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Celestron 9.25 SCT rotating visual back?

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#1 Julio

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Posted 03 January 2013 - 02:16 PM

I have a Celestron 9.25 and I,m a bit concerned because my visual back spins when i tighten an attached 1.25 adapter. Is this rotation normal, can it be tightened? I attempted some clockwise rotation hoping that perhaps it is threaded but it still spins. Again this only occurs when moderate torque is applied by hand. Also will this cause the primary to spin as well possibly affecting optical performance?

#2 rmollise

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Posted 03 January 2013 - 02:57 PM

What exactly is rotating? The visual back, which threads onto the rear port? The rear port itself?

#3 Julio

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Posted 03 January 2013 - 03:04 PM

Hello Uncle Rod, the rear port itself. It occurs when i apply moderate torque to tighten.

#4 bilgebay

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Posted 03 January 2013 - 03:21 PM

I had this problem back in 2006 and was able to fix it following the instructions of Celestron Tech Support. As Iam located in Turkey, sending the scope back to CA wasn't an option. So I had to do it my self.

Below is the comms I had back then:

Loose rear cell/rotating baffle tube

I am not sure that I understand your issue. From your description, the rear cell of the scope is rotating, bt this is not possible. The rear cell is the large casting at the back of the tube where the focusing knob is located. The rear cell is secured to the rear cell by means of three bolts with nuts on the inside of the tube. The rear cell cannot possible be free to rotate. Are you referring to the baffle lock nut? This is the part that has the male threads that your visual back and thread-on filters would attach to, but also has female threads inside of it where it attaches to the rear cell. If this is loose, you should be able to carefully remove it and place Loctite, or other liquid thread-lock to the threads. Replace the baffle lock nut and let it set for at least 24 hours. You should be ready to install your accessories.
Sincerely,

Celestron Technical Services Department



This is bad news. I was under the impression that the baffle lock nut was the only thing that was loose. This would be an easy fix. The baffle tube slides through the rear cell of the telescope and the baffle lock nut threads onto the baffle to secure it into place. We use a liquid thread lock on the baffle lock nut to prevent it from coming loose. If the baffle lock nut and the baffle tube are still fixed together, you are going to have to break the baffle lock nut loose. You will need to remove corrector plate and primary mirror from the telescope by removing the focus knob and bearings and sliding the primary off of the baffle tube. Next, you will have to apply a blow torch to the baffle lock nut to loose the thread lock, while applying force to unthread it from the baffle tube. This will not be an easy task and you may damage the baffle lock nut when attempting to remove it. If this happens and you need to purchase a new baffle lock nut, you will need to contact Astronomics. Due to contractual agreements with our international distributors, we cannot sell parts outside of the United States and Canada.

Sincerely,

Celestron Technical Services Department



1. I'm sorry, but all of our technical and assembly drawings are considered proprietary.

2. The primary mirror and secondary mirrors have marks on the backs of them. The corrector plate has a serial number etched into one side. Line up the marks on the primary & secondary mirrors with the center of the serial number on the corrector plate and you will assure alignment when you reassemble it.

3. A clean environment is good, but not critical. Your telescope optical tube is not air tight, so dust will enter the tube. Evry precasution you can take to keep the roomm clean where you are working is a plus as it will prevent an excessive amount of dust from entering the tube.

4. The tube is secured to the front and rear cellsby means of screws with nuts on the inside of the tube. You will not have access to these nuts until you remove the corrector plate from the inside of the front cell. You can remove the body tube from the rear cell if you wish.

6. The baffle tube is not physcially connected to the rear cell of the scope. The only way to secure the baffle from rotating it to have the baffle lock nut very tight to pull the baffle into the metal surface. Loctite may help here as well.

Sincerely,

Celestron Technical Services Department

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#5 Julio

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Posted 03 January 2013 - 03:37 PM

The baffle appears to be perfectly aligned and only rotates when torqued. Do you suppose its best to simply let it be since the baffle is not misaligned?

#6 bilgebay

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Posted 03 January 2013 - 03:50 PM

I am sure it is flexing and destroying your collimation unless you re-collimate everytime you use the scope. If this is not the case and you are happy with the views, of course leave it alone.

It's a lot of work to fix it but once you do it, it lasts forever. I guess your scope and mine are monday morning scopes :( If the worker who assembled the scope torqued the nut correctly this problem wouldn't occur at all...

#7 Julio

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Posted 03 January 2013 - 04:21 PM

I just rechecked, the light baffle does spin as i turn the hub, baffle nut. I guess this is bad news? :foreheadslap:






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