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Home > Forums > ASTRONOMY > Beginning Astronomy? > Message #836514

Re: barlow basics

Posted by Chris Kelly on 11/11/2017 8:19 AM in response to Re: barlow basics   (44 hits)
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Yes and yes , thanks. I picked up an Orion 2x shorty that works fine. M31 still looks the same. I need more photons in the tube. Or a bigger tube. Thanks for the wealth of info, I think I'm off to my next question.......
Why is glass or pyrex the chosen material for mirrors. It seems to me metal will be a lot easier and cheaper to remove minor spherical caps from flats within nanometer precision. Or a porcelain cast from the blank. ?..... Mirror treatment is all the same..... I am tempted to run a 4"x24" AlMg ingot thru my C&C machine then polish it up. Send it out for treatment. Done 23" mirror ?... Is there a reason why grinding glass is preferred, sounds exhausting.

Thread:

Subject Posted By Date/Time Hits 
barlow basics Chris Kelly 10/28/2017 5:52 AM 89
Re: barlow basics Ed Blankenship 11/1/2017 9:04 PM 69
Re: barlow basics Ed Blankenship 11/1/2017 9:31 PM 52
Re: barlow basics Chris Kelly 11/2/2017 9:57 AM 67
Re: barlow basics Ed Blankenship 11/5/2017 3:51 PM 45
Re: barlow basics Ed Blankenship 11/5/2017 3:58 PM 41
Re: barlow basics Ed Blankenship 11/5/2017 4:31 PM 49
Re: barlow basics Chris Kelly 11/11/2017 8:19 AM 44
Re: barlow basics Thomas Dey 11/11/2017 4:45 PM 50
Re: barlow basics Chris Kelly 11/13/2017 6:44 AM 38

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