Dust on Primary Mirror

[Karlos]

I can see a several specks of dust on my primary, whats the best way of getting rid of them without damaging the mirror?

It is only a few specks, but its like when you have an itch you can't scratch is really annoying!

[John]

Personally I wouldn't bother about it - they will not be affecting the performance of the scope.

If you really have to, just use a manual blower brush above the mirror (no touching !) to blow them off the mirror.

You may need to take the mirror cell off the scope, which may affect collimation, to do this which is why I suggest doing nothing.

[Karlos]

Thanks John for your reply.

I thought it would be wiser to be precautious. I will just have to bite my lip try and ignore that dust, will look manual blower brush should it become a optical issue.

[acey]

Don't worry, after a few months of use the whole mirror will be covered with a fine film of dust and you won't notice those few specks. Nor will you notice any difference to the views you're getting through the eyepiece.

[Peter Drew]

Better to have an itch on your mirror than a scratch! .

[Telrad]

As John said. Unless it impedes the performance of the scope - get a blower... for now I wouldn't risk any damage.

[Pete Presland]

leave it is very good advice i know somebody on here who was advise not to take his eyepiece apart to remove some dust!

10 mins later several lenses scattered on the table and no idea what order or way to put them back lesson learned

[skinnyonce]

Have to agree with the NO touch policy I have an air compressor I use at low pressure and filtered air( no water oil etc) to blow down the tube of my Z-12 and do this every so often.. no damage as a result and the views are just fine

[damnut]

Agree with all of the above, don't have access to a compressor but a can of compressed air computer cleaner is useful, hold upright though!.

[Ursa Major]

Cant you just turn the scope upside down and use a hairdryer to blow air up the tube. Then all the dust will get dislodged and fall out.

Is this damaging in any way?

[Adamski]

I agree with the comments, this was a concern for me shortly after i bought mine. I was advised to leave it alone as it would not affect performance and so far it hasn't affected it at all.

[Karlos]

Cant you just turn the scope upside down and use a hairdryer to blow air up the tube. Then all the dust will get dislodged and fall out.

Is this damaging in any way?

I considered this, but maybe the hairdryer will drag dust in and blow it in also, so would be back to the same spot.

Thanks for all the advice guys, I thought dust even if small would really have a big negative effect like using slight marked eyepieces? Well I think I might get one of those cheap air blower squeezy things, then my I won't have the itch and the mirror won't have scratches

[umadog]

The hairdryer won't work: it doesn't push air fast enough. A little dust has zero impact on the mirror's performance. It just decreases the light gathering power slightly. Dust on the eyepiece can have more of an impact since it can be located near to the focal point. At the mirror, the same dust is no big deal. Consider that the secondary casts a great big shadow right in the middle of the primary. You don't see that when you're observing, do you? I have a mirror with a chunk taken out of it where I dropped the secondary on to it. The damage has made no difference to the views.

Remember that whenever you point a torch at a mirror you will notice a lot of dust, they always look bad when viewed like that. Simply ignore it. Maybe in 9 months or year you can consider washing it.

[acey]

I've been using my current telescope for over two years, I can see dust all over the mirror, and I don't reckon it needs cleaning yet - the dust is making no noticeable difference to the views. Individual specks of dust do no harm and should be left well alone. Whenever the time comes to clean the whole mirror, remember that the secondary will probably need cleaning too.

The 60" Hale telescope at Palomar Observatory gets cleaned every one or two years, when it's also recoated. There's an interesting video of it here:

Ministry of Space Exploration: Cleaning and Aluminizing the Hale Telescope Mirror

[Karlos]

Thanks for the replies guys, I just assumed that optics work best when collimated and are cleaned, I won't touch the mirror as I understand the coating is very delicate, but I did order a silicone dust blower just to get rid of the annoyance

Acey, that video is immense what an operation!

[blackparticle]

That is a mammoth job up there at Palomar.. Great vid.

Good to know that dust etc on the primary doesn't have the same effect as it would on a lens. I was looking at my 130P and thinking 'ewww' .. how am I going to clean that!? .. Now I know.. I just won't bother until it looks like a South American runway.