Spots on my primary mirror

[jeremy1]

Hi Guys I don't get to use my telescope much now-a-days as I work overseas. I have been keeping my 200p in the conservatory at home which as we all know can be prone to damp and cold conditions. I got it out the oher day and noticed a few (5 or 6) small spots on the primary mirror. This did not upset my quick viewing of Jupiter and mars, but I am wondering how do I clean it or should I leave it well alone as it might damage the coatings ?

[ronin]

The real answer will depend on what the spots are.

If left and they are doing nothing other then sitting there as spots then no problems. If they are spots that are munching through the coating and silvering then trouble.

At Astrofest when talking to the gut on the ES stand he said if dust it can be left, if pollen then remove - it decomposes to an acid and destroys a mirror.

The problem is not can say what it is on your mirror.

The only one to decide really is yourself.

[Daniel-K]

take it down the car wash and  use a jet spray just kidding plenty of vids on you tube i done my 14" mirror a while ago and im doing it again tomorrow as it has a fair bit of dust on it from my dark sky outings. just take your time and make sure your well prepped

[ScottS]

See if they can be removed with some sort of air blower (assuming you can reach in far enough). This would also allow you to leave the mirror in situ.

[jeremy1]

The only way I can describe them is a milky spot about a mm or two in dia. Whether they are from dust or pollen I really wouldn't know

[jason.p]

There will be many who say leave well alone, it's surprising how much muck it needs before actually affecting the viewing. On the other hand, if you really can't live with it, and it's going to spoil your enjoyment, it is no big deal getting the mirror out and cleaning it. There's plenty of advice to be had on how to go about it. You'll need to recollimate but if you mark everything up an put it back the same you'll find it's not far out, and it's only the primary that will need a tweak.

Good luck whatever you decide to do.

Jason

[AlexB67]

If they are white looking it could well be  some sort of fungus of sorts and cleaning would not be a bad idea, as well as avoiding storing the scope in a damp humid place long term could be perfect recipe for growth.

http://www.company7.com/library/unitron/graphics/unitron_142_fungus_lenses375240.jpg

The type of things you see in petri dishes in a biology class will look similar so it is recognisable. 

http://www.gopetsamerica.com/bio/pics/molds-petri-dish-2.jpg

The petri dish example is somewhat more developed case, but those tiny white things may be the start of something brewing on there but in its very early stages. 

[Charic]

jeremy1.......Hi, If you mark the end housing screw positions against the tube and remove the 6 circumferential screws(mine has 6) you could remove the mirror and replace it without upsetting the collimation, providing the collimation adjusters are locked down. You could then assess up close what's on the mirror, maybe just a puffer brush or a proper wash may be required?  At some stage in the future, your mirror has to come out for cleaning, but another 4 or 5 hundred spots may be required before most folk would touch their mirrors.

These mirrors have a protective coating over their mirrored surface,  and as long as you follow caution, you cant do to much wrong. Plus you'll learn a bit more about the construction/assembly/set-up of your primary mirror, and the mirror cell its housed in. 

If you misaligned the re-assembly, then collimation would be required. Just take your time and plenty of caution. You still may need to collimate, but that's just part of owning a Newtonian telescope.

( ronin......was he a big guy?   )

[ScottS]

As a preventive measure for the future, maybe one of these would help? May be worth considering if the scope is to stay where it is now.

[Charic]

The 10x spare sachets would be the cheaper option,  with a piece of cotton and elastic band to secure?  I Thought desiccant was best for closed containers. Newtonians are open ended around the mirror cell?

[JimmyC]

Flamethrower - Sure to rid you of the spots problem (probably your mirror too). Hehe, as above really. Just try to give it a quick blast of dry air to shift it. It's best not to physically touch the mirror.

[jeremy1]

Thanks for all your replies. I will have another look when I get home in June.

[damnut]

If you want to clean your mirror unless it is really foul follow these steps.

1. Think about cleaning mirror.

2. Have a cup of tea.

3. If thirsty go to step 2.

[Earl]

Its not worth the effort or risk  unless you know for certain that the mirror is filthy and have a degraded image.

Some people do get very OCD about a clean mirror, dont fall into that trap