Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> ATM, Optics and DIY Forum

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | (show all)
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
17" CDK and Equatorial Mounting
      #5348116 - 08/02/12 03:02 AM

Hello,
I've been working on this for a few weeks already and figured it was time to start to create some kind of work log on here.

I am building a 17" CDK f/6.8 (though I will be buying the optics i.e. mirrors and correctors) and equatorial mounting for it.

All the parts for the telescope have been made already and I have started assembly already. Though I am a little behind on the work log so I will be posting quite a few updates within the next few days!

The assembly should be finished soon, though since I have not ordered the mirrors yet (still saving up) the telescope will be waiting a few months before it sees a light. That being said, I am finishing up the design of the equatorial mounting and should be able to start machining parts shortly. The mount will be tested before the telescope as I have already ordered the worms/gears/motors. This should keep me busy till at least I have the resources for the optics!

I will be keeping my blog updated as I progress.

Here's the first blog entry: http://cooledpix.com/2012/08/01/cdk17-introduction/

and a couple pictures of the CAD work.








Feel free to ask questions about the design. I will populate my entries with as much information as I can.


Post Extras: Print Post   Remind Me!   Notify Moderator  
kfrederick
Carpal Tunnel


Reged: 02/01/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5348233 - 08/02/12 06:52 AM

Nice CAD work!! What is the mounting look like?

Post Extras: Print Post   Remind Me!   Notify Moderator  
polaraligned
professor emeritus


Reged: 12/26/08

Re: 17" CDK and Equatorial Mounting new [Re: kfrederick]
      #5348246 - 08/02/12 07:11 AM

Looks very good. Are the optics from the same source that Planewave uses? I only ask because 17" is not a common size.

Also, how are you able to determine that the center ring where the truss attaches will be stiff enough? I see it is cored out there. Did you do any FEA on it?

I will be following your build with interest. Thanks for posting.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: polaraligned]
      #5348639 - 08/02/12 12:28 PM

I will post the CAD work for the mounting when I am finished. It slightly differs from a traditional GEM. It's all I say for now


I am not sure where Planewave is getting the optics. But yes it is the same diameter and f ratio.

Yes, the middle cell openings were checked with a static analysis of this middle cell.


Post Extras: Print Post   Remind Me!   Notify Moderator  
The bear
Pooh-Bah
*****

Reged: 02/11/08

Loc: rushville, indiana
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5348954 - 08/02/12 04:07 PM

this one is so cool i love it i sent you an pm zytrahus
doc


Post Extras: Print Post   Remind Me!   Notify Moderator  
allardster
sage


Reged: 07/01/11

Loc: Toronto, Ontario, Canada
Re: 17" CDK and Equatorial Mounting new [Re: The bear]
      #5349287 - 08/02/12 08:27 PM

Interesting project, great CAD work.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Dave O
sage
*****

Reged: 12/21/11

Loc: Sri Lanka
Re: 17" CDK and Equatorial Mounting new [Re: allardster]
      #5349531 - 08/02/12 11:32 PM

Looks like a nice compact design. 17" f/6.8 with two corrector lenses ... do you have a prescription for this design? I'd like to see its 'performance' ...

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Dave O]
      #5349661 - 08/03/12 02:20 AM

Thanks guys.
I'll post some optical data soon.

Adding a picture of the parts (they're not all in there) after they came back from anodizing.

The tube assembly in the middle is the corrector/baffle assembly.



Post Extras: Print Post   Remind Me!   Notify Moderator  
TopherTheME
sage
*****

Reged: 02/11/11

Loc: Rochester, MI
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5350304 - 08/03/12 02:31 PM

Very nice. Where are you getting your parts anodized?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: TopherTheME]
      #5350314 - 08/03/12 02:36 PM

A small local shop that goes different kind of plating jobs.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5351063 - 08/03/12 11:37 PM

Quick update for the rear cell assembly:




blog entry: http://cooledpix.com/2012/08/03/cdk17-rear-cell/


Post Extras: Print Post   Remind Me!   Notify Moderator  
polaraligned
professor emeritus


Reged: 12/26/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5351405 - 08/04/12 09:38 AM

Primary is going to be glued in place?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: polaraligned]
      #5351813 - 08/04/12 02:37 PM

Nope there is a 18-point floating mirror cell in between the mirror and back plate. More on this very soon

Post Extras: Print Post   Remind Me!   Notify Moderator  
polaraligned
professor emeritus


Reged: 12/26/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5352079 - 08/04/12 06:30 PM

Only reason I ask is because Planewave glues theirs. Seem it would simplify things. But they are using a conical primary, you obviously are not.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: polaraligned]
      #5352285 - 08/04/12 09:08 PM

the mirror will be glued on the 18 point mirror cell, but I wanted to have some freedom adjusting the primary although collimation should not be too much of a problem. Time will tell =)

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5352604 - 08/05/12 03:29 AM

A couple more pics for the Mid Cell assembly.

http://cooledpix.com/2012/08/05/cdk17-mid-cell/





Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5352656 - 08/05/12 05:50 AM

A work of art.
Just stunning.


Post Extras: Print Post   Remind Me!   Notify Moderator  
TopherTheME
sage
*****

Reged: 02/11/11

Loc: Rochester, MI
Re: 17" CDK and Equatorial Mounting new [Re: johnC]
      #5353152 - 08/05/12 01:26 PM

Whats the approximate weight of this thing going to be?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: TopherTheME]
      #5353192 - 08/05/12 01:51 PM

just about 37 Kg

Post Extras: Print Post   Remind Me!   Notify Moderator  
Happy Birthday Dennis Sakva
Pooh-Bah
*****

Reged: 10/19/04

Loc: Kiev, Ukraine
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5353245 - 08/05/12 02:21 PM

Stephen and how thick is the backplate?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Dennis Sakva]
      #5353833 - 08/05/12 09:32 PM

1/2" - I'll post some pics on the mirror cell itself soon

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5355926 - 08/07/12 04:16 AM

quick update for the primary mirror cell (18 floating points)

blog + info + pics: http://cooledpix.com/2012/08/07/cdk17-primary-mirror-cell/




Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5357219 - 08/07/12 09:52 PM

Another quick update: assembly of the front cell/spider.





http://cooledpix.com/2012/08/07/cdk17-front-cell/


Post Extras: Print Post   Remind Me!   Notify Moderator  
rogercelliott
sage


Reged: 09/19/08

Loc: Redding, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5357339 - 08/07/12 11:17 PM

Wow... awesome. I so miss having access to CNC machine tools!
Cheers
Roger


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: rogercelliott]
      #5358918 - 08/08/12 10:36 PM

Here's the vane preloading mechanism for the spider.



Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5376734 - 08/19/12 10:45 PM

I picked up my worm/gear sets from Mr. Byers yesterday:

For declination it's a 12"-360


And for right ascension it's a 15.25"-485


Both use the same worm, but the RA worm has been diamond lapped for added accuracy.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5376740 - 08/19/12 10:53 PM

I've also built a mobile pier to have a solid base to assemble the equatorial mount that I will start machining shortly. I wanted something decent so that I can also use it from my garage for testing/tweaking (when it's finished) as I won't have the observatory to set everything up just yet...

It's mobile and vastly inspired by the stuff from PierTech to keep things simple.


more info here: http://cooledpix.com/2012/08/19/z-pier-introduction/

and some pics...













Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5382055 - 08/23/12 01:00 AM



Post Extras: Print Post   Remind Me!   Notify Moderator  
m. allan noah
professor emeritus


Reged: 08/14/09

Loc: Virginia, USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5382240 - 08/23/12 07:20 AM

Beautiful machining. However, I note several places where you bring a load into the side of an unsupported span, both in the telescope and the pier.

allan


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: m. allan noah]
      #5389073 - 08/27/12 01:14 AM

lower cage assembly:

link: http://cooledpix.com/2012/08/26/cdk17-lower-cage/




Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5389153 - 08/27/12 03:47 AM

I am following this thread with great interest.
A true work of art.
I cannot wait to see the finished product.
Thank you for sharing.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Dan McConaughy
sage


Reged: 11/11/06

Loc: LA
Re: 17" CDK and Equatorial Mounting new [Re: johnC]
      #5389290 - 08/27/12 07:47 AM

VERY nice. How thick are you spider vanes? Are you going to install cooling fans in front of your primary mirror?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Dan McConaughy]
      #5389629 - 08/27/12 11:58 AM

Hi,
The 3 cooling fans will be on the back plate either pushing or pulling air to/from the mirror (behind it).
Spider vanes are 316 S-S and 2 mm thick (painted flat black)


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5396023 - 08/31/12 02:17 AM



I was hoping I could assemble the secondary tonight but I had to rework a few threads that were a little too tight! Guess the complete mock-up will be finished tomorrow.


Post Extras: Print Post   Remind Me!   Notify Moderator  
TopherTheME
sage
*****

Reged: 02/11/11

Loc: Rochester, MI
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5396706 - 08/31/12 01:05 PM

Nice. Where did you get the CF tubing for poles from?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: TopherTheME]
      #5396952 - 08/31/12 03:59 PM

rockwest composite it was I think, I had them cut to length and checked their length before gluing the fittings in place.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5397605 - 09/01/12 02:34 AM

probably last update on the telescope before a few months of wait for the optics...
I'll be updating with the work I am going to do for the equatorial mounting though..

http://cooledpix.com/2012/08/31/cdk17-ready-for-the-optics/







Post Extras: Print Post   Remind Me!   Notify Moderator  
Dick Jacobson
scholastic sledgehammer


Reged: 12/22/06

Loc: Plymouth, Minnesota, USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5397749 - 09/01/12 08:40 AM

Gorgeous piece of work! I hope it's as much fun looking THROUGH it as AT it!

Post Extras: Print Post   Remind Me!   Notify Moderator  
rguasto
professor emeritus
*****

Reged: 11/18/10

Loc: Long Island, NY
Re: 17" CDK and Equatorial Mounting new [Re: Dick Jacobson]
      #5397762 - 09/01/12 08:56 AM

WOW!

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: rguasto]
      #5398143 - 09/01/12 01:25 PM

thanks guys

Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5398156 - 09/01/12 01:31 PM

Would it be possible to stand next to the scope so we may get an idea of its size?
The completed ota pick is now my desktop wallpaper!
It really is beautiful.
Thank you again for sharing.
Will be looking forward to optics and mount construction.
Best regards
John
UK


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: johnC]
      #5398763 - 09/01/12 09:32 PM

Thank you John,
I will take a picture with a sizable reference object.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5399065 - 09/02/12 02:30 AM

next to the 10" f/4 Astro-Tech. they're about the same length



Post Extras: Print Post   Remind Me!   Notify Moderator  
Dave O
sage
*****

Reged: 12/21/11

Loc: Sri Lanka
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5399077 - 09/02/12 03:03 AM

Stephen -- your design and machining skills as displayed in this thread are nothing short of "awesome". While I do not know what engineering principles have been invoked to assure rigid collimation of the optics; the attention to detail in the construction and aesthetics of this instrument are first class. It looks like something that NASA would build. Thanks so much for sharing. Dave O

Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: Dave O]
      #5399132 - 09/02/12 05:04 AM

Thanks Stephen.
A fantastic work of art.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Dave O]
      #5400347 - 09/02/12 11:06 PM

Quote:

Stephen -- your design and machining skills as displayed in this thread are nothing short of "awesome". While I do not know what engineering principles have been invoked to assure rigid collimation of the optics; the attention to detail in the construction and aesthetics of this instrument are first class. It looks like something that NASA would build. Thanks so much for sharing. Dave O



Thanks for the kind words, Dave.
I've certainly tried to make it work mechanically. This is my first home designed/built telescope so we'll see how it turns out. Optically, I am hoping the optics will be good. Sandwich mirrors clearly make them lighter but their mechanical retention is more of a challenge. I will have to wait several months before I find out.

I am getting ready to start machining parts for the equatorial mounting. This will be a challenge.

I've taken another picture with an object that will be better to get an idea its size.



Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5400555 - 09/03/12 03:42 AM

Stephen, in your configuration, it my be better to mount the spider above the UTA ring. This would shorten your OTA even more. The shorter the better.

More importantly, however, to maintain critical collimation, the spider vanes should be mounted to or directly above the trusses and not in between them. This is how it's done professionally.

Now, having a spherical secondary does relieve some of the strict axial collimation requirements of other Cassegrains, but image degradation is still subject to tilt, if not micrometric centering. A 300 mm f/8 DKC, with a 120 mm secondary, for example, must maintain a tilt to within ± 6 arc minutes. This turns out to be as little as ± 0.1 mm or 0.0004 inches for that configuration. You want all the rigidity and support you can get, so proper spider support is quite critical.

Regards,

Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5400569 - 09/03/12 04:08 AM

Quote:

More importantly, however, to maintain critical collimation, the spider vanes should be mounted to or directly above the trusses and not in between them. This is how it's done professionally.





No Mladen, the best position is at the imaginary crossing point of the trusses. If you mount them higher than that, further away from your primary, your create an extra force in your truss.


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5400585 - 09/03/12 04:35 AM

Quote:

Quote:

More importantly, however, to maintain critical collimation, the spider vanes should be mounted to or directly above the trusses and not in between them. This is how it's done professionally.





No Mladen, the best position is at the imaginary crossing point of the trusses. If you mount them higher than that, further away from your primary, your create an extra force in your truss.



Yes, Benach, that is the best position and that's how the professionals do it (which is obvious from the picture I referenced).

I was suggesting what should be done with the existing setup. If you look at the finished truss and spider couplings, it would be difficult to remedy this problem (i.e. mounting the spider at the truss crossing point) without redesigning and refabricating the couplings - and pretty much the whole UTA.

As for the increased peripheral moment created by moving the spider above the ring, it would be offset by the shorter truss length, which would be necessary to maintain the correct primary-secondary distance.

Regards,

Mladen

Edited by MKV (09/03/12 04:36 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5400911 - 09/03/12 11:31 AM

RCOS does have the spider vanes in between each truss pair. My original 3D model had the vanes right on the truss pair but I ended up doing some FEA to identify which of the two would work best. Unless I completely failed my analysis, the solution I opted for gave better results.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5400991 - 09/03/12 12:21 PM

Zytrahus: That is quite unlikely. Your position is de facto unstable and not statically determined wereas the position I suggested is statically determined.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5401050 - 09/03/12 01:04 PM

I was referring to this: http://www.rcopticalsystems.com/telescopes/16truss.html the spider vanes start from the median between 2 truss pairs.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5401060 - 09/03/12 01:09 PM

Then also RCOS is doing it the wrong way. Nothing to be ashamed of yourself, we're all too human, but it is still undesirable.

Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5401222 - 09/03/12 02:54 PM

With the greatest of respect, this is a wonderful project and being graciously shared with us.
With the engineering skills being evident this is not the thread for picking apart the OP project.

Again i do not mean offence but find your above post a little unsavoury.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: johnC]
      #5401236 - 09/03/12 03:05 PM

John: I like amateurs that are willing to go beyond the usual Dobsonians. In that sense I have full respect for this project. However, that does not mean that this project is without a critical view. So either give arguments against mine and we can continue or stop blaming the messenger.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Datapanic
Carpal Tunnel
*****

Reged: 10/17/09

Loc: Tucson, Arizona
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5401248 - 09/03/12 03:11 PM

Nice project! Can't wait to see the mount design. The Maynard Clark scope was also designed and built by an expert Machinist several years ago and was made to last.

Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5401250 - 09/03/12 03:12 PM

I do not have the technical knowledge to argue, this i freely admit.
I apologise for what may have been a Knee jerk reaction to your post. But as in all things i suppose there are differing views.
In hindsight if the OP is not offended then that is that.

Best regards
John.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: johnC]
      #5401322 - 09/03/12 03:45 PM

It is not a matter of different views John. We're no philosophers here in the sense that there're no final answers. In the field of engineering and science there are usually final answers and usually they are right of wrong and in this case it is wrong. Too bad for OP, but this is the result of the method.
Are you also one of the opponents of Einstein who'd say in 1905 that he's wrong because "it is picking apart Newton's magnus opus Principia"?


Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5401342 - 09/03/12 03:52 PM

I bow to your superiority.
We just do things differently here.
I shall continue watching this project evolve.
I apologize to the OP for diverting the thread.
End of.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: 17" CDK and Equatorial Mounting new [Re: johnC]
      #5401358 - 09/03/12 04:01 PM

We really have heard no critical analysis. A real analysis would examine the allowable flexure and whether the design meets the necessary criteria.

Simply to claim that it is "better" to do something differently is meaningless.

JimC


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: Mirzam]
      #5401465 - 09/03/12 04:54 PM

Mirzam: the arguments were already given above, statically determined vs. non-determined.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5401515 - 09/03/12 05:28 PM

If there is a requirement to absolutely minimize the weight and thickness of the top ring, then your arguments are relevant. Otherwise, if the top ring of this rather small telescope provides adequate stiffness to support the spider irrespective of the truss connection points then arguing for a change in design becomes a matter of philosophy rather than engineering.

JimC


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5401632 - 09/03/12 06:39 PM

Quote:

Then also RCOS is doing it the wrong way. Nothing to be ashamed of yourself, we're all too human, but it is still undesirable.




Since it (obviously) doesn't bother RCOS then it pretty much any concern I could have. But I'm curious and I'd really like to understand what is really fundamentally wrong with having the spider vanes at the median of 2 truss hubs. Maybe if you talk real slow I will be able to follow. =)


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5401813 - 09/03/12 08:39 PM

Quote:

I was referring to this: http://www.rcopticalsystems.com/telescopes/16truss.html the spider vanes start from the median between 2 truss pairs.



The upper ring of the RCOS design appears to be shaped like an inverted "L", or "T" (see the magnified image below).

This ring is tall and thin with all the weight bearing burden placed on the tall aspect of the ring.

The UTA ring on this thread has it the other way around: the greatest stress is placed on the thin aspect of the ring.

Placing the stress on a structure suspended between two points (as in the configuration described on this thread), so that the maximum force is midway between those points, results in maximizes flexure. One doesn't have to be a rocket scientist to understand that.

So, to compensate for the "suspended bridge" design, one can do what RCOS did - create a tall thin ring - or, if minimal structural changes are desired, simply mount the spider on the trusses, where the maximum stress should be, and not midway between them.

http://www.rcopticalsystems.com/telescopes/images/12inchTrussSmall.jpg

Reagrds,

Mladen

Edited by ausastronomer (09/10/12 06:42 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5401854 - 09/03/12 09:13 PM Attachment (67 downloads)

Quote:

But I'm curious and I'd really like to understand what is really fundamentally wrong with having the spider vanes at the median of 2 truss hubs.



How about a picture? Does that answer your question? Which one of these three examples will results in least deflection where the force is applied? Example A is the configuration described on this thread. Example B is the configuration seen on RCOS, and Example C is the spider mounted over the trusses.

Both, B and C will work well, but A is in effect a suspended bridge with maximum force applied midway between the pillars. Or think of it as a shelf suspended at both ends, and all the books placed half way between them. You think it's going to bow? You bet! And when the bowing cannot exceed 0.0004 inches you might want to consider a slightly stiffer option.

Again, if your are going to limit your work to wide field, low power deep sky imaging, then it's a moot point. But if you are talking high power visual observation or imaging, then a slight sag in your secondary could seriously degrade your image quality, especially in an RC.

Regards,

Mladen

Edited by MKV (09/03/12 09:20 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Datapanic
Carpal Tunnel
*****

Reged: 10/17/09

Loc: Tucson, Arizona
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5401933 - 09/03/12 09:48 PM

If you look on page 2 of this thread, strength members are built into the ring via a pair of channeled groves between each truss and secondary vane mount point. I don't know what I did with my old Strength Of Materials book, but that design will greatly affect the stiffness, no matter what the material.

Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: Datapanic]
      #5401984 - 09/03/12 10:15 PM

Quote:

If you look on page 2 of this thread, strength members are built into the ring via a pair of channeled groves between each truss and secondary vane mount point.



Yes, I have seen them. Nice touch, but I see more value in making the wafer lighter then stiffer. That still doesn't explain why not simply mount the spider on the trusses which is logistically just as easy as mounting them midway between them?

Without any data it's not possible to figure out how much flexure will be present, and if it might be detrimental to maintaining critical collimation. I am assuming you did the calculations and found the deflection acceptably small, but someone copying your configuration may not be as savvy in mechanical engineering skills, or use the correct type of aluminum, etc., and end up with less than optimum results.

My point was that it's just as easy to simply put the force on the pillars rather than midway between them (the "suspended bridge" configuration), the latter being inherently more flexible (which is a good thing for a suspended beridge but not necessarily for secondary mirror supports! ).

Regards,

Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5402048 - 09/03/12 10:53 PM

If that matters at all (maybe it doesn't) I chose to most of the calculations with the scope pointing at an altitude 45 degrees. For some reason I thought pointing straight up was a rather special case and it may not represent reality as well. Maybe one of the reasons the calculations brought me in this direction.

One other thing was that I tried to minimize the distance between 2 truss on the secondary. On my first model I had a much larger secondary ring with enough room to fit 2 truss and the bracket for the vane. With a ring of its current size I would have needed to have the bracket for the vane in between the 2 truss ends. But the strength of the truss is also function of the angles which boiled to having the truss ends as close as possible.

One thing to take into consideration was: although it looks decent, in regards to professional instruments, I don't expect it to be remotely comparable. Because I had the resources to design/machine doesn't mean I have the funds for a 5 digits mirror, unfortunately.

edit: It will be used for imaging only, at an imaging scale of .63 arcsec/px.
I am sure I already made some mistakes but nothing that can't be solved by redoing one or several parts, not a big problem. I'll find out quick enough if my optics will be good enough to evidence some of the mechanical problems I created by using shortcuts or just making mistakes.

edit2: in response to your last paragraph: Maybe I should write off a disclaimer ahah More seriously, although I am a mechanical engineer I spent most of my time in grad school doing thermal engineering and this is still what I do everyday. There is quite a bunch of critical aspects of the design of an astrograph or telescope in general that goes above and beyond simple mechanical engineering that clearly call for experience more than anything else. Before starting this project I had been looking for resources for a year or two. Any good book you know that talks in details about the one mechanical aspect we just discussed? I also posted threads here and on the yahoo ATM group looking for plans or resources to make an astrograph. I am not going to lie, I didn't get any response. If you are concerned about readers making mistakes copying a wrong design maybe it would be a good thing to design the perfect one and offer it to the public? There are much more people looking for such plans than actual plans... especially a perfect one

Edited by zytrahus (09/03/12 11:44 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
psi_chemie
sage
*****

Reged: 05/01/11

Loc: Leawood, KS, USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5402086 - 09/03/12 11:11 PM

Sorry I didn't see if you mentioned what software you used for CAD? SolidWorks?

Thx,
-mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: psi_chemie]
      #5402099 - 09/03/12 11:17 PM

Yes, Mike.

Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5402257 - 09/04/12 01:49 AM

Again, it is obvious which configuration is most stable. Why people choose otherwise doesn't change that fact.

And resources have nothing to with it either. Come on, Stephen, in order to attach a spider on the trusses instead of midway between them doesn't require professional resources or a five digit mirror.

All the best in your project.

Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5402302 - 09/04/12 03:16 AM

And again, the most simple fact that some professionals choose otherwise makes the choice clearly not so obvious: At least for the majority of ATMers building an Astrograph, RCOS would appear as a pretty thrust worthy professional.

I'm sorry to disagree but I think the available web resources or literature have a lot to do with it. I understand the explanation you provided and can only hope the ring will be stiff enough, if not I'll redesign it, no big deal... no need for a bashing contest here, please and thanks.

Putting things into perspective, I am not sure if the quality of the optics I will be using is going to be good enough to see any degradation from this configuration.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Datapanic
Carpal Tunnel
*****

Reged: 10/17/09

Loc: Tucson, Arizona
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5402303 - 09/04/12 03:26 AM

I think the ring will be plenty rigid enough for the secondary support.

