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Who Made This Newtonian Crayford Focuser?

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#1 Tom Duncan

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Posted 12 July 2019 - 06:22 PM

I've had one of these 2" Newtonian Crayford flat bottom focusers before but I can't remember who made it. The thin focus wheels with O-rings is the tipoff I think. 

 

Anyone know? 

 

Tom Duncan 

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#2 Ron Moore

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Posted 12 July 2019 - 06:35 PM

Please post the answer when you find out.... I have the same one on my early Obsession and think it is an Astro-Systems but it is not named. Thanks, Ron.



#3 DuncanM

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Posted 12 July 2019 - 06:51 PM

It looks like a JMI Reverse Crayford.



#4 dave brock

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Posted 12 July 2019 - 06:54 PM

Looks like JMI but not a Reverse.


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#5 Tom Duncan

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Posted 12 July 2019 - 07:16 PM

I was thinking possibly early JMI but all the JMI's I've ever met have not had the polished aluminum finish. 

 

I was also wondering what the cutout is between the white thumbscrew lock and one of the focus knobs, revealing into the threaded hole for one of the screws that hold the axle housing. Motor perhaps? 

 

Again, I think the narrow knobs are the tipoff. 

 

Tom 



#6 lphilpot

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Posted 12 July 2019 - 07:52 PM

Yeah, definitely a JMI just with a polished body. I've had two like this (but black anodized) - One had these narrow O-ring knobs and the other had slightly wider knurled aluminum knobs. Not a bad basic Crayford focuser once adjusted.



#7 Sean Cunneen

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Posted 12 July 2019 - 08:34 PM

You can take anodizing off with sodium hydroxide(oven cleaner/draino) pretty easily... So if it looks like a jmi, it probably is.

#8 Bob4BVM

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Posted 13 July 2019 - 01:25 PM

Love the minimalist design.

But a bit surprised to see slotted-head screws on it. Quit using those years ago, ANY other head type is a huge improvement.

CS
Bob



#9 dave brock

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Posted 13 July 2019 - 03:04 PM

Is the top bearing in the 1st pic coming loose?

#10 Tom Duncan

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Posted 13 July 2019 - 03:47 PM

Is the top bearing in the 1st pic coming loose?

I was wondering the same thing but it appear the bolts through the bearings are slightly long such that the head doesn't actually clamp the inner race of the bearings. All are like that to a degree. I haven't established if the bolts are bottomed or just tight. 

 

Tom 



#11 lphilpot

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Posted 13 July 2019 - 04:07 PM

The first JMI I had was one I bought for a 10" scope, and sold with the scope. It had knurled knobs and was in general a decent focuser. This one I got from a friend and it had led a hard life. A few set screws were missing, etc. and it has the O-ring knobs. but maybe a couple of (accidentally soft) photos might help:

 

These bearings are tight, but they also look like they're not. The screws actually impinge against the center sleeve of the bearing (which makes sense). Also note the 1.25" adapter set screw slot and the inside relief for a flush adapter.

 

JMI1.jpg

 

Neither this one nor my 'better' one had slotted tension lock screws:

 

JMI2.jpg

 

Note also the squarer shape of the base, etc. Very similar but a few noticeable differences. I wonder if yours is maybe a prototype?



#12 Tom Duncan

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Posted 13 July 2019 - 04:15 PM

I took off one of the bearing/bolt assemblies and found the inner race is not being held by the bolt. The bolt has a shoulder on it that is longer than the inner race is long so the bearing just rotates around the bolt instead of the outer race rotating around the inner race. 

 

I'm going off to the hardware store to see if I can find some tiny washers to take up the length of the bolt shoulder but not interfere with the outer race. 

 

This does have a 'prototype' air about it...

 

Tom 



#13 lphilpot

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Posted 13 July 2019 - 04:17 PM

We're just sitting here waiting to get (whatever we get) from tropical storm Barry, so what better way to pass the time than fiddle with astro stuff...  :D




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