Celestron XLT Coatings on Celestron CATS

I have a C9.25 that is perfectly collimated and provided excellent planetary
views and images, however this scope does not have the XLT coatings. I am
wondering how much is to be gained in performance by the XLT coatings. I
have seen many of these scopes flipped on Astromart and am considering doing
it myself, taking a small loss, and purchasing another C9.25 OTA with XLT
coatings and possibly carbon fiber. What does everyone think? Has anyone
ever done a side-by-side comparison of a Celestron with XLT to a Celestron
without XLT? What is the difference visually, if any?

Thanks,

-mij

On Tue, 13 Sep 2005 09:38:51 -0700, "Mij Adyaw"
wrote:

I have a C9.25 that is perfectly collimated and provided excellent planetary
views and images, however this scope does not have the XLT coatings. I am
wondering how much is to be gained in performance by the XLT coatings.

If you are primarily doing planetary observations, then don't bother.
There is a school of thought that the enhanced mirror coatings
actually scatter more light and reduce contrast.

If you are into deep sky astrophotography, then there is some benefit
in the increased light transmission of XLT coatings to reduce exposure
times.

---
Michael McCulloch

If you're happy with the current C9.25, you are unlikely to be that much
happier with the XLT version that it's worth the trouble.

But that's primarily a guess based on the difference between a 9" scope and
an 8" scope, which isn't all that significant, although noticeable in a side
by side.

If you have a C9.25 and you want brighter images, it's time to look at a
C11?

-Stephen

"Mij Adyaw" wrote in message
news:zgDVe.88107$Ji4.57349@fed1read03...
I have a C9.25 that is perfectly collimated and provided excellent
planetary views and images, however this scope does not have the XLT
coatings. I am wondering how much is to be gained in performance by the XLT
coatings. I have seen many of these scopes flipped on Astromart and am
considering doing it myself, taking a small loss, and purchasing another
C9.25 OTA with XLT coatings and possibly carbon fiber. What does everyone
think? Has anyone ever done a side-by-side comparison of a Celestron with
XLT to a Celestron without XLT? What is the difference visually, if any?

Thanks,

-mij

Howdy Mij, I can't honestly comment one what differences you'd see
between the two scopes, but if you perhaps live somewhere, where there
are large temp swings/dips during the night, the Carbon Fiber OTA may be
more of a hindrance, than a help.

I would assume the differences would be very minor. You could probably
accomplish a somewhat similar improvement in performance by covering the
interior of your OTA with a sheet of Protostar Flocking Paper.

To add what I've written above, I also don't believe any of the
Celestron OTAs use BK-7 for a corrector material, but instead use some
type of Float Glass.

As another poster noted, you'd probably gain more of an improvement in
planetary detail/resolution (And Deep Sky) by switching to the C-11 OTA.
That's of course if you have a mount that can adequately handle the
added weight? Mark

Mij Adyaw wrote:
I have a C9.25 that is perfectly collimated and provided excellent planetary
views and images, however this scope does not have the XLT coatings. I am
wondering how much is to be gained in performance by the XLT coatings. I
have seen many of these scopes flipped on Astromart and am considering doing
it myself, taking a small loss, and purchasing another C9.25 OTA with XLT
coatings and possibly carbon fiber. What does everyone think? Has anyone
ever done a side-by-side comparison of a Celestron with XLT to a Celestron
without XLT? What is the difference visually, if any?


Hi Jim:

There is a noticeable difference in object brightness. Not a tremendous
improvement, but you can tell the difference when you've got an XLT
scope side by side with a StarBright scope. Would I get rid of my non
XLT C8 OTAs for XLTs? Probably not, but my next scope will have these
coatings. If for no other reason than getting the top-of-the line
coatings always improves resale value. Ask the folks who scrimpted and
bought non-StarBright OTAs back in the 80s to save a few bucks.

Peace,
Rod Mollise