A New Addition To My Telescope Family
Above you see a new addition to my telescope Astro-Weapon Arsenal: a
NexStar 5 SE Telescope. I obtained the used Celestron from an egroup friend
who used it for a year or so to make some incredible drawings. Check
out this link to see his Astro Sketching
I obtained the used telescope and the sturdy tripod it comes with. You can
see the hand controller attached to the side of the NexStar telescope mount.
The controller easily lifts off of the mount for convenient user access.
The NexStar telescope in this image is shown in the alt-azimuth mode. In
this mode, the internal computer uses both azimuth and elevation motors to
guide the telescope. It has a number of alignment procedures from which you can
choose, and once aligned, you can just select a target with the hand controller
and the telescope will move to the target. Alignment is considerably helped if
you first level the tripod. On this model, there is a bubble level on the
accessory tray. It seems quite sufficient for leveling the tripod.
I haven't used all of the NexStar alignment methods yet, but I've found that
one called the Auto Two Star Align works very nicely. On a few
occasions I've gone out to view Jupiter before stars were visible, so I clearly
couldn't use any star alignment procedure. Fortunately, the NexStar also has a
solar system alignment option where you can pick any planet, the moon, or the
sun (with proper filter) on which to align. Thus I was able to select Jupiter
for the alignment, and then view it with full tracking.
To be honest, I've had to do some web searching to learn about some aspects
of the telescope that I thought were kind of glossed over in the NexStar
manual. If you have one of these telescopes or are thinking about getting one,
you might want to consider the The
NexStar User's Guide. It may well help short circuit most of those web
searches for helpful tidbits of information. The NexStar 5 SE is a wonderful
telescope, but may be quite different than you're used to. It was for me. And a
guide like this may be well worth the small cost.
How Is The NexStar Like - And Not Like - My ETX 90?
My only previous experience with a Cassegrain telescope
was with my Meade ETX 90, shown above. It is the old model, with no computer
enhancement, just a simple clock drive motor in the base. I usually use it on a
solid pipe tripod, but
the ETX is shown here with its table-top legs.
At first glance, the NexStar and ETX telescopes (aside from color) look
similar, with very short barrels and the eyepiece at the rear. But they are
different in many ways. The Meade ETX 90 is a Maksutov Cassegrain which uses
all spherical optics, and has a thick, meniscus corrector lens on the front. It
has a built-in star-diagonal mirror to allow the eyepiece to be placed in a
port that is conveniently placed for viewing.
The Celestron NexStar is a Schmidt Cassegrain (often called an SCT), which
uses a spherical primary mirror, and a nearly flat looking aspheric corrector
plate. It has no built-in star diagonal, but uses a conventional star-diagonal
inserted into the rear of the telescope. And, of course, the NexStar 5SE is a
five inch diameter telescope, while the ETX 90 is a 3.5 inch.
Above you can see the NexStar 5SE from a different view. Here you can see
the corrector plate and the secondary mirror support attached to the corrector
plate. With the f/10 optical system of the NexStar, you can see that the
secondary is fairly large, about 40% the size of the primary.
In this image you can also see the large knob that attaches the telescope to
the mount. A few turns of this and the telescope easily un-mounts. The telescope
has a mounting rail along its side that slides into position on the single-arm
I can attest, by the way, to the handiness of the single-arm mount of the
NexStar. My ETX 90, as shown in its image, has a fork mount. The mount is
quite sturdy, but when I want to view something to the north, the eyepiece
is on the bottom of the scope and very inconveniently positioned for viewing.
The alt-azimuth mode of the NexStar single-arm mount points as easily and
comfortably north as it does in any other direction. Far more usable than the
ETX fork mount, or any equatorial aligned fork mount. The tripod and single-arm
mount of the NexStar seem quite sturdy, and I only have one criticism. When
I touch the focus knob, it intrudes a bit of vibration, so I have to make
small adjustments and take my hand off to see the effect. But the vibrations
damp immediately, and when tracking the image is perfectly steady.
Adjusting To A Computerized Telescope
I've had to adjust to the idea of a computer controlled telescope. None of
my other telescopes are computer controlled. In the past I oftened used a
calculator program to aid in pointing my telescopes, and being manual, all can
be quickly and easily moved from position to position by hand. Now, for those
non-computerized telescopes, I use my cell phone and the Star Pointer utility.
It helps me easily point any telescope to a wide selection of targets, whether
the telescope is alt-az or equatorial mounted, as long as the telescope has
But the NexStar must be moved from target to target either with the up/down
left/right keys of the hand controller, or by selecting a target with the
controller. Then I must be patient as the motors whir to the new position.
