Dust on Primary Mirror

PCH (Paul) · #1 30-07-2007, 09:39 PM

Hi Guys,

having recently received my newest toy - a Meade LB 12" Deluxe, - I've had plenty of time to fiddle with the thing thanks to the non-stop Michael Caine these past two weeks here in Perth.

So, having had my first go at collimating, it instantly became obvious what a pain this could be, - especially as I read from you guys that it needs doing every time you set up your stuff

.

So, a set of Bobs Knobs were ordered. Whilst fitting these, I must have removed the dust cover from the Primary mirror at some stage, and before I knew it there was a sprinkling of dust particles on the primary mirror. They look like mini iron filings - the sort of thing that might come out of the screw holes when I was removing the secondary mirror screws.

I'm reluctant to touch the mirror with anything, and yet my inner quest for perfection points me towards getting rid of it somehow. Does anyone have any thoughts on what we do in this situation? Any suggestions much appreciated.

Cheers,
Paul

eqcradle · #2 30-07-2007, 10:46 PM

I've seen a few pages that suggest a camel hair brush for dust removal. I don't know whether a brush would be advisable if they're filings though.

I've used a goat hair brush (from an art store) for dust removal. I gather camel hair is the softest, but I think goat hair is the next best thing.

I rub the brush back and forth on a plastic surface (a calculator cover) to build up a static charge in the bristles. That way it picks up everything with barely a touch. Then rub it over the edge of the plastic again to dislodge what it picked up and 'recharge' it.

CL

erick (Eric) · #3 30-07-2007, 11:49 PM

Paul, when I first read your post I thought "Huff and puff and blow them off", then thought - metal filings?? maybe not - might scratch as they fly across the surface? I think you need to try and tip what you can off - not sure with an LB - can you get the mirror up to vertical without dropping it!! Then, with care (and the mirror vertical in case you drop what you are holding!), wave a magnet over the surface and see if you pick them off - but may well not be magnetizable filings? Then off to the blower and then to a soft brush or maybe straight to a liquid wash as per manufacturer's instructions. I hope that you don't have to go that far. Now, remember these are suggestions from someone who hasn't cleaned a mirror yet!

iceman (Mike) · #4 31-07-2007, 06:05 AM

Are you sure it's iron filings?

I guess a strong blower might be able to blow them off? You have to be careful with compressed air that it doesn't leave the wet residue - then you'll probably have to go ahead and clean your mirror anyway.

Garyh · #5 31-07-2007, 08:33 AM

Good idea to blow them off..
just borrow the misses hairdryer and give it a good blast!!!
If they don`t budge you will have to give it a full clean down..

rmcpb (Rob) · #6 31-07-2007, 08:34 AM

I would agree with Erik, set your mirror on its side and gently blow across the mirror with one of those camera blower bulby things. The puff of air should dislodge the bits then gravity will do its thing.

PCH (Paul) · #7 31-07-2007, 10:45 AM

Thanks for all your helpful suggestions guys. I'll try the easiest first I think, which is the 'little bulby things', followed by the hair drier.

Thanks for replying, - cheers

astro_nutt · #8 01-08-2007, 02:36 PM

Hi Paul...just another thing to try..tilt the mirror till it's verticle then gently tap the mirror from behind with a pencil eraser attached to a knitting needle..so it works like a small rubber mallet..this might "bounce" the heavier bits off and away from the mirror rather than across it!
Cheers!

monoxide · #9 01-08-2007, 03:31 PM

just take it out and clean it

ive never needed to use cotton buds on my mirrors. i pretty much do the same as in Mikes article so follow that for the bits i dont describe

1) rinse all the loose bits off under the tap
2) fill the sink with luke warm soapy water
3) let the mirror soak for however long you think it needs
4) give it another blast under the tap.

if theres anything still on there, repeat till its gone. I never had to do it more than 3 times even with some pretty solid gunk on there, remember to give it a final rinse with distilled/demineralised water

remember: you can only damage your mirror if you touch the surface, solution = dont touch the surface (with anything). simple eh

just be very careful getting it out of the cell, the mirror will be a lot heavier than you first expect and it will more than likely be stuck to the cell with double sided sticky foam pads so take your time.