Secondary Glue/Tape

[bmitchell82]

hey all just looking for a bit O information on whats the best to use silcone and if so what kind, or double sided tape. Currently the 10" SW use's what looks like double sided tape. anybody's thoughts will be welcome

[richardo]

Hi Brendan,
use a non acidic base silicone, generally a clear type that's neutral cure. Give it a good 24hrs to set at room temp. Make sure it's a new tube.
Let it have around 3mm space between the back of the mirror and the mount, this helps cool down as air can circulate. About 5 very small dollops spaced around the mirror will be suffice, 1 in the middle. You'll need to find some sort of spacer arrangement to get the gap even... three of these little spacers will be all you need. Press the mirror to the mounting plate, it will then set to the spacers height.
Job done.

Rich

[Garyh]

Great advice Rich, a good silicone, I used a good glass silicone and made three little spacers around 5mm round and 2mm thick out of some old plastic and stuck them in the silicone blobs. Make sure you prop the secondary up nice and level and let it cure.

[erick]

I've seen elsewhere that matchsticks are recommended as providing the right spacing - pull them out after the silicone sets.

[bmitchell82]

Thanks for the Advice gents, all went off witout a hitch. I went and purchased a tube of good glass silcone with a neutral cure.

The 10" is becoming more of a astrograph!

[AlexN]

Good to hear you're getting that Newt tweaked up and running well Brendan...

Its going to be a killer.

[jha]

Hi, Rich
why can't use acidic base silicone?
I think acidic base silicone is more strong than neutral cure silicone, so secondary won't fall off

[richardo]

Hi Jha,

I have always used this type of silicone through what has been recommended..
Acid base silicones smell like vinegar, they can corrode metals and give off gases even after they are dry. So it could cause damage to secondary mirror coatings! Not good with electronics either.

Hope this helps
Rich

[jha]

Got it thanks
can it be used for primary too? 3 point support

[richardo]

I think you will need to look at 'plop' to work out exactly the best places to put dabs of silicone to a primary. But yes, it will do fine.
A friend has done it this way with no probs.

Rich

[jha]

thanks. got it