Mirror Measles!

[bkm2304]

Hello all,

I have a 16" lightbridge and it has developed a light fog of small (say 0.5mm) grey, transparent spots :eek:. I cleanedthe mirror with detergent and demineralised H2O but it did not remove them. Rubbing firmly on a sliver at the edge does nothing also. The scope is 5 weeks old and has had condensation over it a couple of times. Is this a normal part of oxidation or is there somethig more sinister happening? The pics show it in the worst possible light while looking straight down the barrel with no torch on it hardly shows them.

Richard the nervous :help:

[astro_nutt]

Hi Richard..

Looking at the photos..does the fog also have a swirl pattern around the mirror?
The reason I ask is that the mirror of my 10 inch Saxon has a swirl on it and looks quite alarming when a torch is shined upon it..I have found out that this does not affect the image unless parts of the image are severely lacking in contrast when compared with a new mirror.
If it hasn't got any worse and you are still concerned about it then contact the place where you purchased it from!
The mirror's coating can play tricks on you...one test is to hold the mirror up to a lightbulb..if you can see the structure of the filiment then the coating need to be redone..but this would normally occur after several years of use and washing the mirror too often...
Cheers!

[acropolite]

The meade mirrors are supposedly overcoated, so the mirror shouldn't be showing any signs of oxidisation. As Astro_nutt suggests you should talk to your dealer about the problem, however it is quite normal to see slight imperfections with direct light shone on the mirror.

[RAJAH235]

As already stated. Talk to the supplier.
FWIW. My 10 year old Meade 10" dob, has no such markings in any type of light.
Looks like a replacement may be required.
Good luck. :D L.

[ballaratdragons]

EEK! Doesn't look good, and cleaning didn't alter it!

Contact your supplier.
My mirror is nearly 2 years old and even with light directly on it, it has nothing near those marks.

[ronnierigel]

Hi Richard

my Meade SN-10 mirror developed the same problem after a night when it dewed over. It's not a swirl pattern--just a random patchy haze--much like yours I think. Cleaning does not alter it. I thought it may have been some bad atmospheric Melbourne chemicals interacting with the mirror coat.
It's hard to comment on what effect it has on image quality--it's certainly not strikingly obvious. I haven't recoated my mirror yet.
Given your telescope is young I would enquire about it with your dealer.
May as well err on the side of caution and get what you paid for. (mine happened out of warranty!)

[Omaroo]

I'd hate to be the bearer of bad tidings, but before you get into a possible argument with your dealer have you checked what the Meade warranty form states in regards to customer disassembly and washing the mirrors' surface?

[KG8]

Good point! Best tell them "YOU NEVER TOUCHED IT" ;)

[Zander]

i'm scared too that the mirror on my 12" GSO dob might have the same thing urs has :S. i only got it a few months ago and it has a layer of haze over the surface, i havent taken it out to clean it or anything yet though. i just emailed Bintel then to check whether taking it out voids the wrranty.
fingers crossed that it doesn't.

[monoxide]

my 12" gso had the same thing zander except a good clean fixed it right up :)
as for the 'ohno dont clean it' brigade, in my opinion leaving dust etc on the primary especially when its going to be getting dewed up is asking for problems.
all i did was give it a quick blast under the tap (in the kitchen sink) to get rid of the loose stuff, let it soak in warm soapy water then rinse with the tap + demineralised water, no touching the surface = no damage and from the times that ive cleaned my mirrors using the method above it has come up spotless, the thought of dragging anything across the face of the mirror worries me a bit :)

[davidpretorius]

i have soldiered on with a defective 10" mirror for over 12 months. Like you, nothing gets rid of it. it is like it is oxidising etc under the coating.

straight back the dealer!

[h0ughy]

its a month later from your first post - what are the results so far with getting it looked at?

[norm]

Hi Richard,

As most people have said, contact the dealers and see what they say, especially if you have parted close to 3K !

Good Luck.:)