Peterson Engineering EZ FOCUS

[Albireo380]

I bought a Peterson Engineering EZ Focus kit for my LX90 in the late Spring, and with a few hours spare this afternoom, the Sun shining and SWMBO out into Town, I had a bit of free time.

I am completely handless and so was very nervous about "messing" with my trusty LX90, which has served me well for 4 years now. But I was getting more and more irritated with the amount of focus shift, particularly irritating when trying a bit of prime focus Astrophotography. The "EZ Focus" is billed as reducing the "play" in the focus markedly.

Basically the kit consists of 4 things. An instruction leaflet (4 pages of A4 - with poor quality B&W photos), 2 "thrust bearings" - wee washers with rollers in them, an Allen key and big blob of grease.

The instructions seemed easy to follow, so heart in mouth I turned the focusser anticlockwise until there was no more travel, unscrewed the 3 screws holding the focus assembly to the OTA and gently eased the focus thread off the spindle in the OTA. The focus assembly was then easily disassembled (in 2 minutes) into 5 components (see image). A focus knob (left), 4 plastic washers covered in thick, black grease, a "top hat" (which fixes the focus assembly to the OTA), a small steel washer and then a brass focusser body with threaded steel shaft.

The idea was to replace the plastic washers with a greased "thrust bearing" and the wee steel washer with the other greased "thrust bearing". Seemed simple enough - at least the piccies in the instructions matched the disassembed focusser laid out on my bit of kitchen towel.

Having cleaned of the black "gunk" on the focusser I regreased using the Peterson stuff (which seemed a LOT lighter and less like axle grease), replaced the Meade washers with the Peterson ones and then reassembled the focusser. All okay so far.

The fun bit was then trying to rethread the focusser shaft onto the LX90 mirror focus spindle, through a 1" keyhole in the back of the OTA. Good light is needed (and perhaps some training in keyhole surgery would help as well). However, after ensuring that the focusser was fully turned on its thread anticlockwise, a few minutes careful work had everything sitting nicely.

I tightened the focsser screws back up again and all seemed okay.

I then popped the OTA onto the tripod and pointed to the TV mast on the top of the high rise flats about half a mile away. YES - It did focus, and in the full glare of day, focussing seemed easy and with no backlash - of course, I need to check under the stars to have a proper test of this.

At least the focus mechanism still work (so I an't broken anything).

Roll on a clear night and I will do a focus test under the stars.

Tom (off to get a beer)

[Jeff RV]

Glad it all went smoothly Tom, i was reading waiting for the clanger

Hope you enjoy that well deserved beer mate

Jeff.

[Albireo380]

The clanger could still happen Jeff. Until I try it out under the stars I don't know if it has improved the image shift or backlash. It could also have changed the focus point on the travel of the focus knob - if the focus knob thread wasnt palce on the same point pf the OTA mirror spindle. I guess that could mean that binoviewer or some such item on the back of the OTA wouldn't reach focus. But hey, time will tell ... I am awfully good at figuring out what problems might arise. Although in this case I suspect the EZ Focus kit is fairly "idiot proof" - even for someone as non-DIY as me.

Cheers

Tom

[Jeff RV]

Well it's good luck then Tom, You'd think Meade would have improved this by now in the manufacture of the scopes, especially with the prices they expect.

Jeff.

[dogfish]

Good work Tom,

Mirror shift is annoying with SCT's. After having the delights of the dual speed focuser on my wee Megrez, it now seems even more so. Starizona do something similar for C8's, so I might treat myself when I've got a bit of spare cash.

Enjoy your beer, Martin

[Albireo380]

Well it's good luck then Tom, You'd think Meade would have improved this by now in the manufacture of the scopes, especially with the prices they expect.

Jeff.

Yeah,

The Peterson Engineering parts probably have a value of under 50p if they were part of the Meade manufacturing process. I can't think of a good reason why Meade penny pinched on this - it can't have saved them more than a few pence profit, and yet means their 'scopes are not as good as they could be.

Sheer bad management and poor manufacturing standards on Meade's part.

Tom

[barkis]

Hope it works for you, but how does this modification stop the mirror moving in the slide when the focus direction is changed.?

Ron.

[Albireo380]

Hope it works for you, but how does this modification stop the mirror moving in the slide when the focus direction is changed.?

Ron.

Not sure Ron. I suspect the "thrust bearings" grip better than the Meade plastic washers, so you get finer control and tend not to "overshoot when trying to focus.

That's all I can think.

A friend upgraded his LX90 this way a few months ago and swears it has made image shift / backlash a small fraction of what he had before.

I will see how it performs and will post an update.

Tom

[Paxo]

Tom,

I did the same upgrade on an LX200R just under a year ago and it made a hell of a difference, minimal image shift while focusing now. It's just a shame to think that I paid just under 4k for a scope which is vastly improved by replacing the 6 very flimsy nylon washers with two precision thrust bearings which cost 50p each, come on Meade, get your act together.

Steve..

[Albireo380]

Well, just had half an hour out in the back garden with the LX90 and its EZ Focusser upgrade. It seems to work well. I spent about 20mins on Jupiter and focussing seemed very smooth and precise in comparison with what it was before. I wasn't bothered with image shift at all (x125 mag) and I spent some time racking the focus in and out, just to check. Everything seemed smooth and as crisp as one can get from a low-down boiling Jupiter. Pretty salmon pink Nth & Sth Equatorial belts, Southern Polar region and just a hint of other cloud belts.

Then on to Albireo - easily split at this magnification, and again focus seemed very precise. Okay, not that "snap to" you get on a refractor with a Crayford - but pretty good for an SCT, and MUCH better than before.

It still isnt really dark this far North (at any time of the night), so serious observing will have to wait about another 3 weeks - but at least I am ready for it now.

If you have an LX90 or LX200 - get this upgrade, it is cheap and easy to fit.

Tom

[barkis]

I am very pleased it has made the difference Tom. The proof of the pudding and all that.

I know image shift is very annoying, and you can even lose the image at high powers if it is bad.

I was satisfied fitting the Crayford which is only a single speed one, but with the mirror locked, it is easy peasy now.

Ron.

[Nightjar]

I too read the OP with heart in mouth, waiting for the clanger. Very glad to see that everthing went according to plan.

I've been considering this upgrade for a long time ... waiting for the confidence boost that you've just provided.

So .. many thanks,

NJ

[RosalinaandLuma]

I have just purchased this for my Meade LX 10, and about to start 'surgery' tonight