Nexstar 5i vs 8i. . .

I've decided to create a new thread for this topic as it was a little off
topic in the "Local Shops" thread.

The down and dirty is that I am waiting on a [Celestron] Nexstar 5i whose
price just increased on me. It got me looking at the 8i a little more and I
realized I could get an 8i with Goto & Tripod (with Starbright non XLT
coatings) for $1199.

While this might sound like a "No Brainer" to most ("Go fer the 8!") I do
have some portability concerns.

I want to be able to take this camping with us which means it needs to be
stored in a reasonably sized case (the 8i case is pretty large).

If there is little to move/store, I am more apt to use it frequently. I am
assuming the setup time for 5i and 8i are basically the same.

Is there anyone out there with an 8i that wishes they went with something a
little smaller?

How about people with the 5i realizing that the difference in size between
the 8 & 5 is "negligible"?

I am quite sure that if I go with the 8i AND it meets my portability
requirement, I will probably have purchased the last scope for quite some
time.

I am a little worried about purchasing the 5i and wishing I'd gotten the 8i
in about 6 - 12 mos. . .

Thanks in advance. . .

-=SkyHawke=-

On paper, the 8i would make a big difference...


"SkyHawke" wrote in message
news:X6x5b.259792$cF.81845@rwcrnsc53...
I've decided to create a new thread for this topic as it was a little off
topic in the "Local Shops" thread.

The down and dirty is that I am waiting on a [Celestron] Nexstar 5i whose
price just increased on me. It got me looking at the 8i a little more and
I
realized I could get an 8i with Goto & Tripod (with Starbright non XLT
coatings) for $1199.

While this might sound like a "No Brainer" to most ("Go fer the 8!") I do
have some portability concerns.

I want to be able to take this camping with us which means it needs to be
stored in a reasonably sized case (the 8i case is pretty large).

If there is little to move/store, I am more apt to use it frequently. I
am
assuming the setup time for 5i and 8i are basically the same.

Is there anyone out there with an 8i that wishes they went with something
a
little smaller?

How about people with the 5i realizing that the difference in size between
the 8 & 5 is "negligible"?

I am quite sure that if I go with the 8i AND it meets my portability
requirement, I will probably have purchased the last scope for quite some
time.

I am a little worried about purchasing the 5i and wishing I'd gotten the
8i
in about 6 - 12 mos. . .

Thanks in advance. . .

-=SkyHawke=-

For what it's worth, I have a Celestron 5 (vintage 1980) and a Meade 8-inch.
I have owned a NexStar 5 (non-i) and had to sell it due to financial
constraints.

My Celestron 5 gets a *lot* of use, especially when portability is involved.
Not only is the telescope a lot more portable, so is the tripod.

For years it was my only telescope and I saw all the Messier objects with
it.

Steve:

If it is portability you are concerned with, go with the 5i. It is
very portable, the stock tripod is light but stable, and the goto
accuracy and tracking is good, especially if you spend time with the
scope and properly align and set backlash.

You will, eventually, want a larger scope. But, you are correct, they
are bulkier and heavier. That is why I purchased the 5i. I have to
drag a scope over 100' to set up, and an 8" with counterweights,
tripod, and doodads takes more time to set up and cool than a 5i. The
5i can be carried with one hand, assembled. Don't get me wrong, having
an 8" is also worth it, and the difference in views is noticable. But,
the 5i is no slouch either, even in dark skies. I had mine in Central
Oregon at Kah Nee Tah several weeks ago, and it's views were
absolutely great.

I have an LX90 and absolutely love that scope. It has a beefy tripod
and worm gears, and is a cut above an 8i. Mind you, the 8i stock
tripod is the same as the 5i, and that tripod is not stable enough for
the 8i, so you would have to upgrade. Furthermore, don't bother with
the 8i - at that point, go with a better quality 8" scope...like an
N8GPS or LX90...you would not regret it.

Don

"Michael A. Covington" wrote in message ...
For what it's worth, I have a Celestron 5 (vintage 1980) and a Meade 8-inch.
I have owned a NexStar 5 (non-i) and had to sell it due to financial
constraints.

My Celestron 5 gets a *lot* of use, especially when portability is involved.
Not only is the telescope a lot more portable, so is the tripod.

For years it was my only telescope and I saw all the Messier objects with
it.

On Thu, 04 Sep 2003 02:06:47 GMT, "SkyHawke" ...reflected:

I've decided to create a new thread for this topic as it was a little off
topic in the "Local Shops" thread.

The down and dirty is that I am waiting on a [Celestron] Nexstar 5i whose
price just increased on me. It got me looking at the 8i a little more and I
realized I could get an 8i with Goto & Tripod (with Starbright non XLT
coatings) for $1199.

While this might sound like a "No Brainer" to most ("Go fer the 8!") I do
have some portability concerns.

snip

There's one other thing about the 5" SCT that you should
know. Notice that in the advertisements the telescope's corrector
plate is rarely, if ever, visible. It's always pointing away, and with very
good reason, as the secondary obstruction is, comparatively...HUGE!

ENORMOUS!

COLOSSAL!

STUPENDOUS!

Why, I'm beginning to sound like a carnival hawker.


Eventually, I'm going to get AT LEAST an 8" SCT; maybe
even a 9.25" or 10", depending. Then I'll have one fine example
of each of the three major types.

Of course, a modestly-dark dark-sky site is just right outside my door.

Alan

"Alan W. Craft" wrote in message
...

There's one other thing about the 5" SCT that you should
know. Notice that in the advertisements the telescope's corrector
plate is rarely, if ever, visible. It's always pointing away, and with
very
good reason, as the secondary obstruction is, comparatively...HUGE!


If you have obstruction-phobia, this will alarm you. It's about 1.8 inches
(vs. 5 inches aperture) -- that is, about 36% of the diameter, or 13% of the
area.

But why should this be objectionable?

Light loss? Well, the C5 still has the same effective aperture as an
unobstructed 4.6-inch. The 13% light loss costs you 0.15 of a magnitude in
light grasp.

Diffraction? Well, that works both ways. It slightly reduces contrast on
certain types of planetary detail (so that the C5 is comparable to perhaps a
3.5-inch apo refractor), but it improves the view of double stars. My C5 is
very good with double stars.

"Light scatter" or "Loss of contrast"? None, apart from what I just
mentioned. Those are widespread misconceptions about the effect of central
obstructions.

In particular, people sometimes say, "A 36% (diameter) obstruction costs you
36% of the contrast." It does nothing of the sort. The obstruction
*removes* some of the light; it doesn't scatter it randomly over the image!

See my computerized telescope book for more about this, including computer
simulations.


P.S. By "C5" I mean Celestron 5, the same optics as the NexStar 5i.

--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

On Sat, 6 Sep 2003 15:23:19 -0400, "Michael A. Covington" ...reflected:


"Alan W. Craft" wrote in message
.. .

There's one other thing about the 5" SCT that you should
know. Notice that in the advertisements the telescope's corrector
plate is rarely, if ever, visible. It's always pointing away, and with
very
good reason, as the secondary obstruction is, comparatively...HUGE!


If you have obstruction-phobia...

In that Parks has yet to determine the size of the secondary within
my 8" f/5, and based upon measurements in conjunction with a yet-to-
be-delivered JMI NGF-DX3 focuser...

....indeed I do.

...this will alarm you. It's about 1.8 inches(vs. 5 inches aperture) -- that is,
about 36% of the diameter, or 13% of the area.

I must admit; that's pretty alarming.

But why should this be objectionable?

Light loss? Well, the C5 still has the same effective aperture as an
unobstructed 4.6-inch. The 13% light loss costs you 0.15 of a magnitude in
light grasp.

Diffraction? Well, that works both ways. It slightly reduces contrast on
certain types of planetary detail (so that the C5 is comparable to perhaps a
3.5-inch apo refractor), but it improves the view of double stars. My C5 is
very good with double stars.