The motors have several speeds, however, and at max slewing speed only a few
(or few tens) of seconds get the telescope to a new position. And I've found
that if I've correctly entered my position and time into the controller, the
NexStar 5SE is very good at landing on selected targets. I may be able to move
my other telescopes quickly by hand, but even with calculator assist I
sometimes have to do a bit of searching to find my target. Usually that's
because I misread the setting circles. Not a problem with the NexStar. With a
good alignment, searching or reading setting circles isn't necessary.
You Can Easily Align The NexStar Secondary
The previous owner of my NexStar installed handy thumb knobs for collimating
the secondary, as shown above. These handy collimation screws are Bobs
Knobs Celestron 5" SCT f/10 Collimation Knobs Metric Secondary C5MET, and they definitely make collimation easier. A
snap, in fact.
I consider the ability to tweak the collimation of the NexStar a real plus.
And with the knobs, it takes only a few minutes to swing over to a bright star,
defocus, and get the collimation to near perfect. It's much easier than
collimating my Newtonian.
For comparison, above you can see an image of the front end of my ETX 90
Maksutov. The secondary on the Maksutov is just a silvered spot on the back of
the corrector plate. As the ETX is an f/13.8 system, the secondary is a bit
smaller by proportion to the NexStar, being a bit over 30% the size of the
primary. But you'll notice no knobs or screws of any kind associated with the
secondary. The only way to adjust the collimation of the Maksutov is to pull
off the entire back of the telescope and fiddle with the collimation of the
primary itself -- and no, I've not done that nor do I intend to. As to that,
however, the Maksutov design of the ETX rarely needs collimation.
You may notice, in the first ETX 90 image, that the fork mount is tilted.
My older model ETX, with only a single motor in the base, must be in
equatorial mode for the clock drive to work. The NexStar, with two
motors, operates perfectly well, and more conveniently, in alt-azimuth mode.
But, if I want to take long exposure (several minutes) astro photographs with
the NexStar (and I do), I must be able to use the NexStar in equatorial mode
(and -- I can).
For Astrophotography, The NexStar Goes Equatorial
Above you see the NexStar 5SE in equatorial mode. Notice that the entire
single arm mount is tilted, and at left there is a rod that extends and locks
in place to accommodate any Latitude. The base doesn't happen to rotate to help
in alignment on Polaris (you have to move the tripod), but adjusting for
Latitude is rather easy. The NexStar controller has a equatorial alignment
mode, and the telescope can operate in the equatorial position. While the drive
isn't accurate enough to take unguided long exposures, it is quite possible to
take a sequence of shorter photos and stack them.
Can You Do Astro-photography In Alt-Az Mode?
The short answer is yes, but with qualifications. The telescope is
most native in its altazimuth mode, and alignment in this mode is rather
easy. In this mode, however, as the telescope tracks with its two motors,
the field of view rotates. The rotational rate depends upon the users
latitude, and the azimuth and elevation of the target. Exposures in this
mode must be short, perhaps 20 to 40 seconds, with the dependencies in mind.
Still, it is possible. Below is a May 2016 image of Mars near the peak of
the 2016 opposition. It was taken using the NexStar in Alt-Az mode, with a 2.5x
Barlow projecting into a Celestron NexImage
web cam. The resulting image is a stack of about 60 images (frames from a
Mars, May 2016, NexStar 5SE
During the 2016 opposition, Mars was about 18 arc-seconds in apparent size.
When I first processed this image with my home-grown stacker program, I was
disappointed. It seemed that only darkening at the poles was visible. But I
noticed that the
smudges just left of the pole darkening to the bottom
right of the image showed in most processed pictures. In fact, the right smudge
is Granicus Valles region, and the left is the Phylegra Dorsa
region, the two bracketing the great volcano far too small be captured by the
NexStar, Ellysium Mons. Actually details themselves subtle enough that
they are difficult to see, but the NexStar picked them up.
Below you see the same image with some reference labels for the
Another effort the same night in May, 2016 was Jupiter, and as luck would
have it, the GRS was visible. Below is that effort. As with the Mars effort, at
first examination I was a bit disappointed, but I did see that some structure
was visible in the SEB just next to the GRS. Hopefully, my next
effort will do better. As with the Mars effort, the Jupiter image was
produced with around 60 stacked frames.
Jupiter, May 2016, NexStar 5SE
On the moon, the views through the NexStar 5SE are stupendous. You can use
the following image of the Lunar Apennine mountains as a guide. This image was
taken in June of 2016 through the NexStar 5Se using the NexImage camera. This image is the stack of about 100 frames. Talk about lunar details. You can see
more images taken with the NexStar 5SE at
NexStar 5SE Astrophotos.
