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Old 11-10-2011, 05:45 PM
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sopticals (Stephen)
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Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 226
Quote:
Originally Posted by ColinandRos View Post
Yes, still at it in Oz.

I finished a 20inch a few months ago.

I do not see anything amaterish about your endeavours.

I have mirrors to be made better before getting any more glass.

Where do you get yours from?

Colin.
Hi Colin, thanks for the post. I agree with your philosophy, regarding improving the glass you have. When I put my Dob together I will first of all test the primary without coating on moon, planets and stellar objects.I know only around 5% of incoming light will be reflected (about the light one would expect of a 6" reflector), but even with the diminished light one can evaluate to some degree resolution etc. If that test is passed satisfactorily then the next step would be to silver coat, which I can have done for around NZ$50. If everything was ok I would Aluminize. Otherwise a further figuring iteration would be the order of the day.

I have a son connected to the domestic glass/mirror industry so my glass is not too expensive. However the thickess I can get here in NZ seems to be 19mm float so a little limited on how big a mirror one can go. I have tried suppliers in asia for large blanks but invariably (so far) have been quoted US$5000 plus for blanks (borosilicate) of 30" diameter with thicknesses of 30 to 40mm. So well outside my budget. My current Dob (completed) should come in at around NZ$1000-1200. Where do you source your glass in OZ? I hear 1" plate can be got in Sydney.

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