problems:  To my mind, the big design flaw in this thing is that it has only TWO adjustable screws, one at 12 o'clock and one at 4 o'clock.  It is impossible to make precise final adjustments with only two points of adjustment.  To go in certain directions, you have to figure out how to use BOTH screws at the SAME time, sometimes both to the right, sometimes both to the left, sometimes one to the right and the other to the left, sometimes the other to the right and the other to the left.  ARGH!!  It is a great frustration, also because you wind up getting to the end of the thread of one of them and can't go anymore.  My old Meade LX3's finder scope had three points to adjust, 12, 4 and 7 o'clock, and had these on both the front and the rear o-rings.   I NEVER had an issue making very fine adjustments to align with the OTA.  I do not have an answer, just want to share my experience and my explanation of the problem.  Wait! maybe the answer is to find one of those old meade 9X50 finderscopes and strap that to your C11...I know that you didn't want to buy a new one, but maybe your birthday is coming up and you could ask for that?

 

https://www.cloudyni...r-finder-scope/


Edited by psyhiker, 23 January 2020 - 01:12 AM.



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