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Focus problem

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#1 Winks

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Posted 16 July 2020 - 04:00 AM

Took my 3.5 out this evening and went to focus on Jupiter and....nothing. No matter how far in or out I turned the focuser, nothing happened.  Can anyone give me an idea what is going on? Is it self-fixable or does it have to be sent to Questar? Really bummed. Thanks in advance.



#2 JREnglar

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Posted 16 July 2020 - 05:22 AM

Took my 3.5 out this evening and went to focus on Jupiter and....nothing. No matter how far in or out I turned the focuser, nothing happened.  Can anyone give me an idea what is going on? Is it self-fixable or does it have to be sent to Questar? Really bummed. Thanks in advance.

Pardon what may be a stupid question but you weren’t inadvertently in finder mode were you (in which focus doesn’t change with the focus knob)? Other than that I would suggest you look down the tube from the front and see if the primary mirror moves when you turn the focuser.
 

Also, what year is your scope?  Early models had a black “Synthane” rear piece (later aluminum) that the threaded focus shaft passed through and the threads in the Synthane could wear out preventing the focus knob from moving the primary mirror.

 

JRE


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#3 Winks

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Posted 16 July 2020 - 09:03 AM

I wish it was just me doing something dumb. No, I had it in regular, non finder mode. I checked that a couple times. It is from the mid 70's. And, no, the primary mirror is not moving when the foucs knob is turned.



#4 Johninuk

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Posted 16 July 2020 - 09:08 AM

Have you checked whether the grub screw in the focusing knob is loose, and the shaft is not turning?

John.

#5 Winks

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Posted 16 July 2020 - 10:00 AM

It's tight. Shaft turns all the way out and all the way in.



#6 Johninuk

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Posted 16 July 2020 - 10:14 AM

I would think that the end of the focusing screw has become detached from the mirror arm.The only way to check is to unscrew the main tube from the control box.Mine was really tight and took some force to unscrew.Others have found it easy.
If the focusing screw is detached,it's a "fairly"easy job to reattach it yourself without a visit to Q.
Look at Ben's excellent how to guide in the Questar Zone.
John
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#7 Winks

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Posted 16 July 2020 - 10:55 AM

Thanks. I will do. Where is the Questar Zone?



#8 Winks

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Posted 16 July 2020 - 11:09 AM

Thank you all.  Unscrew the barrel - tight but not too - and sure enough - the focusing screw detached. Reattached and now it is working fine. THANK YOU!!!!


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#9 RMay

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Posted 16 July 2020 - 11:25 AM

Brilliant! What a forum... 👍👍👍

Ron

#10 Johninuk

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Posted 16 July 2020 - 11:52 AM

Excellent!! Google "Questar Zone"

#11 Les Aperture

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Posted 16 July 2020 - 05:00 PM

YEAH!

Why to go Q forum!

 

"Les"


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#12 Optics Patent

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Posted 16 July 2020 - 10:36 PM

The big warning is to keep the scope pointed up. If the mirror is detached from the focusing shaft then there is nothing holding it onto the spindle. Pointing down could result in a worst vase catastrophic crash as the mirror hits the corrector.

#13 Winks

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Posted 17 July 2020 - 10:52 AM

Thanks, Ben. The moment I realized it was not focusing (pointed up at Jupiter), I kept it in that position.  Not sure what caused it - the extreme Phoenix heat perhaps?




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