help me test out a used Meade telescope

February 18, 2009 8:36 PM

I'm about to buy a small Meade telescope used. It has that gee whiz motoring/pointing/slewing technology. What kinds of things should/can I test in a couple minutes just to verify that it's mostly working?

FWIW, this is a Meade ETX 70 or Meade ETX 90 (I'm looking at buying one or the other from separate sellers). I'll be bringing batteries so that I can fire it up and see if it ... does something.

I built my own telescope (a Dobsonian) about a decade ago so I'm familiar with telescope basics. But I don't know a thing about these autotracking gizmos.

I basically just want to see the thing turn on, display something on the handheld controller, and move on both axes. Just to be sure that the electronics aren't fried or the mechanism is busted.

If I just power it up, will I be able to just put it into some sort of manual mode and command it back and forth? This is likely to be happening during the day so I won't be able to do a full start alignment test, and I don't want to have to go through a leveling/alignment just to test the movement mechanisms.

If you're familiar with these particular models, any chronic failures to watch out for?

posted by intermod to Technology (6 answers total)

Best answer: When you first boot up, it will prompt you to answer some questions about your location and what time it is. It'll then try to calibrate to whatever stars should be visible. (It chooses two based on your location and time of day.) If it's during the day, and you tell it so, well, I'm not really sure what happens, but you WILL be able to move it around manually, however, you need to hit 9 first to make sure it's at top speed--the base-level speeds move literally almost imperceptibly; they're used to track star movement, but you could swear nothing is happening.

For what it's worth, it will also try to slew on its own to the calibration stars when you set it up, since you're supposed to point it north. This should be two-axis slewing, so it'll move along the x and then the y, and that should be enough to tell.

Also, if you're looking at one or the other, if UHTC is an option on your glass, get it. It seriously helps.
posted by disillusioned at 9:49 PM on February 18, 2009

Best answer: For the record, the ETX 70 was a short-tube achromatic refractor; the ETX 90 is an f/13.8 Maksutov-Cassegrain. Optically they'll be quite different. I believe the 90 has a more extensive database as well. Make sure the ones you're looking at have Autostar; the earlier RA models did not. The PE models have UHTC.

My gizmo telescope is a Celestron, not a Meade, so I can't speak to the ETX line personally, but if they're similar, you should be able to use the controller to slew it manually. From what the guys at the telescope store told me, the Meade ETX is normally noisy -- they don't call 'em Meade grinders for nothing.

Of possible interest: the FAQ on Weasner's Mighty ETX Site.
posted by mcwetboy at 5:30 AM on February 19, 2009

Response by poster: Wow, great info so far, it's humbling how little I know. Actually, this is part of a larger plan ... I was going to buy a new, big scope, but then got into a time crunch (going to FL next week) and decided to just grab a small used one for now and get familiar with this stuff.

I didn't know that the 70 was a refractor -- I should have guessed! Glad that I put in an offer first on the 90 last night. But I'll still go for the 70 if the 90 rejects me.

FWIW, the 90 is an Meade ETX-90EC. Which, looking at the Weasner FAQ, tell me that it doesn't have Autostar function. Gulp. OK, I need to look harder at this, or decide if I can live without that for now ...

I'll look for UHTC when I do buy the big new scope -- and do more research too.
posted by intermod at 6:22 AM on February 19, 2009

You may get more satisfaction from a pair of binoculars and a good book for astronomy beginners - Turn Left at Orion and Astronomy for Dummies. It will give a better understanding of the sky, and give you hints about the kinds of things you enjoy finding in the night sky, which will steer you in the direction you want to go when it's time for a big 'scope.

I'm generally a big fan of technology leveling the playing field for non-experts, so everyone can get in on the fun, but I'm not into go-to electronics - the whole point of Astronomy is to see what's in the sky, and that means learning what there is to see and how to find it.

(I hate fish-finder sonar for the same reason. You're fishing, not harvesting fish. Learning how to catch a fish using your experience and intuition is the whole point of it sitting out there with a fiberglass stick.)
posted by Slap*Happy at 1:27 PM on February 19, 2009

Response by poster: Thanks SH, but you may have missed it in my original post ... I'm not new to telescopes or stargazing. I built my own dobsonian (8" primary) a decade ago. In fact my experience has taught me that I really need to have tracking (to compensate for earth rotation) and want the ability to just "go to" an object. Manually slewing suuuuuucks.

What I'm not familiar with is the motorized pointing stuff that you get with a nice commercial telescope these days.

Anyway, right now this is all moot because now both sellers have ignored my emails to them offering to purchase. I didn't offer their asking price. I guess that means I get the ole stink eye!
posted by intermod at 1:36 PM on February 20, 2009

Response by poster: Update: the first ETX-90 I made an offer on didn't pan out (the guy was asking for way too much, and stayed firm). Then another one came along, just in time, and I picked it up today! He fired it up for me and put the motors through their paces, so that was easy enough. Turns out that these things come with a smaller manual controller, so if you connect that instead of the full-blown computer thingy, it just moves when you push the arrow buttons.

Before this one came along, on Tuesday I went to the local independent telescope shop (support your locally-owned businesses!) and looked seriously at just buying a big new scope this week. But I wasn't happy with the choices available on short notice, and really didn't want to rush it. So it's great that this 2nd ETX-90 popped up.

I'm taking it down to Florida on Monday to go watch the shuttle launch! And enjoy some dark skies on the beach.
posted by intermod at 7:43 PM on March 5, 2009