Sky and Telescope
$1000.00 to $1500.00 depending on options
and mobile GOTO Schmidt Cassegrain.
Schmidt Cassegrain on an Alt-Az GOTO mount with a small reflex
have been observing since I was 6, and now that I am 29 I have acquired
the financial autonomy to buy an eyepiece now and then. I would not rate
myself as an expert observer as I have been in and out of the hobby, and
as most amateurs, especially those who are married, have children and live
in urban areas, have too little quality observing time. I have two places
to observe: my garden in Northern France with 120 clear nights a year and
Mag 3.5 skies, where I just give a little glimpse when it's clear at the
moon and planets (the Orion nebula is "seeable" but a sure
disappointment) , and a place in rural, southern France with darker and
clearer skies. There I hunt galaxies and globulars which are my favorite
targets, but I only have a handful of good nights there per year. My
e-mail is email@example.com.
I have at my disposal for a couple weeks a Nexstar 5, which was second
hand, and could not resist the temptation to write you guys about it. I
have been a low-tech astronomer all the way (the highest tech scope I had
ever used was a RA-driven '79 Celestron 8, all others have been undriven)
, so I wanted to see if GOTO scopes were such a great thing. Also, as the
scope is a couple years old, this review also serves to report how these
I tested the scope with my usual Plossl and Lanthanum Eyepieces (lately I
sold a lot of my "budget" eyepieces, reducing my collection to
single figures!), and also with two Ultima eyepieces I received with the
scope. But the goal of the test was more in the mechanics than the optics.
scope was delivered to me in a JMI case (on which I won't report because I
only used it for travel once). It came with the cigarette-lighter-type
first surprise was the Schmidt corrector did not stand firmly in place. It
had a little lateral wobble. This did not prove a problem while observing,
I would star-test the corrector into place (moving it until the shadow of
the secondary was aligned with the out-of-focus star disk). Not very
elegant but totally effective. Finally I realized the corrector was
retained into place by a two-hole ring like the retaining ring inside
eyepieces, so I used a compass point to screw the ring tight (I somehow
managed not to scratch the corrector plate in the process).
Using the scope shows contrast is good, and that is obviously thanks to
serious baffling. However one will notice the inside 'Cassegrain' baffle
is very narrow, meaning you cannot use a "long-tube" Barlow
lens. My short-tube Barlow fitted well however.
tripod looks cheap, but for visual use is fine. It is the standard-issue
Chinese tripod, the same as on the EQ3-2. I am happily surprised at how
well it holds it.
is very smooth, and as a result the view does not wobble when you adjust
focus (I had an AZ mount before, by the time the vibrations had dampened
out, Jupiter had vanished out of view).
is one complaint, which is mechanical but has an effect on the seeing: the
knob has a "tick" feeling to it, and sometimes at high power you
have the feeling that you are half a tick inside or half a tick outside of
focus. On the Moon and Mars, I could achieve focus at high power, but had
to be careful to turn the knob by less than a full tick.
Back / Diagonal
1 1/4" visual back has two tightening screws, and it is a good thing
as the diagonal wobbles noticeably in its barrel. It is mildly irritating
and you have a little fear that heavier eyepieces might fall off (they do
not, but you have to be careful to tighten those screws hard). I did not
have extra diagonals at hand so I cannot say if the outside diameter of
the diagonal barrel is too small, or if the inside diameter of the visual
back is too wide. Price issues are obviously at work here.
N5 comes with a Starpointer finder (which I reviewed elsewhere), which you
use only for alignment purposes. Nothing wrong about this thing, to the
Using the Scope
scope came without a manual but it was OK. The only thing which took me a
while to get is that the arrows you must use in the menu are not the same
arrows you use to point the telescope. So for about an hour every time I
tried to change alignment stars, methods, etc, the OTA would slew up and
The first thing you do with this scope is align it. There are two
procedures : "auto align" and "2 star align". I think
the auto-align is for absolute beginners who know nothing about astronomy,
but are experts in time zones and geography. You have to put
latitude, longitude, determine the north, local time, what time zone you
are in, if you are in Daylight or Standard time... blahblah. Even if you
can automate some parameters, it's a drag. I think the 2 star alignment is
much easier: you choose in a list a star (let's say Vega: the stars are
ordered by name), slew the scope to Vega with
the hand paddle, press "align", then pick another star, like
"Arcturus", slew there and press "align", and voilą!
The longest part of the alignment procedure is the slewing between the two
alignment stars, so at most it's a two minute operation.
After a handful of objects, the alignment tends to slip out, so you can readjust.
Let's say you are looking at M27, you notice that the scope puts M27 on
the edge or even outside the field of view. You center M27 and press
"Align" to instruct the Nexstar to use M27 as a new reference
point, and everything should be better. I suspect that after a couple
years, something in the gear department must wear down, and the tracking
is not that good anymore (you are instructed not to move the scope by
hand, but someone IS going to move that tube at some time and it may
damage the gears). If some of the good people at Celestron want to react
to this they are welcome.
However the alignment, or its influence on GOTOing, is not super-sharp.
You need to put a low-power eyepiece if you want to be sure the object is
in the field. That might become a problem if you hunt faint galaxies or
small planetary nebulae. However with a 5-inch scope, you are not going to
knock down an NGC Marathon anytime soon. It looks like the instruction in
the alignment procedure that asks to point the tube roughly at horizontal
is quite critical. Maybe you should invest in one of those stackable
The GOTO has a distinct advantage from urban locations: you don't need to
know the stars, and it's a good thing as you can't see them. I saw M13 and
M92 without being able to see the
I discovered objects I had never or seldom seen, that are bright and
interesting but which I had never seen because they are out of easy
star-hopping patterns, the best example being M3.
