OK to use Silicone in SCT?

[davewaldo]

Hi everyone!

I'm building a cooling/ventilation system for my C8 and I was planning on using Silicone sealant to glue and seal a few items inside the Cooler (such as an air filter).

This cooler will be the removable kind. ie. Insert cooler, run for an hour then remove cooler to use telescope. (No alteration to the scope)

Basically I want to know if there would be any issues with me using Silicone in this system as I know Silicone does out-gas some fumes.

Would these silicone fumes be harmful to the scope?

Are there any kinds of Silicone experienced ATMers recommend?

I know many people use silicone in Newtonian mirror cells however these are open tubes and therefore I figure fumes are not an issue. However I've not heard of people using silicone in close contact to an SCT.

Any advise is appreciated.

Cheers,

Dave.

PS. Once I have built my top secret SCT cooler I will be posting all the details.

[wasyoungonce (Brendan)]

Make sure you use a "non Acetic acid silicone" as they can corrode and out gas.

The out gassing of the acid as this type cures can corrode aluminium coatings and lens coatings.

Something like RTV3145

[Karls48 (Karl)]

I don’t know about silicone but definitely do not use Superglue on anything in optical train. I stuffed up diagonal by using Superglue to lock barrel in diagonal body. As it cured the vapours from the Superglue deposited kind of milky coating on the diagonal mirror.

[citivolus (Ric)]

To second this, one product datasheet I was looking at for an acetoxy type RTV silicone warned not to use it on mirrors or lenses with coatings. I'm not sure how easy it is to find a non-acetoxy (methyl alcohol) RTV silicone, but it would be the one to use.

[davewaldo]

Right... I'll have to go and have a look for some of this non-acetoxy Silicone, the silicone which doesn't use Acetic Acid.

I'll let everyone know what I find. I'm pretty sure I've seen this sort at Bunnings.

Also, to minimise outgassing I plan to allow the Silicone to cure in Hot sun which apparently greatly minimises outgassing when the Silicone is at lower temps (like at night).

Thanks guys!

[Glenhuon (Bill)]

Check out some of the products made by Loctite. They make sealing compounds suitable for alloy. Not cheap, but neither is an SCT

Cheers
Bill

[Omaroo (Chris Malikoff)]

I think that the non acetic silicone is also sold as "automotive" silicone - and is usually black. Try any auto store.

[skeltz (Rob)]

Okay ,use a neutral cure silicon and you will be perfectly fine no worries1

[monoxide]

aslong as you allow the silicone to *fully* cure before you poke the cooler into your scope you should be fine

i'd probably leave it to cure for atleast a few days before i put it in the scope though

[skeltz (Rob)]

Agreed ,i would even leave it for five days to cure,thats the minimum i will be doing for my primary.

[davewaldo]

Great! Thanks everyone for all the advise!

[davewaldo]

Hi Everyone,

I have bought some silicone and I'd thought I'd let everyone know what I found...

I was looking for a natural Cure Silicone and I found that Selleys Wet Area Silicone is 100% silicone and natural cure. And its only $8.00

I did find aquarium silicone however this was an acetic cure.

I assume as long as I allow plenty of cure time this should be very good and safe silicone to use.

Thanks again,

David.