First - There are technically 2 curved "T" beams around the ring with the embedded groves - if they were made for reducing weight or strength, it doesn't matter, end result is they add a lot of strength. The back mount brackets for the spider vanes also reinforce the whole ring. I think it would take a lot of force to bend that ring anywhichway, let along make it bend 0.0004 of an inch from gravity alone. Heck, I bet thermal expansion of high grade/low expansion aluminum is more than that!


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5402315 - 09/04/12 03:50 AM

Stephen, RCOS designed its UTA ring differently, as is obvious form their image. I hope your configuration works well, but I also wanted to point out why the spider is best mounted on the truss or why the UTA rings are made stiffer if it's not, the way RCOS did. There is no bashing contest here. Just facts.

Dan, I don't know how big that secondary is but if it's anything like a 12-inch f/8 DKC it should be somewhere between 6.5 and 7 inches. With all the hardware it's not a featherweight. You also don't know the thickness of the spider vanes and the type of aluminum used. All that and more is part of the equation.

No one should take this personally. It's all about facts. Thanks for your discussion.

Cheers.

Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
Ryan W
sage
*****

Reged: 10/26/10

Loc: Port Matilda, PA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5402604 - 09/04/12 09:50 AM

Stephen,

Beautiful project, very well thought out! I have only ever done civil engineering related CAD work and have a healthy respect for the well thought out CAD project followed by what looks to be a very well executed (so far) final result!

One question I have: Did you achieve considerable savings ($) doing all of this yourself as opposed to purchasing the final product from planewave or another? Or was it more about the journey and fun of doing it than the savings.

MKV,

I see the center spaced spider vanes as a non issue unless, for some reason, the material used for the upper ring is not rigid. Perhaps a placing the vanes over the truss connections would have been ideal, but if the critical analysis said otherwise then why argue with it? The flexure caused by that small of a load (secondary and vanes) on what I assume is an aluminum upper ring is almost certainly negligible. I am sure the upper cage was designed to resist the moment imparted on it by the center spaced spider and secondary.

Non issue IMHO.

again, great work, love the pictures!

-Ryan W


Post Extras: Print Post   Remind Me!   Notify Moderator  
Dave O
sage
*****

Reged: 12/21/11

Loc: Sri Lanka
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5402606 - 09/04/12 09:51 AM

Quote:

You also don't know the thickness of the spider vanes and the type of aluminum used. All that and more is part of the equation.




Mladen ... had you read the thread, you would have seen:

Quote:

Spider vanes are 316 S-S and 2 mm thick (painted flat black)




Cheers. Dave O


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Dave O]
      #5402829 - 09/04/12 11:48 AM

Ryan: Yes it has a lot to do with the journey. In the end it will cost me less than the quarter of the price of the Planewave, but my optics won't be as good, so it makes it hard to compare.

Post Extras: Print Post   Remind Me!   Notify Moderator  
EddWen
Pooh-Bah


Reged: 04/26/08

Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5402843 - 09/04/12 11:53 AM

As a retired engineer and business owner, I find this a curious statement.

As the chief engineer of teams consisting of two to twenty engineers, there were always multiple solutions to just about any design facet.

My job was to cull out the best fit for the company, with regard to design requirements, cost, company capabilities, machining efficiency, etc.

I'm more of the opinion there is more than one satisfactory way to...........


Quote:

It is not a matter of different views John. We're no philosophers here in the sense that there're no final answers. In the field of engineering and science there are usually final answers and usually they are right of wrong and in this case it is wrong. Too bad for OP, but this is the result of the method.
Are you also one of the opponents of Einstein who'd say in 1905 that he's wrong because "it is picking apart Newton's magnus opus Principia"?




Post Extras: Print Post   Remind Me!   Notify Moderator  
John Jarosz
Astro Gearhead
*****

Reged: 04/25/04

Loc: Fairfax, Iowa
Re: 17" CDK and Equatorial Mounting new [Re: EddWen]
      #5402863 - 09/04/12 12:05 PM

Stephen:

Beautiful work. Keep right on going and trust your instincts.

I can't really comment on the writings of the naysayers, as most of them are on my ignore list. I highly recommend using that feature as it makes reading CN much less stressful. Trolls need responses for their strategy to work. Constructive criticism will always filter thru and will be helpful in the end.

John


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike I. Jones
Post Laureate
*****

Reged: 07/02/06

Loc: Fort Worth TX
Re: 17" CDK and Equatorial Mounting new [Re: John Jarosz]
      #5403251 - 09/04/12 03:22 PM

Stephen,
WONDERFUL workmanship, the best I've seen since Preston Engebreton's 20" RC hit the forum.

Agree with JJ - you build it exactly like YOU want to. Thank you for going to the trouble to share it here on CN - a LOAD of people are diggin' it and learning from it, me included. Questions from everyone about how you thought out your design are constructive, with answers that educate. But if someone goes beyond just asking, and starts arguing with you about how you did something, and wants you to build yours their way, I say let 'em build their own! Constructive analysis degenerates to harassment if any critics are overly persistent in insisting their ideas be incorporated, with the goal of claiming partial credit for a finished product they had no part in funding or laboring over.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
polaraligned
professor emeritus


Reged: 12/26/08

Re: 17" CDK and Equatorial Mounting new [Re: Mike I. Jones]
      #5403469 - 09/04/12 05:18 PM

I agree with Mike above!!!
Beautiful project and thanks for sharing. There is more than one way to skin a cat. If it works, great. If not, you correct it and learn. You could stiffen the top ring easy enough if need be. Don't pay the howling dogs any mind.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: Mirzam]
      #5412031 - 09/09/12 05:53 PM Attachment (89 downloads)

Jim&Zythrahus: this has nothing to do with weight. Weight is not stiffness and vice versa. RCOS is simply doing it the wrong way. period. Look at how it is done at the VLT, the Subaru, the Keck, the Gemini etc etc.

What is wrong with putting the spider at Zythrahus' position, is that the upper ring has the least amount of stiffness there. It will bend by itself the most there and you even put a large weight on that position. If you put it at the position between the trusses' crossing, the deflection is far less, almost zero.
Mladen's comparision is correct, it is like a suspension bridge. In fact, it is the same equation (Euler-Bernouilli beam theory) that determines the deflection. You can also see exactly the same effect on every suspension bridge. Look eg. at the collapse of Tacoma Narrows Bridge, aka Galloping Gertie, http://www.youtube.com/watch?v=j-zczJXSxnw
The biggest deflection always happens between the biggest distance between the constraints. To give any evidence for my statements, I did the following comparision: I designed a ring in SolidWorks. Ring is a model of the upper cage. I put the material properties of Aluminium 6061 on the ring. The ring has a outer diameter of 370mm and an inner diameter of 350mm. Thickness is 5mm. I applied a force (purple arrows) of 100N on four points (four-vane spider) and I constrained with 4 pairs of constraints, green arrows, first between the forces (Zythrahus' method) and then the method that I am advocating.
In the attachment you can see the results of my analysis. It is pretty convincing. The deflection of Zytrahus' method is about 300x bigger than in my method. No, this has nothing to do with the design of the upper cage. It scales inversely linearly with the stiffness of the upper cage. Neither does it have anything to do with the dimensions of the cage. I used the same design for the comparision and even if you'd use a design with different dimensions, the deflection would again scale linearly.
I am wiling to answer questions concerning this. I am also willing to help here. But I don't want a flame war because I am advocating something which is non-mainstream without arguments (Yes John Jarosz&Polaraligned, I am also referring to you now.)

Mike: You disappoint me here.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5412423 - 09/09/12 10:02 PM

Thanks Benach for your post: I think you'd agree there isn't such thing as right or wrong here unless the ring ends up not being stiff enough. If a deformation of X is acceptable, doing 300 better than X is still going to be nothing else but acceptable.

I obviously can't speak for RCOS but as mentioned in earlier posts there were other factors that I took into considerations that lead me to this choice. But I have a hunch that RCOS had reasons as well.

RCOS and myself are not the only doing it this way: you can Alluna-Optics's RC's, Sky-Vision (their OT structure), and I am sure others.

I hope this will turn out OK for me, if not, a little bit of re-design won't be a problem.

thanks again Benach.


Post Extras: Print Post   Remind Me!   Notify Moderator  
David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5412458 - 09/09/12 10:23 PM

Ok, kids. You've beaten this horse well past its death. Time to put this one to bed. This thread has two engineering philosophies that aren't going to change.

David


Post Extras: Print Post   Remind Me!   Notify Moderator  
David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5412536 - 09/09/12 11:27 PM

It's unlocked, but only because of a couple of passioned pleas by participants. I ask that if you can't add to the discussion without your editorial comments, then don't bother posting. Your expertise is an asset to the others, but if it's accompanied by infantile remarks, it becomes a distraction.

With that said, consider this thread on probation. This isn't a school yard and you're not school kids.

David


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5412775 - 09/10/12 04:41 AM

Stephen, would it be too much to ask what is your estimate of maximum deflection? Just curious. Thanks.

Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5412808 - 09/10/12 06:46 AM

Quote:

RCOS and myself are not the only doing it this way: you can Alluna-Optics's RC's, Sky-Vision (their OT structure), and I am sure




Stephen, SkyVision is actually mounting their spider on trusses and not midway between them (see top portion of their official site):

http://www.skyvision.fr/wordpress/?page_id=81&lang=en

The lower portion, however, does show a spider mounted midway between the trusses, but they compensate for it with a much thicker and heaver (solid square tube) ring structure, the way RCOS and Alluna do with their tall thin rings.

Ragards,

Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5413154 - 09/10/12 11:46 AM

I'm glad the thread has been unlocked and I'd like to keep it that way. This topic has been discussed enough and unless I have to make modifications to it down the road, I won't reopen the topic.

Feel free to open a new thread to discuss it though, I am sure David P. will love the entertainment.

Thanks.


I've started the machining of the parts for the base of the equatorial mounting. I will post some pictures in a few days.


Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5413194 - 09/10/12 12:07 PM

Looking forward to further updates Stephen.
Best wishes with the rest of the project.
Really interested in seeing the mount.

John


Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucke
member


Reged: 03/12/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5413699 - 09/10/12 04:47 PM

Hi Zytrahus,

It will be interesting when your get your optics to find out how good they are. If they are ok I may look into a similar setup.

Chuck


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Chucke]
      #5413812 - 09/10/12 05:45 PM

Hi Check,
I am a little anxious about this I hope they turn out to be decent enough!


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5413820 - 09/10/12 05:48 PM

Hi John,
I made a few renderings of the complete project. You'll get an idea of what I've done.

The pier is only a temporary thing as I didn't have a practical bench to assemble the mounting on and it will be a practical thing to have when I start testing things out from home.





I made a little blog entry with some quick explanations of what I've tried to do. More details about that will follow as I progress through the machining / assembly.

if you want to take a look: http://cooledpix.com/2012/09/10/eq-z-introduction/


Cheers,


Post Extras: Print Post   Remind Me!   Notify Moderator  
gregj888
professor emeritus


Reged: 03/26/06

Loc: Oregon
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5414087 - 09/10/12 08:55 PM

Can I ask a naïve question? In the analysis above it looks like the only forces being considered are along the optical axis and the only constraints are those of the tubes. Isn’t this a 3 space problem and doesn’t the spider constrain the ring in 2 dimensions?

My question-- how would one do a more complete model to look at this in 3 space and at different orientations?

Stephen, beautiful work!!

thx,


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5414252 - 09/10/12 10:12 PM

Thanks Greg.
It looks like the analysis you referring to was done in the specific conditions of the OTA aiming at Zenith. In any other orientation there would be forces in the other 2 directions.


Post Extras: Print Post   Remind Me!   Notify Moderator  
gregj888
professor emeritus


Reged: 03/26/06

Loc: Oregon
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5414371 - 09/10/12 11:57 PM

Stephen,

That's what it looks like. Again, I'm not trying to start anything, I'm just curious. It seems like a lot of things are missing and I’m not smart enough to know if it will matter.

With the 1.5m for the Alt Az initiative the Cal Poly students ran a lot of FEA and dynamic simulations looking at resonant frequencies, Q (in my world) and dampening. Much of this relates back to mass and stiffness, but in 3 dimensions.

Again very nice scope, I can only hope my 20" turns out halfway close.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5414383 - 09/11/12 12:06 AM

Greg: do you have a link to your work-log (if you've got one)? I'd love to check it out.
Re: simulation: I won't comment as it's not mine but I think it was mainly there as an illustration to give a general idea of the deformation, that's all.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5415225 - 09/11/12 01:12 PM

Greg: the only difference is then that the force vector will be decomposed in a vector downward and a horizontal vector. The effects of downward force on the truss are fairly small because this will result in buckling. However, a truss is not sensitive to buckling although I must admit that in Zythrahus the chances of buckling are much bigger because the force vector will be excentric to his trusses. The horizontal force is nearly not important because the upper ring should be stiff already. Hope this is clear. If not, please rephrase your question.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5415258 - 09/11/12 01:26 PM

Quote:

Thanks Benach for your post: I think you'd agree there isn't such thing as right or wrong here unless the ring ends up not being stiff enough. If a deformation of X is acceptable, doing 300 better than X is still going to be nothing else but acceptable.

I obviously can't speak for RCOS but as mentioned in earlier posts there were other factors that I took into considerations that lead me to this choice. But I have a hunch that RCOS had reasons as well.

RCOS and myself are not the only doing it this way: you can Alluna-Optics's RC's, Sky-Vision (their OT structure), and I am sure others.

I hope this will turn out OK for me, if not, a little bit of re-design won't be a problem.

thanks again Benach.




Zythrahus: I cannot speak for other's considerations. But this stiffness difference should make you reconsider your thoughts. If you think your design is still acceptable, which I doubt, I'd like to see a tolerance analysis of your telescope supporting a FEM analysis proving that your secondary mirror will remain within tolerances for all positions. I have already seen a very sketchy tolerance analysis by MKV and if that one is correct, if it is applicable to your telescope, it is highly unlikely that it will be good enough.
And to make myself clearer: the deflection of a beam supported by two constraints (This particular case) goes with the third power (of the smallest distance) between the force vector and the constraints.

But suppose it fails the analysis mentioned above, what are you going to do to correct this? Readjust your system for every altitude?
Even worse: what is so difficult in changing the radial position of your upper cage and increase your stiffness about 300x? I don't see the problem.


Post Extras: Print Post   Remind Me!   Notify Moderator  
TopherTheME
sage
*****

Reged: 02/11/11

Loc: Rochester, MI
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5415317 - 09/11/12 01:50 PM

What kind of hardware and electronics are you planning on using to operate the mount? Something off the shelf or scratch built?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: TopherTheME]
      #5415348 - 09/11/12 02:01 PM

Quote:

What kind of hardware and electronics are you planning on using to operate the mount? Something off the shelf or scratch built?




Using 2x byers gears/worms a pair of Maxon motors/gearbox/encoders controlled by my Gemini-II.

Cheers,


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5415741 - 09/11/12 05:12 PM

Just an offer from me to Zythrahus: Can you contact me offlist and I'll give you an e-mail adress. You can send a SW model of your scope to me and I am willing to have a critical look at certain other mech. engineering thingys. However, be prepared that I might conclude that some things have to be redesigned.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5415844 - 09/11/12 06:11 PM

Thanks but at this point parts are made so I think I'll just wait till the optics come in so I can do some actual imaging tests to validate my design. It doesn't make sense to change anything now and until I've done some actual imaging.

Post Extras: Print Post   Remind Me!   Notify Moderator  
gregj888
professor emeritus


Reged: 03/26/06

Loc: Oregon
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5416046 - 09/11/12 08:07 PM

Benach, thank you. It's the dynamic analysis that I think would be interesting.

Stephen, sorry no log as such. Just the files from foucault testing. The real problem is time to would on it, with a clear head. BTW, I would do some imaging before changing too, why not.

I'll post an interferagram of my mirro when I get one here soon.

Greg


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5416494 - 09/12/12 12:56 AM

Greg: a telescope is not a dynamic instrument, at best quasi-static. Buckling is, after all, quasi-static. So I am not going to invest a lot of time in a full dynamic analysis here. Simply a matter of priorities.

Zythrahus: ehm, you're going to image your aberrations? Good luck with that one. How steady is your air there in Southern California? How do you make the distinction between a pure optical aberration and an aberration due to misalignment? Having seen a couple of CDKs myself, I know that they are extremely sensitive to misalignment and especially when the mirror position is overdetermined, you cannot determine with certainty that the position and/or correction is at optimum.


Post Extras: Print Post   Remind Me!   Notify Moderator  
David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5416537 - 09/12/12 01:26 AM

Looking forward to the next few pictures of your progress. And may I be the first in line for an autographed copy of your first APOD!

David


Post Extras: Print Post   Remind Me!   Notify Moderator  
gregj888
professor emeritus


Reged: 03/26/06

Loc: Oregon
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5416550 - 09/12/12 01:40 AM

Benach,

IMHO Vibration dampening and resonant frequency are a big part of telescope design, especially as you get larger. It's not so much the mount moving as wind buffeting or something in resonance with say a motor drive frequency. The static flexure (which is quasi-static) is also important. I'm not suggestion one over the other, just that it would be nice to have both analyses during the design process.

A side note, with my 20" starting out as a CDK (is now planned as a corrected Classical Cas.) I have looked at the alignment issue a bit. All Casses are sensitive to mis-alignment but the Dall Derivatives tend to be the least sensitive. With a spherical secondary, all the secondary mis-alignment terms more or less drop out as long as the mis-alignment is fairly small. "Reflective telescopes” has a section on mis-alignment sensitivities.

I needed to be able to select the final f/# of the scope using different secondaries, hence the Classical.

Thx,

Greg


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5416588 - 09/12/12 02:25 AM

Greg: There is no active damper in your telescope, is there? So at best it is Rayleigh dampening. I've never heard of an amateur calculating their resonance frequencies and comparing them to actual measured vibrations. So yes, theoretically speaking you're right, but then there is so much more engineering you have to take into account, that this is just the final part.
I am willing to help you to think along the way from a professional (opto)mechanical PoV but that is not the same as doing all the analysis for you

I agree that a secondary of a DK is the least sensitive to misalignment of all Cassegrain derivatives but the optical alignement of the primary is extremely sensitive and the final focal plane quality is also sensitive to this. also the conical constant and radius of curvature requires quite some accuracy. I remember that in a friend's 14" f/4.7 CDK the primary's Conical constant had to be within 0.02 and the RoC within 1mm. That is quite wild for a f/3.6 primary and beyond the abilities of most amateurs.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom and Beth
Post Laureate


Reged: 01/08/07

Loc: Tucson, AZ
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5416632 - 09/12/12 03:35 AM

Hope you don't mind, but I'm following this discussion with interest. I have a mirror set for a 300MM F20 DK and sifting through designs from which to build the Mechanics for a truss. I'll be using an AP1200 for the mount. Of particular interest are the details of the tube connections-

It would be nice to have access to my own machine shop, but the CFO would prefer I keep this simple.


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5416686 - 09/12/12 05:44 AM

Quote:

I would do some imaging before changing too, why not.




Imaging is relatively low resolution. If it's going to be a camera then the tolerances are much more relaxed.

An f/8's Ary disc is 11 microns. Even if quadrupled in size due to errors or scintillation, whatever, it's still a dot to the eye. And if you print it at 10x that scale it's still no bigger than the dot on your computer screen. It's still a dot to the human eye.

But if you want to use it visually, that's a different story. Visually you should be able to use 75x per inch magnification, or even higher, and see no imaging flaws. That's a whole new ball of wax.

M


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5416720 - 09/12/12 06:46 AM Attachment (60 downloads)

Quote:

I have looked at the alignment issue a bit. All Casses are sensitive to mis-alignment but the Dall Derivatives tend to be the least sensitive. With a spherical secondary, all the secondary mis-alignment terms more or less drop out as long as the mis-alignment is fairly small.



Gregg, CDKs are relatively less sensitive to axial misalignment (since the spherical secondary really doesn't have an axis), but not to tilt. The same goes for the corrector elements, which are also spherical. Here is an example of a 300 mm f/8 CDK. In the upper left corner you see two columns of spot diagrams representing images on-axis, half way and at the edge of the FOV.

The column on the left has zero tilt. The column on the left is tilted by 1/10 of a degree (6 arcminutes), or 0.07 mm at the edge of the secondary. Clearly even the on-axis image shows blatant coma. The PSF on the lower right shows the same axial image if the secondary were titlted only 0.05 degrees (3 arcminutes), or 0.033 mm at the edge. Even here the image is decidedly assymetrical and the coma is still perceptible.

This is the effect of only one possible element being tilted and all others being perfect, which is of course never the case. If you add a mixture of tilt in the corrector lenses and the corrector as a whole, you'll get an even more complete idea of how critical this is, and why final collimation must be done by autocllimation.

Also, all along we are assuming that the very fast primary is a perfect ellipsoid. At ~ f/3.5 ot 3.6 its conic profile would have to be within 99.99% of the theoretical value to satify 1/4 wave limit at the best focus! Figure out what this would mean in terms of knife-edge readings!

But, like I said, if you're looking at a prime focus camera, rather than a visual telescope, then of course all this is moot. You can have a 1/2 wave camera and still make good astrophotos - especially with photo art software and stacking options. In fact 1/2 wav seems to be industrial standard for fine photographic commercial optics

Mladen

PS The vertical bar on the lower right is the normalization scale of the PSF function and is not related to the tilt in any way.

Edited by MKV (09/12/12 07:04 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: Tom and Beth]
      #5416767 - 09/12/12 07:25 AM

Quote:

Hope you don't mind, but I'm following this discussion with interest. I have a mirror set for a 300MM F20 DK and sifting through designs from which to build the Mechanics for a truss. I'll be using an AP1200 for the mount. Of particular interest are the details of the tube connections-

It would be nice to have access to my own machine shop, but the CFO would prefer I keep this simple.




I totally don't mind , but I don't see what your point is. You want advice on how to do the mechanics better than Zythrahus? I think he's done some things correctly, but certain things leave much to be desired for.


Post Extras: Print Post   Remind Me!   Notify Moderator  
don clement
Vendor (Clement Focuser)


Reged: 02/02/11

Loc: Running Springs, California
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5416904 - 09/12/12 09:24 AM

Quote:


How steady is your air there in Southern California? How do you make the distinction between a pure optical aberration and an aberration due to misalignment?




When all the speculation, simulations, and postulations by engineers and designers were done and said for the Hale 200”, the final star testing and optical figuring was done by Don O. Hendrix under the steady air of southern California’s Palomar mountain. Too bad a star test wasn’t performed for the Hubble before it was launched instead of relying on the assumptions, postulations, and simulations of the engineers and designers.

Don


Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: don clement]
      #5416926 - 09/12/12 09:39 AM

Good post Don.
At the end of the day you have to credit the people that actually get out there and do it.
I am totally in awe of this project and look forward to seeing it progress to completion.
I am totally sure that if something required adapting it would not phase the builder in any way.


John


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: don clement]
      #5416956 - 09/12/12 09:55 AM

Sure Don, but I think that you and I agree that with nowadays cameras the criteria of the optics have increased fairly much. Who was talking on eg. periodical error correction or subpixel imaging (and therefore imaging near the Rayleigh limit) when Mt. Palomar was build?

Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: don clement]
      #5416963 - 09/12/12 10:01 AM

Quote:


When all the speculation, simulations, and postulations by engineers and designers were done and said for the Hale 200”, the final star testing and optical figuring was done by Don O. Hendrix under the steady air of southern California’s Palomar mountain. Too bad a star test wasn’t performed for the Hubble before it was launched instead of relying on the assumptions, postulations, and simulations of the engineers and designers.



