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Venetia2004
sage
Reged: 08/27/05
Posts: 260
Loc: Lynnwood, WA
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Quote:
L&L did my 16" Cass optics last Feb. They did a great job. I live close enough to them that I got to drive over and see the operation. I think they stillcoat mirrors but just don't advertise as they do a lot of industrial and Government work that is far larger than the amateur astronomer market.
I recently contacted L&L to have my mirror set coated. I received an e-mail from them with a Excel file attachment that I could not open because I use an older Excel version . I e-mailed them back twice explaining that I could not open their file but I receved no reply. It seems that they do not care about the ATM's any more... Do-it-yourself if possible or a smaller company that provide coating services to everyone is the way to go.
Vic
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2159
Loc: salem, OR
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For glass dust? Water - the mud is easy to handle safely. If it dries wet it down again before cleanup. You can mix it with concrete, or run it through your local garbage service, but leave it wet.
This is an interesting discussion. I'd like to hit one or two points - in almost any discussion I have with people with experience about coating the same point comes up time and again - mirror preparation by coaters who serve the amateur market. The best coatings can only be applied to clean mirrors, and that really calls for ion beam cleaning as the final prep stage. Horror stories abound of coaters who've used their own particular, uhm, methods to clean precision mirrors...and left them damaged.
Secondly, pure Al works, it will gradually oxidize on exposure to air, obviously. It has to be treated with care during that stage, which I believe takes on the order of a month or so. From what I understand it cannot be handled at all at first though, and appropriate care would need to be taken.
Is there a difference in reflectance or more importantly, spectral response for Al alone vs Al + SiO2 (or the admixture generally achieved Si2O3)?
Best,
Mark
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grendel
sage
Reged: 04/12/09
Posts: 243
Loc: Canterbury, Kent, UK
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Have you tried open office - its free and will probably handle the newer excel files OK.
Grendel
Quote:
Quote:
L&L did my 16" Cass optics last Feb. They did a great job. I live close enough to them that I got to drive over and see the operation. I think they stillcoat mirrors but just don't advertise as they do a lot of industrial and Government work that is far larger than the amateur astronomer market.
I recently contacted L&L to have my mirror set coated. I received an e-mail from them with a Excel file attachment that I could not open because I use an older Excel version . I e-mailed them back twice explaining that I could not open their file but I receved no reply. It seems that they do not care about the ATM's any more... Do-it-yourself if possible or a smaller company that provide coating services to everyone is the way to go.
Vic
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Venetia2004
sage
Reged: 08/27/05
Posts: 260
Loc: Lynnwood, WA
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Hi Grendel,
Thanks for the suggestion. No, I have not. I expected to hear back from them in a "regular" e-mail. However, it's too late now, I shipped my mirrors to another company.Silence is an answer...
Vic
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dave b
Post Laureate
Reged: 05/10/05
Posts: 3534
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Quote:
Quote:
our club used to have a working coating chamber. we were charging members $10 to recoat.
Did you do the glass on that 30"er?
Clear Skys -Rick
no our chamber only went to 18", my 30 was last done by intermountian
--------------------
dave bonandrini
30" f/5.2 Dobsonian
President of GCAC
Astromart Moderator
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PitchHitter
member
Reged: 09/23/09
Posts: 23
Loc: Southern Sierras
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Ion cleaning would energize the low potential residual on the mirror and that would be nice. I believe only the Keck out of hundreds of professional observatories does that and I am not sure for a fact they even do. I was priced $25,000 for a broken Ion Gun at a surplus shop in San Diego County. I would like to have one but I am not going to let having less than the best keep me from having the freedom to do a pretty darn good coating when I want it. I also have an idea I want to test that may be more effective than an ion gun.
I have no intention of being a commercial coater. If someone wants a coating they will have to bring their mirror and do it themselves under supervison of course.
