mvsopen
Joined: 25 Sep 2006
Posts: 5
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 Posted: Thu Dec 07, 2006 5:00 pm Post subject: Primary Mirror Quality vs. Performance? |
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As a group project, several of us are going to build a medium sized Dob, 12 to 18". My question: How important is having a precision mirror (Pyrex, F5 or better, laser tested, enhanced coating, etc) to the finished scope? Plate glass mirrors can be had for less than $500, while the enhanced coated, optically perfect "Obsession" style of mirror costs at least $1500 or more. Are there dramatic differences in resolution and brightness between mirrors at the polar ends of the price spectrum? If a precision mirror created a 'scope rated a "10" on a 1-10 scale, would a less expensive mirror knock the rating to a "4", or only down to a "9"? While I'm not against purchasing a top of the line mirror if necessary, I also want to make sure that spending 2x the price of the less expensive mirror would be worth the initial investment.
Also, the choice for a focuser seems rather confusing. I've found plastic focusers for $35, and precision focusers with prices all the way up to $600. Saying a focuser is a "Crawford style" really tells me nothing when I see them in the magazine advertisements. But I'd hate to ruin something that probably costs $2000 by putting a sub-standerd focuer on it. Thoughts?
-Rich |
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