10" Truss Dob Build

Wanna make a scope? Or better still, grind a mirror yourself. Or, you have some good tips in making a really useful accessory? This is the place to show what your hands can do...
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VinSnr
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Post by VinSnr »

10000rpm wrote:Thanks Richard. I have checked the Prostar website but it does not seem to state the wave PV. Other than that, it sounds impressive and apparently, Carl Zambuto's choice.
Don't worry...the Protostar is good too. They gurantee a minimum of 1/10 but I guess the final reading is in the report.

The Antares one comes with the report too...and the 1/20 wave version is about the same price as the ULS quartz....so you make the call.
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rlow
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Post by rlow »

Thanks Richard. I have checked the Prostar website but it does not seem to state the wave PV. Other than that, it sounds impressive and apparently, Carl Zambuto's choice.
Yes, I have correponded personally with Carl, and that is also his recommendation to me. The Protostar website does qualify its mirrors at 1/10 peak-to-valley measured edge-to-edge surface rating (rated at 650nm wavelength) as a minimum flatness quality. I will go with the reputation of the mirror-makers, and not just based on impressive claims of 1/20 or 1/30 wave. Thats also the same way I choose my primary mirrors.
Richard Low
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10,000rpm
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Post by 10,000rpm »

I will go with Protostar n confirm sizing by this weekend.
Last edited by 10,000rpm on Sat May 08, 2010 12:04 am, edited 2 times in total.
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10,000rpm
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Post by 10,000rpm »

I just spent the whole afternoon since noon till just now [including a 2 hour nap and a 45 min run :mryellow: ] drawing up a full scale plan which I can't say enough how useful it proved to be.

I determined that I can use a 1.83 inch secondary mirror which was confirmed with NEWT and for illumination field of the secondary, I used a computer program by Alan Adler (called Sec) which shows that I will achieve between 50% to 75% illumination for the secondary for a 2 inch eyepiece and 1.25 inch eyepiece respectively which I understand from Gary Seronik's website, a contributor to Sky & Telescope, should be good enough as long as it does not go below 50% at the edge of the field [which is roughly ½ magnitude]. He says at 50%, it will not be noticeable.

As a result of my full scale plan, I also realise that I must go with a 4-truss design because a 3-truss design makes one of the truss too close to the alt bearing with not much space for a truss of a sufficient width.

I have also determined the truss length which is 64 inches.

I am however concerned whether when the all the parts are put together would enable me to achieve collimation and if my secondary mirror will be positioned correctly to reflect 100% of the reflected rays from the primary to the eyepiece.
Last edited by 10,000rpm on Sun Feb 21, 2010 10:32 pm, edited 3 times in total.
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10,000rpm
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Post by 10,000rpm »

Mod please delete this post cos I double posted. Thanks
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