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Ideas for a 2 speed Crayford focuser mod?

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#1 Ivandn

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Posted 04 March 2017 - 02:10 PM

Hi all, I have a Celestron 6" f5 newt that came with a 2" Crayford single speed focuser. I would like to get a dual speed focuser but the cheapest option is a gso for $130. I was wondering if there are any diy options or ideas to add a dual speed reduction to my existing setup.

I've done some searching but it mostly yields motorized options which I'm not really looking for at this point. Any ideas are welcome! Thanks

Edited by Ivandn, 04 March 2017 - 02:12 PM.


#2 Rapier

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Posted 04 March 2017 - 02:27 PM

My stock focuser knobs are 32mm. I changed one knob for a 64mm plywood knob that I made myself (with 1mm of clearance from the OTA).

No, it's not 1:10, but it didn't cost me a penny and it gives me a 1:2 focus upgrade.

 

20170202_143530sm.jpg


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#3 Jon Isaacs

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Posted 04 March 2017 - 07:11 PM

This is a pinch lever I made for my Orion Crayford.   It's not a 2 speed but it helps with fine focusing. 

 

http://www.cloudynig...orion-crayford/

 

Jon


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#4 Ivandn

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Posted 04 March 2017 - 07:40 PM

Thanks guys, these are good simple ideas!
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#5 kfiscus

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Posted 04 March 2017 - 07:44 PM

Hang out in the CN and Astromart classifieds to pick up a good used focuser?  They show up all the time.



#6 Chriske

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Posted 05 March 2017 - 06:08 AM

http://www.orenellio...eduction-drives


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#7 Ivandn

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Posted 05 March 2017 - 12:16 PM

http://www.orenellio...eduction-drives


That's perfect! Thanks!

#8 JupiterOwl

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Posted 07 March 2017 - 09:01 PM

Rapier looking at what you did there gave me an idea. What about using a large diameter whip focusing knob? Similar to the knobs used on the RA/DEC adjustments.

 

I wonder if a whip type knob would also eliminate or at least reduce telescope movement when focusing?



#9 Jon Isaacs

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Posted 08 March 2017 - 03:24 AM

Rapier looking at what you did there gave me an idea. What about using a large diameter whip focusing knob? Similar to the knobs used on the RA/DEC adjustments.

 

I wonder if a whip type knob would also eliminate or at least reduce telescope movement when focusing?

If you are thinking of the slow-motion cables that are used with both RA-DEC and Alt-Az mounts, in my experience, they act like spring-mass systems one you release them and can cause the mount and scope to wobble.  On the end of the telescope lever, it would be worse.. 

 

:shrug:

 

Jon


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#10 Rapier

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Posted 09 March 2017 - 02:34 PM

Rapier looking at what you did there gave me an idea. What about using a large diameter whip focusing knob? Similar to the knobs used on the RA/DEC adjustments.

 

I wonder if a whip type knob would also eliminate or at least reduce telescope movement when focusing?

 

I wouldn't do that. In addition to the reason that Jon Isaacs gave, in reality all you would be doing is extending the focuser knob shaft further away from the focuser and that's not really a solution.

 

Working from the basic idea that I introduced with a larger knob, you could conceivably fashion a detachable lever thereby giving your focuser knob a much larger radius. I don't know your mechanical capabilities so I can't begin to guess what is or is not within your abilities.

 

Think of it like this: take 12 inch long clothes pin and grasp the focuser knob axle with it. The longer the "clothes pin" the larger the radius, and therefore the greater the reduction in focuser tube travel. The trade off with any idea like this, though, is that you will have the unintended consequence of introducing more spurious momentary wobble in your scope, making focus a little more difficult, momentarily, because you won't be able to see past the wiggling image. But you will probably get better at using it with time.



#11 Miranda2525

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Posted 12 March 2017 - 05:31 AM

http://agenaastro.co...pgrade-kit.html



#12 Jon Isaacs

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Posted 12 March 2017 - 02:55 PM

 

A machinist friend once helped me modify a JMI RCF with a GSO two speed:

 

6174831-JMI RCF-1 + GSO Two Speed.jpg
 
I am currently pondering the idea of adapting a GSO two speed to a JMI DX-1..
 
I find the friction drives meant for electronics interesting but I wonder if they can handle the torque required.  Electronics usually requires very little torque.  
 
Jon


#13 Rapier

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Posted 12 March 2017 - 10:17 PM

 

UGH You've given me something to mull over til I can figure out how to make it work for me.

LOL Like I need more to think about.



#14 Ivandn

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Posted 13 March 2017 - 03:32 PM

 

 

UGH You've given me something to mull over til I can figure out how to make it work for me.

LOL Like I need more to think about.

 

I've been doing the same.. 

On their website, they have 2 different 6:1 drives, 1 priced at $15 and the other at $42. Being the cheapskate that I am, the $15 model stood out to me and 6:1 seems sufficient for focusing purposes and would be a vast improvement over the 1:1 I currently have. The other option was 10:1 which was also $42. 

 

I emailed OrenElliot about the differences between the 2 and this was their response. 

 

The B1N6X0 ($42) has machined "caps" -- the parts with conical surfaces, between which the balls are sandwiched, forcing the balls down into a groove in the shaft.

The BD602 ($15) has stamped caps -- so the BD602 is less expensive.  The B1N6X0 is a little more robust, and is sealed, so the grease can't leak out.

 

Grease leaking out sounds awful but again, focusing is relatively light duty and these will hardly be moved for the most part so I'm again more inclined to the cheap option as "good enough". 

 

Now the downside to this is that shipping for these little drives are $16.51 no matter quantity or product which does put a damper on the $15 option. 

