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Collimation help for a sick C11 really needed

Collimation Celestron
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#1 Sky King

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Posted 08 May 2021 - 06:34 PM

Thanks for some help here! I got a old orange C11 used a while back, and it had some rash on the collector, so I carefully removed the collector, marking it's orientation, and tried to clean it on the inside. Unfortunately it was the coatings that were damaged. The coating rash looks worse in the pictures than it is. So I put it back together and tried to bring it to focus and nothing doing. I tried the 5.475" back focus recommended by Celestron and also the Celestron t adapter and a DSLR. Then I started checking the collimation. I recently got a Hotech SCA-2C laser and thought that would do it. I can't see anything out of this scope. I saw some tips in this thread and tried a rough collimation. Here are the results so far. The first picture is a roof. This is the best it would do. (The redness is my astro-modified T2i.)

 

Roof.jpg

 

Here it is before any adjustments.

 

Before.jpg


Edited by Sky King, 08 May 2021 - 06:49 PM.


#2 Sky King

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Posted 08 May 2021 - 06:35 PM

Here is another before:

 

 

Before rough adjust.jpg

 

 

 

 

 



#3 Sky King

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Posted 08 May 2021 - 06:45 PM

 And after moving the laser to the bullseye with the Hotech.

 

After Hotech.jpg

 

There is something wrong with this scope.  If you have any steps to suggest I'd like to hear them.  You can't do a star test when you can't see a star... I don't know how much the coatings add to the problem, but I doubt very much as 85% of the collector is clear.


Edited by Sky King, 08 May 2021 - 09:17 PM.


#4 Bean614

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Posted 08 May 2021 - 06:52 PM

Well, I don't know how far away that roof is, but..... a C11 needs a LONG, minimum distance to come to focus!  Pick a telephone pole at Least 1/4 mile away, or better yet, a bright star at night, with a 25mm eyepiece! No Camera!!  You'll have better results.


Edited by Bean614, 08 May 2021 - 06:54 PM.

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#5 J A VOLK

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Posted 08 May 2021 - 07:00 PM

You don't need any expensive equipment to collimate an SCT, and coating degradation on the corrector will not keep you from getting an image. Sounds like you just haven't found the focus point.  There is huge focus variation with the moving mirror.  Try pointing at a distant terrestrial object as previously suggested, the further the better .   Move the focus knob all the way one direction.  Then start moving towards the other side of focus while monitoring the image.  It will likely take numerous turns.  If the object is quite distant than you won't be too far off when you move to a star.


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#6 happylimpet

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Posted 08 May 2021 - 07:02 PM

The moon is always the best target for getting focus when youve no idea where to start.


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#7 Sky King

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Posted 08 May 2021 - 07:15 PM

Well thanks, I will certainly try all those ideas and report back. Here's another after laser collimation photo.

 

IMG_1381.jpg

 

 



#8 charlesgeiger

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Posted 08 May 2021 - 07:46 PM

The reflections from the front of the telescope are terribly wrong.  You may need to pull the corrector again and make sure your primary baffle tube nut is tight against the main mirror.  Look for a bolt protruding inside the telescope from the area of the rear cell which could be tilting your main mirror badly by binding against the side or periphery of the main mirror.  Does your secondary have a baffle attached?

Is the primary relatively clean?  And if it is not, you don't want to do any mirror cleaning until you get some information as the primary and secondary mirror coatings are very fragile.  

Take the knob off the focusser and see if the unit has a screw in the center holding your primary  in place.  Do not tip the front of the scope down as the primary can fall against the secondary and break all the glass if your focusser is not attached with a screw in the center.

And make sure your secondary mirror is held in place correctly.  If any of the three screws in the front of the secondary are loose or stripped, the secondary could be badly tilted.  Make sure you do not remove all three screws as the secondary can fall back onto the primary.

Make sure also that your corrector is sitting in position against the cork gasket flat onto the surface of the corrector cell.

Let us know what you find.

Charlie


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#9 Sky King

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Posted 08 May 2021 - 08:17 PM

Well I have some progress! I set up outside and aimed at a palm tree. I can't see very far from my back yard. The tree wouldn't focus but a small power cable jumped into sharp focus! Just a power line, but that means it's working! So I think I'm really for the moon test!  I have taken my C8 apart many times and never had a problem. But this C11 is a different kind of beast. Thanks!! Charlie the bolt rubbing against the mirror is a real possibility, see picture. I will replace those with shorter ones, one at a time. Secondary has no baffle and is firmly attached. I put the corrector back on exactly as it came off. I did replace the three collimation screws as the old ones the heads were worn. Got an exact match at the hardware store. Both mirrors are very clean. Didn't need cleaned. Thanks Bean614, I hadn't looked through an eyepiece for over a year. Used a Orion Deepview 28mm. Thanks all!  I love this C11 relic and can't wait to take this baby for a spin once it's all tuned up!

 

IMG_1382.jpg


Edited by Sky King, 08 May 2021 - 08:27 PM.


#10 Sky King

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Posted 08 May 2021 - 08:52 PM

I think it's a 1980's...

 

IMG_1384.jpg



#11 Sky King

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Posted 09 May 2021 - 12:54 PM

Thank you! I struggled for months and I saw images for the first time last night! I tried to go with just an eyepiece, but I keep getting blank space, so I switched to a ASI174mm and then the T2i Canon cameras, hoping to plate solve. For four hours I keep changing spacings and couldn't get focus with the camera either. So I went to the DSLR and the Celestron t adapter that was supposed to work and it did after a lot of fiddling. There may still be work needed, but it's 100% better than it was! So here's my pictures. First a badly deformed donut, then after some luck with the collimation screws, a much better donut. Then M81! Then the battery died in the DSLR so I put on the ASI174mm with the same spacing. I tried to get to M16, but only got a little patch of space close to M16. I take photos of the camera and spacers used so next time I should be able to start near focus. I'm just thrilled. What fun! Thanks!

 

First.jpg

 

 



#12 Sky King

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Posted 09 May 2021 - 12:55 PM

This looked like a great start!

 

Second.jpg



#13 Sky King

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Posted 09 May 2021 - 12:58 PM

At several points my mount stopped tracking and my stars trailed. Could be some of that here. But by now I knew the C11 was working.

 

M81

 

Third1 M81.jpg


Edited by Sky King, 09 May 2021 - 01:09 PM.


#14 Sky King

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Posted 09 May 2021 - 01:05 PM

This was a surprise, I thought I had plate solved and landed on M16, the Eagle Nebula. I didn't expect to see it with the black and white ASI174mm and no filter. I was close to M16 as this shows.  With the C11 I'll have to be more precise. This is 13.6 x 8.56 arcmin. The image does show the C11 up and running. I was just out of ideas on how to fix this scope. Thanks!

 

close to M16.jpg


Edited by Sky King, 09 May 2021 - 01:17 PM.


#15 alphatripleplus

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Posted 09 May 2021 - 03:10 PM

Sounds like you are on your way...


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#16 Sky King

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Posted 25 May 2021 - 04:20 PM

Really appreciated the help with this, thanks again! The collimation isn't spot on yet, but it's getting there. Last night I got this image from a ASI174mm, 2000 frame SER, best 300 frames. Clear skies!

 

22 04 10 300F moon

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#17 MarMax

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Posted 25 May 2021 - 09:31 PM

If you've got it close, which I'd say you have, you should try a Duncan mask. You can search it up and get plenty of info. My sig also has an image that if you print to scale you can cut out of cardboard and try it out.


Edited by MarMax, 25 May 2021 - 09:31 PM.

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