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Want to build a 22" Newtonian???

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#1 Timber

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Posted 19 April 2009 - 12:37 PM

If this is not the correct forum someone will likely move it.

I have a 22" f3.6 Steve Kennedy mirror on order for delivery sometime around the beginning of the year.

Before I commit to having it made into a Dob I would like to consider having it made into a Newtonian to be semi-permanently mounted on a Beyers Series II GEM, which I already have.

If you have an interest in building this, lets start a conversation. Send a PM.

Richard

#2 michael

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Posted 20 April 2009 - 10:33 AM

Hi Richard,
My first question would be how much weight is the mount rated for ? Are you looking to do visual or ccd or both ?

Consider that you have a mirror that will weigh about 45 pounds, then the OTA. Your looking at a total OTA weight of about 75 to 100 pounds.

Mike

#3 Timber

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Posted 20 April 2009 - 07:21 PM

Hi Mike,

The mount is rated for well over 150#, that part doesn't seem to be an issue, The McDonald Observatory in Ft Davis Texas is using this mount for a 22" Cassegrain, I would probably mount a TV NP 127 along side and that might have the camera, an SBIG 2000, both of which I already have.

I would like to think of it initially as a visual unit but eventually for it to be a mix of visual and CCD.

Four issues that seem to me to be foremost are; balance; eye piece height; not having the Byers just be a replacement for a rocker box mounted on the deck; and maybe most important, mid structure rigidity in order to maintain collimation. There are likely other issues that I should be concerned about, but right now just seeing if this is feasible is step one.

Thanks for the interest

Richard

#4 gatorengineer

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Posted 22 April 2009 - 12:33 PM

Just a comment from a dob owner with a rotating cage. You would need to decide if you want rotating rings or a rotating upper cage...... Pluses and minuss to both with rotating rings you would blow your 100 lb ota budget...... Without alot of machining you would potentially have collimation issues.

Check out a thread in ATMs on a 12.5" astro videograph...... concept could be upscalled.

Hope you dont mind random comments.

#5 Timber

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Posted 22 April 2009 - 06:42 PM

"Hope you dont mind random comments".

Not at all, all info is useful to me at this stage, thanks for the input.

Richard

#6 Timber

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Posted 22 April 2009 - 08:33 PM

Just a comment from a dob owner with a rotating cage. You would need to decide if you want rotating rings or a rotating upper cage...... Pluses and minuss to both with rotating rings you would blow your 100 lb ota budget...... Without alot of machining you would potentially have collimation issues.

Check out a thread in ATMs on a 12.5" astro videograph...... concept could be upscalled.

Hope you dont mind random comments.


Mark, my searches bring up every post, every thread and every response in the ATM forum, this machine is just too smart for me. Are you able to zero in on the thread a little closer for me, much appreciated. Thanks

Richard

#7 Timber

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Posted 22 April 2009 - 08:38 PM

Gatorengineer,

Hi Mark, would you have any photos of your Dob that you would be willing to post? I'm interested in your rotating cage.

Thanks, Richard

#8 davidpitre

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Posted 23 April 2009 - 08:08 PM

You might get more input on this on the ATM forum.

#9 Timber

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Posted 23 April 2009 - 10:51 PM

Thanks David, I'll give it a try.

Richard

#10 bbasiaga

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Posted 29 April 2009 - 08:58 PM

Since you've stated you don't mind random comments...

Yes I want to build a 22" dob. But I want to KEEP it when I do. :)

Seriously, would you mind PM'ing me with who you shopped around for mirrors from, your experiences, thoughts etc? This is a next 3-4 years type project for me, but it never hurts to start researching. My concept is to do something ultra compact like the new 18" Obsession.

-Brian






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