Umm, sir, the Hubble fiasco was not due to engineering "speculation" and simulation (the engineered design was correct!), but on a faulty nulling device, better yet - on the individual(s) who made it incorrectly, and on their refusal to even entertain the possibility that it might be faulty (they either refused to make or use a backup), and on the arrogance of so many that just because something looks "perty" it must be beyond reproach, untouchable.

Mladen

Edited by MKV (09/12/12 10:52 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Datapanic
Carpal Tunnel
*****

Reged: 10/17/09

Loc: Tucson, Arizona
Re: 17" CDK and Equatorial Mounting new [Re: David Pavlich]
      #5417001 - 09/12/12 10:32 AM

Quote:

It's unlocked, but only because of a couple of passioned pleas by participants. I ask that if you can't add to the discussion without your editorial comments, then don't bother posting. Your expertise is an asset to the others, but if it's accompanied by infantile remarks, it becomes a distraction.

With that said, consider this thread on probation. This isn't a school yard and you're not school kids.

David




Thanks David - I hope the thread stays on topic. Many of us have an interest in watching this project unfold.


Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: Datapanic]
      #5417024 - 09/12/12 10:43 AM

Me too, really enjoying this project.
Even more so now that i have used the ignore button for the first time ever.
So much better to read.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Benach
Pooh-Bah


Reged: 01/24/08

Re: 17" CDK and Equatorial Mounting new [Re: Datapanic]
      #5417327 - 09/12/12 01:36 PM

Quote:

Quote:

It's unlocked, but only because of a couple of passioned pleas by participants. I ask that if you can't add to the discussion without your editorial comments, then don't bother posting. Your expertise is an asset to the others, but if it's accompanied by infantile remarks, it becomes a distraction.

With that said, consider this thread on probation. This isn't a school yard and you're not school kids.

David




Thanks David - I hope the thread stays on topic. Many of us have an interest in watching this project unfold.



Me thinks that giving feedback on an important detail of a project is still on topic.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Dave O
sage
*****

Reged: 12/21/11

Loc: Sri Lanka
Re: 17" CDK and Equatorial Mounting new [Re: Benach]
      #5417439 - 09/12/12 02:43 PM

Quote:

Me thinks that giving feedback on an important detail of a project is still on topic.




Your feedback has been noted. My suggestion would be that if you think it is so important a topic; you move it to its own thread per the OP's request ... place a link here if you want to tie the two together. Dave O

Edit. I am actually quite interested in the topic; and believe it is worthy of its own thread where the experts (and there are many here) can chime in and perhaps even teach a few of us something ... without distracting from the OP's report on his project.

Edited by Dave O (09/12/12 02:57 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
gregj888
professor emeritus


Reged: 03/26/06

Loc: Oregon
Re: 17" CDK and Equatorial Mounting new [Re: Dave O]
      #5420345 - 09/14/12 02:19 AM

Mladen

I agree, though think of it differently. Tilt of a spherical surface can be though of as decentering. The reason I down play this it that it's the only alignment issue theat's fairly easy to see and correct (with a laser colimator). This is also in contrast to an asphere, that is down right ugly... tilted or decentered :-)


Post Extras: Print Post   Remind Me!   Notify Moderator  
gregj888
professor emeritus


Reged: 03/26/06

Loc: Oregon
Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5420348 - 09/14/12 02:21 AM

Benach

No worries, I wasn't looking for you to do the work, just courious about the more complex modeling.

Thx,


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: gregj888]
      #5420458 - 09/14/12 06:20 AM

Quote:

I agree, though think of it differently. Tilt of a spherical surface can be though of as decentering. The reason I down play this it that it's the only alignment issue theat's fairly easy to see and correct (with a laser colimator). This is also in contrast to an asphere, that is down right ugly... tilted or decentered :-)



Aspherics are much more difficult, no argument there. I only illustrated that even a small tilt of one element in a DKC will degrade the image and make it unacceptable. And in a DKC you are not dealing with one element but with four - the secondary mirror, the corrector lenses and the corrector itself as a unit. Lots of trial and error repetitions to get it collimated for visual use. But this is off topic, so I am out of here.

Regards,

Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #5431994 - 09/21/12 12:21 AM

Quick update with the assembly of the first few parts of the equatorial mounting.






http://cooledpix.com/2012/09/20/eq-z-base/


Post Extras: Print Post   Remind Me!   Notify Moderator  
David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5432273 - 09/21/12 08:42 AM

Looks like some dandy hardware!

David


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom and Beth
Post Laureate


Reged: 01/08/07

Loc: Tucson, AZ
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5433307 - 09/21/12 07:21 PM

Quote:



I was hoping I could assemble the secondary tonight but I had to rework a few threads that were a little too tight! Guess the complete mock-up will be finished tomorrow.




I started another thread looking for help on Truss Tube Ends. Are these something you made at home or found somewhere where a rank ATMer like me could procure them?

FWIW, I will be working with 1.25 inch OD Aluminum Tubes to fashion a 300MM F20 DK.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Tom and Beth]
      #5433323 - 09/21/12 07:31 PM

I couldn't find anything off the shelf so I ended up making them.
If I am not mistaken Moonlite makes some truss components but I am not sure if they would be suitable for your project.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tom and Beth
Post Laureate


Reged: 01/08/07

Loc: Tucson, AZ
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5433335 - 09/21/12 07:39 PM

I was a fraid you would say you made your own. I have seen Moonlights, and if nothing else their articulated double end (for lack of a better description) looks promising.

Post Extras: Print Post   Remind Me!   Notify Moderator  
droid
rocketman
*****

Reged: 08/29/04

Loc: Conneaut, Ohio
Re: 17" CDK and Equatorial Mounting new [Re: Tom and Beth]
      #5433389 - 09/21/12 08:13 PM

Scope looks beautiful....best of luck on ,it.....
and David your doing a good job moderating this thread.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Escher
Pooh-Bah
*****

Reged: 08/30/07

Loc: Fenton, MI
Re: 17" CDK and Equatorial Mounting new [Re: droid]
      #5433450 - 09/21/12 08:58 PM

Beautiful work Stephen!

As a side note - I have been considering learning SolidWorks - are you self taught? I'm watching this thread with much interest, not only because of the workmanship, but as a FEA / CAE professional I'm interested in the discourse.

At the risk of being mentally pummelled by other ME's who know much more about the topic than I...

If there is too much flexure - it would seem that you could simply add a second upper ring, with multiple attachment points to effectively double or even triple your stiffness with the right beam section. With your skills, I would think this would be a pretty simple addition.

Looking forward to seeing more progress!


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Escher]
      #5433692 - 09/21/12 11:57 PM

Hi Escher,
I did some Solidworks in School but most of the Mechanical design and analysis courses were based on Catia V4 initially then V5 and some FAE under Nastran. That was already over 10 years ago and for the past 7 years I've only worked with Solidworks with minimal FEA as most of my professional work is thermal/fluids i.e. CFD analysis.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5451249 - 10/02/12 01:25 AM

Really small update with the assembly of the 2 motor/worm assemblies:






pinion/spur should be there soon to complete the drive system.

I've also made the Alt / Az adjustment bolts/barrels/knobs.

Next I think I am going to start working on the tougher work with the RA housing...


Post Extras: Print Post   Remind Me!   Notify Moderator  
polaraligned
professor emeritus


Reged: 12/26/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5451388 - 10/02/12 06:35 AM

Is that black paint or anodize? Looks like paint in the pictures. Very nice job.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: polaraligned]
      #5451741 - 10/02/12 11:32 AM

it's anodizing like the other parts, this point and shoot camera is doing way too much sharpening (and i always sand blast the parts before anodizing)

Post Extras: Print Post   Remind Me!   Notify Moderator  
Steen27
sage


Reged: 05/26/06

Loc: Torrance, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5454128 - 10/03/12 08:21 PM

Thank you very much for sharing your work and pictures of your project - it's very inspirational.

Post Extras: Print Post   Remind Me!   Notify Moderator  
johnC
member
***

Reged: 08/24/06

Loc: Hucknall Nottingham UK
Re: 17" CDK and Equatorial Mounting new [Re: Steen27]
      #5454495 - 10/04/12 02:13 AM

Continues to be a fantastic thread.
My wife and I are facinated with the progress of this project. As Jim said...very inspirational.

John


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: johnC]
      #5454527 - 10/04/12 02:50 AM

John, Jim, thank you very much!

Post Extras: Print Post   Remind Me!   Notify Moderator  
David PavlichAdministrator
Transmographied
*****

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5454716 - 10/04/12 09:02 AM

That's some nice work!!

David


Post Extras: Print Post   Remind Me!   Notify Moderator  
drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: 17" CDK and Equatorial Mounting new [Re: David Pavlich]
      #5455263 - 10/04/12 03:21 PM

stephen, three comments.

i am completely gobsmacked by the beauty and ambition of your project. i have to say some emotion between laughter and tears overtakes me when i remember the 6" telescope i made as a teenager with my father, using plumbing joints and babbitted bearings after the instructions in thompson's book. how things have advanced!

i am really pleased you chose a dall kirkham, a scope design that i thought was unfairly reviewed in a recent optical handbook, and look forward to details of your optical specs, optical supplier, and reasons for your choices of both.

i want to complement you on your maturity and poise. you know what matters and what doesn't in the path to get where you are going ... which is a rare thing in my experience. the fact that you also have the generosity to document your work here is just the icing on the cake.

good luck and keep posting!


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: drollere]
      #5455837 - 10/04/12 10:20 PM

Thank you very much for the kind words, Bruce.
I hope to be able to get the optics soon... as I can't wait for the first light! But there is still quite a bit of work ahead.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucke
member


Reged: 03/12/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5456917 - 10/05/12 05:51 PM

Hi Zytrahus,

I see you are in So Cal. Are you a member of OCA?

Chuck


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Chucke]
      #5456931 - 10/05/12 06:01 PM

Yes I am, I go to Anza at least once a month. Will be there tomorrow if the weather permits but it doesn't look so good right now...

Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike I. Jones
Post Laureate
*****

Reged: 07/02/06

Loc: Fort Worth TX
Re: 17" CDK and Equatorial Mounting new [Re: TopherTheME]
      #5456981 - 10/05/12 06:49 PM

Stephen,
Some questions on your CDK:

1. Did Planewave give you any tolerance data for airspacing, allowable tilt and decenters? Do you have an idea about how closely you must build your hardware to nominal values, and how much tilt/decenter adjustment you must provision for?

2. Is Planewave going to analyze and optimize your as-delivered optics with real as-manufactured values for radii, lens thicknesses and glass melt data? Or are they assuming your delivered system meets nominal prescription values that were manufactured perfectly? (I hope not).

3. Did they also design the primary and secondary baffles for you and you are building to those drawings?

Thanks,
Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Mike I. Jones]
      #5457017 - 10/05/12 07:19 PM

Hi Mike,
I haven't been in contact with Planewave at all. HO provided me with some mechanical specifications about their optics such as mirror spacing, back focal distance, corrector to primary distance, "some" dimensions for the baffles, and I'm probably forgetting a few others. I have no data on tilt/decenter adjustments. I've designed primary and secondary cells so that I can adjust tilt/decenter and spacing, hopefully that'll give me flexibility during adjusting/collimating.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucke
member


Reged: 03/12/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5459640 - 10/07/12 05:50 PM

I am at the upper pads. I have the 16" on a big GEM. You should come up to visit sometime. I will be out next weekend weather permitting.

I am looking forward to seeing your scope when it is done.

Chuck


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Chucke]
      #5459700 - 10/07/12 06:34 PM

Hi Chuck, I was there last night for some testing of my new camera. It was cloudy most of the night but clear enough for the kind of tests I needed to do. Provided I can modify my 10" f/4 Newtonian this week I will be visiting the SDAA dark site next week-end. If I still need some testing done on the Newtonian/new camera I will be going to Anza instead.

