Newtonian reflector maintenance

[starscy]

What sort of maintenance does a Newtonian reflector require? Being an open tube design does it require frequent cleaning? Do mirrors have an "expiration" date?

[yeti monster]

If you keep the open end covered, this will prevent a lot of dust ingress and also help stop birds and small rodents building nests in there whilst you await a gap in the clouds.

Mirrors have a long life, so long as you don't touch them or expose them to unnecessary abuse, such as brillo pads and scouring powder when cleaning.

Oxidation can be a killer to the coating, I believe. This can be avoided by ensuring your scope isn't over exposed to moisture from dew and drizzle, also, those small packets of silica gel which come free with electrical goods are handy to pop into the tube during long lay ups, or if you have to keep the scope in the shed etc.

[Merlin66]

I still have an excellent Wildey mirror, a 6" f8 made back in the 1950's.

The 200" at Palomar was ground and polished in the 1940's and still going strong...

If you look after your mirror it will outlast you, and the the kids!!

Ken

[yeti monster]

200"! imagine the eyeful you could get from that!

Note to self, plan a visit to Mt. Palomar observatory.

[brianb]

Modern dielectric coatings have a very long lifetime. Older "plain" aluminized coatings do need to be renewed - after 5 years or so but this depends on the environment - salt in the air is bad, so coastal environments or sites near main roads (gritted in winter) are worse than those well away from coasts & main roads.

There are plenty of sites with instructions for cleaning mirrors, the only thing I'd add is not to do it too often - a small amount of dust has no impact on optical performance, but scratches caused by careless handling may do so.

[Rusty Strings]

Being an compulsive tinkerer, I'm always looking down my newt tube to what looks like a filthy mirror and feel the urge to clean it, but I have to say that the views are still great so maybe I'll wait a year or two.

John

[part timer]

Everyone always seems to go on about this sort of thing but really I have found that the advice above is spot on.

Modern mirrors take many, many years to degrade. They often look dirty but you should not bother cleaning them until there is a genuine impact on the views. This will be almost never if you are a very demanding observer. For everyone else it will be even closer to never!

My newt is 8 years old, lives in an old shed and gets hard usage but the mirror is almost perfect. I cleaned it when it was about a year old but needn't have bothered!

[Astro_Baby]

Palomar gets a new coating every few months. They have a huge rig which supports the mirror then they ubolt the mirror cell and trundle it over to a machine which bolts onto the mirror face and recoats it.

Newt maintenence for the rest of us - keep the dust caps on, dont clean the mirror more often than necessary - they can be filthy looking but still work well and of course collimation.

Best is to treat the scope like what it is - a precision instrument.