Dust on Secondary Mirror

[bendiddley]

Hi all. I had a great time trying to align my secondary mirror last night (not), which I realised was actually aligned correctly anyway, I did learn a lot about aligning the secondary mirror though through the process, although it took me over an hour to do (doh). Anyway as a result a spec of dust has appeared on the secondary mirror and I am wondering what is the best way to get it off, I def do not want to take the mirror out, having gone through all that last night, so is there another way like some sort of optical brush I could use to gently sweep the spec off or similar, or is it not worth bothering about? Any comments?

[NGC 1502]

The most often given advice is to leave it be. You could try to shift it with a bulb blower pointed down the focuser. Rack the focuser in to get a bit closer. This may work, but bits of dust can be very resistant to shifting. Sounds like you had a lot of hassle, so as you say, best not to remove the secondary and go through all that again.

There are ways of cleaning the secondary in situ, with a micro fibre cloth (camera shop) and some isopropyl alcohol (chemist) and a lot of care, no rubbing or pressure. But there are risks to this, if you scratch the mirror, you will wish you had left it alone.

It takes a lot of dust & crud on mirrors to affect the view, so I'd leave it alone myself.

Regards, Ed.

[bendiddley]

The most often given advice is to leave it be. You could try to shift it with a bulb blower pointed down the focuser. Rack the focuser in to get a bit closer. This may work, but bits of dust can be very resistant to shifting. Sounds like you had a lot of hassle, so as you say, best not to remove the secondary and go through all that again.

There are ways of cleaning the secondary in situ, with a micro fibre cloth (camera shop) and some isopropyl alcohol (chemist) and a lot of care, no rubbing or pressure. But there are risks to this, if you scratch the mirror, you will wish you had left it alone.

It takes a lot of dust & crud on mirrors to affect the view, so I'd leave it alone myself.

Regards, Ed.

Thank's ed. So a brush is not a good idea then?

[ollypenrice]

One speck of dust??? When you have 500 specs you might just - just - consider cleaning it. Leave it alone. Endless cleaning is a classic beginner's mistake. I let our big Dob's mirror get very dusty over a year or so before giving it a clean and it makes no difference whatever to the view when I do it. This scope lives in a draughty roll off in the dry and dusty climate of Provence.

Olly

[Rob]

I've used a scope with a mirror so dirty I could not see my own reflection in!.. I still managed a great obs night. Let it be...

[bendiddley]

I've used a scope with a mirror so dirty I could not see my own reflection in!.. I still managed a great obs night. Let it be...

Great stuff, this is all very encouraging! Glad I don't need to worry about it.

[Rob]

You dont need to worry at all.. just enjoy your scope!

[FarSide]

Aside from the advice that you are getting from these guys for not cleaning it yet, which is all true, you'd have to also collimate the entire scope again. In my opinion collimating your spider is the most tedius thing to do. Leave it alone for a little while longer!