Attaching secondary mirror

[asteria]

Hi there - what is recommended for attaching a secondary mirror to its mounting block? I am going to be making a secondary mirror set up and am not sure how to attach the mirror. Any advice appreciated. Thanks. Ed

[Freff]

Personally, I'd use 3M (4611 F) double sided tape. It is an acrylic foam industrial strengh tape which has very strong grab properties, and the holding power is exceptional.

This is the only tape that would hold my Discovery rear view mirror in place during offroading.

Other solutions are two pack epoxy resin type ahesive, but they are more permanent. With 3M tape you can get a blade behind it if need be.

HTH

[Peter Drew]

Double sided tape is OK as long as it has a reasonable thickness, if too thin the non optical surface of the holder face can "print through" and distort the mirror surface. Epoxy resin is just too hard a fix, could also distort the mirror figure and it would be difficult not to damage the mirror whilst removing it for realuminising. Silicone sealant has been used successfully, the Dow Corning product is recommended.

[Nevy]

The best stuff to use is aquarium silicone , use 3 blobs ( about 1/2" round blobs) 120 degrees apart and use toothpicks between the mirror and holder for the right depth as spacers , let the silicone cure for a couple of days before pulling the toothpicks out.

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[Freff]

Double sided tape is OK as long as it has a reasonable thickness, if too thin the non optical surface of the holder face can "print through" and distort the mirror surface. Epoxy resin is just too hard a fix, could also distort the mirror figure and it would be difficult not to damage the mirror whilst removing it for realuminising. Silicone sealant has been used successfully, the Dow Corning product is recommended.

Agreed.

The 3M tape referred to is 1.5mm thick and black.

[asteria]

Hi there - many thanks for your help and advice - there's a few options there which is useful. I will shy away from the epoxy, and might try the tape - sounds less messy than the silicone ! I'm not the most practical type.

All the best. Ed

[Nevy]

Sticky paded tape is what allot of scopes have as standard from the factory, it's ok but a lot of people take it off and restick it with silicone as tape can sometimes cause astigmatism.

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[asteria]

I'm going to go with the silicone - I was able to get a small tube from the pet store, presumably used to repair fish tanks. Will let you know how I get on. Ed

[Freff]

Good luck, hope it goes well.