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3.5" Questar Finder Focusing

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#1 Stephen S

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Posted 13 October 2012 - 08:24 PM

I have a minor issue with my new (to me) 3.5" Questar. It's a 1992 version if that matters. Just about everything with the scope is fantastic. The one issue I'm having is that I cannot get the Questar Brandon eyepieces to come into focus with the finder. They get very close but come just short of coming into focus when fully screwed in (using a Questar eyepiece holder that adapts for other 1.25" eyepieces). Ironically, my only eyepiece that comes to focus in the finder is my 68 degree ES 24mm eyepiece.

When I switch from finder to scope, the image shifts slightly as well. I can find the target quite quickly when moving the scope up (if I remember correctly). All this makes me think that the finder mirror is slightly off. Does this sound reasonable? If so, does anyone have experience with this issue? Something I can tackle myself or should I send it into Questar for service?

Not a critical issue. Focus is close enough that I'm able to use the focuser with my Brandons. That said, I would much prefer to be able to focus the finder if possible. Any input would be appreciated.

Thanks! Steve S.

#2 Stephen S

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Posted 17 October 2012 - 08:32 PM

No thoughts on this issue? Any input would be helpful.

Thanks! Steve S

#3 Panotaker

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Posted 18 October 2012 - 02:59 AM

Is this a regular Questar, or is it the Questar Birder. Can you take a couple of the scope so we can see if it looks normal.

#4 EddWen

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Posted 18 October 2012 - 12:53 PM

The eyepiece holder on my '89 rotates for finder focus. I've had mine 'stick' sometimes from lack of use, but it should rotate.

#5 Steve's 50th

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Posted 18 October 2012 - 04:53 PM

I'm with Edd, does the eyepiece holder rotate? Is the Brandon screwed in completely? I'm probably wrong but I don't think your diagonal mirror is the problem. It's not unusual for the mirror to cause some error in aiming the scope but as far as I know not the focus of the eyepiece.

#6 Panotaker

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Posted 18 October 2012 - 05:57 PM

The reason I brought up the Birder, is because the finder on the Birder could be focused separately if the finder barrel is a little loose. If it is a little loose, you can slide the barrel on the 10X finder in and out and make just about any eyepiece come to focus with the finder. If the barrel is pushed all the way in accidentally, no eyepiece will come to focus.

If it is a regular Questar, It is probably the diopter adjuster on the eyepiece holder that got accidentally screwed in all the way and it is now stuck.

#7 ColoHank

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Posted 19 October 2012 - 01:12 PM

I offer this comment in the belief that a picture is worth a thousand words:

The threaded barrel of the Questar's eyepiece holder screws firmly into the control box (red arrow) at the rear of the scope. When firmly seated, the barrel of the eyepiece holder should not rotate (loosen) during focusing.

The threaded barrel of the eyepiece should screw firmly into the top of eyepiece holder (blue arrow). When focusing, the eyepiece should not rotate (loosen) relative to the knurled collar on the eyepiece holder.

With the holder and eyepiece barrels screwed frmly in place, the knurled collar (yellow arrow) and the stainless steel ring of like diameter below it on the eyepiece holder should rotate freely to focus the finder. If the knurled collar is tightly jammed all the way up or all the way down, you probably won't be able to achieve finder focus with your Brandon eyepieces, and you shouldn't attempt to achieve finder focus by unscrewing either the holder barrel from the control box or the eyepiece from the eyepiece holder. The remedy for a jammed focusing collar is to remove the entire eyepiece holder assembly from the control box and free up the knurled collar so it rotates freely through the entire focusing range.

Hope this helps.

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#8 Stephen S

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Posted 19 October 2012 - 05:09 PM

This is incredibly helpful info! Thank you! Based on this info, I am fairly certain the knurled collar is jammed. This would absolutely explain my challenge. I am tied up at work tonight but will definitely give this all a try tomorrow. Thanks again for this feedback. Most helpful.

Thanks! Steve S.

#9 Michael Lomb

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Posted 20 October 2012 - 08:17 PM

I had the same problem with my 1978 telescope, subject of an earlier post. I removed the eyepiece holder, and clamped it on a wood vice, then used a wrench protected with cardboard as not to mark the metal and unscrewed the jammed ring. The other thing is to check that this is not a Televue adapter which is a different height to the Questar adapter. Mine came with both.

#10 Stephen S

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Posted 21 October 2012 - 11:55 AM

Got my Questar out last night. After fiddling with things a bit, it was clear that the adjusting collar was stuck all the way out. Once I realized this, it was fairly easy to unstick the adjusting collar. The finder focuser now works great with my Brandon eyepieces!

So nice to be able to focus the finder. I was able to easily locate several clusters that would have been difficult otherwise. Thank you for all you help in figuring this out. ColoHank, I really appreciate the picture. It made it easy for me to see the problem with my scope. It's all working great now and I could not be happier with the Questar.

Thanks again for the feedback. I really appreciate it. :bow:






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