Can primary mirrors go mouldy?

[stargazerlily]

Hi everyone,

Had a great session on Saturday night ... first time for a long while.  Even managed to capture a few good quality web cam videos for processing.

Anyway ... when I was packing up I thought I would check the scope tube before putting it to bed.  I looked down into the tube ... and to my horror (and surprise) saw what at first glance looks like mouldy patches on the primary mirror.  I've taken a couple of photos to show the features.  The photos are not perfect but they show the mirrors are not perfect mirrors.

I checked the mirror of my 150PL and that has similar features but not as abundant as in my 200P.  

Both tubes are stored vertically and covered up in a large box in the garage.

Is this a common feature?  Can backing silver degrade overtime especially if stored in a garage?  I can't see if the mirror surface has any pit marks ... it just looks like blemishes on the surface.

Next question ... can anything be done to remove the blemishes?

Many thanks

Pete

[ronin]

If stood upright then moisture will collect on the primary and any imperfections in the coating will allow this at the silvering.

Now moisture is acidic - mild carbonic acid and aluminium is reactive. So yes it will get damaged.

You will find it looks worse then it is, shining a light down the tube of a newtonian usually results in 1)Panic or 2) Coronary, occasionally both.

It will (should) not be mould but oxidation.

Huge amount depends on the quality of the protective coating.

It might simply be a deposit from whatever moisture has made it to the mirror surface - that can be cleaned off carefully. It is oftan a calcioum (chalk) deposit.

This will I suspect be the most likely.

Worst case is that it is a mould, there are ones that "eat" glass they leave sort of etched marks on the glass (occurs on camera lens) but very doubtful for the newtonian mirror.

Really the next action is

a] Ignore it.

b] Remove mirror to examine it closely (could then be a case of it is not too bad, clean it, resilver it.)

How old is the mirror/scope ?

[Northern Soul man]

Hi Ya Pete, using a "flashlight" as in a flash with the camera always shows up what looks to be a very "poor" mirror - all mirrors are the same as they are produced using the same techniques, there are differences in the high end mirrors - but at a cost.

You say you store in the garage, if its heated you will get a large temp difference when you bring the scopes into the garage - this will create "dew" - so you will probably see water marks - like streakes on the surface of the mirrors.  I store my scopes out in a concrete shed and have not had any problems with the mirrors, but the shed is probably the same or near as to the outside temp - so not a problem.

Wait for a few more to add, but if your worried and it is fungus/mould on the surface it would be better if you can take the mirrors out and clean them, as the mould will "eat" into the coatings.

Don't worry about the "flashlight" view of the mirrors- they are all the same.

Paul.

[ghostdance]

You will find it looks worse then it is, shining a light down the tube of a newtonian usually results in 1)Panic or 2) Coronary, occasionally both.

Lol....first time I did it, I damn near dropped the torch! I try to avoid looking now.

But if and when I ever get to reflocking - I guess Mr Mirror will finally meets Miss Sudsy!

[stargazerlily]

Thanks Ronin, Paul & Ghostdance,

Thinking about it again (and having another look this evening) it makes perfect sense about the marks being residue from dew droplets on the mirror.  The scope is only 4 years old and it's been stored in an upright position in the garage all the time when not in use (garage is just an ordinary detached garage, no heating).  I don't think it is mould any more ... phew.

Yeah, was a major shock looking down the tube with a spot light (and flash on the camera).  Think I was expecting a Hubble-type perfect mirror reflection.

Wonder if we could make a film ... 50 ways of Mr Mirror getting together with Miss Sudsy

Thank you for your comments.

Pete

[LittleSkink]

very doubtful it is mould or fungus (imo) they tend to form in optics with multi coatings and warm, damp conditions - unless I am mixing up photo optic woes with astro

I had a 500mm catadioptric lens for my Olympus film camera years ago and that developed fungus from being stored in the wardrobe - the mirror was ok it was the coating that were going