Older C8 corrector plates/Upgrading older C8 scopes

I was recently looking at an older C8 (1980)and noticed that the
corrector plate (with special coatings) had several small pits in it.

Now I know the history of this scope and it has always been properly
stored and doesn't have a scratch on it elsewhere. Also when I have
looked through it, the images are quite good.

I guess the question I have is did this scope come with these
imperfections in the corrector plate or is this the natural progression
of time?

The only thing the owner mentioned was that years ago he had installed
a ring magnet on the center of the secondary holder to hold a solar
screen in place and that magnet had slowly disintergrated (moisture?)
and had to be removed. There is no sign of rust on any of the metal
components so I seriously doubt high humidity caused any problems that
could have affected the corrector plate.

Take a look at your corrector plate if you have an older C8 and tell me
if you see any imperfections.

Last question, this user has asked me if he would gain much from buying
a new optical tube from Celestron to place on his Ultima mount (with
PEC). What is your opinion of the quality of the new Celestron
offerings (C8) compared to the older (1980) C8 product?
Thanks for whatever advice you may have to offer.

TMT

Too_Many_Tools wrote:
I was recently looking at an older C8 (1980)and noticed that the
corrector plate (with special coatings) had several small pits in it.

Last question, this user has asked me if he would gain much from
buying
a new optical tube from Celestron to place on his Ultima mount (with
PEC). What is your opinion of the quality of the new Celestron
offerings (C8) compared to the older (1980) C8 product?
Thanks for whatever advice you may have to offer.

TMT

Hi:

Those "pits" will have no effect on performance. In fact, they may not
even _be_ "pits". Small specks of grease can look for all the world
like coating imperfections.

As for your buddy, I'm a little confused, as the Ultima (8 or 2000) was
not being made in 1980.

There is no doubt in my mind, however, that current C8s are probably
the best the company has produced.

Peace,
Rod Mollise

Hi Rod...thanks for responding, I was hoping that you would weigh in on
this.

Sorry about the confusion...the optical tube is a pristine orange one
with special coatings that was definitely purchased new in 1980...I've
seen the purchase receipt. It has been stored very carefully over the
years in climate controlled conditions...I don't think there is even
one scratch on it.

This optical tube was then mounted on a like new surplus Ultima (with
PEC) mount of early? 90's vintage. I believe the owner was trying to
have both the best of the older optics and the best of the mounts that
Celestron had produced.

The pits that I am talking about are actual physical voids in the top
surface of the corrector lens. One can actually see the depressions.
They are very small and randomly distributed across the surface....not
many of them but they are definitely there.

They seem to have no impact of the image the scope offers.

Did the earlier scopes that used plate glass? for the corrector plate
have these very small imperfections? I have not seen a large number of
Celestron scopes nor have I had the chance to view these scopes closely
over the years so that is why I am asking about them.

From what I can see, I cannot think of anything that would have caused
the pits after production (except for the tiny random pits the
corrector plate looks like new) so I have to consider that they were
there during manufacture. Are corrector plates of SCTs prone to small
defects? If they were, it is news to me but again I have not been
around alot of scopes.

The only thing post manufacture I can possibly think (and this is a
long shot) of is that ring magnet (iron based) deteriorating (due to
moisture being trapped under the lens cap - dew?) and particles of it
(rust?) lying on the corrector plate corroding the plate glass. SInce I
have known the owner for years and realize how extremely careful he is
with his equipment in use, I know that he is very careful to not trap
moisture in his equipment before storage. And there is no indication of
any other rust on the scope's metal parts so that is why I am
scratching my head on this one.

Any information you may offer is appreciated.

Also, I just LOVE your great website and your book is on my list to
buy.

Thanks,

TMT

Howdy!

Too_Many_Tools wrote:
Hi Rod...thanks for responding, I was hoping that you would weigh in
on
this.


The pits that I am talking about are actual physical voids in the top
surface of the corrector lens. One can actually see the depressions.
They are very small and randomly distributed across the
surface....not
many of them but they are definitely there.

I assume he's sure it wasn't like this as delivered? I can't think of
too many things that would cause this. Acid rain/dew left on the
corrector

They seem to have no impact of the image the scope offers.

Did the earlier scopes that used plate glass? for the corrector plate
have these very small imperfections? I have not seen a large number
of
Celestron scopes nor have I had the chance to view these scopes
closely
over the years so that is why I am asking about them.

Never noticed anything like this...but I've never gone after a
corrector with a high-power magnifier, either. ;-)

The only thing post manufacture I can possibly think (and this is a
long shot) of is that ring magnet (iron based) deteriorating (due to
moisture being trapped under the lens cap - dew?) and particles of it
(rust?) lying on the corrector plate corroding the plate glass. SInce
I
have known the owner for years and realize how extremely careful he
is
with his equipment in use, I know that he is very careful to not trap
moisture in his equipment before storage. And there is no indication
of
any other rust on the scope's metal parts so that is why I am
scratching my head on this one.

Any information you may offer is appreciated.

Also, I just LOVE your great website and your book is on my list to
buy.

Thanks!


Thanks,

TMT

Peace,
Rod Mollise

Hi,

No, the defects are visible to the naked eye.

They are definitely there and are randomly distributed.

Have you ever seen any corrector plates that have any defects visible
in them?

TMT

Don't sweat the pitted glass - unless there are a LOT of them, you'll
never know they are there. Calculate the surface area of ALL the pits
and compare that to the open aperature of the scope - hardly worth a
mention.

Gil