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Nexstar 4SE-gray tube issues

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#1 PopPopJ

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Posted 27 July 2013 - 09:29 AM

Sorry if any of this is redundant to this forum, or in the wrong category. I just got a Celestron NexStar 4SE from a Goodwill auction. I expected it to have issues, why else would someone donate it? I didn't expect something rattling around inside the tube. The "reflection shield"(?) around the secondary mirror, on the corrector was laying on the primary mirror, and has caused some scratches. I was able to remove the corrector, remove the "sticky tape" (used to mount to shield) with freon, and remount it.

I wanted to remove the primary mirror to see if what I'm seeing are scratches or remnants of the glue from the shield. I've found disassembly instructions for an 4SE, but they are the orange tube and totally different from the gray tube assembly.

I have two questions: How do I disassemble the tube, in order to access the mirror, focuser, etc? I can find no screws that are holding the ends, and no easy way to get either end of the tube off. And, once disassembled, if necessary, where can I get the mirror re-aluminized (I assume it's not silvered).

Thanks in advance for any input.

Jay

#2 Tel

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Posted 27 July 2013 - 02:08 PM

Hi Jay,

Welcome to CN and to this Nexstar forum in particular ! :bow::bow:

If your 4" Nexstar has a grey tube then, likely as not, its an early Nexstar 4.

Now, I seem to recall that this inquiry arose once before and not so long ago on this forum with regard to this model's primary mirror cell removal and I thought I'd logged the procedure, but unfortunately I can't locate it.

I believe, however, that in the case of the Nexstar 4, as opposed to the Nexstar 4SE, the primary cell unscrews as a whole unit, but maybe someone else will confirm this.

As to the mirror coating, it will certainly be aluminium (aluminum) but assuming you live in the US, (your spelling of "Gray" being a possible give-away ! :lol:), I can't help you in respect of where you might get it re-aluminised if required.

Sorry not to be of much help.

Best regards,
Tel

#3 hamdul

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Posted 27 July 2013 - 02:32 PM

Jay,
I have no idea where you are but there are several firms that do Mirror aluminizing. Give me a hint as to your location and I'll see what there is available for you. :help: :question:
Fred

#4 BigC

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Posted 29 July 2013 - 12:48 PM

Sorry if any of this is redundant to this forum, or in the wrong category. I just got a Celestron NexStar 4SE from a Goodwill auction. I expected it to have issues, why else would someone donate it? I didn't expect something rattling around inside the tube. The "reflection shield"(?) around the secondary mirror, on the corrector was laying on the primary mirror, and has caused some scratches. I was able to remove the corrector, remove the "sticky tape" (used to mount to shield) with freon, and remount it.

I wanted to remove the primary mirror to see if what I'm seeing are scratches or remnants of the glue from the shield. I've found disassembly instructions for an 4SE, but they are the orange tube and totally different from the gray tube assembly.

I have two questions: How do I disassemble the tube, in order to access the mirror, focuser, etc? I can find no screws that are holding the ends, and no easy way to get either end of the tube off. And, once disassembled, if necessary, where can I get the mirror re-aluminized (I assume it's not silvered).

Thanks in advance for any input.

Jay

I saw a gray Nexstar on auction from a Florida Goodwill store-if that is the one you have,I believe it is the Nexstar 4GT model. Goodwill people are not telescope experts and often list scopes incorrectly.

My experience is that some people simply do not wish to have a yard sale or strangers coming to their home in answer to classified ads, and donate many perfectly working items.The care taken in handling those items varies tremendously so the scope may have been "roughed up" after donation.

#5 Geo.

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Posted 02 August 2013 - 05:57 PM

The main tube threads into the rear cell (right hand thread). A couple of rubber strap wrenches will get it apart. I've seen a lot of these secondary baffles get loose inside the tube. They rarely damage the mirror. I use 3M 5200 to stick'em back on.

#6 Pisces1

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Posted 03 August 2013 - 06:42 PM

Maybe you can contact Celestron directly for help or find some information on their website. They helped me recently with a program issue (boot loaded 080 problem). www.celestron.com
Good luck

#7 Robert Sheaffer

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Posted 29 December 2013 - 03:25 PM

I just bought a gray-tube Nexstar 4 at a swap meet, and it, too, had a small piece of plastic or something rattling around inside the OTA! After considering - and rejecting - ways to disassemble the tube, I tried using a "grabber" with expanding fingers at the end. Point the tube down, and the piece falls down against the corrector plate, where I can see it clearly. The problem with this was, when you push the grabber in the eyepiece hole, it hits the secondary reflecting mirror - no way! However, I was able to put a big enough kink into the grabber's wire, so that I could get around it. Once I had the business end of the grabber down at the corner of the corrector plate, it was easy to grab the little piece, and carefully remove the grabber.

Now what I need to do is get a hand controller that works! Unfortunately, the one that came with it either displays garbled characters, or none at all. But the motors are all working.

#8 termhn

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Posted 29 January 2014 - 12:45 AM

Hey,I have a gray tube 4 inch celestron as well. My remote was doing the same as yours the first time I dusted it off after a few years, try replacing batteries and turning it off and turning it back on a bunch of times. It seems like there's probably some bad electrons in there and they need to be cleared out. Started to work for me eventually.

#9 Geo.

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Posted 31 January 2014 - 02:34 PM

The connectors used in these scopes, well many scopes, are really not up to the job. Pull all the connectors apart and clean them, including the one in the HC.






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