Lunar Apennine Mountains, NexStar 5SE
As the title of this section says, these pics were taken with the telescope
in Alt-Az mode. It appears that if you keep to exposures of 30 seconds or less
(or movies that extend 30 seconds or less), you can get pretty nice planetary
images if you stack frames. Figure on stacking 30 or more frames (up to 200 or
so) to get best results. You can read more about stacking frames at the Celestron NexImage
My Few NexStar Woes
The only issues I've had so far with using the NexStar are learning how to
best use the AC adapter and accidentally bumping one of the tripod legs when
I move around the telescope. Of course, bumping a tripod leg messes up
I certainly recommend getting an AC adapter, because if you happen to go
for a NexStar, you'll find that it will only operate on 8 Alkaline batteries
for a couple of hours.
I started out using the NexStar exclusively on the AC adapter -- with no
batteries in the mount at all. But I found that when I did that, at least a
couple times in an observing session the telescope would basically lock up.
Apparently the computer either momentarily lost contact with the motors (an
error would show up on the hand controller display), or the controller would
blink off. As with kicking a tripod leg, this unhappy event always necessitates
As I experimented with the mount to determine the source of the glitches, I
determined that the power switch was often making poor contact. Eventually I
went to the Celestron
Spare Parts page and ordered a new switch. Since replacing that, I've had
no more problems with the AC adapter powered telescope.
A Handy Hint For The Hand Controller
One thing the previous owner had found out is that when observing, there
needs to be some place to conveniently place the hand controller. As the
photographs illustrate, the controller does fit nicely into the side of the
single-arm mount. But in the dark, getting the controller into its home is
cumbersome. The previous owner neatly solved that problem by putting a piece
of Velcro on the back of the controller, and the matching piece of Velcro
on the top of the base. Even in the dark, it's easy to place the controller
on the base, and the Velcro secures it.
And How Are The Optics?
The NexStar 5SE is certainly a mechanical wonder. I started astronomy when I
was a teen, and that was decades ago. I never imagined that I would one day be
able to afford a fully computerized SCT telescope -- or even just an SCT
telescope. But with today's technology, virtually any astronomy enthusiast can
likely afford one, if not new, than used as I obtained mine.
Now all of that computer business can't make up for a poor optical system.
Fortunately, with all of Celestron's experience in producing quality SCT's for
all the decades I've been into astronomy, the NexStar telescope computer
doesn't have to make up for a poor optical system -- because it has a great
The manual makes a big deal out of the Starbright XLT coatings on the
optics, which they say gives much better light transmission and efficiency to
the system. As near as I can tell, that isn't all hype. I've made a few
comparisons between the NexStar 5Se and my 6 inch F/5 Newtonian
telescope. The 6 inch, by virtue of it's larger diameter, should have about a
44% advantage in light gathering power. But when one factors in the
Starbright XLT coatings, that diminishes to only about a 30% advantage,
just above noticeable. And that's what I've found, the 6 inch advantage is just
A couple of things popped out at me when doing comparisons. One evening
I was just sighting in Polaris with the NexStar for alignment purposes, and I
noticed an easily visible companion star. I knew Polaris had some companions,
but I'd never noticed one so easily before.
On that same evening, the Plato area of the moon was under a good
illumination. It's one of my favorite lunar regions, and I've looked at it many
times before with each of my other telescopes. But on this occasion, a few of
the Plato craterlets jumped out at me. I've hunted for them many times, usually
in vane, and here the NexStar threw them in my face. I looked for them in my 6
inch Newtonian, and did see them. But they were more noticeable with the
I've looked at a handful of star objects as well. The open clusters I've
looked at, particularly M35, M36, M37, and M38 look about the same in both the
NexStar 5SE and my 6 inch Newtonian, when viewed at similar magnifications.
Likewise the globular cluster M3. With the NexStar, I decided to take advantage
of the computerized mount and search for M101. I've never found it before from
my moderately light polluted sky, and I hoped that the NexStar would put me on
it so I wouldn't have to search and likely miss it. The NexStar did what I
I had to look for awhile, but I didn't touch the controls, I just trusted
the NexStar system. After staring for a few minutes, a ghostly apparation
appeared -- M101 at last. I was able to find it with the 6 inch as well, but
only because now I knew what I was looking for. And it didn't look perceptibly
different in the 6 inch.
My conclusion is that the NexStar 5SE has excellent optics, and the contrast
is surprising. I have to say that I'm a confirmed believer in the Starbright
XLT coatings. The computerized mount works very accurately if I put in my
location and time correctly. I definitely recommend it.