Cleaning Reflector Mirror

[Taff]

Hi' Instead of taking the mirror out of the reflector tube.Is there any other way of cleaning the mirror because i have got bits of dust on the mirror surface Thanks.Mark

[ronin]

Dust until really bad will make little real difference. Eventually it will build up enough that you really do need to clean it as after time it tends to stick and then it can be a problem. The catch is sort of the more often you clean it then more chances of something going wrong - likely in a small way, but if left too long then it takes more to remove the accumulated crud and so a greater chance of something going wrong.

A lot depends on how you feel, it would drive me nuts having a dusty anything.

Mirror will have to come out, cannot think of any other way to do it.

If you haul the thing out then read up on what you need to get and to do and consider it all, then do it carefully and sensibly, take time you are in no rush. the next clear night is likely to be a few weeks away. Car jet wash thingy not advised.

[Charic]

Unless your mirror is covered with dried Cola, leave it well alone, dust wont affect the outcome.

My mirror has had possibly  two cleans in three Years, but there's no difference to the images, just the knowledge that its cleaner!

Looking down the open end of a Reflector with a torch doesn't help either as the dust appears magnified,  and when the mirror is out, you'll wonder why you bothered ?

On my scope the Skyliner, If I undo the circumferential screws surrounding the mirror cell, the whole assembly pops out , whereby you could just blow away the dust with something like a Giotto Rocket blower, but once its out, it will probaly get a wet/damp wash of sorts, such is the temptation.
Mark the mirror cell alignment with the scope before removal, and if done carefully, its possible  to re-align the mirror assembly whereby the mirror will remain collimated!

[Taff]

I have had my scope reflector for 13 years and the mirror have never been cleaned.Mark

[Charic]

...........Still have caution in the method you choose. If its as dirty as an old attic skylight window, its your call.
At first, 'Bits of dust' sounds insignificant, and  even with 13 Years  of  use, it still may be ok to leave it alone.

I stripped my  telescope the first day if I recall,  as there was an issue with the secondary mirror end cap assembly. The second strip was to inspect some metal fillings  I'd  noted from one of the collimation  adjusters ? It was at this stage  I  wet cleaned the mirror with a proprietary window cleaner ( i kid you not) though   NOT advised by anyone else here!  It worked, there's  no apparent damage  and my scope has been clean since, due to the way I look after the scope, end caps, shower caps, dust sheet, plastic sheet,  stored inside its own cupboard!

[Rainmaker]

IF it is just a few bits, just use a blower to move them, if the surface is more extensive covered with dust or dew marks, remove the mirror cell and wash it.

I clean my mirror every six months, but mine is a truss scope.

My procedure is simple, I lift the mirror out and set it down on an outdoor chair on a 45º angle in the shade,

I then hose it down with the garden hose at low pressure with a constant stream until all loose material is washed off (3 minutes)

I then use a spray bottle with some warm water and a few drops of dishwashing liquid and spray the entire surface and keep it continually wet to dissolve any sap etc,

The mirror is then rinsed with a continual stream of distilled water (about 10 litres)

I then cover the chair in a cloth so that the cloth does not touch the mirror but keep dust and bugs off and leave it to air dry...... this ensures that there are no marks from drying

I don't subscribe to the theory that a dust covered mirror gives the same image as a clean one..... test this under high magnification if you don't believe me....

 

[Dave In Vermont]

Get an air-blower such as:

https://www.amazon.co.uk/Giottos-AA1910-Medium-Rocket-Blaster/dp/B000L9OIQC

And a super-soft brush made just for cameras and telescopes.

https://www.amazon.co.uk/LENSPEN-LP-1-Lenspen-Original/dp/B000KO0GY6

The brush on the Lenspen can be safely used on telescope-mirrors. DO NOT use the cleaning-tip on mirrors.

Blow the mirror clear. If dust is still there - brush very, very gently in a downward direction one pass at a time.

Do NOT use a torch to examine a mirror. Even a spotless telescope-mirror will look horrible with a torch-light. Just use ambient light - sunlight - to see by.

Best -

Dave

 

PS- More damage is often done to mirror's by unneeded cleanings! Dust is almost never a good reason to clean. Nor is abject boredom.

[StarryEyed]

Forget about it.

[Taff]

Thanks everyone, for your reply.Mark

[Paz]

I had my mirror out once to check out how the mirror cell worked so I know how to walk my mirror up/down and how much asjustment I had.

I gave it a clean just with the rocket blower which did clear off some dust and it did look better, but I also admit the temptation to then give it a wash was huge and it took a lot of self-discipline to leave it!

[Rainmaker]

On 12/19/2016 at 10:22, Paz said:

I had my mirror out once to check out how the mirror cell worked so I know how to walk my mirror up/down and how much asjustment I had.

I gave it a clean just with the rocket blower which did clear off some dust and it did look better, but I also admit the temptation to then give it a wash was huge and it took a lot of self-discipline to leave it!

What were you going to wash it with that made you so worried?  Even just pouring distilled water onto the mirror will clean most dirt off and will not harm the surface. Much more damage is being done to your optical coatings by airborne sap, fungal spores etc.

My mirror is 23 years old and still has the original coatings in near perfect condition..... 

[Paz]

 

On 20/12/2016 at 19:56, Rainmaker said:

What were you going to wash it with that made you so worried?  Even just pouring distilled water onto the mirror will clean most dirt off and will not harm the surface. Much more damage is being done to your optical coatings by airborne sap, fungal spores etc.

My mirror is 23 years old and still has the original coatings in near perfect condition..... 

I was not planning to wash it at that time, as it was not necessary. I'm ok with washing a mirror when it is necessary.