Which pad are you using? one of those on Mars Hill? Do you own an observatory or just the pad?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucke
member


Reged: 03/12/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5461422 - 10/08/12 11:18 PM

Hi Zytrahus,

I am on upper pads at the top of the hill or as we used to call it The Upper Pad Yacht Club. I don't have an observatory. I thought about building one once but decided that I wasn't going to stay in CA long enough to justify the cost. I am on the eastern row of pads second one from the north hidden by a tree.

Chuck.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Chucke]
      #5472614 - 10/16/12 12:46 AM

I received the spur gear for the drive system, I'll get it installed and post some pictures. I'll probably do some tests with the Gemini controller and see how that goes!

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5481282 - 10/21/12 01:09 AM

Here's a picture with the spur gear installed



Post Extras: Print Post   Remind Me!   Notify Moderator  
TxStars
Pooh-Bah
*****

Reged: 10/01/05

Loc: Lost In Space
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5481324 - 10/21/12 02:12 AM

Where did you order the spur gears from?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: TxStars]
      #5481328 - 10/21/12 02:22 AM

From Mr. Byers. He made them to my specs.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5492553 - 10/28/12 01:31 AM

Quick update with the RA bearing blocks:

http://cooledpix.com/2012/10/27/eq-z-ra-bearing-blocks/





Next I will make the rest of the parts for the RA housing and there is quite a bit of work there =)


Post Extras: Print Post   Remind Me!   Notify Moderator  
angusb1
member


Reged: 06/14/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5492600 - 10/28/12 02:43 AM

Hi Stephen,

I've been following your build over the last few weeks and you're coming to the part I find particularly interesting now, the building of the equatorial mount. I hope you don't mind me asking what size shafts/bearings you're using? Also, will the shafts be solid or hollow, and what kind of bearings are those?

Fascinating build, thanks for sharing it in such detail.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: angusb1]
      #5493603 - 10/28/12 07:49 PM

Thanks Angus, these are tapered roller bearings the bigger one is 150 mm OD and the smaller one is only ~130 mm. Both RA and DEC shafts will be hollow and about 110 mm to the front and 90 mm to the rear.

Post Extras: Print Post   Remind Me!   Notify Moderator  
angusb1
member


Reged: 06/14/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5494198 - 10/29/12 08:10 AM

Thanks Stephen.

Post Extras: Print Post   Remind Me!   Notify Moderator  
123456
sage
*****

Reged: 11/05/06

Loc: mid tenn
Re: 17" CDK and Equatorial Mounting new [Re: angusb1]
      #5495697 - 10/30/12 02:04 AM

great thread stephen

just wondering how are you setting the pre load on the bearings ?

joe


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: 123456]
      #5495712 - 10/30/12 02:38 AM

preload is done with a preloading plate (made of thick SS) that is bolt on the rear of the shaft in 6 points (60 degrees apart). The front of the shaft is shouldered to sit on the inner ring of the front bearing.

Post Extras: Print Post   Remind Me!   Notify Moderator  
coinboy1
sage
*****

Reged: 05/03/11

Loc: Tulsa, OK
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5495828 - 10/30/12 07:18 AM

I have to say this build is amazing and inspiring. I have dreamed of using CNC equipment to build a scope such as this. Your engineering and machining skills are excellent. I am loving it.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Baxstar
member


Reged: 09/15/12

Loc: The Netherland
Re: 17" CDK and Equatorial Mounting new [Re: coinboy1]
      #5496200 - 10/30/12 01:35 PM

Where can i order? No just kidding, really like your project and I will be following it!

Casper


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Baxstar]
      #5590200 - 12/26/12 07:55 PM

It's already been more than 1 months since I have put more work on this but unfortunately, I've had a real busy end of year and I am hoping I will be able to make more parts early 2013.

One good news though, the optics for the CDK are being made and I should have them in 3 months!


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #5778401 - 04/04/13 07:21 PM

Quick updates, I haven't had a chance to make any other part, 2013 has been busier than expected but I have good hopes for the next few weeks!

The optics are almost finished (probably a couple of weeks + another 4 weeks for surface shipping)!

Also I am hoping to move to the mountains (mount Pinot area, CA) toward the end of the summer, where I'll finally be able to build a small observatory.


Post Extras: Print Post   Remind Me!   Notify Moderator  
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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
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

Post Extras: Print Post   Remind Me!   Notify Moderator  
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/


Post Extras: Print Post   Remind Me!   Notify Moderator  
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!


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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/


Post Extras: Print Post   Remind Me!   Notify Moderator  
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)



Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
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).




Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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

Post Extras: Print Post   Remind Me!   Notify Moderator  
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.


Post Extras: Print Post   Remind Me!   Notify Moderator  
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


Post Extras: Print Post   Remind Me!   Notify Moderator  
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.







Post Extras: Print Post   Remind Me!   Notify Moderator  
Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6054683 - 08/30/13 04:05 PM

Very interesting design Stephen!

I like the idea of basically using bushings for the sliding surfaces. I see the retaining ring holding a small washer style bushing to sandwich the rotation assemble into the other plate eliminating slop. It also looks like each piece has 2 bolts through a split, used to tighten the bore to the sliding surface. IS this correct? Are all these rings custom machined parts? Will they be ground steel or some other material?

As for the gears, Are these all custom machined pieces? Or can some of them be bought off the shelf?

Nice Work.

-Adam


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Adam Brunette]
      #6054713 - 08/30/13 04:22 PM

Hey Adam,

I have two clutches (one of the focuser and one for the rotator) with featuring a split each for tightening and friction adjustments.

the drawtube has these 2 bushings + 3 large dowel pins for guiding and preventing rotation. We don't see this on any of the pics but the drawtube also has a mechanical stops when reaching maximum travel.

Yes the gears are going to be custom - I know I'll have to go custom for the large gear on the rotator so I'll just have them all done by the same shops. I could have probably found some off the shelf pinions for the focuser gearbox...

All the parts will be made out of 6061 mostly, with maybe a couple parts out of SS.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6061059 - 09/03/13 01:35 PM

Here's a couple of pics of the fit check I did for RA gear/shaft/clutch mechanism.

Hopefully I can do the final assembly this coming week-end - just gotta cut the gear sleeve bearing to length and to find some dry ice for the roller tapered bearings assembly.





Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Adam Brunette]
      #6108319 - 09/29/13 10:15 PM

Hi,
I made some good progress on the mounting this week-end:

http://cooledpix.com/2013/09/29/eq-z-ra-housing-and-shaft-assembly-part-1/

frosted shaft right after front bearing install


RA housing getting assembled


RA shaft + bearing block

+ video: http://www.youtube.com/watch?v=e4Az1otffDQ

RA gear + sleeve PTFE bearing


Second friction plate + clutch pins


Post Extras: Print Post   Remind Me!   Notify Moderator  
jhayes_tucson
sage
*****

Reged: 08/26/12

Loc: Bend, OR
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6108357 - 09/29/13 10:36 PM

Stephen,
I've been quietly following your project since your first post and I have to say that it is VERY impressive. You do very nice work. I'm working (very slowly) on a mount design that will be less massive but will share a number of similar design features. I've been thinking about chilling & heating my components for bearing assembly as well so thanks for sharing your experiences. Once I start cutting metal, I'll share my experience as well, but it will never be as impressive as what you are pulling off. Keep it coming...I love it!
John


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: jhayes_tucson]
      #6108480 - 09/30/13 12:12 AM

Thank you much John - Glad you found some useful information you're welcome to ask any question!
Looking forward to see your work


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6111160 - 10/01/13 12:49 PM

one more pic from last night, finished the install of the clutch (which is working fantastic by the way) and installed the second bearing block + part of the housing. Everything is spinning very smoothly



Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6120942 - 10/06/13 04:47 PM

A few more pictures of the RA assembly getting together..

















http://www.youtube.com/watch?v=vrRT7599iZ8&feature=youtu.be


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6120952 - 10/06/13 04:56 PM

and a couple more








http://cooledpix.com/2013/10/06/eq-z-ra-housing-and-shaft-assembly-part-2/


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6137209 - 10/14/13 02:44 PM

The CDK optics are ready and being shipped now!

And here's my setup to adjust concentricty between RA shaft and RA high resolution encoder:



Post Extras: Print Post   Remind Me!   Notify Moderator  
polaraligned
professor emeritus


Reged: 12/26/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6138468 - 10/15/13 07:55 AM

Quote:

The CDK optics are ready and being shipped now!
]




Good news. Interested to hear how well Hubble Optics did on this CDK set.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: polaraligned]
      #6139021 - 10/15/13 01:02 PM

I am no expert in mirror making/testing/analyzing so I'll (personally) only be able to judge during the first light/imaging sessions.

Maybe some of you experts in the art will have an idea of the quality? Anyhow I can't wait for the first light!

http://cooledpix.com/2013/10/15/cdk17-optics-shipped/







Post Extras: Print Post   Remind Me!   Notify Moderator  
jhayes_tucson
sage
*****

Reged: 08/26/12

Loc: Bend, OR
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6139077 - 10/15/13 01:34 PM

Stephane,
Did they supply any interferometric data? I'd love to set up your OTA and test it against a master flat with a PhaseCam. Unfortunately, that's not very easy to arrange. You are doing such a stellar job ( ) on this project that it would be cool to have some world class optical test data.
John


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: jhayes_tucson]
      #6139091 - 10/15/13 01:38 PM

Hi John
Thanks I would love to have the optics tested to add to the project but as of now I haven't really looked into it. And I am not sure I am going to have any budget to allocate to it. The images I just published are all I have so far.


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: jhayes_tucson]
      #6139904 - 10/15/13 10:07 PM

Quote:

Stephane,
Did they supply any interferometric data? I'd love to set up your OTA and test it against a master flat with a PhaseCam. Unfortunately, that's not very easy to arrange. You are doing such a stellar job ( ) on this project that it would be cool to have some world class optical test data.
John



John, can you elaborate on the wavefront error on the report of PV 1/8.9 and RMS 1/55.4 lambda? I know there is no direct relationship between PV and RMS, but there is usually a 1:3.5 ratio between the two for very good mirrors. This is more like 1:6.2!

regards,
Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6139912 - 10/15/13 10:11 PM

Stephen, the primary looks exceptionally smooth and the edge is incredibly clean (it looks like it was snapped off!). However, it's really impossible to judge the mirror beyond that -- since it is a Ronchi image, which is only qualitative.

Also, where is the corrector?

regards,
Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #6140088 - 10/15/13 11:57 PM

the corrector and the two mirrors are coming as a set since they're providing all of the optimum spacing requirements based on the actual specs of each element. I made the mechanical housings for two corrector lenses. I'll take some picture of the assembly when I'll do it!

Thanks for your comments on the results. Really looking forward to a star test.


Post Extras: Print Post   Remind Me!   Notify Moderator  
jhayes_tucson
sage
*****

Reged: 08/26/12

Loc: Bend, OR
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #6140142 - 10/16/13 12:42 AM

Quote:


John, can you elaborate on the wavefront error on the report of PV 1/8.9 and RMS 1/55.4 lambda? I know there is no direct relationship between PV and RMS, but there is usually a 1:3.5 ratio between the two for very good mirrors. This is more like 1:6.2!

regards,
Mladen




Mladen,
The ratio between PV and RMS depends on the type of aberration present. You can work it out exactly for the pure 3rd order Seidels but it varies depending on how you combine aberrations—particularly if the surface doesn’t fit one of the polynomial terms. That’s why we generally say that the ratio is “generally” somewhere between 3 and 5. That ratio only counts for a full 3D map of the surface deviations—not for a single radial slice. The problem with the knife-edge test is that it is computing the surface along a single diameter using VERY few data points and an estimation of where each zone (across the center) nulls. It does this by measuring the transverse aberations (assuming axial symmetry,) computing a surface slope, and then using a 2D polynomial fit to depict the shape (as shown in the OP’s mirror data.) That shape is then subracted from the ideal profile to determine the error. In most cases, the absolute accuracy for this kind of test is terrible. Don’t take that to mean the KE test is worthless—it’s not. It is very good at establishing qualitatively the smoothness of the figure, it can easily show anamorphic errors, and it can tell you roughly how well corrected the surface is. Remember that correction in this case relates to how well the surface matches the idea parabolic shape. The one thing that a lot of folks don’t realize is that the accuacy of the correction (i.e. parabola fit) required to meet the Rayleigh criteria isn’t very high. A mirror with a peak surface error in r^4 of a half wave can simply be refocused to meet the1/8 wave Rayleigh diffraction limit. So, to achieve the diffraction limit the test itself only has to estimate the correction to within about a ½ wave (on the surface.) Doing that along one diameter is not the same as establishing that the mirror is good to 1/8 wave over the whole surface. Other errors can be much more important because they can’t be removed by simply refocusing. The take away is that the KE test is simply not a good way to produce **quantitative** data on the full shape of the mirror (or a full optical system.) Any PV, rms, or Strehl number based on a single KE test should include very large error bars.

