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two arms vs. one

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#1 paulsky

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Posted 11 October 2005 - 06:23 PM

Hello,

Is very superior 8" LX90 vs. 8" Nexstar?

- Optics
- Stability
- Mechanic
- Goto


Thanks,
Paul

#2 Guest_**DONOTDELETE**_*

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Posted 11 October 2005 - 07:00 PM

Optics-no difference
Stability-LX90 is more stable with the dual fork
Mechanically-LX90 has more accurate pointing and tracking
For strictly visual use, go for the Nexstar since it is portable and has nice aperture without being too expensive.
If you have high expectations and want more accurate goto and tracking, more stable mount, and some astrophotography potential, go for the LX90, but it is more expensive.
If you only want visual use, get the Nexstar and use the money you save to pick up some nice accessories.

#3 Bob Pasken

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Posted 11 October 2005 - 07:14 PM

There is no evidence that two fork arms are better than one. The 8" single arm nexstar is just as stable as the two arm LX-90. There is also no evidence that Celestron's goto is any less accurate than Meade's The S&T reviews that say that if you follow the manufacturers instructions for goto use, both scopes perform equally well. The Nexstar is a better built scope in my opinion because of the metal castings and servo-motor goto. The Meades just have too much plastic and a dead-reconing system. The optics of a Celestron have always been better than the Meade optics.

#4 jrcrilly

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Posted 11 October 2005 - 07:32 PM

There is no evidence that two fork arms are better than one. The 8" single arm nexstar is just as stable as the two arm LX-90. There is also no evidence that Celestron's goto is any less accurate than Meade's The S&T reviews that say that if you follow the manufacturers instructions for goto use, both scopes perform equally well. The Nexstar is a better built scope in my opinion because of the metal castings and servo-motor goto. The Meades just have too much plastic and a dead-reconing system. The optics of a Celestron have always been better than the Meade optics.


Hi, Bob.

You may be comparing the Nexstar to the ETX rather than to the LX90. The single-arm Nexstars are mechanically solid but the drive system is far sloppier than any of the other midsize forkmount drivebases. Because there is no worm, all the slop in every gear pair transfers directly to the optical tube - you can wiggle the optical tube up and down and observe this. I've owned several and while they do work the precision just isn't there. This slop prevents them from being as accurate as the others. What they offer is drive performance nearly as good in a much lighter package. For those who are very concerned about weight it's a reasonable compromise.

You are correct that they use servos and metal fork arms, as do all the other midsize Meade & Celestron forkmounts. If they used a worm drive they would be as accurate (and probably as heavy) as all the rest.

#5 southmike

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Posted 11 October 2005 - 11:14 PM

visually I give the nexstar the edge ..mainly it is lighter , easier to carry,and easier to setup (physically)
The Lx90 might excel somewhat better in imaging but for that I, take the extra step to a nexstar gps, or an lx200.
I like the fact that meade has manual functions, so it will work without power...but without goto. the nexstar also has a design that isn't affected by cord wrap..though the controller on the arm bothers some.

#6 Bob Pasken

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Posted 12 October 2005 - 11:54 AM

No, John I am comparing the 8" Nexstar to an 8" LX-90. I compared them at several star parties over the last two years as I was considering a Nexstar 8i. I found that the Nexstars 8i's did have slop in the gears as you point out, but that the LX-90's construction material made the LX-90 nearly as bad the Nexstar 8i. As I said the Nexstar 8i isn't suitable for photography but the LX-90 is only slightly better in this regard. You pay for the small increase stability with a large increase in weight. The two arm versus one arguement is entirely bogus.


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