Best,
Rick
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About 20 telescopes from a 200mmAPO up
Fav is Meade 10" f:4.5 using my 3" 40mm 96°AFOV
BUT! In Progress:
14.5" f:5 grab n' go with DSCs will offer 2.4 degrees at 45 power and 8mm exit pupil (Light Bridge Buster)
16.25" f:7.5 to refigure
(20th wave ruined in a fire at the coaters)
22" f5: New mount almost done
(old all aluminum mount was stolen)
16" Varian Vapor Deposition Coater.
Looking for larger chamber.
Edited by PitchHitter (10/03/09 06:12 PM)
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PitchHitter
member
Reged: 09/23/09
Posts: 23
Loc: Southern Sierras
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Quote:
Hi Grendel,
Thanks for the suggestion. No, I have not. I expected to hear back from them in a "regular" e-mail. However, it's too late now, I shipped my mirrors to another company.Silence is an answer...
Vic
This illustrates my point.Southern Californians are simply being treated wrong on their coatings and the service. I miss the old Panchro. Many local coaters are now wholesale only. They tell me amateurs are needlessly too picky for one thing. L&L coatings are available but now you must take your optic to a retail outlet that repairs telescopes.
Clear Skys
--------------------
About 20 telescopes from a 200mmAPO up
Fav is Meade 10" f:4.5 using my 3" 40mm 96°AFOV
BUT! In Progress:
14.5" f:5 grab n' go with DSCs will offer 2.4 degrees at 45 power and 8mm exit pupil (Light Bridge Buster)
16.25" f:7.5 to refigure
(20th wave ruined in a fire at the coaters)
22" f5: New mount almost done
(old all aluminum mount was stolen)
16" Varian Vapor Deposition Coater.
Looking for larger chamber.
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DanNie
journeyman
Reged: 11/18/08
Posts: 6
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Mark,
Freshly deposited aluminum oxidizes very quickly. Pure aluminum is soft; unfortunately, the naturally-developed oxide is so thin, even after a month, that it doesn't offer much protection. The main reason for the silicon monoxide/dioxide overcoat is mechanical improvement (scratch resistance). The silicon oxide overcoat may improve or degrade the overall reflectance a few percent, depending on thickness and the actual index of refraction as-coated.
Truly enhanced aluminum reflectivity usually means a two layer (low, then high index) or four layer (LHLH)dielectric coating on the aluminum. Again, these have to be deposited in such a controlled manner that the thicknesses and complex refractive indices are according to thin film design and repeatable - hence the added cost over simple aluminization.
I'm not an apologist for commercial coaters, especially regarding their attitudes towards ATM customers. However, any coater large or small has to deal with regulatory compliance or risk being shut down and/or fined (particularly in the fair state of California). Some of the cleaning and stripping chemicals are regarded as hazardous, and the used ones are regarded as hazardous waste. Again, an added cost is passed on to the customer.
Despite all this, the allure of coating mirrors at home or as a group project is strong. I for one would like to hear from some that have made a go of it: what equipment, process, and materials they used, and the degree of success and failure.
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mark cowan
Vendor (Obsidian Optics)
Reged: 06/03/05
Posts: 2159
Loc: salem, OR
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Thanks for the confirmation on pure aluminum, but my question was about spectral difference between bare aluminum and Al with, variously, SiO, Si2O3, SiO2 overcoats, not enhanced coatings. 
If you want responses on home coating successes/failures, ask on the ATM List (www.atmlist.net) for plenty of views - traffic is very light currently.  Particularly check the archives (searchable back to '95) here.
The difficulty commercial coaters have with ATM mirrors is that ATM mirrors are typically heavily contaminated with pitch residue, cerium oxide, and sometimes other stuff, much of which vaporizes into the chamber and fouls it. I've heard this several times from different coaters. Hence they need to purge the chambers well, and they can't afford to do a mixed run of ATM mirrors, due to the risk of cross-contatmination, which increases their overhead.
Best,
Mark
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Venetia2004
sage
Reged: 08/27/05
Posts: 260
Loc: Lynnwood, WA
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"...L&L coatings are available but now you must take your optic to a retail outlet that repairs telescopes".
If I'd known that they had changed the way they deal with the ATM's I would have never contacted them. It's too complicated...
Vic
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