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Equipment Discussions >> ATM, Optics and DIY Forum

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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5829978 - 04/29/13 11:38 AM

Last night, I adjusted both motor/worm block assemblies for a perfect contact between the two pinions. And I also worked on temporary wiring for the motors/encoders to test both motor assemblies on the Gemini-II controller. I should be done tonight. Selecting motors that would work with this controller was kind of challenge considering the current limitations of the IC's but it should work!

I've also sent out the RA shaft for manufacturing, all the lathes I could use for this were just too small. I've got an ETA of 2 weeks for the shaft, meanwhile I'll try to finish the RA housing (several CNC parts) as well as the DEC housing which needs to be installed at the end of the RA shaft before it's assembled on the mount.


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5837482 - 05/02/13 11:46 PM

I just finished interfacing my maxon motors/encoders to the Gemini-II controller.
It was a little tricky as some electronics (line receivers/comparators) but it works!
Everything was done on test boards, I am going to make a couple of PCB for a more compact/reliable interface.


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5838733 - 05/03/13 04:50 PM

1 motor and 1 worm in action: http://www.youtube.com/watch?v=1b9FS-6H2M8

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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5875050 - 05/21/13 12:38 AM

Here's the RA shaft



http://cooledpix.com/2013/05/20/eq-z-ra-shaft/


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Escher
Pooh-Bah
*****

Reged: 08/30/07

Loc: Fenton, MI
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5875340 - 05/21/13 08:55 AM

I had all but forgotten about this beauty! Thanks for reminding me!

Awesome work thus far - Cant wait to see the finished product!


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Escher]
      #5879380 - 05/23/13 12:15 AM

Thank you sir

I'm making some modifications to the rear end cap of the RA shaft by adding a high resolution shaft encoder (resolution of 0.41 arcsec). It doesn't change things much especially as I had not made any of these parts yet. The encoder will probably not be initially supported by the controller but it should at some point


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5885036 - 05/26/13 02:45 AM

Here's some pictures of the PCB I had to make to interface the motor/encoder's to the Gemini-II controller.







more information on this page: http://cooledpix.com/2013/05/25/eq-z-motor-interface/


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5886470 - 05/27/13 01:30 AM

And here's a recent screenshot of what the final product will look like (new Dec housing - easier for me to machine than bigger turned parts, clutch window on the RA gear cover, rear cap on the RA axis hosts a high res renishaw encoder, and that's about it)



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Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5886646 - 05/27/13 07:53 AM

Looks really nice! You might want to use a beefier dovetail saddle design. For example, Astro-Physics uses something called a P-style or Planewave style saddle and dovetail design.

Astro-Physics

JimC


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Mirzam]
      #5886868 - 05/27/13 11:01 AM

Thanks for the link Jim. I've been thinking of doing something to the saddle for some time now, it's a good suggestion.

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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5895392 - 06/01/13 01:25 AM

I can't do exactly an AP saddle but I was able to do something substantially stronger, I'll have to re-machine a dovetail for the scope but I needed one of them to be longer anyway (to have a little bit of freedom to adjust the balance).




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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5977131 - 07/18/13 12:59 AM

I'm updating this thread real quick...
Currently in the process of moving to a new home where I'll have the observatory for this project. Still waiting on the optics, final figuring has been taking longer than expected apparently.

I am in the process of finishing the parts for the RA housing.

Cheers


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s800
member


Reged: 03/19/08

Loc: Wisconsin
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5978813 - 07/18/13 10:13 PM

Really fantastic to read this- thanks for the details and the pics.

A couple questions:

What goes in to bearing selection? I'm not at versed in bearings and am curious how one selects a bearing that won't introduce errors in tracking.

What type of problems (if any) have you had going from Solidworks->Real world? Is the workflow really Solidworks to CNC and everything truly fits together?

Thanks! Amazing build


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: s800]
      #5979095 - 07/19/13 02:03 AM

Hi and thanks for the kind words!

I went with high quality tapered roller bearings which should be adequate, practically I don't know yet if this was a good choice or not.

In terms of translating CAD work into actual parts, I spent a bit of time making sure dimensions and tolerances would be adequate and then it's a question of respecting this during the manufacturing process. Luckily I have some experience here and so far everything's been working fine. But it's far from complete.


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6002500 - 08/02/13 01:47 AM

super quick update. I've anodized the 2 rolled aluminum gear covers (for RA and DEC) as well as the RA shaft.



Also I am moving to my new house this week-end. I was there last night to drop some stuff. The last 10 miles are absolutely dark (blue zone) - we could make out the Milky-Way looking through the driver side window of my car... I knew skies were good (kind of why we chose this area) but that good? wow. I never had the chance to test the skies before moving! I'll be imaging from there this week end with my wide field setup. Anyway kind of off topic just to say that I'll start working on the observatory shortly also!


Cheers


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gregj888
professor emeritus


Reged: 03/26/06

Loc: Oregon
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6003564 - 08/02/13 05:06 PM

Stephen

Great to see this pop up again. Really like what you are doing. I have a lot of other things going on, but haven't touched my mirror in a year.

With envy... :-)

Greg


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #6004256 - 08/03/13 01:43 AM

I know the feeling Greg ^_^ I had not the chance to touch it for 6 months and it gave me an itch haha

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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6051629 - 08/28/13 10:44 PM

I've got all the parts to do the RA housing/shaft assembly.

Loving the new house, spent some time with Dan this week-end to try our hands on a 8" concrete pier for the G11. Next month, we'll tackle the large 14" concrete pier and the observatory.

Lots to do still!

Oh and I also designed a focuser/rotator combo from scratch.. I really want to give this a try, though focusers are really difficult so we'll see how that goes. If someone is interested I'll post a few images.


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6051969 - 08/29/13 06:14 AM

I would love to see some pictures and details on your focuser. What kind of travel did you design it for?

-Adam


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zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Adam Brunette]
      #6052380 - 08/29/13 11:41 AM

I got 18mm travel.
backfocus of the whole thing is 62mm. I got a M72x1 Male on the drawtube - to go right into my soon to be modified (reinforced) SX AO.
Telescope side, I have 6 threaded holes - same spacing as on my 17" back plate. I'll most likely have a 50-60 mm extension in between - depending on the final specs (back focus) of the optics.

As I said it's got a rotator built-in. I am using 2 stepper motors with timing belt for the rotator and gearbox for the focuser. The focuser gives me 1.5 um / step.







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