John has coated all four of my mirrors. I have been pleased with all of them. I haven't finished the 16" scope yet but the mirror looks good. I plan to have the 16" done by the end of March. Last time I went down there I had him show me the equipment and process. It was real interesting. The only complaint that I have heard is that he doesn't have a set fee schedule and sometimes has charged different prices for coatings on two mirrors of the same size. Dave -----Original Message----- From: Brent Watson [mailto:brentjwatson@yahoo.com] Sent: Monday, February 17, 2003 4:51 PM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Comet Catcher Chuck, No I didn't do any throughput testing. I do think the contrast increased slightly, but the secondary color also is more apparent (My estimations). John Ross does this in his basement at home. He is retired from Hiill AFB where he did this for a living. Therefore, he has no brochures, no web site, and works from word of mouth only. He will do any coating, including aluminum and gold. Some folks around have a different opinion as to quality, but Ihave had no complaints with his work. He can do up to about 16" optics. Brent --- Chuck Hards <chuckhards@yahoo.com> wrote:
Hey, guys, MgFL2 will only work for ONE wavelength- thus the current rage over multi-coatings. Hopefully this one wavelength is centered in the visual spectrum- I didn't get that far before sleep overtook me.
It is an interference coating, so thickness is critical. The idea is that the reflection off the glass surface itself is 1/2 wave out-of-phase with the reflection off the coating surface, thus they cancel out, no reflection at that wavelength. (For multiple wavelengths, you must use different materials & coat them to the thickness appropriate for the desired wavelength.)
Now, you may ask, OK, no reflection, but how does that contribute to total throughput? After all, the relfected light is being cancelled by phase shifting; it's not being re-routed back through the glass to the focal plane.
We have entered the weird, counterintuitive world of quantum mechanics and probabilities...apparently, if no light is lost to reflection, it must be going through with the rest! I know, I don't fully understand it either.
But make sure that Mr. Ross knows what wavelength you want to dampen- that will determine the coating thickness. Just seeing a blue tint on your glass is indicative of- a blue tint.
Brent, did you do any throughput tests, before and after?
I'd like to see Mr. Ross's work. Does he have a website, or brochure perhaps? A local source is SO convenient!
Chuck
--- Greg Taylor <astronomus_maximus@yahoo.com> wrote:
Great! I will do that. I am generally vehemently opposed to uncoated optics (oh no, a strong opinion ;) ).
Greg
--- Brent Watson <brentjwatson@yahoo.com> wrote:
Greg,
I just fot back from Wyoming and saw youe post. You can have magnesium flouride applied by Joh Ross in Clearfield. He coated all four surfaces of my refractor and the 12"window in my 10". His phone number is:825-2130. His address is 423 Marilyn, Clearfield, UT 84015. Taking it to him is easier than trying to find the reference!
Brent
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