Tumbleweed Observatory's

Astronomy Hints


HOME

LINUX
SCI FI
ASTRO
BLOG

MENU

The Celestron NexStar 5 SE - A Marvel

Shop Amazon Telescopes

A New Addition To My Telescope Family



NexStar 5SE On Tripod

Above you see a new addition to my telescope Astro-Weapon Arsenal: a Celestron 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 Tutorial.

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.


keendesigns tshirt banner

How Is The NexStar Like - And Not Like - My ETX 90?

Etx With Table-top Tripod

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.

NexStar 5SE corrector plate

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 mount.

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 setting circles.

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

NexStar with Bob's Knobs

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.

ETX 90 Corrector Plate and Secondary

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

NexStar 5SE in equatorial mode

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 movie).

Mars during 2016 opposition
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 captured features:

Mars during 2016 opposition

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 GRS, May, 2016
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 Mountans through NexStar 5SE
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 review page.

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 the alignment.

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 a realignment.

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

NexStar 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 optical system.

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 above noticeable.

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 NexStar.

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 needed.

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.