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Star Diagonal Service Life

Started by markvcostello3, 01/26/2010 09:44PM
Posted 01/26/2010 09:44PM | Edited 01/26/2010 09:54PM Opening Post
Hi all,

I've had an enhanced star diagonal for almost six years that I've used for about 600-900 hours. Having recalled reading a post here that enhanced star diagonals will degrade over time, I'm wondering if it's time to replace it. If its reflectivity out of the box was 98% (it's a 2004 William Optics 2" diagonal), how long would it take for it to deteriorate to a reflectivity of less than 87%?

If I have to replace it, I'll do it with a dielectric star diagonal which I understand won't deteriorate significantly over time. Is this correct?

Thanks in advance for your responses and advice.

Mark Costello
Matthews, NC

Mark Costello
Matthews, NC, USA

"I hear you're mechanically inclined. Did you ever do anything with perpetual motion?"

"Yeah, I nearly had it a couple of times."
Posted 01/26/2010 10:51PM #1
You won't notice 87%. That is not the reason to get a dielectric.

Dielectrics are cleanable without developing micro scratches, which degrade planetary contrast. If you never look at the planets, you won't see much or any difference on deep sky objects.