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MI 250 mount maintainence and support

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#1 pubquiz

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Posted 20 December 2012 - 04:42 AM

Hi All

I have seen a Mountain Instruments MI 250 mount for sale here in the UK and was wondering if there would be any future maintenance issues if i bought it.

I have read only good things about the mount and the support from Larry Meyers when it was in production and supported.But wondered what the situation was now particularly for UK owners.

I have read that on early models a clean and re-grease of the gears/worm is a 'send back to the states' job which puts me off a bit.

I have a G11 which is 'push to' with an argo navis which I love but am very tempted by the MI 250 with the Gemini Goto..and it's extra capacity. I have had aperture fever in the past...I think I have mount fever now.

Any thoughts on long term maintenance issues appreciated.

Tom

#2 Raginar

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Posted 20 December 2012 - 04:51 AM

Hey Tom,

Come on the MI250 Yahoo Group!. I think you'll find there is a another Tom (Tom Hilton) who maintains the website for it (with some maintenance instructions), along with the Gemini 2 website, and he runs the Yahoo! Group too. I think you'll find the entire group very helpful and from what I've heard the mount is very accessible.

I was in the same boat when I decided to purchase mine. I was worried about a non-existent manufacturer; however most of the parts are available through Losmandy (motors, gearboxes). I think the only thing I haven't found a replacement part for is the worm assembly and really that shouldn't go bad.

Issues I've heard about with the mount are pretty much nil. There is potential interaction between the declination and RA axis if you allow it to track to meridian; but if you're using Gemini2 you can program that out. There is also a 'mod' that involves making an adapter to push the declination axis out a few inches and prevent the problem entirely.

Honestly, it's a solid mount that I don't think you'll be dissatisfied with. I think many of the old owners end up moving on to AP mounts, but I haven't run into one that didn't love their MI250.

Hope that helps, and we'll see you on the boards.

Chris

#3 pubquiz

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Posted 20 December 2012 - 05:01 AM

Wow Chris thanks for the rapid reply....especially since it is 3.00AM in South Dakota...you must be imaging or an insomniac :)

Good info there ...if I do get it (will have to see how much money I have...it's low with being Xmas :))I will certainly join the MI 250 forum.

Tom

#4 Raginar

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Posted 20 December 2012 - 05:09 AM

Sent you a PM :).

#5 Bowmoreman

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Posted 20 December 2012 - 05:38 AM

I echo Chris. Bought mine used three years ago, only issue was a scrambled Gemini after a near miss lightning strike. Repaired for only $85. Still using Gemini I, though II looks interesting. If I ever tstruck it rich, I'd maybe get a Paramount MX, but the 250 easily handles my loads... Either a C11 and FSQ106ED side by side, or when I change out to dual Taks, with my TOA 130... Total load range around 65 pounds or so... I get great tracking and almost never throw out subs. Previous owner had measured the error at plus/minus 2"... I've never had reason to doubt it, or bother measuring. My STV guides it like a champ.

As pointed out, it won't track too far past meridian, but that's easily planned for most of the time. I would recommend the Maxxon motors tho...

A great mount, and a classic, IMHO

#6 pubquiz

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Posted 20 December 2012 - 07:42 AM

Thanks for that Dave will see if I can afford it over Xmas :)

And thanks for the PM's Chris

Tom

#7 David Pavlich

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Posted 20 December 2012 - 08:57 AM

I'll join the chorus. Negatives first: The previously mentioned lack of imaging past the meridian, about 40 minutes with the stock motors. The base is designed to cover a 10° swath. Example: mine was built to cover from 25° to 35° latitude. For it to work for someone at 40° latitude, you'd have to have a new base designed or build a wedge to compensate. The other minor complaint that I have is that the Alt and Az adjustments could be a bit tighter. I've thought about taking mine off the pier and having the adjusting rods and fork made with SAE thread instead of USS thread.

My mount is powered by SiTech, a distinct improvement over Gemini. I also changed the motors to Maxons. Once you get to the MI250 group, you'll find several other modifications as well. One thing about the mount, it is WAY undervalued as far as capacity is concerned. These things are built like the proverbial brick observatory. One other thing I did was install and ADM counterweight shaft and had all my counterweights bored and drilled for locking screws. Another big improvement. Larry's use of a large threaded rod wasn't the best idea. But the overall capability of the mount is exemplary.

David






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