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#1 Atl

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Posted 28 January 2013 - 08:27 AM

From reading this forum I have come to understand that I have offset my secondary incorrectly by a few millimeters. It give good views now, but I want it correct at 3.5mm as it should be. It is in place with silicone rubber. Does any one know a good way to remove it cleanly from the back of the secondary? I have picked it off by hand before but this takes a long time. Thanks.

#2 wky46

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Posted 28 January 2013 - 08:31 AM

Xylol/Xylene removes silicon

#3 Atl

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Posted 28 January 2013 - 11:56 AM

Will it damage a mirror it accidentally touches?

#4 KerryR

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Posted 28 January 2013 - 12:12 PM

You probably don't need to remove the silicone-- cut the secondary free (that's the hard part), then scrape the excess off the secondary mount and the back of the mirror with a razor blade, and re-glue. The new silicone will bond to the silicone that's left over on the surfaces. Give both surfaces a wipe with rubbing alcohol if you think you've gotten the surfaces oily while working, let it dry completely before applying the new silicone.

#5 Gordon Rayner

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Posted 28 January 2013 - 01:02 PM

Today, where does one buy xylene/xylol in California? It and/or toluene/toluol, are still to be found in small quantity , expensively packaged and marketed, additives for gasoline. Where else?

The vigilant air pollution control districts have severely limited/constrained/banned useful products, thereby causing collateral damage to small-scale hobby or household, non-industrial, use.

I was only half surprised, therefore, to find that Home Depot and paint stores no longer offer the solvents above, and that the odorless mineral spirits for California take longer to dry.

Has anyone tried the potent smelling all-purpose industrial thinner at Home Depot, said by Kleen-Strip in Memphis to be a substitute for several banned solvents? I bought a quart, but have not tried it for silicone removal.

Are Las Vegas, Reno, Tucson, Phoenix, Yuma, etc. supplied via California, and therefore similarly afflicted?

#6 neotesla

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Posted 28 January 2013 - 01:46 PM

Xylene will not damage glass or aluminized surfaces. Easiest way to remove is as KerryR stated, scrape/cut it off with a razor blade. After all, its on the back of your mirror.

#7 neotesla

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Posted 28 January 2013 - 01:48 PM

Xylene, toluene and the like is getting harder to buy on the consumer market due to health concerns. They are considered possible carcinogens, hence the decline in their use for other than conbusted use.

#8 wky46

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Posted 28 January 2013 - 01:57 PM

Thanks NeoTesla.

#9 okieav8r

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Posted 28 January 2013 - 04:10 PM

I don't know about California, but I purchased Xylene at either Lowe's or Home Depot here in Oklahoma last fall.

#10 ischua

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Posted 28 January 2013 - 06:49 PM

Dental floss will cut thru silicone and foam tape holding things together. Safer than a knife.

#11 Atl

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Posted 28 January 2013 - 09:30 PM

Well I prepositioned it. I used my pocket knife you cut it away. I keep a very sharp knife so no danger of cutting myself...it came away easily. I cleaned the mirror back with my knife and left the rubber and toothpick slavers on the holder. I needed a 3.5mm offset. I missed it by about 1.5mm. I hope that's good enough.

#12 KerryR

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Posted 28 January 2013 - 10:04 PM

Depending on your scope's design, you should be able to get the correct offset(s) by tweaking whatever you're using to support the secondary, usually the spider.






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