 

With that in mind, If anyone else is interested in getting these, I can order 2 or more, and ship them out to you for about $6.50 in flat rate shipping and split the overall cost to about $25.00 per drive. I know i'm being cheap here but if I can save myself and someone a few dollars, why not?

 

If you're interested let me know or just post here. 


Edited by Ivandn, 13 March 2017 - 04:03 PM.

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#15 Bob4BVM

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Posted 13 March 2017 - 04:15 PM

There is another way to do this, if you are looking for an extremely-fine low speed focus.

Like the idea of a clamp lever already discussed, it uses a lever which can be loose on the shaft and clamped to engage.

The difference with what i call a tangent-arm focus is that you can add a fine-pitch screw to drive the arm so as to get extreme resolution in a much smaller footprint than would be the case for a very long lever.

I'll let the pix tell the story. I did this on my 3" focuser build pictured below. I am using a micrometer head to drive the tangent arm, which gives me a repeatable drawtube travel resolution of less than 1/10,000th of an inch per click of the mic head.

 

But don't let the mic head scare you away, a simple 10-32 machine screw tapped thru the mounting block would also work fine in its place, albeit a little coarser adjustment.  But still extremely fine compared to any knob-type reducer mechanism.

 

In the side view pic you can see the slotted tangent arm on the shaft. I have since added a lever to the clamp screw on the arm for easier in the dark operation.

CS

Bob

IMG_4164s.jpg IMG_4169s.jpg


Edited by Bob4BVM, 13 March 2017 - 04:21 PM.

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#16 Rapier

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Posted 13 March 2017 - 09:03 PM

 

 

 

UGH You've given me something to mull over til I can figure out how to make it work for me.

LOL Like I need more to think about.

 

I've been doing the same.. 

On their website, they have 2 different 6:1 drives, 1 priced at $15 and the other at $42. Being the cheapskate that I am, the $15 model stood out to me and 6:1 seems sufficient for focusing purposes and would be a vast improvement over the 1:1 I currently have. The other option was 10:1 which was also $42. 

 

I emailed OrenElliot about the differences between the 2 and this was their response. 

 

The B1N6X0 ($42) has machined "caps" -- the parts with conical surfaces, between which the balls are sandwiched, forcing the balls down into a groove in the shaft.

The BD602 ($15) has stamped caps -- so the BD602 is less expensive.  The B1N6X0 is a little more robust, and is sealed, so the grease can't leak out.

 

Grease leaking out sounds awful but again, focusing is relatively light duty and these will hardly be moved for the most part so I'm again more inclined to the cheap option as "good enough". 

 

Now the downside to this is that shipping for these little drives are $16.51 no matter quantity or product which does put a damper on the $15 option. 

 

With that in mind, If anyone else is interested in getting these, I can order 2 or more, and ship them out to you for about $6.50 in flat rate shipping and split the overall cost to about $25.00 per drive. I know i'm being cheap here but if I can save myself and someone a few dollars, why not?

 

If you're interested let me know or just post here. 

 

 

I would jump all over that except that I don't have the metal work equipment to modify the focuser knob axle. And the odds of me randomly finding a replacement axle with the correct rack & pinion pitch that would let me use the planetary reduction drive is not likely.

So don't wait for me. You go ahead and order without me.

But I am going to continue to mull this over. This idea is too good to let it get away.



#17 Chriske

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Posted 14 March 2017 - 04:15 AM

If you buy one you should modify this dual speed knob a little bit.

At arrival they do not work smooth as they should at all. The units has to be taken apart completely, degreased  and re-assembled again.

When assembling care has to be taken not to squeeze it to tight. While re-assembling the correct amount of tension should be applied. I usually add a drop of WD40 and this knob and after that it can compete with any fancy and expensive dual speed knob available on the market.

If needed I will post some pictures of the disassembled knob. I've post this before, but I don't know....scratchhead2.gif

 

 

 

 

 

 

UGH You've given me something to mull over til I can figure out how to make it work for me.

LOL Like I need more to think about.

 

I've been doing the same.. 

On their website, they have 2 different 6:1 drives, 1 priced at $15 and the other at $42. Being the cheapskate that I am, the $15 model stood out to me and 6:1 seems sufficient for focusing purposes and would be a vast improvement over the 1:1 I currently have. The other option was 10:1 which was also $42. 

 

I emailed OrenElliot about the differences between the 2 and this was their response. 

 

The B1N6X0 ($42) has machined "caps" -- the parts with conical surfaces, between which the balls are sandwiched, forcing the balls down into a groove in the shaft.

The BD602 ($15) has stamped caps -- so the BD602 is less expensive.  The B1N6X0 is a little more robust, and is sealed, so the grease can't leak out.

 

Grease leaking out sounds awful but again, focusing is relatively light duty and these will hardly be moved for the most part so I'm again more inclined to the cheap option as "good enough". 

 

Now the downside to this is that shipping for these little drives are $16.51 no matter quantity or product which does put a damper on the $15 option. 

 

With that in mind, If anyone else is interested in getting these, I can order 2 or more, and ship them out to you for about $6.50 in flat rate shipping and split the overall cost to about $25.00 per drive. I know i'm being cheap here but if I can save myself and someone a few dollars, why not?

 

If you're interested let me know or just post here. 

 

 

I would jump all over that except that I don't have the metal work equipment to modify the focuser knob axle. And the odds of me randomly finding a replacement axle with the correct rack & pinion pitch that would let me use the planetary reduction drive is not likely.

So don't wait for me. You go ahead and order without me.

But I am going to continue to mull this over. This idea is too good to let it get away.

 


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