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Mirror re-aluminising

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Mirror re-aluminising

Posted by Mark Jones at 12:58 on 2011 Nov 17

Hi all.I'm on the point of moving to a house which will have space to store my 12.5 inch Dobsonian (bought in 1993 and mothballed in my parents' garage for well over a decade now!).The mirrors need recoating and I am wondering if anybody has any recommendations as to where to get this done in the UK. I've seen on the internet that companies like Orion Optics and Vacuum Coatings Scientific offer this service, but are there any others and is one better than the others? Also, Orion for instance offers a higher level coating which is meant to be more reflective. Is this worth the extra money? I've read comments for and against.Much obliged for any advice.Regards,Mark

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Re: Mirror re-aluminising

Posted by Callum Potter at 14:34 on 2011 Nov 17

Hi Mark,I had a diagonal re-aluminised by Vacuum Coatings in the summer, and they did a good job. Helpful in advance, and returned in expected timescale, and coating looks fine.I have been thinking about getting my main mirror re-aluminised too, but I have been thinking about OO for that, mainly because Crewe and Saturday morning opening makes it a bit easier for me to take the mirror to them and collect. As its 52cm I'm not so keen on shipping it.But I think i will try giving it a clean first, as i'm not sure it really needs re-aluminising yet. I cleaned a small centre area to respot it over the summer, and it looks fine there. So, you might find that the coating is still good but dusty.Regards, Callum

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Re:Mirror re-aluminising

Posted by Gary Poyner at 16:30 on 2011 Nov 17

Hold the mirror up to a light source and look through the bottom. You will soon see if it needs re-coating or not, as you will see light shining through the worn area's. Washing a 12 inch is fairly straightforward, but try not to use any liquid which contains lanolin, as this 'may' leave small white marks on the mirror surface. Always use distilled water too.My 51cm mirror is from OO and has Hi-Lux coatings. It's great! I've also compared a 25cm with and without Hi-Lux, and the Hi-Lux wins every time. If you do get the primary done, have the secondary done as well, whether you think it needs doing or not. Good luck,Gary

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Re:Mirror re-aluminising

Posted by Mark Jones at 21:33 on 2011 Nov 19

Thanks Callum and Gary. Good point about seeing if I can see light through the coating, I'll try that first. I am only assuming it'll need doing but perhaps it just needs a careful clean. All the best,Mark

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Re:Mirror re-aluminising

Posted by David Malamatenios at 09:52 on 2012 Feb 19

I am about to have the mirrors re-aluminised on my Astro-Systems 6 inch Newtonian (bought in 1987 from Astro-Systems of Luton - alas, they are no longer in business). The company that has been recommended to me is Galvoptics. They will also re-aluminise the secondary mirror for free.

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Re:Mirror re-aluminising

Posted by Paul A Brierley at 17:19 on 2012 Feb 19

I have Hi-Lux mirror coatings on both my 254mm F4.8 and 200mm F4 Orion Newtonians.And I agree with Gary.They are well worth having, because the reflectivity is better, but also. The life of the mirror coatings is considerably longer, than with out this extra coating.With your 12.5" Dob and HiLux coatings. You will gain an extra inch in light grasp

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Re:Mirror re-aluminising

Posted by Grant Privett at 22:44 on 2012 Jul 05

One query. The OO Hilux coatings, are they dielectric coatings?

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Re:Mirror re-aluminising

Posted by David Mottershead at 20:03 on 2012 Jul 17

I'm not 100% as Orion Optics UK describe their Hilux coatings as 'Advanced Aluminium'and 'AR', but I can't find anything that says whether they are dielectric or not. The contact given for optic enquiries is john@orionoptics.co.uk so might be worth contacting them to enquire.