8" SCT v. 11" SCT

I have an 8" Celestron SCT w/ Starbright XLT coatings, and am considering upgrading to an
11" Celestron SCT w/ Starbright XLT coatings. While I have looked through another amateur
astronomer's 11" SCT and was very impressed, that experience was at a dark sky location,
and I'm accustomed to urban skies. So I'm hesitant; how different will the 11" really be?
What more can I expect to see that I cannot see with my 8"? Any experienced responses would
be appreciated.



--

SDF Public Access UNIX System - http://sdf.lonestar.org

The one thing to remember, is an 8" compound scope (of mostly any type
note), is not technically a 8" scope due to secondary obstruction.

The 11" will show you more detail, nebulosity, fainter stars, and split
closer doubles under virtually any sky conditions, urban, suburban, and
dark sky. Naturally, aperture will truly shine, and have the advantage
under dark, transparent sky conditions.

Also to remember, the larger the aperture, generally, the longer the
cooldown period. There are ways around this. Lymax cooling fans,
setting scope up prior to an observing run, etc.

Dark sky conditions are not needed to do serious Planetary-Solar-Lunar
observation-imaging. What is needed is a steady calm atmosphere, and
equilibration of the scope.

With Solar Imaging-Observing, there probably wouldn't be much gained
between the 8"SCT, and the 11" SCT with white light filter. Mark

Unless you have a very well trained eye, the difference will be
disappointing----you are chasing small increments of "improvement". From
your 8", the next real step upwould be a 18" DOB.

Doink


"Mark D" wrote in message
...
The one thing to remember, is an 8" compound scope (of mostly any type
note), is not technically a 8" scope due to secondary obstruction.

The 11" will show you more detail, nebulosity, fainter stars, and split
closer doubles under virtually any sky conditions, urban, suburban, and
dark sky. Naturally, aperture will truly shine, and have the advantage
under dark, transparent sky conditions.

Also to remember, the larger the aperture, generally, the longer the
cooldown period. There are ways around this. Lymax cooling fans,
setting scope up prior to an observing run, etc.

Dark sky conditions are not needed to do serious Planetary-Solar-Lunar
observation-imaging. What is needed is a steady calm atmosphere, and
equilibration of the scope.

With Solar Imaging-Observing, there probably wouldn't be much gained
between the 8"SCT, and the 11" SCT with white light filter. Mark

Unless you have a very well trained eye, the difference will be
disappointing----you are chasing small increments of "improvement". From
your 8", the next real step upwould be a 18" DOB.


Upgrading from 8" to 11" aperture, assuming same quality and type of
instrument means a nearly two fold increase in light gathering and 27%
increase in resolving power, respectively. That is _quite_ significant
even to the
casual observer. Planets will be more colorful and show more detail,
the
Moon will be painfully brillliant, and DSO's will have substantially
greater
visibility. And-- you can run the magnification up to 150x higher than
with the
8"er if conditions warrant it; I'd say that's more than a "small
increment
of improvement". A longer cool-down time will be required though.

Dan Chaffee

Unless you have a very well trained eye, the difference will be
disappointing----you are chasing small increments of "improvement". From
your 8", the next real step upwould be a 18" DOB.
Doink
======================================

This statement you have made Doink I have to disagree with in part.

First off, I believe the differences would easily be seen by a rank
beginner, particularly, if each of these scopes previously mentioned sat
side by side, and I feel that the differences would not be
"disappointing" as you say. Nor, is the next real step up from an 8"
SCT, an 18" Newtonian.

I feel that in the SCT department, once one starts to go above 8" of
aperture, thats when one can start to appreciate the increase in
aperture. An 8" SCT has always left me wanting more. I've found
personally, that an 8" SCT usually just begins to resolve many globular
clusters, while the larger SCT's will resolve them quite nicely.

While as you say, small increments will be noted, and this will be
somewhat true under light polluted skies with DSO's, the difference in
planetary detail using an 8" SCT vs an 10"-11" SCT will be quite
apparent on Planetary.

Naturally, the downside becomes size, and weight with the larger SCT's.
Mark

Another Oink from Doink..... oink oink!


Doink wrote:

Unless you have a very well trained eye, the difference will be
disappointing----you are chasing small increments of "improvement". From
your 8", the next real step upwould be a 18" DOB.

Doink

"Mark D" wrote in message
...
The one thing to remember, is an 8" compound scope (of mostly any type
note), is not technically a 8" scope due to secondary obstruction.

The 11" will show you more detail, nebulosity, fainter stars, and split
closer doubles under virtually any sky conditions, urban, suburban, and
dark sky. Naturally, aperture will truly shine, and have the advantage
under dark, transparent sky conditions.

Also to remember, the larger the aperture, generally, the longer the
cooldown period. There are ways around this. Lymax cooling fans,
setting scope up prior to an observing run, etc.

Dark sky conditions are not needed to do serious Planetary-Solar-Lunar
observation-imaging. What is needed is a steady calm atmosphere, and
equilibration of the scope.

With Solar Imaging-Observing, there probably wouldn't be much gained
between the 8"SCT, and the 11" SCT with white light filter. Mark

The C11 is a heavy beast, however I believe that it is significantly lighter
than a Meade 12.

"Pierre Vandevennne" wrote in message
...
(Mark D) wrote in news:6143-4338D1DE-530@storefull-
3177.bay.webtv.net:

aperture. An 8" SCT has always left me wanting more. I've found
personally, that an 8" SCT usually just begins to resolve many globular
clusters, while the larger SCT's will resolve them quite nicely.

Can't agree more. Whereas M13 just hints that it actually contains stars
in
an 8" (my skies are poor, your mileage may vary), it definitely sparkles
in
a C11. The difference isn't as marked visually on the planets, afaic, but
that mostly is due to the fact that my site doesn't really have good
seeing
but, as soon as one uses a webcam, the difference is blatant.

If you haven't seen a C8 and a C11 side by side, I suggest you take a
look.
You might be surprised by the bulk of the C11.

This statement you have made Doink I have to disagree with in part.

First off, I believe the differences would easily be seen by a rank
beginner, particularly, if each of these scopes previously mentioned
sat
side by side, and I feel that the differences would not be
"disappointing" as you say.
-----------------

I agree, the difference between an 8 inch and an 11 inch SCT is
substantial and the difference is clearly noticeable. The 11 incher
gathers about 90% more light and has potentially about 40% better
resolution. Combine these two, planetary views will be brighter and
sharper and those DSOs will be brigher and the fainter ones will be
more evident.

Of course one need not stick with the SCT design when upgrading. That
2800 mm focal length of the C-11 can start constricting things,
narrowing the field of view. Before upgrading, I would suggest taking
a gander through a Newtonian or two. My first scope was an Orange
Tube C-8 and I did have some good times with it but I do much prefer
the simplicity and comparatively fast focal ratios of the Newtonian. A
low power richfield view in a 12.5 inch scope is a real thrill.

jon

"Zane" wrote

On Mon, 26 Sep 2005 18:04:39 -0700, "Doink"
wrote:

Unless you have a very well trained eye, the difference will be
disappointing----you are chasing small increments of "improvement".

(snip)

In only fairly dark skies, that "small increment" means you can see
nearly twice as many stars.

Zane, thank you for your comment. Newbies need to know what's right from
wrong. The difference between my 6" and 8" Newtonians, used in the same
location, is substantial.

Howard Lester

I found a huge improvement in quality between the C8 and C11.
Perhaps there is less variation in the C11.

If you want to see more deep sky objects a 10" or 12" dob makes more sense.
And the wider field of view will allow objects to be found much more
easily.

JD