The GOTO has the full Messier,
NGC Catalog, plenty of stars and double-stars. The double star catalog
uses common names (Mizar, 95 Her, etc...) but the star catalog uses
"proprietary" numbers. I did not bother using it, nor did I use
the GOTO to look for planets (it will ask you date, time, etc...).
there are many slewing rates (9), but I think fewer would have sufficed.
For example you can't tell the difference between speeds 4 and 5. On the
slower rates, there is an awkward feeling: when you press the button, you
hear the motors for a couple seconds, then the slewing begins. I was told
by the previous owner (who, by the way, answered promptly to my myriad
questions) that it is a backlash effect and that there is a menu in the
Autostar to adjust this. I wonder why this is not factory-programmed. The
good point is that it does not seem to affect the alignment much.
On slewing itself, there is something I hate about these paddle-operated
scopes: you never know which way it is going to move. I operate a 16"
Dobsonian and trust me, when you slew it, you feel it, and you know which
direction you are going. Here you don't have the physical feedback helping
you; and when the scope slews fast, it goes too fast for you to see which
way the stars are moving (especially faint ones). It's probably a personal
there is the tracking once you have locked onto an object. It is nothing
to write home about, but is fine for visual use. You can center (I should
write centre as I am Canadian) an object at 100x, get inside to check your
atlas or put the laundry in the dryer, get back 10 minutes later and the
object is still there. So you do not have much more to ask from this
function. On high-power planetary work, however, you will need to adjust
now and then.
single tine mount is perfect, especially with the hand paddle fitting in
the arm. For visual work, even at high power. There is nothing wrong with
the tripod, either with legs up for stand-up use or down for sit-down
my suburban home, M13 was resolved. M3, kind of. The Ring nebula is a
nebula shaped like a ring. The Dumbell nebula is shaped like a dumbell.
However the Owl Nebula is not visible from here. I have observed the same
objects with my now-departed Tak Sky 90 and the Nexstar 5 is better on
deep sky, both for resolution and light gain. I have read elsewhere that a
TV85, or some other high end refractor in that aperture range, would
outclass a C5, but I think here the N5 is slightly better than those
refractors, at least on deep-sky objects.
only planet I have had the opportunity to see is Mars, at about 18"
on the eve of its historical opposition. Very good. In the dawn sky, the
planet being only 30° above the horizon and 10° above the nearby apartment
buildings, I could see the features that the ALPO website afterwards said
I should see (to avoid the "Schiapparelli effect" and convince
myself I was seeing features that were not there, I made a sketch of what
I saw, and then compared it to the simulated wave on the website). I had
guessed there were three dark features in the south tropical region, and
they were actually . And I had not looked at Mars in years, so did not
"remember" what was to be seen.
This was done at fairly high power for such a scope. A 4mm Plossl giving
312x was the max, the atmosphere obviously the limiting factor but the
view still pleasing. Mars was gibbous and even at that power I could tell
the sunlit rim was sharp and the terminator was softer. A Barlowed 12mm
Radian showed that there was no detail to be gained past 200x, but at 312x
the view still held.
The moon was OK for a 5-inch telescope; typically the atmosphere is the
limiting factor, not the optics.
finally, I must admit that this scope has given me a liking for double
stars. I used to think double-star observing was so 30 years ago, with
people spending their money on 3" refractors and then comparing them
with 2.4"s. Well, I still think that way, because splitting the
double-double gives me nothing like an M13 rush, and I'd rather test my
telescope and observing skills on a 13th Mag. galaxy. But it also look we
are in the golden age of the 4" Apo, and thanks to the GOTO I have
taken the habit to check out doubles while the sky gets dark and the scope
cools down (I hear the veins of double-star observers everywhere popping,
and those guys jumping off their chairs, yelling: 'what! This guy is
insulting us! And then he insults double stars themselves by looking at
them during twilight, with, of all things, a thermally-unequilibrated SCT!')
Blah blah blah, so both colorful double stars such as Albireo are a treat,
and close ones like Epsilon Lyrae work well. On Epsilon you see that this
is a small scope, with a rather large Airy disk, so the Airy disks of the
pairs are merged together, but the stars themselves are clearly separated.
I am not experimented in the seeing double department so I will not
elaborate. I think seeing doubles was easier with the Tak 90, where there
was less light dispersed in the airy disks. I think.
The GOTO module is a godsend but not a miracle: you will save plenty of
time and see many more objects than before, but you will still have to do
a little panning now and then to find stuff.
Optically, this is a surprisingly good 5" telescope, considering it
is Airline-overhead-bin compatible and sells for around $1000 (looks like
if you wait your time you can have the GOTO paddle and tripod free at that
At that price, the prism diagonal with a 1.2489" barrel is a no-show
against your $250 luxo-diagonal, but you can suggest an upgrade to a
decent diagonal as a great Christmas gift.
watch out to that narrow baffle if you want to get a Barlow or any other
OTA-intruding equipment with it.
- Great scope for deep-pocketed, small-car beginners, with enough aperture
to do a little deep-sky work.
Great SECOND scope for experienced observers who want a travel scope or a
quick-out scope. I do not think one would want to step down in aperture
for portability's and GOTO's sake. It was nice to have it around but if I
only had $1000 to spend on a scope I would take something else.
Submitted by Mathiew Chauveau - firstname.lastname@example.org