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Questar 700 Repair

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#1 jm56

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Posted 19 January 2021 - 09:59 AM

Hi all - 

 

When my grandfather passed away I was given his Questar 700 that he and I used when I was growing up. Unfortunately, within 10 minutes of receiving it, one of my toddlers went into my office and knocked over the tripod damaging the eyepiece.  It also appears that an internal piece was either already loose or was knocked loose.  I admittedly don't know much about this equipment so I'm not sure if a self repair would be an (wise) option but am interested in getting it evaluated/repaired and was looking for suggestions on for where/for what type of place I should be looking.  Or any other suggestions for that matter.  I'm in San Antonio, TX if that makes a difference.

 

Thanks.



#2 jm56

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Posted 19 January 2021 - 10:01 AM

Pictures for reference

Questar 700 1.jpg



#3 jm56

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Posted 19 January 2021 - 10:03 AM

Picture for reference

Questar 700 2.jpg



#4 Erik Bakker

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Posted 19 January 2021 - 11:32 AM

Sorry to hear that. My advice is to give Questar a call (they are not the e-mail type company wink.gif ) and discuss this with them. They will help you to decide what is the best cure and how much that would cost.



#5 Optics Patent

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Posted 19 January 2021 - 11:45 AM

The loose piece looks in the photos like a black ring, but I suspect it is a thin matte black paper cone.  The light baffle applied to the rear surface of the corrector.  Am I right?

 

If so, just unscrew the front retainer ring, remove the corrector (good time to clean the often-fogged rear surface) and reapply the baffle.  Or discard and suffer presumably minimal contrast loss when shooting close to a bright light source.

 

Also, I made a video on the entire process for taking down and reassembling one of these. The first minute will be helpful.



#6 telescope200

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Posted 19 January 2021 - 02:00 PM

Looks like the secondary spot baffle fell off. Its a wide, beveled ring. Is was glued in place and I would assume the (rtv?) glue has failed since it seems to be leaving goopy ring marks on the inside of the front lens (called the "corrector"). Dropping it was probably the final straw but any kind of glue will not last forever.

 
Its a pretty easy fix... if you are handy and you don't think you have anything to lose. Looks like you would remove the front retaining ring, remove the corrector lens, clean off the lens and the baffle, re-glue it with RTV Silicon rubber, and put it back.
 
You would need a spanner wrench to get the retaining ring off (could use two mini screwdrivers c-clamped to a piece of wood) and cleaning up RTV can be a mess, maybe it will clean up with alcohol, we use to use Benzine (nasty stuff). There seem to be some safer RTV cleaners out there. You would also have to get the optics clean and the baffle centered.
 
You could also just open it up and remove the baffle, leave it for a future project... it is in danger of falling on the mirror so definitely don't use the scope or point it up till you get it fixed.
 
A visit to a local astronomy club may turn up people who can help you fix it.
 
Or there is always mailing it to Questar... hope the baffle doesn't bash the mirror in the mail.
 
Robert S

Attached Thumbnails

  • questar 700 baffle.jpg

Edited by telescope200, 19 January 2021 - 07:43 PM.


#7 Optics Patent

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Posted 19 January 2021 - 10:52 PM

Search “lens spanner” on eBay for the under $20 solution.

I also suggest a “lens sucker” suction cup tool to lift the thick corrector out and replace it. Right fit will cause it to bind if not handled deftly. My video demonstrates.

I’d call Q to ask what kind of adhesive. They would also share if the baffle was really superfluous. They admitted to
me that the lens edge blackening was optically needless and just cosmetic and not worth the mess and risk.

#8 Tom3

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Posted 20 January 2021 - 02:21 PM

Would you like to have on a GOTO mount?  If so you could ask around on how to do that.

 

Tom




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