by Jay Reynolds Freeman
So in early April, 2001, I ordered a NexStar 8 from Eagle Optics, at the quite good price of $1499. See, I am not really a Luddite, I have been setting you up. After all, I bought a touch-tone 'phone when the 20th century had two whole years left to run, and I occasionally think about getting a television. I usually feel better when I lie down.
There were many go-to telescopes to choose from. At the high end, Roland Christen's latest mounts are not just computer controlled, but voice actuated. That's scary. I might wisecrack "Scotty, beam me up!", and disappear in a shower of sparks, to who knows where. Seriously, Astro-Physics's offerings were too big and too costly. Losmandy recently introduced a go-to option for the G-11, yet I needed a smaller mounting, and problems have been reported with early Losmandy units.
The well-regarded Meade LX200s are not really too noisy -- you can always select a slew rate slower than espresso grind -- but they are much heavier than Celestron's counterparts, and their two-arm fork mounts are more difficult to adapt to other telescopes than are the Celestron single-arm forks. Meade's small entries are not all two-arm forks, but they seem not to be very accurate.
Celestron offered several options, but the NexStar 11 is too big, and the very small stuff is also reportedly inaccurate. The NexStar 5 and 8 have larger databases and more software features, including a rapid two-star alignment that facilitates evading banzai charges by my yard's anti-astronomer ninja attack trees. I went for the 8 instead of the 5 because aperture wins, and for nostalgia: A generation ago, Celestron turned amateur astronomy upside down with the compact, inexpensive Celestron 8, but I had never owned one.
Eagle provided exemplary service. UPS messed up delivery, but Eagle promptly responded to my EMail with help chasing down the missing parcel. Celestron's overseas manufacturers messed up, too -- the tripod arrived with the wrong attachment hardware for the accessory tray -- but Eagle promptly called Celestron on my behalf, arranged for replacement parts, and 'phoned to let me know they were on the way. (The tripod box showed no sign of having been opened previously; I am confident the problem was not some kind of restocking error.)
My initial impressions were unsurprising -- everything worked, the mechanicals seemed robust, the user interface to the software was easy to learn, and the optics were good. NexStar 8s are pretty common by now, and have been reviewed in Sky & Telescope (November 2000), so there is ample information available to let newcomers decide whether they want one. Thus the thrust of my report will be how well this telescope suits an observer more experienced than a beginner, how well the software works, and what interesting modifications you can make to the telescope if you need a substitute for a life.
First light was Sunday evening, April 22, in the San Francisco Peninsula hills. High haze reduced transparency, and the air was very wet. Setup took only a few minutes, and my stab at "north and level" was good enough that the telescope slewed within a few degrees of the stars it chose for alignment. I started hunting Messier objects through the haze, and found them rapidly.
Even with no tripod tray to make the mount rigid, pointing accuracy was acceptable. Most objects ended up well within the field of the 40 mm Plossl eyepiece that Celestron supplied, even after long slews. The software makes it easy to let whatever object you are looking at become one of the alignment reference points; I did that frequently. Slewing was a tad slow -- I can find most Messier objects without charts, and could have gotten to them sooner with a hand-powered mount.
I did not have a dew shield for the NexStar, and had not brought my big battery, so could not use one of my Kendrick anti-dew heaters on the OTA. Thus I was not surprised, given the wet weather, when the corrector dewed. Quick alignment facilitated a simple solution. I moved the tripod next to the car, pointed the tube into the open door, started the engine, and swiveled a heater duct to blow hot air on the corrector. The dew disappeared in minutes, whereupon I realigned and continued to observe with the door open and the heater running. The extra warmth kept the optics dew free. The heat probably didn't help with seeing, but at only 51x, who cares? I logged 56 Messier objects and a few other things in about two hours.
Two nights later, I had bought a dew shield, but conditions at the same site did not require it. The tray hardware had arrived, so I set up with the tripod legs extended about a foot beyond minimum length, to provide a more comfortable eyepiece position, and started working on Herschel 400 objects. Finding accuracy was again good enough to bring nearly all of them into the 51x field. Pointing seemed worse a long way from the last alignment target, so I realigned often. The slow slew rate was less bothersome, for two reasons.
First, I organize my H-400 lists into strips of sky an hour wide, each sorted by declination. I work north or south in one strip at a time, so most slews are quick ones, through short distances.
Second, between checking my lists for the next object, and occasional reference to a chart to untangle a rich or confusing field, I made good use of the slew time. Typically I would be viewing one object with the NGC number of the next one already in mind. I would enter it and set the telescope slewing while I did paperwork, turned chart pages, and memorized the number of the next object to come.
I logged 124 H-400 objects in three hours. I can work that quickly by star-hopping, when I zig-zag across whole atlas pages, where targets are only a few degrees apart, but for objects as widely spread as the H-400 stuff, that's fast. I didn't spend a lot of time observing specific objects -- in many cases, there wasn't much to see -- but even with abbreviated viewing, it was pleasant not to have to spend noticeable time finding things in the first place.
At the end of the evening, I tried higher magnification, using a Brandon 8 mm for 254x. Seeing became noticeable: The Airy disc and first ring or two were visible, but generally in motion, so higher magnification would not likely have provided more detail. Collimation was a tad off, so I tweaked it, and star-tested on Polaris (which split nicely even at only 51x). With four or five interference rings visible, images on opposite sides of focus looked the same, though better seeing would be required for a more precise test. I slewed over to Epsilon Bootis, and had an easy split at 254x, then called it a night.
The third session was a few days later, on an evening when everyone but me thought the coastal marine layer would get far enough inland to clobber our best local site. It didn't. I had a clear, dark sky all to myself, for another run of deep-sky observing, plus a view of an occultation of mu Gem and a quick look at Mars. In three nights with the NexStar 8 I had logged 251 objects from the Herschel 400 list, 92 Messier objects, and a small handful of other things. Clearly, the telescope is usable and friendly.
My list of NexStar 8 pros and cons of interest to an experienced observer so far includes the following:
1) Set up and take down are *very* fast -- well under five minutes each, much less if you have a quick and easy way to stow the telescope for transportation. The whole thing is light and portable enough to keep set up indoors (perhaps with a lamp shade to disguise it in the living room) and take outside in a single trip, as well.
2) Slewing is not as fast as by hand, but many observers will likely have other things to tend to while the telescope is in motion.
3) Alignment and object-finding seem sufficient to put things in a low-magnification field of view with great regularity, but ...
4) Serious users will probably want a finder, not only to save the bother of switching to a low-magnification eyepiece for finding things, but also for occasional orientation to charted stars when the eyepiece field is confusing due to an imperfect slew, and the object is so nondescript as to be unidentifiable if you don't know precisely where in the field to look for it. (Such objects include faint fuzzies, and also double stars too close to resolve at low magnification.)
The "right" finder is probably something like a 15x50 or a 20x50 -- such an instrument will show all the stars on my Millennium Star Atlas even in a less than perfectly dark sky, and its two or three degree field will include the target and plenty of surrounding stars even with a very poor "find" by the NexStar. Finders with that much magnification are scarce. I expect I can cobble one up, or a 7x50 or so would probably do, but there may be an opportunity for an entrepreneur to offer a special, high-magnification finder, for a niche market.
5) Battery life is an issue. I have been using rechargeable alkaline batteries, and after three hours of heavy use they are drained enough that slewing is a lot slower. Nickel/ metal-hydride units are perhaps better, but they don't hold charge very long. The NexStar will run off a car battery -- Celestron lists an adapter for NexStars -- and an AC adapter comes with the telescope, so there are plenty of ways to provide external power.
You may well need to haul a big battery for an anti-dew system. If so, there is little penalty in using it to power the telescope, as well.
| I | II | III | IV | V | VI | VII | VIII | Next |