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Classical vs XLT Coatings

Started by mte1955, 05/15/2009 11:13AM
Posted 05/15/2009 11:13AM Opening Post
What is the difference in brightness using a C8 and what would this mean at the eyepiece?
Posted 05/15/2009 09:06PM | Edited 05/15/2009 09:16PM #1
You might find this interesting. It does NOT answer your question but does show that the difference between the XLT and standard Starbright is 16%.

http://www.analyticalsci.com/Astronomy/Telescopes/imagesc/StarBright%20XLT/StarBright%20XLT.htm

And here's a counter view:

http://sci.tech-archive.net/Archive/sci.astro.amateur/2007-11/msg00785.html
Posted 05/17/2009 06:14AM #2
Michael,

I had the same question a few years ago and received conflicting answers. The folks with Starbright coated scopes liked those better, those with XLT would not have it any other way. Others pointed me to comparisons done under lab conditions. Having no clear direction I set out to compare the coatings and formulate my own opinion. Over the past three or four years I have owned identical apperture SCTs with Sb and XLT optics. I did side by side tests from my backyard but was too lazy to drag two sets of mounts and scopes when I traveled to the Everglades for darker skies. What follows below are my own findings.

I can't see a difference in object brightness or see any deeper from my mag 3.5 location under casual observation. However, under semi-dark skies (mag 4.5 - 5) I was able to see fainter stars around the Ring nebula. Will not comment on the contrast and visibility of deep sky objects since I did not have the scopes side by side making my comments highly subjective.

One big plus of the XLT compared to the Starbright is color rendition. With XLT coatings Jupiter is pure white, just like in my AP140 refractor. With the Starbright coatings is has a yellowish tint.

I ended up with a C8 and C14. Both with XLT optics and both have superb optics. As most Celestrons I have owned, independent of coating type.

If I was in the market for a Celestron SCT and planetary observation was my primary target or had access to dark skies, XLT would be my ONLY choice.

Regards,

Angel