ETX125 vs Nexstar 5i

I am planning to buy a computer telescope and still can't make decision
between ETX125 and Nexstar 5i. I heard from many newsgroup and users in my
place that Nexstar 5i has better optic. But I am attracted by the autostar
system and is ability to upgrade by myself. Anyone can give me comment about
these 2 telescopes and in my place Nexstar 5i is about US$200 more expenisve
than ETX125.
Thank you very much!!
Clear skies~~

"Carlos Moreno" wrote in message
.. .
Alfee wrote:
I am planning to buy a computer telescope and still can't make decision
between ETX125 and Nexstar 5i.

I think the decision can not be more obvious in this particular case:
Go for the MEADE ETX125, with UHTC coatings, for a better optic.


The 5" Celestron SCTs have a very good reputation regarding optical quality.
I also have a much higher opinion of Celestron's quality control.

Check the images of both, you'll notice that the Nextar has an arm
that supports the optical tube by one side only, whereas the MEADE
has a *fork* support that grabs the optical tube at two points.
(in fact, the Nexstar GPS series of Celestron do have a fork support)

Frankly, I don't know what the hell were Celestron engineers thinking
when they did that; I'm no mechanical engineer, but the design of
that support is, IMO, plain retarded.


As long as the single support is strong enough, it doesn't matter.
Additionally, the Celestron 5" SCT OTA is much lighter than a comparable
ETX. Can you point me to any report that shows the Nexstar 5i has stability
problems ?
In comparison, any telescope on a German Equatorial mount has exactly the
same single support.


Just imagine driving through a bridge that has supporting pillars
only on one side of the way...


???

Jeroen.


HTH,

Carlos
--

Frankly, I don't know what the hell were Celestron engineers thinking
when they did that; I'm no mechanical engineer, but the design of
that support is, IMO, plain retarded.

Just imagine driving through a bridge that has supporting pillars
only on one side of the way...


I am a mechanical engineer.....

Many bridges are supported only at one end, is called a cantilever bridge. Not
a big problem if designed properly, look around and you will see cantilevers in
many situations.

GEMS are balanced cantilevers, the wheels on your car are cantilevered, so
while you are complaining about the NextStar 5 design, I would guess you are
plenty comfortable with the way the front wheels of your car are only supported
from one side.......

This is about design and optimization. One advantage the Next5 design has over
the Meade ETX design is that it does require a flip mirror and thus one is not
stuck with a fixed viewing position.

Something to think about....

Jon

Jeroen Smaal wrote:

The 5" Celestron SCTs have a very good reputation regarding optical quality.
I also have a much higher opinion of Celestron's quality control.

Maybe... But seeing such an unsound engineering design kind of makes
me lose all faith in their technical competence.

Frankly, I don't know what the hell were Celestron engineers thinking
when they did that; I'm no mechanical engineer, but the design of
that support is, IMO, plain retarded.

As long as the single support is strong enough, it doesn't matter.

I'm not sure it doesn't matter. It matters less than if it was a
heavy unit, but I wouldn't say it doesn't matter.

In comparison, any telescope on a German Equatorial mount has exactly the
same single support.

Not at all!!! The GEM has support in the center of mass (roughly),
and the support can be wide enough to behave close to a dual-point
support (yes, never as solid as a fork support, but not like a
single point support)

Just imagine driving through a bridge that has supporting pillars
only on one side of the way...

???

This is how bridges a

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(cars would move in the direction perpendicular to the screen)


Here's how Celstron (well, the engineers that designed the support
for the Nextar i's) would have made bridges:


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Here's what could be the equivalent of a German Equatorial mount
with the bridge analogy:

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The GEM is not as good as the dual-point support, but not nearly
as unsound as the one-point-on-the-side support.

Carlos
--

"Carlos Moreno" wrote in message
.. .

Just imagine driving through a bridge that has supporting pillars
only on one side of the way...

Imagine a motorcycle with a single arm to hold the rear wheel. g

"Carlos Moreno" wrote in message
.. .
Alfee wrote:
I am planning to buy a computer telescope and still can't make decision
between ETX125 and Nexstar 5i.

