hi,
i just wondering how many years can last for C8 primary mirror coating?
any one can answer it?
C8 primary coating resilience
It all depends on how well you take care and maintain the optics. I have a friend with the orange C8 that is probably about 20 years old and it is still in a very good condition (I help him to maintain the optics occasionally). It still gives a sharp and clear images despite some small permanent spots on the primary mirror as these spots do not noticeably affect the final image viewed.
Richard Low
- Airconvent
- Super Moderator
- Posts: 5784
- Joined: Tue Sep 30, 2003 11:49 pm
- Location: United Federation of the Planets
Some guy did some study previously and discovered the reflectivity increases with time. Standard coatings degrade much more slowly than exotic ones. So while the Starbright and UHTC coatings offer better performance when new, they also degrade faster. He did emphasise that inspite of this, the difference is obvious by measurements but doubt you can see real life difference unless you are looking at a very faint object and trying to resolve it above the threshold.
rich
rich
The Boldly Go Where No Meade Has Gone Before
Captain, RSS Enterprise NCC1701R
United Federation of the Planets
Captain, RSS Enterprise NCC1701R
United Federation of the Planets
- weixing
- Super Moderator
- Posts: 4708
- Joined: Wed Oct 01, 2003 12:22 am
- Favourite scope: Vixen R200SS & Celestron 6" F5 Achro Refractor
- Location: (Tampines) Earth of Solar System in Orion Arm of Milky Way Galaxy in Local Group Galaxies Cluster
Hi,
Base on the sentence behind:
Have a nice day.
Base on the sentence behind:
Standard coatings degrade much more slowly than exotic ones. So while the Starbright and UHTC coatings offer better performance when new, they also degrade faster.
I think it's quite obvious that this is a typo error... it's should be "decrease" instead of "increase".Some guy did some study previously and discovered the reflectivity increases with time.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance."
I don't think it's a typo, because everybody knows as a fact that reflectivity decreases with time, no need to be discovered. Only this "few guys" discovered that it actually increases over time.
I think this whole thing is a hoax, same as the comments about modern coatings degrade faster. Wait, degrade? i thought coating performance should increase over time?
I'm confused
I think this whole thing is a hoax, same as the comments about modern coatings degrade faster. Wait, degrade? i thought coating performance should increase over time?
I'm confused
Last edited by ariefm71 on Sat Aug 11, 2007 1:15 pm, edited 1 time in total.
- Airconvent
- Super Moderator
- Posts: 5784
- Joined: Tue Sep 30, 2003 11:49 pm
- Location: United Federation of the Planets
haha weixing..you are right and wrong depending on whether we are talking about the mirror or the corrector plate. I had actually changed the word from "decrease" to "increase" because of this but now realise he is asking about mirrors and not corrector plates..hehweixing wrote:Hi,
Base on the sentence behind:Standard coatings degrade much more slowly than exotic ones. So while the Starbright and UHTC coatings offer better performance when new, they also degrade faster.I think it's quite obvious that this is a typo error... it's should be "decrease" instead of "increase".Some guy did some study previously and discovered the reflectivity increases with time.
Have a nice day.
In this respect, it should decrease with time...
The Boldly Go Where No Meade Has Gone Before
Captain, RSS Enterprise NCC1701R
United Federation of the Planets
Captain, RSS Enterprise NCC1701R
United Federation of the Planets
- Airconvent
- Super Moderator
- Posts: 5784
- Joined: Tue Sep 30, 2003 11:49 pm
- Location: United Federation of the Planets
Hi richIIrlow wrote::roll: Pardon me, but where is your reference source?Some guy did some study previously and discovered the reflectivity increases with time.
I can't seem to find the link now and my bookmarks do not have it. I think I lost it when my pc surrendered on my some years back.
Else will link it here. This old guy has tens of scopes bought since the late 60s. From what I gathered, his house is a scope museum. He is (or was) in the optics industry so he has equipment for testing his scope's transmission and reflection properties. He took detailed readings of selected SCTs and refractors with standard and new coatings and then redo the measurements 6-10 years later. His conclusion is for exotic coatings (on corrector plates) when new , they far exceed standard coatings but then the degradation is faster, so at the end of 10 years, its performance is similar to standard ones.
By year 12, the standard coatings out performed the exotic ones, only because the degraded slower. But he did indicate at some point the degradation will stop because glass is transparent to a point after all.
Clay sherrod also did some tests on Meade coatings but stopped short of measuring them over a period of time.
richI
The Boldly Go Where No Meade Has Gone Before
Captain, RSS Enterprise NCC1701R
United Federation of the Planets
Captain, RSS Enterprise NCC1701R
United Federation of the Planets
- weixing
- Super Moderator
- Posts: 4708
- Joined: Wed Oct 01, 2003 12:22 am
- Favourite scope: Vixen R200SS & Celestron 6" F5 Achro Refractor
- Location: (Tampines) Earth of Solar System in Orion Arm of Milky Way Galaxy in Local Group Galaxies Cluster
Hi,
Anyway, if this is true, why put the coating in the first place... this doesn't make sense.
Have a nice day.
Why coating performance should increase over time?? Coating will degrade over time, so the coating performance should also decrease over time.I think this whole thing is a hoax, same as the comments about modern coatings degrade faster. Wait, degrade? i thought coating performance should increase over time?
You mean corrector plate performance will increase over time?? Hmm... Logic tell me that this should not be true: The coating on lens and corrector plate is basically use to reduce reflectivity and scattering. Therefore increase the transmission (uncoated lens(2 surface) loss about 8%, single layer coating lens(2 surface) loss about 4% and multilayers coating lens(2 surface) loss about 1%). Over the time as the coating degrade, the transmission will decrease.haha weixing..you are right and wrong depending on whether we are talking about the mirror or the corrector plate. I had actually changed the word from "decrease" to "increase" because of this but now realise he is asking about mirrors and not corrector plates..heh
In this respect, it should decrease with time...
Anyway, if this is true, why put the coating in the first place... this doesn't make sense.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance."