Ezy, If you use the hairdryer, just be careful not to direct it straight onto the surface ie; 90 degs. Never know what might get picked up in the H/D & blown onto the mirror. Better off with a 'puffer brush' from the camera shop.
How bad is it? If it looks really bad, it may need a wash! Seeing as you have just recently purchased it, I would suggest using it for a while & if poss, take it to an open night or local club night for others to inspect.... A mirror has to be 'really dirty/dusty' to have any great effect on the quality of image. The contrast may be down a little, but you will not notice it.
My mirror has been 'washed' 2 x in the 12 yrs I have owned it.
I hope this helps a bit. L.
Rajah bought up some good points, avoid doing anything to the mirrors unless it is absolutely necessary (besides collimation). Surface dust on primary mirrors is a fact of life, you cannot get away from it, it's always going to be there.
I have seen closed tube SCT's with dust on them without degrading their performance (well not the eye can pick up) A friend of mine has an 8" f7 scope that hasnt had its mirror washed since he got it over 10 years ago. If you cover the tube and keep the telescope in a clean space you shouldnt have a problem.
If you really do need to clean the mirrors, goto your local Astronomical society and ask around for some expert help, learn from them how to do it yourself in the future.
Like Astro and Raj say, unless it's a really serious case of dust, don't worry about it.
My newt mirror's got what appears to be a fair amount of dust on it but it works fine. It's as bright and clear through the EP as it was when I first got it. At least to my eye, the difference is negligible.
But as Astro says, if you're really worried about it take it along to your local astro club and let them have a look and show you how to do it correctly... and safely
Better a thin layer of harmless dust than a network of scratches!
What the guys above say is true, however I also believe that a dirty primary mirror just has to have a negative impact on what you're viewing, and when i'm doing high-res planetary imaging, I don't want light scatter or lack of contrast or decreased resolution because of a dirty mirror.
I clean my mirror fairly regularly (2-4 times a year if it's needed), and I think most people have an irrational fear that cleaning their mirror will scratch it - therefore they conclude that a dirty mirror is better than a scratched mirror. And that's true, but if you take the proper precautions then there's no reason you should scratch it, and there's no reason you shouldn't clean it if it needs it.
I also agree with above though, that you need to determine if it's dirty enough to *need* cleaning. I don't clean mine at the first sign of dust.. but after a very dewey session at Lostock over the weekend, my primary mirror had water condensing right on the mirror, and so now it's left many residue spots so it still looks like it's wet.
Yes you can still view through it, but I plan to clean it again before I do any imaging with it.
many thanks for your help guys. ok, i bought the telescope secondhand and got no idea how old it is so im going to give it a go at washing it from the link iceman posted. Do i have to rinse it off in the end with disstill water? or can i just use ordinary water?
Definitely distilled water.. it doesn't leave any residue. Any spots that don't run off, just grab a paper towel and use the corner of it to dab on the spot and soak it up.
Hi EzyStyles, if you are just visually observing planets and DSOs I wouldn't be terribly concerned about a bit of dust on your primary mirror - the decrease in contrast caused by a little dust is negligible compared to other factors such as poor collimation, insufficient scope cool down, or bad seeing.
If you are doing hi-res planetary imaging then you need to have everything perfect and cleaning your mirror every 3 months is just part of the fun and games
If you do want to clean your mirror, I don't think a hairdryer is the way to do it - blowing tiny abrasive particles across the surface of your mirror may cause fine scratches. Follow the link that iceman has provided to learn how to clean your mirror properly.
OK, just saw your last post - good luck with the washing. Yes, do use distilled water so there is no residue after the water dries.
I'm one of those guys that has an irrational fear of cleaning mirrors for fear of scratching them... no matter how careful I've been I always do, but them I'm not exactly a neat and clean sort of guy and my house is like a shrine to dust, so I suspect that if you are of the neat, clean and organised variety like Mike says you should have no trouble.
Having said that I'm also amazed at how little impact dust and even fine dew has on views and imaging. Some of my best planetary images have been taken with fine dew spotting up the corrector plate on my SCT and what looks like a desert of dust on my DK cassegrain mirror. What I'm getting at is it really isn't such a big deal, so see how you go as others advise. It's probably something that takes you from 97% to 99% performance.
Dirt happens, and in moderate amounts it has remarkably little effect on performance. In his book Star Testing Astronomical Telescopes, Harold Richard Suiter analyzes the effects of dirty optics mathematically. His conclusion? "The maximum amount of dirt [that a perfectionist] should tolerate on the optics is about 1/1000 of the surface area, [which is] the size of a single obstruction about 1/30 of the diameter." In other words, on a 10-inch mirror this is the equivalent of a completely opaque dirt blot 1/3 inch across. That's quite a pile of crud before there's any detectable effect on contrast.
"Don't decide to clean mirrors on the basis of shining a light down the tube at night," advises Suiter. "All mirrors fail such a harsh inspection." After you've done what you can to prevent dust, ignore it.
re: your comments about mirror scratches and your house being a shrine to dust etc etc
I'm going to check birth records to see if we weren't twins separated at birth
But seriously, I'm only recently starting to appreciate comments along the line of "don't look at the dust on your mirror, look at the view through the eyepiece".
its easy, i am bringing a 20litre drum of distilled water to the snake valley camp (near ballarat) in early march. Come along, enjoy the company of us grumpy bums and we will go through washing mirrors like we did last time.
There is a thread for the camp, or even if you just come out for saturday during the day for a drive. Dave47tuc is organising the camp, so pm him for any extra details that you can't find in the thread.
By the way, for the next few weeks i will shamelessly plugging the camp for all VIC people!
relief.. just cleaned my primary and secondary mirrors. Wasn't that hard actually.
1) take primary/secondary mirrors out.
2) clean sink
3) fill sink with warm water with detergent
4) blast both mirrors with warm water without touching it with fingers
5) dip both mirrors in sink with detergent
6) leave mirrors in sink for 5-10 minutes
7) rinse both mirrors with warm water under tap
8) rinse again with disstill water
9) sit mirrors on the side and let it dry. Use paper towel to dap large water drops
10) once dry, put mirrors back together
One thing though, i left the primary mirror rear holder/case as it is when placing it into the sink as i don't want to remove the primary mirror from it. I also adjusted the screws holding the mirror (not too tight).
Many thanks for all your help all. Much appreciated.
You did take the mirror out of the mirror cell before soaking it ... ... right?
Uh, sorry, just read your post properly. I don't think soaking the mirror cell and all is a very good idea. Now what's done is done. Just make sure it all dries properly, and, as they say, don't do it again.
I would still take the mirror out of its cell and thoroughly dry everything before reassembly. You could end up with rust, or worse even, mold.
errr yep. I soaked it with the mirror cell.. what happens now? will it stuff it up?
with the secondary i didnt dip it with the spider. took "just" mirror/holder out but primary as seem in pic i dip the whole thing in.
take the 3 sets of 2 screws out carefully that are on those clips holding the mirror. lift up clips and move to the side. gently lift mirror by the edges and place in safe area.
now get hammer and smash the crap out of it!!!
(just joking for the hammer)
make sure the supports ie cork is dry etc.
re-assemble, but make sure that the screws are only done up just finger tight. If they are too tight, then they can warp the mirror.
Best to take the mirror out of the cell. Moisture could remain between the cork pads and the glass for a long time, and there is a good chance of mold taking hold. You might want to disassemble the rest of the mirror cell and dry each component separately with a towel and then let dry completely. You don't want your collimation screws and springs going rusty.
The other problem with doing this is that there is usually a lot more dirt and dust on the mirror cell and housing than on the mirror itself which will wash into the water, so you end up soaking the mirror in more dirty water than you otherwise would have.
Same for the secondary. If it has a holder where a clamp is stopping it sliding out, then disassemble and thoroughly dry everything. In the GS scopes there is usually a clump of foam that could soak up plenty of water behind the secondary. It's good to do that anyway to make sure the mirror is not being pinched. Just make sure everything is dry before it all goes back together and it will be fine.
Well that's one way to learn all about your scope.
L.
... right? 
