Reflectors mirrors life

[captaincaveman]

You always hear about the degrading of the mirrors in reflectors, How long do the mirrors last before its noticable?

How long would you expect from a mirror and what do people do? are they costly to replace?

Jay

[Capricorn]

Difficult to give an answer.

The mirror is simply alumimium deposited on the glass surface.

Since aluminium is fairly reactive they have to be coated.

A good mirror will have a reasonable amount of aluminium deposited on a well prepared glass surface, then the protective coating will also be consistant and well applied.

I think a good one can last 10 years.

A poor one could I guess last 3 years. If no protective coating then only 1 year could easily be possible.

If the scope/mirror is used often the there is the fluctuating temperature to take into account.

Throw in that the more it is outside the greater amount of condensation it will encounter and this will be acidic..

After that consider storage - how well it it allowed to dry before being stored (probably) mirror down.

Refurbishment is usually fairly simple, places like galvoptics will strip and recoat a mirror. Although what always amazes me it that when the coating fails the glass seems to be pitted underneath to a fairly extreme amount yet we store concentrated acids in glass bottles.

Buy a nice refractor.

[John]

Orion Optics claim a 25+ year life for their Hilux coated mirrors. Mine are 4 years old and still look pristine, apart from a little dust.

[captaincaveman]

Ok thanks, im a refractor and mak/sct fan but may consider a large dob in the future

Im surprised most manufacturers dont quote a average life expectancy like you see on many other products

[Merlin66]

I have a Wildley mirror going back to the late 1950's - needs recoating but as good as is was when it left Henry's hands.