The Biggest of The Small Scopes
Written: Sep 13 '03 (Updated Aug 25 '08)
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Product Rating:
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Pros: Compact, light, mobile, good optical performance, cool package deals common
Cons: Does nothing without power, tube not removable
The Bottom Line: For a beginner, this will give a lot of capability to do a lot of things from the get go.
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| Pirich's Full Review: Celestron NexStar 5i (300 x 127mm) Telescope |
The NexStar 5i is the latest incarnation of Celestron's 5" Schmidt Cassegrain astronomical telescope (SCT). It now comes with more capabilities than ever before in a small tracking package. In my view, this is very much a worthy successor to this line of unparalleled telescopes. More information on telescopes and choosing one for yourself is in my review on Picking a Telescope.
To help organize this review, I have divided it into the following sections:
Background
Description
Observations
Tips/Notes
Summary
Background
This type of telescope first appeared as the Celestron C5 in 1971. It was quite literally a small version of the successful C8 8" diameter SCT, introduced a year earlier as a result of nearly ten years of development. The C8 was in the midst of spurring a revolution in amateur astronomy as individuals, schools, and clubs could buy telescopes with quite a bit of capability all in one instrument, compared to the long focal length refractors and limited Newtonians available at the time.
The C5 started in a different era than we live in now. For starters, the premium on telescope mobility hadn't begun. It's hard to imagine, but a large number of all night lit businesses simply didn't exist. As a result, the night sky was visible for most people. The need to head out into the countryside to be able to see the stars wasn't a priority until much later as a veritable light-cult appeared in the US.
The motivation for a 5" diameter version of the C8 was to make a cheaper version of the telescope. The idea of charging as much for something smaller would have been laughed at in that time period because large size wasn't the mobility barrier to seeing the night sky it is today. Machining a smaller telescope isn't necessarily cheaper. True, the material used is a lower cost, but all of the tolerances must be tighter as the mechanism shrinks, and the original C5 was a miniature C8 down to having a mini version of the beam stiffened cell in the back and a screw-in retaining ring in the front and appearing on a small twin arm fork mount. The C5 was also sold separately as a telephoto lens in both the f/10 version used for the astronomical telescope as well as an f/6 version with a large secondary mirror which made it less suitable for astronomical use sold as a 750 mm telephoto lens.
Despite all of the work done on it, the fundamental problem was a simple one of economics. As Alan Hale, founder of Celestron commented, the C5 sold for less than a C8, but the miniature telescope cost more to produce. All of the different versions of the C5 were retired and the astronomical version was discontinued in 1983 and for a time there simply were no 5" SCTs to be found.
Celestron reintroduced the C5 in 1992 with a totally new optical tube which only had the name in common with its predecessor. This version fixed tolerance problems by designing a new scope from a clean sheet of paper to be a good 5" SCT. What is most extraordinary is how Celestron revisited this concept. In the 19 years since the first C5 appeared, the world had changed. 1992 came with all-night gas stations, giant malls, chain stores, and massive housing subdivisions all jam packed with poorly designed light fixtures wasting most of their output in directions other than the ground under the light. The night sky had moved out and away from towns and cities. Anyone interested in viewing the night sky had two peculiar problems:
(1) Dim night sky objects need reasonable telescope aperture to bring out their details.
(2) Big telescopes requiring AC power were a complete no-go for heading to the countryside.
A third item which started showing up was the observation small telescopes appeared to be less affected by city lights than large ones, due to the nonlinear response of the human eye to dim light. Large telescopes in the city appeared to make the light pollution bright so fast it washed out objects which appeared more visible in small scopes.
The new C5 came on a single arm clock-driven mount which made it very easy to transport compared to larger telescopes like the C8. A second version of this telescope, with the enhanced transmission coatings on the optics introduced with the larger Celestron SCTs was called the C5 , and was the version which stayed in production until 1999. This version stuck, and the C5 optical tube on the NexStar 5i is a direct descendant of this design.
Not everything went smoothly for this new C5. Many people looked at the single arm mount and assumed there must be vibration problems (I have been using one for about 3 years now- it damps out in about 3 seconds, which isn't unusually bad vibration). The C5 mount was also expensive with a list price of $1200 and a discount price if you looked around of $1000. The mount was compact, but this price had the telescope mounted on a wedge plate with feet. The tripod was extra. As a result, it was expensive enough to find 8" SCTs and fairly large Newtonians and Dobsonians for the same amount of money. The advantage this telescope offered was a compact light weight telescope rugged enough to survive transportation on a regular basis. The mount had a clock drive which will run about 50 hours on a 9 volt battery (for what it's worth, I've started keeping track- this may be a conservative run-time estimate). This mount could have digital encoders put on its axes, but all slewing to objects would have to be done by the user. It is a bit unusual, and as a result has a sort of cult following, but otherwise hasn't shown up in the larger numbers of other types of SCT. Among these telescopes, it was the only model a single person could pick up and move while still attached to its tripod.
Celestron introduced a new version in 1999, called the G5. This was the same optical tube (telescope assembly), but now it was painted gloss black and came mounted on a German equatorial mount- the type with a counterweight opposite the telescope tube. This version had no provision for encoders to allow computer guidance, but it did offer a massive price break compared to the C5 . This variant started out at $700, and currently can be acquired from Woodland Hills, www.telescopes.net for $600 with a motor drive. Given the C5 optical tube alone with no mount sells for $550, this equates to getting the equatorial mount and motor for $50.
At the high end, Celestron chose the C5 optical tube to become part of something new- the NexStar series computer guided mounts. Celestron had produced one complete do-it-all computerized motor driven mount up to this time in the form of the Ultima 2000, which used an 8" diameter scope. Technically this is a breakdown to move telescope, but i have seen someone move one in one piece by folding the tripod, lowering the legs, and then laying the whole thing down across the back seat of a Suburban. But I think this is an exception which clearly demonstrates the rule is valid.
Description
This telescope now comes mounted on a drive base with built-in electric motors which looks identical to the drive base on the original NexStar 5 on first inspection. The easiest way to tell them apart is to look on top of the drive base. Where the original NexStar 5 just had the lid to the battery compartment, this version has two phone-jack type sockets on the top to allow auto guidance devices to be attached.
The new telescope has the option of adding a GPS receiver (a module about the size and shape of a paperback book which bolts on top of the telescope) to turn it into an equivalent of the larger GPS guided NexStar telescopes. The mount comes with a simple paddle type controller, but every seller is currently bundling the telescope with the computerized controller used by the larger NexStars for free. As a result, I see little reason to spend much time on the paddle controller except to point out the size and shape of it are slightly different from the full computerized controller, so you need to unscrew a secondary flange installed in the hand controller's slot to make room (why aren't they the same size and shape? It's a good question).
The battery compartment has a pop-top lid to cover the 8 AA batteries this mount takes. The telescope has the two sockets mentioned earlier in this area, and they actually protrude through holes in the battery compartment cover. So, you need to unplug the auto-guider to change batteries. Inside, the compartment is flat bottomed and square. The batteries are held by metal clips, so they are very secure once they are installed. Putting them in and removing them takes a little dexterity, so if you have any doubt about having enough juice, change them in daylight before you take the scope out. The scope can remain attached to the tripod for this, which is convenient. Currently, the telescopes are also coming bundled with Celestron's nifty starter kit, which includes a car adapter, so if you are driving out to the countryside to do some observing, you don't need to play with batteries. The power plug as well as the on/off switch are at the base of the arm on the outside.
The tripod has been completely redesigned and is a huge leap forward from the original NexStar 5 tripod. This piece of equipment is also being bundled with these scopes, so the entire ensemble is about $900, with more equipment than the original C5 came with. Considering everything else it does, as well as the effects of inflation, this is a real bargain for a very complete "First serious scope." The new tripod has tubular steel legs in place of the aluminum rectangular legs previously used. The mount has a spring-loaded stiffener mechanism to hold the legs in place so all you need to do is pull down on it and rotate it to free the legs to collapse (if you have a large NexStar GPS scope, that tripod is similar, but larger and the spider is held by a nut you must unscrew to free it to move). The mount also has one other feature I really love- the bolts for attaching the telescope are now spring loaded and captive in the top of the tripod. This means you don't have to take them and hold on to them when the scope comes apart- they stay in place. It also means when you are putting it together, all you have to do is set the telescope mount on top so its center aligns with the pin in the middle of the tripod, and then turn it until you hear the bolts pop up into place. Then you screw them in and you're done. As a mechanical engineer, this feature makes me say to myself "This is how all of these should go together."
The mount has a tilt-plate built in to the tripod so the same mount serves to equatorially align the telescope. The alignment is done with a sliding flat bar with rough latitude gradations on it. In reality, if you are serious about photography, you will need to do an optical drift method alignment, and these markings are only accurate enough to get the scope in the ballpark. There is no bubble level, so getting the setup perfect will take a little work. On the other hand, these are cheaply available as stick-on levels at places like www.grainger.com. Given the scope does have an auto guider port, it does have the capability to do serious deep sky photography. It is fairly clear this was intended to be a general purpose telescope capable of doing everything, and the hardware is good enough to deliver that promise.
Observations
The NexStar 5i is a refined version of the original NexStar 5. The tripod is actually easier to fold and unfold than the original, so it is very easy to pull down on the spider holding the legs out, turn it, fold the legs, and then pick the whole thing up and walk outside with it. I am making this capability my cutoff point for a big or small scope. The NexStar 8i has a C8 optical tube on an identical mount, but after using a C8 for a while, I have serious doubts about the wisdom of trying to carry one around that way. In comparison, the C5 is a compact and light optical tube, so it is easy to keep it from running into things while carrying the assembled mount and tripod.
It seems Celestron planned to sell this as a bare-bones scope which could be upgraded to a Goto telescope simply by adding the hand controller. In practice, this would have been sort of like having a C5 which could be turned into a NexStar. However, the world moved on between the time this concept came together and the telescope went to sale. Within Celestron's own product line, the small NexStar scopes such as the NexStar 80GT provide all of the GOTO features in a light motorized mount along with a tripod for a third of the cost of the base NexStar 5i with no GOTO controller (which would be $149) and no tripod (a further $225). As a result, Celestron has bundled these features with the NexStar 5i as a rolling "Special" so you can get all of these capabilities. If they didn't, then users who wanted a light GOTO mount could buy a NexStar 80GT, remove the optical tube, install the Baader bracket, a sort of universal shoe made by Baader Planetarium of Germany (sold by Alpine Astronomical, www.alpineastro.com), which lets you attach a C5 optical tube to that mount, thus creating a very inexpensive GOTO scope with a few performance limitations compared to the NexStar 5i, but at far less cost than the NexStar 5i plus the tripod and plus the controller. Note: If you already have a NexStar 60,80, or 114 GT, this approach is how I would recommend going about upgrading to a C5.
The kit of equipment now sold with the NexStar 5i includes everything but the GPS unit, which isn't necessary, anyway. This setup does give you your money's worth since it really is ready to do just about anything out of the box. The C5 SCT optical tube is the smallest telescope capable of mounting all SCT accessories, which are the widest available for any type of telescope.
The performance of the telescope itself I have found to be a very good balance between portability and capability. The C5 optical tube is about the size of a coffee can. The main barrel is 5.75" in diameter and the full tube with visual back is about 14" long. It will show Saturn's Cassini division with ease, has enough light grasp for Messier objects. This performance is contingent on having the telescope well collimated, so taking the time to do this really is well spent.
The moon is really beautiful when seen through one of these scopes and will show a new view of the cratered landscape each night as the sun shines across a new section each night. With Jupiter and Saturn coming up this fall, the Mars opposition is really just the tip of the iceberg for observing this year. Mars will still show its ice cap and dark areas on the surface. We seem to have been lucky this year and a global dust storm didn't kick up to obscure Mars' features. However, this planet should only serve as an introduction. The other planets and the moon have much more to offer. Saturn will show detail and color in its beautifully spread rings. In a night of clear skies, this planet is very pretty indeed in a 5" scope and will hold its beauty at high magnification, and 2-3 of its smaller moons are visible. Jupiter is a unique even unto itself, since its visible features are constantly changing.
I have recently been working on taking photos of Jupiter, and have finally succeeded in producing one which looks like the visual image in the C5: http://www.buytelescopes.com/gallery/view_photo.asp?pid=13212&c=35913. Note, the contrast is subtle, as on the real planet. If you increase the contrast on the image, the Great Red Spot and other features become more obvious, but the original view is similar to what is visible to the unaided eye. Learning to see the features at low contrast is a skill you will build with more observing which turns out to be extremely useful in everyday life.