John

Edited by jhayes_tucson (10/16/13 12:43 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6140157 - 10/16/13 12:54 AM

Quote:

the corrector and the two mirrors are coming as a set since they're providing all of the optimum spacing requirements based on the actual specs of each element



I was hoping you'd say that, Stephen! I couldn't imagine you going through all the details so carefully and not having the optical set configured as a unit. Truly an impressive project overall.

regards,
Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: jhayes_tucson]
      #6140164 - 10/16/13 01:01 AM

Quote:

The ratio between PV and RMS depends on the type of aberration present....



Thanks John. It's late here on the East Coast, so I will be brief. I still don't see how they arrived at PV to RMS ratio of 1 to 6.2. Other than that, I am fully aware of the single unidimensional and undersampled problems associated with the knife-edge test when it comes to integrating errors over the entire surface, as well as the ever present uncertainty of the zonal nulls.

regards,
Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #6141298 - 10/16/13 04:59 PM

Thanks Mladen

John, what type of equipment do you have to do these interferometric tests? Do you have a website where you published some of your tests and such? I'm getting curious about your work


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6157451 - 10/25/13 01:11 PM

I did the concrete poor for the 14" pier last week-end.
Will try to do the 4 footings soon so I can start on the flooring asap!




Post Extras: Print Post   Remind Me!   Notify Moderator  
s800
member


Reged: 03/19/08

Loc: Wisconsin
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6158166 - 10/25/13 08:44 PM

Thanks for continuing to post your progress... great read and great work!

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: s800]
      #6180053 - 11/06/13 09:45 PM

Super small update:

* I've installed the gear cover - That's it I can't add anything else to it before it's permanently installed on the pier!
* I've poured concrete for the 4 footings and should be able to start working on the structure (floor) this week-end


http://cooledpix.com/2013/11/06/eq-z-ra-housing-and-shaft-assembly-part-3/







Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6187767 - 11/10/13 11:11 PM

slow progress on the observatory this week-end.
One of the 2x6 was way too twisted to be useful and I didn't have any spare, so I couldn't install any of the 2x4 floor joists.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6195167 - 11/14/13 06:28 PM

Hi
I finally decided to get a Sitech ServoII controller for the mount. I initially intended to use my Gemini2 controller but I am not sure how long it would take for it to support High Resolution encoders. Has anyone with a home made mount any experience with it? Do you like it?


Post Extras: Print Post   Remind Me!   Notify Moderator  
cloudmagnet
sage


Reged: 12/04/08

Loc: Georgetown, Texas
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6195267 - 11/14/13 07:13 PM

Forgive the intrusion, but I feel a comment is in order. In your post containing the photo above (the one of the corner posts and "rim" joists) you state that you intend to use 2 X 4's for floor joists. Are you sure about that? It appears that the floor is about 10 feet square. I was in the home remodeling business for over 25 years and have also built dozens of decks. For a floor this size, I would use 2 X 10 rim joists, and at least 2 X 8's for joists- assuming 16" O.C. Am I missing something???

Post Extras: Print Post   Remind Me!   Notify Moderator  
polaraligned
professor emeritus


Reged: 12/26/08

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6195293 - 11/14/13 07:24 PM

Hi Stephen.

Looking fantastic. Probably the best build ever posted here.

I was wondering if you could comment on the cost of your telescope and mount vs if you purchased a CDK17 and a Paramount ME?

I am assuming that you are doing all the design work and having a local machine shop produce all the parts?

Thank you.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucke
member


Reged: 03/12/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6195298 - 11/14/13 07:29 PM

I am using a Servo II although I don't use the high-res encoders. What do you need to know?

Chuck


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: cloudmagnet]
      #6195338 - 11/14/13 07:45 PM

Quote:

Forgive the intrusion, but I feel a comment is in order. In your post containing the photo above (the one of the corner posts and "rim" joists) you state that you intend to use 2 X 4's for floor joists. Are you sure about that? It appears that the floor is about 10 feet square. I was in the home remodeling business for over 25 years and have also built dozens of decks. For a floor this size, I would use 2 X 10 rim joists, and at least 2 X 8's for joists- assuming 16" O.C. Am I missing something???




Hmm, you're probably right - I had skyshed plans which I had to modify to fit my needs of using concrete posts. I found a few plans of "sheds" which used 2x4 they were only 8x8 though. The floor isn't done yet, maybe I should follow your guide. (however note that none of the astro equipment will load the floor - if that makes any difference)


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: polaraligned]
      #6195344 - 11/14/13 07:47 PM

Quote:

Hi Stephen.

Looking fantastic. Probably the best build ever posted here.

I was wondering if you could comment on the cost of your telescope and mount vs if you purchased a CDK17 and a Paramount ME?

I am assuming that you are doing all the design work and having a local machine shop produce all the parts?

Thank you.




A fraction of the cost - I only paid for material for everything, I did all of the CNC programming and machining myself (minus the 2 shafts since I didn't have access to a lathe was big enough).


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Chucke]
      #6195350 - 11/14/13 07:49 PM

Quote:

I am using a Servo II although I don't use the high-res encoders. What do you need to know?

Chuck


Just random feedback Also I would be interested in knowing the tracking capabilities of the system when using high resolution encoders.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucke
member


Reged: 03/12/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6195638 - 11/14/13 10:27 PM

Like most non-trivial systems there is a learning curve although it is mostly involved with figuring out what settings apply to you and the values of the settings. Once you have that figured out it pretty much takes care of itself. Print the manuals and study them.

The tracking is quite good. It continually amazes me how good it is. I am running at about 2700mm with a 16" newt. My mount also uses a 15" Byers gear for RA and a 12" for Dec. I have an 80 point model (overkill) and am guiding with an AO8. I can go 15 to 20 minutes without a mount bump.

Objects are always placed near the center of my chip (ST10XME). If I am set up for multiple nights, at the beginning of the session I unpark, take an image, and solve it. Then I am good to go. If I am freshly set up I can often use the same process. It just takes a little longer to solve. In the worst case you have to manually synch on an object. Be careful when you synch that you have the correct side of the mount selected. It is a check box on the synch screen. Note that to plate solve SiTech will connect to Maxim, Nebulosity, or Astroart. It can also be pointed to a specific path to find the image although I have never tried that. I use Maxim. It does not support CCDSoft or SkyX for camera control although SkyX can slew Sitech.

The most aggravating problem I have had was getting park/unpark to work. Once you get it to work all is good until you have a computer crash. When that happens the mount does not not know where it is pointed and you have to manually tell it by synching on an object. Afterward you may or may not have to reset the park position.

PXP does not have the same problem with synching as t-point does. You can synch as often as you want and it will not affect the model, If you somehow mess up the active model you can delete it and reload from a saved copy.

The most important piece of setup is to input the correct number of encoder ticks per rev of the worm gears. That will be easy for you because you are using gears. It is more of a problem for dob guys or eq mounts using rollers. Note that you can set the motor voltage and maximum current draw for each motor individually in ServoConfig.

SiTech is a really great system. Dan deserves endless kudos for it.

Chuck

Edited by Chucke (11/14/13 10:29 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Chucke]
      #6196365 - 11/15/13 11:24 AM

Thank you so much, Chuck this is very good feedback!

Your paragraph about park/unpark and computer crashes makes me wonder what type of connection is used to connect to the mount? I am guessing USB? Does it mean that you need to keep the mount and computer powered on at all time (in the case of a remote observatory). I've got a PDU to start and stop equipment (mount, computer, etc) remotely, and I was hoping I could turn everything off after a session until the next morning. So I guess my questions are:

Do you have any problem getting everything connected which is it's better to keep everything on?
In the case of turning the controller (and PC) off, the model would get wiped off every time the controller is power cycled, right? That's why it's good to keep a copy on the PC to reload it every time? Plus, syncing to a star afterwards.

Thanks again


Post Extras: Print Post   Remind Me!   Notify Moderator  
cloudmagnet
sage


Reged: 12/04/08

Loc: Georgetown, Texas
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6196402 - 11/15/13 11:41 AM

Quote:

Quote:

Forgive the intrusion, but I feel a comment is in order. In your post containing the photo above (the one of the corner posts and "rim" joists) you state that you intend to use 2 X 4's for floor joists. Are you sure about that? It appears that the floor is about 10 feet square. I was in the home remodeling business for over 25 years and have also built dozens of decks. For a floor this size, I would use 2 X 10 rim joists, and at least 2 X 8's for joists- assuming 16" O.C. Am I missing something???




Hmm, you're probably right - I had skyshed plans which I had to modify to fit my needs of using concrete posts. I found a few plans of "sheds" which used 2x4 they were only 8x8 though. The floor isn't done yet, maybe I should follow your guide. (however note that none of the astro equipment will load the floor - if that makes any difference)




Even for an 8X8 floor 2X4's are too small, unless they are sitting right on grade (generally not a good idea for several reasons). I would urge you to check with some local builders.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Chucke
member


Reged: 03/12/10

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6196547 - 11/15/13 01:15 PM

I am using USB to connect. It will also support serial. There is a jumper to select which interface.

If you power off the computer or close SiTech.exe without a valid park point it will loose its location. If you park before powering off then unpark when you restart, all is good. It will automatically activate the current pointing model when unparked after a successful park. The model information is actually stored in the park information file when a successful park has been done. Unfortunately it is not easy to determine if the park was successful until you unpark. If the part was not successful the unpark will tell you at that time.

The first time you set a park point it would be a good idea to close SiTech.exe, restart it, and unpark. If that is good you can then park it and be confident that when you restart the mount will know its location to within the accuracy of the computer clock. BTW, there is a clock calibration utility in SiTech.

No problem with connections. I start SiTech first, then Maxim, then TSX, then Focusmax. You want to connect Maxim to SITech in the Observatory window (unless you are using CCDAP), and connect TSX to SiTech. I have found this sequence to be reliable for my setup.
Chuck


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Chucke]
      #6196667 - 11/15/13 02:39 PM

Thank you so much for the detailed response, Chuck. That's all I needed to make sure basically

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6196821 - 11/15/13 04:38 PM

One other thing I wanted to share/inquire with you guys. I initially wanted to use a Moonlite focuser since I heard they were working on rotator/focuser combo and expanding their line with a 3.5" however, it doesn't seem it's ready yet.

I designed my own but considering how busy I am with finishing the mount it's very unlikely that I will be able to have it done in time especially considering it will probably need quite a bit of work adjusting everything together. I posted some 3D models some time ago.

Anyway at this time I am not what focuser I should be getting. There isn't much choice.. I like the Fli Atlas but it's pricey it would require special adapters. My friend Dan just reminded me about Don Clement Focusers and I am pretty ashamed that I had actually never seen a picture of one. I am impressed by the design and capacity numbers, fact it is controllable with a simple Robofocus is kind of a plus for me and it's quite a bit cheaper than the Atlas.

So I was wondering if anyone would recommend me to go with Don's 3.5" focuser? I've already emailed him and hopefully he'll come back at with good news about making a custom flange to match my cell!

Thanks


Post Extras: Print Post   Remind Me!   Notify Moderator  
DigitalArtist
journeyman


Reged: 02/10/13

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6202841 - 11/18/13 11:54 PM

Have you considered Hedrick Focuser of Planewave?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: DigitalArtist]
      #6202875 - 11/19/13 12:21 AM

Hi - Hmm that may be a good suggestion...