I think the decision can not be more obvious in this particular case:
Go for the MEADE ETX125, with UHTC coatings, for a better optic.

Check the images of both, you'll notice that the Nextar has an arm
that supports the optical tube by one side only, whereas the MEADE
has a *fork* support that grabs the optical tube at two points.
(in fact, the Nexstar GPS series of Celestron do have a fork support)

Frankly, I don't know what the hell were Celestron engineers thinking
when they did that; I'm no mechanical engineer, but the design of
that support is, IMO, plain retarded.

Just imagine driving through a bridge that has supporting pillars
only on one side of the way...
Imagine a fork mount, with only a bearing below the tube to support the
assembly....
(When running on a wedge, the bottom bearing has to work a lot harder than
the one on the arm).
The support on the 5i, works OK. It requires that the bearing exhibit
significantly more rigidity than on a fork with bearings each side of the
tube, but actually removes one other engineering problem (of aligning the
two bearings, which on larger scopes can definately be a problem)...

Best Wishes

I think the decision can not be more obvious in this particular case:
Go for the MEADE ETX125, with UHTC coatings, for a better optic.

Hi:

I wouldnt' choose on this basis. I've used a 125 fairly extensively, and like
it. BUT...

I do think the NS5 is superior for several reasons:

--More robust build...the NS has metal where it counts.

--Easier to use, more user-friendly computer/hand paddle.

--Standard SCT back that will take many if not all accessories developed for
use with SCTs over the years.

The computer on the Meade IS very nice and full featured, and Meade has taken
steps to improve the scope's bearings and strengthen the fork, but the NS still
comes out ahead in my opinion. The C5's typically good optics pretty much match
those of the MCT at a smaller focal ratio to boot.


Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

Maybe... But seeing such an unsound engineering design kind of makes
me lose all faith in their technical competence.

Hi:

Maybe so...but in practice, the single arm fork works more than well enough,
just as it did on those high-toned Quantum Maksutovs of yore! ;-)

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

Carlos Moreno wrote:
Alfee wrote:

I am planning to buy a computer telescope and still can't make decision
between ETX125 and Nexstar 5i.


I think the decision can not be more obvious in this particular case:
Go for the MEADE ETX125, with UHTC coatings, for a better optic.

Check the images of both, you'll notice that the Nextar has an arm
that supports the optical tube by one side only, whereas the MEADE
has a *fork* support that grabs the optical tube at two points.
(in fact, the Nexstar GPS series of Celestron do have a fork support)

Frankly, I don't know what the hell were Celestron engineers thinking
when they did that; I'm no mechanical engineer, but the design of
that support is, IMO, plain retarded.

The C5+ I have is also a "half-fork" mount and works fine. I have an
ETX-90EC and the mechanical design of my C5+ mount is far superior. I
suspect that is true for the NS 5i also.

The C5+ is the same optics they use the NS 5i and, with Starbright
coatings, really outstanding. And I believe you can now buy the NS 5i
with the optional XLT coatings.

Phil

alfee wrote:

Thank you all for the valuable comments! So I think Nexstar 5i can have as
least the same stability as ETX125. But are they (i mean both etx and
nexstar) stable enough for me to take photo of deep sky objects? Is it
possible for long exposure?

I think this is the same with both the NS and the ETX: if you want to
use them for long exposure, you need a wedge that "converts" the
mount into a polar aligned equatorial one.

The telescopes are able to track an object's position, but not the
object's orientation -- in other words, the object will "rotate" in
the image plane, making it impossible to take a long-exposure shot.
(actually, it depends on the object's position, but generally speaking,
the problem is there)

Not sure if wedges are available for either the MEADE or the Celestron,
or if their optical quality is enough for such application (I would
guess that yes -- maybe for objects brighter than 9 or 10, I would
estimate). You could check their web sites for the available
accessories and to see if they mention long-exposure photo as one
of the applications.

HTH,

Carlos
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