The mount is actually very nimble and will slew at 5 degrees per second. The scope's accuracy is dependent on the quality of the initial alignment. The mount does nothing without power, so the first action to get it set up is to drive it to have a level tube and point north. This isn't a critical alignment, so don't spend a lot of time on it. When it slews to the first star, the telescope will need to be as carefully centered as you can get it, with the up and right buttons as the last commands when you press the align button. This gives the telescope the best idea of where it is pointed. There is more about this in my review of the computer controller for the NexStar 5i's telescope.
Tips and Notes
(1) If your alignment isn't looking all that good, with items not well centered, it's actually a better idea to just turn the telescope off and start over on the alignment rather than trying the "Replace star" method the controller offers. It sounds easier, but I have yet to see this result in better pointing accuracy. The best way is to pop in a high power eyepiece during alignment and get precise centering. When this is done, the pointing is extremely accurate, even across the sky from where you did the alignment.
(2) A dew cap/ glare shield is really a useful item. The reduction in glare from other objects improves the image, and not getting the corrector plate in front fogged will keep your evening's observing from coming to a sudden end. I have instructions for making one for about $2 in my review on the NexStar 8 GPS.
(3) This telescope really is built to do it all, so I suggest anyone who gets one as a beginner really should try things. This telescope has enough aperture to do deep sky photography, so go ahead and take a crack at it. The scope also has the ability to use different accessories designed for use with SCTs, so this really is a flexible platform for finding out what type of observing you enjoy most.
(4) Do not try to do solar projection with this telescope. You may have seen this done with small telescopes, such as 60 mm refractor. A C5 will either shatter its eyepiece, burn internal components, or possibly destroy the secondary mirror. Also do not attempt to use an eyepiece solar filter. These can and do shatter without warning resulting in instantaneous and permanent eye damage. Even if it is labeled "Zeiss," this isn't the way to go. To safely and economically view the sun, you can use Baader Solar Film, available at Astro Physics, http://www.astro-physics.com/products/accessories/solar_acc/solar_acc.htm.
(5) The task of collimating this telescope gets much easier with Bob's Knobs, which replace the screws in the secondary mirror for doing this. Instead of having to use an allen wrench, you can use your fingers. Although you still have to make sure you don't touch the glass, the step of having to insert an allen wrench into a screw in the dark is eliminated. Note, high performance optical coatings make the corrector difficult to clean and any cleaning of a high performance telescope risks damaging its coatings, so make sure you avoid having to.
(6) If you look up at the sky in the late afternoon and it looks clear, so you are thinking about doing some viewing, take the telescope and move it somewhere it can cool or warm to the outside temperature. A garage is ideal. In many areas, the scope shouldn't be left in such an area because high humidity can damage the optics. It can take 45 minutes to an hour to reach ambient temperature, and until it does, the images are not as good as an equalized scope. In summer, this also keeps the scope from fogging when you take the lens cap off, so this has become my standard practice.
Summary
The C5i is a refined light weight astronomical telescope with a remarkable balance of mobility and flexibility. The assembled weight of the mount, scope, and tripod is around 23 lb., so it is easy to pop outside for a quick look, or to take it along on a trip to the countryside's dark skies. This is still a small telescope, but it has enough aperture to make deep sky objects such as nebulas and galaxies come through. It is compatible with the gamut of SCT accessories, so it can serve as a travel scope, or an ideal first scope capable of growing with a beginner for years. It can even be upgraded to use GPS location finding.
However, the cost effectiveness of this instrument hinges on whether Celestron continues the "Specials" for this telescope. It was introduced as a modular telescope, with a bare bones instrument with a simple controller and no tripod, where it would only operate from at table top. However, the cost of this configuration makes taking other telescopes and assembling your own GOTO telescope significantly cheaper. The specials with the tripod, starter kit, and NexStar 40,000 object controller included make this a cost effective do-it-all first telescope. Currently an eyepiece set is offered when purchasing a telescope for $99, which has a nice case, selection of 6 eyepieces, 7 colored filters, and a magnification doubling Barlow lens which really makes an economical and very complete starting package with the telescope.
And I have to admit I am scratching my head on whether to keep the older C5 , which has faithfully worked for years, or to sell it and go to the NexStar 5i as something easy to take out when the seeing is nice.
Recommended:
Yes
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Epinions.com ID:
Pirich
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 in Electronics |
 - Top 500 |
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Member: Rich W.
Location: Tucson, AZ
Reviews written: 137
Trusted by: 40 members
About Me:
Dad, Engineer, Scientist, Astronomer, Traveler; order may vary.
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