Post Extras: Print Post   Remind Me!   Notify Moderator  
justforfun
newbie


Reged: 08/28/08

Loc: Lees Summit, MO USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6203196 - 11/19/13 08:41 AM

I have been following this great project for some time.

Might it be possible for you to post some photos of the parts being machined?

I have as much interest in how something is done as what is being done.

Thanks


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: justforfun]
      #6204889 - 11/19/13 11:20 PM

I'll try to take some pictures of the last parts I'll make as I just finished working on the bearing blocks and housing parts for the Declination sub-assembly. They're currently being anodized, and I will probably put them together this week-end.

I finished the floors of the observatory. I ended up using 2x6 12" on center that's all I had. Joists are covered by 23/32" plywood. The whole thing seems pretty strong.



to the walls now..


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6206451 - 11/20/13 08:55 PM

here's the first wall - I need a second pair of hand to get it in place though ^_^



Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6212341 - 11/23/13 11:15 PM

I've got the 4 walls up - I'll cover them with OSB tomorrow, then probably do the concrete for the two footings that will hold the structure for the roll-off rails.




Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6214028 - 11/24/13 08:48 PM

Today I got the OSB done on the 4 walls and the siding on 3 of the 4 walls.



Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6242520 - 12/09/13 12:11 PM

I haven't been super lucky with the weather lately - ~6in of snow on Saturday kept me from doing the last footing and lay the structure for the roll-off rails. It's looking better for next week-end.
Meanwhile, I started working on the new CF tubes since the original length was slightly too long for the final specs of the optics. I ended up using thicker wall and larger OD for the CF tubes (redoing the tube ends and support).

I've got the DEC shaft done as well as the two bearing blocks for DEC (you can see those on the pic below).




Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6256520 - 12/16/13 03:42 PM

Hi,
My optics are finally here!
I have next week off so I should be able to get a bit of work done.


Post Extras: Print Post   Remind Me!   Notify Moderator  
R Botero
Pooh-Bah


Reged: 01/02/09

Loc: Kent, England
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6256668 - 12/16/13 05:20 PM

Great news Stephen! Looking forward to seeing the mirrors mounted.

Post Extras: Print Post   Remind Me!   Notify Moderator  
dmcnally
super member
*****

Reged: 03/17/12

Loc: Lompoc, CA
Re: 17" CDK and Equatorial Mounting new [Re: R Botero]
      #6261741 - 12/19/13 11:28 AM

Thanks for sharing the build process. I just found this thread and I think your design and craftsmanship is awesome.

Quote:

Next is the second Delrin washer and the installation of four M3x8 dowel pins. These will force the whole clutch to spin with the shaft and preventing to loosen/tighten. Since I use a “captain wheel” that screws onto the shaft to compress the clutch spring,




The quote above is from your "EQ-Z – RA Housing and Shaft Assembly (Part 1)" web page.
Do you have any pictures you could post of the clutch spring assembly that show how it mates to the dowel pins?

thanks,
Dave


Post Extras: Print Post   Remind Me!   Notify Moderator  
seryddwr
Innocent Bystander
*****

Reged: 02/19/10

Loc: La-la land.
Re: 17" CDK and Equatorial Mounting new [Re: dmcnally]
      #6261802 - 12/19/13 12:13 PM

Stephen, a lot of the early pics in this thread are showing the broken image icon. Is the website where you were hosting them dead?

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: seryddwr]
      #6261830 - 12/19/13 12:34 PM

Hi,

Dave:

Here's a quick section view that shows the pins (you can only see 2 of the 4 in this view).




Greg:

yes, I decided to move my WP.com to a WP.org blog. While I was able to have all the images working on the new blog, most of the forums links are broken, and most CN posts are old enough that I can no longer edit them.

all pictures are available on the blog though (zytratech.com)


Post Extras: Print Post   Remind Me!   Notify Moderator  
dmcnally
super member
*****

Reged: 03/17/12

Loc: Lompoc, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6261868 - 12/19/13 12:55 PM

Hi Stephen,

Thanks for posting the drawing. Again, fantastic craftsmanship on the mount and the CDK.

thanks,
Dave


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: dmcnally]
      #6263903 - 12/20/13 02:53 PM

I haven't opened up the optics yet, however I finished putting together the DEC gear housing. Just like for RA, the rolled aluminum part is one of the few parts I didn't do and I am not super satisfied with the respect of tolerances, not a big deal since I kind of expected and took that into account.

With a bit of luck I should be able to do the roof next week, in which case I could finally start finalizing the assembly of the mount.



Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6269611 - 12/23/13 10:32 PM

The roll-off structure is finally done.



Uploaded with ImageShack.us

Hoping to have a roof before the end of the week


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim57064
Pooh-Bah
*****

Reged: 08/23/12

Loc: Southeast South Dakota,USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6270695 - 12/24/13 01:37 PM

Stephen,Looks like things are coming along nicely.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: tim57064]
      #6278324 - 12/29/13 12:24 AM



Just gotta put on the shingles and the roof will be done


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6278906 - 12/29/13 10:56 AM

Stephen, you do realize everyone is holding their breath and waiting for the jaw-dropping finish and some deep sky photos. That's truly an amazing project.

regards,
Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #6279273 - 12/29/13 02:20 PM

Thanks Mladen, I'm holding my breath too haha

Post Extras: Print Post   Remind Me!   Notify Moderator  
TxStars
Pooh-Bah
*****

Reged: 10/01/05

Loc: Lost In Space
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6279306 - 12/29/13 02:44 PM

You could always remake the DEC gear cover out of a solid piece.
The other day I ordered a 4"x13"x17" piece of 6061 to mill a DEC housing from for my Series II.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: TxStars]
      #6279480 - 12/29/13 04:19 PM

Yep but it won't be worth it, there isn't that much of a gap and it doesn't affect anything.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6286726 - 01/02/14 12:14 AM

Almost done with the roof


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6294757 - 01/05/14 08:37 PM

a few pics of the finished shingles.
Remaining exterior work: A little bit more tweaking on the rails to make the roof roll a little smoother, siding of the triangles, finishing touches and paint.
Remaining interior work: drywall, flooring, cutting the bolts for the mount's base plate.

I should be able to bring the mount in here very soon. I am off to CES all of next week, though.






Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6315719 - 01/16/14 12:38 AM

I haven't worked on the observatory but was able to finish the parts for the mount.



Post Extras: Print Post   Remind Me!   Notify Moderator  
Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6318404 - 01/17/14 11:30 AM

Hello Stephen,

I am curious how you attached the shaft to the block of aluminum, in the last picture.

Looking great!

-Adam


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: Adam Brunette]
      #6318517 - 01/17/14 12:19 PM

Hi Adam, it is simply threaded. Shaft and counterweight are from AP by the way

Post Extras: Print Post   Remind Me!   Notify Moderator  
jhayes_tucson
sage
*****

Reged: 08/26/12

Loc: Bend, OR
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6318578 - 01/17/14 12:49 PM

Stephen,
Hey, it's looking really fantastic!! Keep the pix coming…this is a really impressive project and I totally enjoy all of your updates.
John


Post Extras: Print Post   Remind Me!   Notify Moderator  
christheman200
sage


Reged: 06/12/13

Loc: Toronto, Canada
Re: 17" CDK and Equatorial Mounting new [Re: jhayes_tucson]
      #6319042 - 01/17/14 04:24 PM

I hope that some day I'll build something as amazing as this!
I truly can't wait to see this come to fruition.


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: christheman200]
      #6327403 - 01/22/14 12:02 AM

Thanks for the kind words guys

Below is the mount's IO panel. The Sitech controller is on the inside, I've got a USB hub on the outside





Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6367284 - 02/09/14 10:09 PM

I was finally able to resume working on the observatory.
Had to move the 4x4 that's across the roll-off structure to clear the path of the garage door opener mechanism. That was a bit hectic but got it done. Then spent a bit of time trying to make the roof with less force. The rail/bearing wheels have limited play (1/8" on each side) which makes adjusting everything a little more difficult than it should. It's already much better and I think I'll add some steel brackets to keep the critical lumber as straight as possible.
Finished off by installing the garage door opener. Just gotta grab a few of the 1' extension and I think next week-end I should have a working roll-off roof (hopefully xD)



Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6425572 - 03/23/14 10:53 PM

a quick update
we had some good snow and bad weather for about 4-5 weeks in feb/march.
I wasn't happy with the rails and small wheels, it was really hard to roll off - so I decided to replace it with large 2.5" wide aluminum rails and 5" casters. The lumber on which the old rail system was attached to wasn't very straight and it didn't allow for enough play.

It's working much better now, but man that was a project... lifting that roof high enough to install wheels and rails was really hard and tricky. Did it alone which forced me to find a better solution than just brute force and lift the whole thing with enough muscle.

Anyway, just finished it - the install of the garage door opener was MUCH easier than I anticipated. I brought the screw drive for electroless nickel / tin plating to make them rust resistant. Had to find a 3' extension for opener and that wasn't easy. I was glad to see the opener has no trouble opening/closing the roof.

Here's a quick video (poor quality though)

https://www.youtube.com/watch?v=tqcenD3gJa0&feature=youtu.be


Post Extras: Print Post   Remind Me!   Notify Moderator  
MKV
Carpal Tunnel
*****

Reged: 01/20/11

Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6425731 - 03/24/14 12:27 AM

Stephen, that's awesome, but what happens when it rains?

regards,
Mladen


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: MKV]
      #6426251 - 03/24/14 10:36 AM

I haven't installed siding to the triangles yet
And the sides will be covered by skirts to protect the inside from rain/snow - I should have mentioned that :P


Post Extras: Print Post   Remind Me!   Notify Moderator  
tim57064
Pooh-Bah
*****

Reged: 08/23/12

Loc: Southeast South Dakota,USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6426275 - 03/24/14 10:47 AM

Good to hear you got the opener working better. A pic of the exterior install of the opener would be nice to. Do you have any pic's of the new rollers and the install of them? When you say aluminum rails,do you mean flat plate? A shot of that would be nice. Are the wheels metal or what? Were you able to finish up the new build of the mount?

Edited by tim57064 (03/24/14 10:48 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: tim57064]
      #6426307 - 03/24/14 11:05 AM

The aluminum rails are U channels and the casters have metal frame/bearing but urethane/polypropylene wheels.

I'll post some pictures

I've got all the parts for the mount but I was waiting for the ob to be finished before I finalized the assembly as it's already too heavy and I can't the dec assy without making the whole thing impossible to move


Post Extras: Print Post   Remind Me!   Notify Moderator  
herrointment
Post Laureate
*****

Reged: 03/12/11

Loc: North of Hwy. 64
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6426353 - 03/24/14 11:39 AM

That roof scoots!

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: herrointment]
      #6426399 - 03/24/14 12:13 PM

yeah I am going to run a couple of metal cable in a cross pattern on the H structure because the roll off beams kind of shake a little bit when the roof is out. xD

Post Extras: Print Post   Remind Me!   Notify Moderator  
tim57064
Pooh-Bah
*****

Reged: 08/23/12

Loc: Southeast South Dakota,USA
Re: 17" CDK and Equatorial Mounting new [Re: zytrahus]
      #6426421 - 03/24/14 12:24 PM

Wow, +1 Just watched the video myself and that thing does move quite fast. I plan to install an opener myself when it warms up a bit. You can really hear it moving also hope it does not bother the neighbors at night when you close it. Would not think that Urethane wheels would be that loud.

Post Extras: Print Post   Remind Me!   Notify Moderator  
zytrahus
professor emeritus


Reged: 06/16/09

Loc: Long Beach, CA
Re: 17" CDK and Equatorial Mounting new [Re: tim57064]
      #6426433 - 03/24/14 12:28 PM

it's mostly the motor/screw drive that you hear. We're the only people living full time there, most neighbors only come here once a month or so

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | (show all)


Extra information
5 registered and 19 anonymous users are browsing this forum.

Moderator:  ausastronomer, richard7, Starman81 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 20129

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics