Need to clean secondary mirror

[Marko of Oz]

There's a great article on mirror cleaning in the Projects and Articles section(thanks Mike) but I have question before I begin;

Is distilled water and demineralized water the same thing? :shrug: In the article distilled water is used. If they're not the same thing is one as good as the other?

I ask because without really looking I grabbed demineralized water off the shelf. :doh:

thanks

[mill]

To my knowledge both are the same thing.
Both have taken out the minerals that would stay on your mirror.

[iceman]

Yep, same thing as far as their use is concerned.

[Mr. Subatomic]

I can be very pedantic about my scope, I can't imagine the state I would be in if I lost one of my dust caps. I keep it in very good condition, but how often will I have to clean the mirrors?

And does anyone know a good way to blow a gust of air accross the primary mirror to knock off small dust particles (while the mirror is inside the scope)?

Also, does the secondary mirror ever need to be cleaned, if so, as often as the primary?

Thanks for your help guys,

Cheers. :D

[astro_nutt]

When do you need to clean your primary mirror??...I would say when the images are noticeably lacking in sharpness/contrast when compared to a new mirror..and not by shining a torch down the tube and see a horrible dirty layer of goodness-knows-what!!..
I would dust off the primary every 6 months or so by removing the mirror and cell and stand it on it's edge on a towel and supported by a few heavy books..using canned airbrush raised on another book so the nozzle is pointing to the mirror's centre..give it a test spray away from the mirror to ensure no liquid is present in the nozzle..then gently rotate the can towards the mirror being careful not to jar the can and give a few quick bursts..and that's it!!..what ever doesn't blow off can stay there until you are ready to wash it!!
The secondary is less likely to cop the amount of dust..etc..and unless something is spilt on it..leave it!
Cheers!

[Marko of Oz]

thanks guys,

my secondary really does need a clean as you can see in this shot of Venus. The dark area is not surface/atmospheric detail, it's one of several spots/smears on the mirror.

Well I hope they're just cleanable spots, won't know till I get it out for a good look.

cheers

[Mr. Subatomic]

Speaking of Venus, I just got my first few views ever in a telescope in the last two nights, absolutely stunning how you can clearly see its phase.

I seem to remember a small, dim 'star' just above or below Venus. I know definitely that it wasn't Saturn and that Venus has no natural satellites. Does anyone have any idea, or am I just seeing things? :)

[erick]

Mr Subatomic

Yes, the crescent is great to see - I'm looking forward to watching it develop further over the next month. With respect to the star, you might wish to check a program such as Stellarium. I made it to be an orange star and I think it was psi Leo - mag 5.35 - quite prominent in the scope and very close to Venus. Closest was around 18:40 on 3rd July. Looked lovely!

Eric :)

[ballaratdragons]

Just to set your mind at rest, Demineralised water is Distilled water.

They 'de-mineralise' it by 'distilling' it. :thumbsup:

[Solanum]

Not necessarily true actually. Demineralised/deionised water, in the lab setting at least, is created by passing the water through an ion exchange column and a .44 micron filter. This gets rid of 'minerals' and does a pretty good job of cleaning it up. However, it can and does leave non-polar impurities if they are present, e.g. some organic compounds.

On the other hand distillation doesn't get rid of anything with a boiling point below 100C (unless it's been distilled very carefully).

As far as cleaning your mirror there is unlikely to be much difference though!

PS Apologies for my pedantry!

[mill]

pedantic can be good and i learned something new because of it.