Excelsis - Display Vote

Celestron NexStar 80 GT

THE OTA:

The optical quality of the air-spaced 80 mm doublet is on a par with the typical short tube refractors available from several companies. Remember these are not high-end refractors. You're getting a binocular lens designed to work best at 20X, not 240X, and they're intended for wide field, low-power views. Don't expect much at magnifications higher than 40X (the max with the supplied 10 mm eyepiece), and you won't be disappointed.

The mechanics of the OTA are typical Chinese plastic and pot-metal. The lens cell is entirely plastic, but the rack & pinion focuser is in a cast-metal rear cell assembly. The inside of the OTA is blackened, with one baffle ring located about halfway down the tube. The focuser was smooth, but the clamp that holds the diagonal was weak, and it could use another set screw for better security.

The rear cell also has a dovetail slot for the included red-dot finder. This is a nice accessory, but I found it wasn't really needed because this scope has such a wide field of view. The OTA attaches to the mount very easily with a single thumbscrew and clamp, and it can be rotated to position the focus knobs.

NEXSTAR GOTO MOUNT:

I bought this scope to get a look at the NexStar mount. I was curious to see how well Celestron managed to fit a two-axis servo and goto in such a small and elegant design. Considering the price, I think they did a good job, but there are compromises that serious observers should note.

The tripod is all-aluminum, and not suited for high magnifications because it's too shaky. This isn't a big deal at 40X, but Celestron uses this same tripod for other scopes, so buyer beware on this one. A plastic, "deluxe" (?) accessory tray is included with the tripod and comes in handy for holding eyepices. The separate goto assembly attaches to the tripod easily with one captive mounting screw.

The goto mount assembly is a combination of cast-metal and plastic parts. The load-bearing arm is metal, but all of the other parts are plastic. A separate battery pack holds eight AA-size cells, and attaches to the mount with an extension cord and plug. This battery pack drains very quickly, so take the advice others have given, and buy a portable 12V power pack to run the scope.

The Nexstar hand controller is all plastic with a 2-line LCD display and white, rubbery buttons. It attaches to the mount with a coiled cord and the typical RJ-11 phone jack. A plastic bracket is supplied to hang the controller on one of the tripod legs. I was happy to find that the hand controller has red backlighting for the display and buttons making it easy to read while observing.

HOW WELL DOES IT WORK?

Celestron's marketing department seems to have exagerrated the features of this version of the Nexstar system. The most important procedure for any goto system is the initial alignment because this tells the computer where you are, and allows it to generate the coordinates for finding other objects. With this controller, _only_ the auto-align mode can be used. This means that only the computer can select the objects used for aligninment. Celestron's manual is unclear about this, and seems to imply that the user can select objects for alignment, but apparently this is only true for the more expensive and elaborate Nexstar controllers.

One problem with letting the computer pick the alignment stars is that sometimes they're behind a tree or building. Users can tell the controller to go to another star when this happens, but it goes through its list of available stars in alphabetical order, and this wastes a LOT of time. I found it very frustrating to repeatedly go through several levels of menus to set up the system. The manual is not clear about what information gets saved and survives a power-down, and the display does not show any previously entered values.

Goto accuracy is fine for placing objects in the FOV for a low power eyepiece, and for this scope it works well. The motors are (to me) noisy when slewing at high speed, and they make weird (again to me) sounds while tracking in alt-az mode. The controller has a menu for an equatorial tracking mode, but there is no way to use it with this tripod.

This set up is a reasonably good value (I paid $330), but I'm giving it a "6" rating because the various components aren't durable enough for long-term use, and because the controller limits selection of alignment stars. From previous experience, I know the plastic parts on the tripod won't survive cold weather observing sessions. The supplied battery pack is inadequate, and must be replaced as well.

Overall Rating: 6
Weight: 6 (Veritable Vote)
Date: 10/07/2001 05:16:54 am PST
By: Anonymous (xxx.xxx.168.172)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=40841

Back