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Focuser question

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#1 Quinnipiac Monster

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Posted 12 October 2019 - 03:16 PM

Hi all,

 

A few nights ago I dropped the screw that keeps my eyepieces in place, and never found it again. Nothing I have in house screws in, does anyone know what the focuser's brand is, and what kind of threading it uses? I bought it second-hand at Stellafane (see picture), it seems to be nicely manufactured and it works great.

 

Thanks!

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Edited by Quinnipiac Monster, 12 October 2019 - 03:18 PM.


#2 Quinnipiac Monster

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Posted 14 October 2019 - 05:15 PM

All right, I found what it is. Apparently, an early JMI NGF-mini, the version for Newtonian telescopes. Still looking for a replacement eyepiece screw, but meanwhile there's another problem I've noted recently. At times, the motor would just not work; you press the buttons on the controller, nothing happens.

 

The behavior seems to be rather erratic, in the course of an observing session the focuser would work at first, then nothing for a while, then on again. I tried a different controller (I have a spare one), same same. After disengaging the motor, I  found that the hand knob is very hard to turn, is it possible that the tension screw is just too tightened and the motor has a hard time turning it?

 

A JMI instructions sheet for a similar focuser I found online (http://www.physics.c.../ngfs_instr.pdf) stresses that everything else is factory tested and should never be touched, as pusher bearing alignment (for example) is extremely critical. 


Edited by Quinnipiac Monster, 14 October 2019 - 05:18 PM.


#3 25585

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Posted 14 October 2019 - 05:50 PM

Best thing is to buy small assorted bolts and try them out for fit .



#4 Jon Isaacs

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Posted 14 October 2019 - 09:39 PM

It's either a 6-32 or 8-32 screw, probably a 6-32. A nylon thumbscrew is nice because it doesn't Nick the eyepieve or adapter.

 

Jon


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#5 kfiscus

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Posted 14 October 2019 - 09:45 PM

Check for a loose connection somewhere since you've already eliminated the controller as being the problem.



#6 Quinnipiac Monster

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Posted Yesterday, 07:40 AM

It's either a 6-32 or 8-32 screw, probably a 6-32. A nylon thumbscrew is nice because it doesn't Nick the eyepieve or adapter.

 

Jon

Thanks! :)



#7 Myk Rian

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Posted Yesterday, 08:09 AM

OR, a  4 or 5mm. Are those hex screws sae or metric?

 

I go through all the hardware stores' fasteners section looking for sae and mm thumbscrews.



#8 Redbetter

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Posted Today, 12:52 AM

The 2003 vintage JMI on my Obsession has 6-32 screws for the 2" and for the 1.25" adapter.  I checked them a few moments ago.




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