"Light scatter" or "Loss of contrast"? None, apart from what I just
mentioned. Those are widespread misconceptions about the effect of central
obstructions.

In particular, people sometimes say, "A 36% (diameter) obstruction costs you
36% of the contrast." It does nothing of the sort. The obstruction
*removes* some of the light; it doesn't scatter it randomly over the image!

See my computerized telescope book for more about this, including computer
simulations.


P.S. By "C5" I mean Celestron 5, the same optics as the NexStar 5i.

I took long, hard looks at C5's, and back in the days when $1000+
telescopes were out of my reach. For that matter, so were the $500-...

If you walked up to a display table at an astronomy convention,
and there was a brand-new Celestron C5 optical tube assembly on
one side, and an equally pristine Meade ETX-125 optical tube
assembly on the other, which one would you grab up and
run with, when no one was looking of course, and why?

Alan

"Alan W. Craft" wrote in message
...
On Sat, 6 Sep 2003 15:23:19 -0400, "Michael A. Covington"
...reflected:

If you walked up to a display table at an astronomy convention,
and there was a brand-new Celestron C5 optical tube assembly on
one side, and an equally pristine Meade ETX-125 optical tube
assembly on the other, which one would you grab up and
run with, when no one was looking of course, and why?

Actually, the Orion 5-inch Maksutov

But the C5 cools down very quickly, which is also an advantage for
grab-and-go observing.

And my impression -- admittedly unconfirmed -- is that the NexStar 5 mount
is smoother than the ETX-125.

(Admittedly, one thing I like about my old C5 is that, with two fork arms,
it is very sturdily mounted.)

I wish Meade would make a 5- or 6-inch version of the LX90.

On Sun, 7 Sep 2003 14:06:56 -0400, "Michael A. Covington" ...reflected:


"Alan W. Craft" wrote in message
.. .
On Sat, 6 Sep 2003 15:23:19 -0400, "Michael A. Covington"
...reflected:

If you walked up to a display table at an astronomy convention,
and there was a brand-new Celestron C5 optical tube assembly on
one side, and an equally pristine Meade ETX-125 optical tube
assembly on the other, which one would you grab up and
run with, when no one was looking of course, and why?

Actually, the Orion 5-inch Maksutov

I've looked at that one, too, and have actually envisioned
entering my card info on the webpage...

I wonder where it's made...Taiwan(formerly Formosa)...mainland
China; certainly not in Japan.

But the C5 cools down very quickly, which is also an advantage for
grab-and-go observing.

And my impression -- admittedly unconfirmed -- is that the NexStar 5 mount
is smoother than the ETX-125.

I may very well end up getting one of those 5" xxx-Cassegrains,
and primarily as a spotting scope, but I haven't decided on a suitable
mount, that is, whether to get one with the mount already included,
or purchased separately.

(Admittedly, one thing I like about my old C5 is that, with two fork arms,
it is very sturdily mounted.)

Yes, fancy, they used to come that way, that is, the way they should
come still.

I wish Meade would make a 5- or 6-inch version of the LX90.

Ah, but not with that comparatively ENORMOUS secondary obstruction.

I wish fluorite blanks and master opticians were cheap and plentiful...

Well, we all have our dreams.

Alan

"Chuck Scappaticci" wrote in message
et...
Alan, I think a lot of folks put down the importance of central
obstruction
because our favorite commercial scopes (SCTs) tend to have relatively
large
(33%) ones. I loved my Ultima 9.25 and my current N11, but would give
up
some aperture to have a 9.25 with a 25% central obstruction. Based on
everything I've read and the true experts who make state-of-the art
scopes,
a large central obstruction (greater than somewhere between 25%
significantly reduces contrast compared to an unobstructed scope). Is it
worth the tradeoff to have larger less portable OTAs with a longer focal
length for the additional contrast? It's a personal decision.

"Reduces contrast" is misleading. It shifts energy from the central disc to
the diffraction rings. This only affects the contrast of details of a
certain size. As I said, it impairs the view of planetary detail but
improves the view of double stars.