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Webster Telescopes Forum :: View topic - Never use a sock or a cloth bag to cover the secondary.
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Never use a sock or a cloth bag to cover the secondary.
http://webstertelescopes.com/forum/viewtopic.php?f=7&t=609
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Author:  jimwebster [ Fri Sep 23, 2011 1:25 am ]
Post subject:  Never use a sock or a cloth bag to cover the secondary.

Recently, a customer sent us his 2 year old secondary mirror.

It is a good example of why we tell everyone never to put a sock or a "Crown Royal" bag over the secondary mirror.

What happens is that tiny bits of grit fall or get blown into the cloth. The grit becomes imbedded in the weave and over time creates small scratches in the coatings. The scratches tend to form in a similar pattern, usually in one local area.

The scratches can be hard to see when the mirror is in the holder, but here on our lightbox, they are quite evident.

Attachments:
31 secondary scratches.jpg
31 secondary scratches.jpg [ 54.84 KiB | Viewed 23678 times ]

Author:  ScopeKing [ Wed Oct 05, 2011 1:46 am ]
Post subject:  Re: Never use a sock or a cloth bag to cover the secondary.

I've been using a Crown Royal bag for over a year. I hate to think how scratched up my secondary is.

Can you see the scratches without a lightbox?

Author:  Eric [ Wed Oct 05, 2011 11:20 am ]
Post subject:  Re: Never use a sock or a cloth bag to cover the secondary.

You can see the scratches just by lighting it up from behind with a flashlight.

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