One of the best accessory purchases I've ever made.

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One of the best accessory purchases I've ever made.

Postby Apollo XX » Sat Jan 28, 2017 9:20 pm

Some time ago, through the generosity of a coworker, I acquired an older Meade ETX90 that was in need of some work. The OTA was dismantled from the fork mount, the mount was missing some attachment hardware and the electronic controller was non-functional.

After a good cleanup and some TLC, I was able to determine that about the only thing really wrong with the whole shebang was that the hand paddle was no good. I found a brand new one on Ebay for under $25.

Since then I’ve gotten a ton of enjoyment out of the little scope. It’s been just dandy for lunar and planetary outreach as long as the wind isn’t blowing too hard, and it makes a great grab-and-go lunar explorer at home. It’s set up for equatorial tracking, and I’m not kidding when I say it can be aligned and up and running in under a minute. It’s not much of a deep sky tool, but it puts up perfect star images on the brighter stuff.

Anyone who has owned one of these can attest to the optical quality of the Mak/Cass design, but they can probably also attest to the shortcomings of the mounting system. Shakiness is a hallmark of these scopes, and it’s because of the flimsy construction in the RA base. There really isn’t much you can do about it. It’s built in and part of the design.

If there’s one area where the little scope that could, couldn’t, it’s in focusing it with the little hand knob on the back of the optical tube. Every time you touch it the scope wiggles like you just whacked it with a bat. Accurate focusing with that knob is at best a guess, and more often than not I didn’t guess right.

One day while browsing a favorite seller on Ebay, I came across an electric focuser for sale that would fit the scope. It was listed at $40, and I figured if it worked it would be money well spent. Man, was I right!

The ETX90 on the field tripod in equatorial mode;
Image

There’s plenty of motor focusers available on Ebay if you need one;
Image

The motor focuser installs easy enough; take off the knob, put on a spacer and the gear, and bolt on the motor. Plug the cable into one of the AUX ports and you’re done;
Image

The little EC hand paddle already has the focuser adjustment knobs built in. It works like a charm;
Image

This past week I finally got around to putting the motor focus on and getting the scope out under the stars to try it out. The improvement in the usability of the scope is hard to overstate. It is so nice to be able to push the buttons and home in on perfect focus without the scope moving. I was messing around with Alnitak, which some might be aware is a close binary system that can be a challenge to split. I laid a 3x barlow in under a 12mm eyepiece, which brought the setup up to 312x, and had no problem focusing the pair into view. It really is that good.

Here’s the moral of the story; if you’ve got an ETX that’s giving you fits while focusing, get the motor focuser. You won’t regret it.
Mike M.
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Re: One of the best accessory purchases I've ever made.

Postby Dr. Powell » Sat Jan 28, 2017 9:57 pm

That is a bute.
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Re: One of the best accessory purchases I've ever made.

Postby mrgizmo65 » Mon Jan 30, 2017 1:05 am

Mike,I don' t know if you know it but it will function as a go to with an autostar controller.
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Re: One of the best accessory purchases I've ever made.

Postby Apollo XX » Wed Feb 01, 2017 9:38 am

mrgizmo65 wrote:Mike,I don' t know if you know it but it will function as a go to with an autostar controller.


Thanks, Jerry.
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Re: One of the best accessory purchases I've ever made.

Postby Bruce D » Wed Feb 01, 2017 10:23 am

You are right Mike, that's a fine little scope. I have the 125 and I would say the optics are as good as the 90 and motorized focuser probably would be a great accessory. It looks like the one you got won't fit the 125 but I'm sure they make one. I don't use the scope as much as I probably should, the long focal length (f14 or f15?) can be a bit cumbersome and the nylon gear train leaves a lot to be desired (and hinders the accuracy of the GOTO function) but for splitting the trapezium etc. it sure is "the little scope that could". Maybe I should defork the tube and put it on a GEM...

I've never used it in polar align mode- without the autostar controller I guess you have no choice if you want it to track. I wonder if that would make the GOTO more accurate. How do you polar align it, just get Polaris near the center of the EP field of view?
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Re: One of the best accessory purchases I've ever made.

Postby mrgizmo65 » Wed Feb 01, 2017 1:04 pm

Bruce, the focuser motor is made only for the 125 that's what telescope ware house told me. A mod that some have done, is remove the complete rear as se mbly,and replace it with a wood plate drilled to mount acrayford focuser.with great sucess . I 'all try to find the info for you.
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Re: One of the best accessory purchases I've ever made.

Postby Apollo XX » Thu Feb 02, 2017 1:00 am

Bruce D wrote:You are right Mike, that's a fine little scope. I have the 125 and I would say the optics are as good as the 90 and motorized focuser probably would be a great accessory. It looks like the one you got won't fit the 125 but I'm sure they make one. I don't use the scope as much as I probably should, the long focal length (f14 or f15?) can be a bit cumbersome and the nylon gear train leaves a lot to be desired (and hinders the accuracy of the GOTO function) but for splitting the trapezium etc. it sure is "the little scope that could". Maybe I should defork the tube and put it on a GEM...

I've never used it in polar align mode- without the autostar controller I guess you have no choice if you want it to track. I wonder if that would make the GOTO more accurate. How do you polar align it, just get Polaris near the center of the EP field of view?


I looked around Bruce, and the electric focuser for the 125 is prohibitively expensive. Perhaps one of those cable extensions would be a good alternative? http://www.ebay.com/itm/ExtendFlex-Focu ... 0204047631

As far as polar aligning is concerned, at first I squared the base to the tube with a level, then I adjusted the alt and az of the tilt head on the tripod until I had Polaris about where it belonged in the eyepiece (3/4* toward Kochab). Now all I do is take it outside and sight up the RA axis towards Polaris and it's fine for visual use. You're right about the gearing and drives. I don't see mine ever working in a goto setting. As it is it sometimes "jumps" when moving in DEC, and in RA it "settles" every time you let off of the slew button. I don't care though. For what I use it for it's just fine.
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Re: One of the best accessory purchases I've ever made.

Postby Bruce D » Thu Feb 02, 2017 8:54 am

Thanks Mike, though I'm loath to spend $20 for a 6" cable hahaha

The electric focuser for the ETX 125 has always been expensive- (about $140 last I looked?) when I saw you focuser for $40 I figured they had all come down in price. Not so, in fact the focuser for the 125 is almost impossible to find unless you want a used one from the classifieds. JMI has an electric focuser for the 125... for $170...

hahaha hahaha - that was a good one! Thanks for the laugh JMI !!

I did find this article for adapting the ETX 90 focuser that you have to an ETX 125, looks pretty straight forward...

http://www.weasner.com/etx/techtips/200 ... nstall.pdf
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Re: One of the best accessory purchases I've ever made.

Postby Apollo XX » Thu Feb 02, 2017 11:34 am

Bruce D wrote:
I did find this article for adapting the ETX 90 focuser that you have to an ETX 125, looks pretty straight forward...

http://www.weasner.com/etx/techtips/200 ... nstall.pdf


That looks simple enough, and it might cause you to use the scope more. They're great lunar/planetary/binary star machines.
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Re: One of the best accessory purchases I've ever made.

Postby Bruce D » Thu Feb 02, 2017 11:51 am

Yuh Mike, from the article it looks like the only reason they had to develop a completely different focuser for the 125 is because they forgot to drill the hole in the back plate- can it be that simple?

When you installed yours did you have to do the detail of placing the gear on the focuser shaft and did you have to grind a flat spot for the set screw?

The GOTO was often off by up to 5 degrees, very often I would have to do a "box search" to find the target- BUT... I must say that being somewhat dyslexic and never having got the hang of star hopping, my first night out with the ETX I saw dozens more deep sky objects than I had previously in my entire lifetime- that first night I couldn't pack the thing up and put it away. And that was from my yard in Taunton- lots of contrast in that scope, I wonder if it's the long focal length.
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Re: One of the best accessory purchases I've ever made.

Postby Apollo XX » Fri Feb 03, 2017 4:32 pm

[quote="Bruce D"]Yuh Mike, from the article it looks like the only reason they had to develop a completely different focuser for the 125 is because they forgot to drill the hole in the back plate- can it be that simple? [quote]

It is that simple. They didn't forget to drill a hole, it's just that on the 90 it uses one of the visual back screws. With the 125 you're just going to use a sheet metal screw to hold the focuser motor to the visual back.

I didn't have to grind a flat on the shaft as it seems to hold the gear just fine, but I had to make a slot in the plastic adapter to get access to the screw that holds the gear on. Took about 30 seconds with a Dremel tool.
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Re: One of the best accessory purchases I've ever made.

Postby mrgizmo65 » Fri Feb 03, 2017 8:50 pm

Mike,Bruce,the. mod Isaw the entire back,with the flip mirror. was removed, then the rod was unscrewed and the rod. removed.The plastic housing is used to trace the outline onto. a 3/8thspiece of wood.Then the wood is cut along the out line then a hole is opened for the focuser and the block us mounded to the back of the. scope.I have searched allover the place to find it.I do remember there was company that did. make an aluminum casting to do the job of the piece of wood.
Celestron eq5 advanced series goto with gps
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