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Small Observatory Needs Help LX200 16" Help

Meade Mount
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#1 cmjocius

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Posted 10 July 2021 - 12:30 PM

Good morning and thank you for stopping by. I am told this is the place to be for all my telescope needs. We run a small public outreach nonprofit observatory in SE Wisconsin. We have a 20' dome and 16" Meade lx200 ACF with GPS on a Az/Alt pier mount. One major problem throughout the years is the scope does not always know its end point and continues slewing until the command is aborted or I have to do a quick shut down. After which I need to perform a full alignment and that is often an unfortunate delay during a public show.  I have done a few full rotations and did what I though was a reset on the parameters within the hand held and the program (TheSky Professional) we use to control the scope. There did not seem to be a correlation to the slewing past the end while using the program vs using the Autostar II, as it failed using both or either at certain times. We replaced the battery and the power supply and recently this has been less of an issue until last last night. It reached the point while I had a full group and I was unable to reach the power switch before it made a horrible grinding sound and now will no longer rotate. We can hear the motor turning but I assume a gear has slipped or stripped. The clutch seems fine as it turns normally with the hand knob and clutch released. 

 

I know what we need to do access the RA assembly from underneath and also I have read that the plastic gears that come on the lx 200 are a common issue which is somewhat easily replaced with new brass gears from Peterson engineering. All of this is speculation until we remove everything and look under the hood. 

 

My main question is how do I get this scope to always know which way to slew so it never hits this end point? 

 

My second question is why do I have to tell the scope what the date and time is every single time I turn on? My toaster knows what time it even after I unplug it and plug it back in. 

 

While I am a Physics and Astronomy pro, I am a complete telescope novice, so please use beginner speak in any and all descriptions or help that you may be able to provide. I attempted to read through the forums and found that I do not understand a large majority of professional telescope coded language and had to Google quite a few acronyms and still had difficulty understanding what parts they were describing.      

We are concerned over how long we will be down and how difficult it may be to replace any Meade parts. As far as I can tell Meade is no longer providing any help on their products what so ever. 

 

If anyone has any information that might help or know of any walk-through videos, we would really appreciate the help. 

 

https://hawthornholl...rg/observatory/



#2 nitegeezer

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Posted 10 July 2021 - 12:54 PM

While I am a owner of an LX200, it is my understanding that the 16" is a different beast so there are some details that only another owner of a 16" can provide.  Unfortunately, I don't know what those differences are so take my comments with that in mind.

 

The crash stop is in place to insure there is no internal cord wrap in the mount.  For this to work properly, the mount needs to be set up with the control panel facing a known position, I am not sure whether this is north or south for a 16".

 

Meade did not put a real time clock in any of their mounts that I am aware of.  The battery backs up information to help the GPS lock faster, it does not power a clock.  If the battery dies, it just takes longer for the GPS to find satellites.  Since your mount has the GPS, you should be able to obtain time from it unless the dome is causing interference.  The GPS that Meade used is not near as sensitive as the ones we have in our phones, this design is years old.  If you want to try the GPS, in the Telescope Menu, there is a setting for the GPS.  I believe the choices are Off, On At Startup, and On When Needed.  I always have mine set to On At Startup.

 

I am not even going to address anything about the internal mechanics due to it being a 16".

 

Good Luck


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#3 dcaponeii

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Posted 10 July 2021 - 01:28 PM

It sounds like the same kind of encoder issues others are having with their LX 200’s and LX 600’s. Not knowing the 16” base I can’t comment on the difficulty but it was an easy fix on my 12” LX 600. Good luck from another physicist.
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#4 carolinaskies

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Posted 10 July 2021 - 05:39 PM

Sounds like the GPS may be the older version needing a firmware update and the button battery replaced.  

As it's mounted in a permanent location you should be able to use the Park command and I would suggest reading up on how to do this.  Using the Park command and then UnPark will bypass the startup Center-Tip-Tilt routine

BTW, we have a group specifically for 16" LX200s over on Groups.io  https://groups.io/g/16-LX200/messages  

Over there you'll get direct responses from owners to help.  

 



#5 OzAndrewJ

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Posted 10 July 2021 - 05:57 PM

Gday cmjocius

 

My main question is how do I get this scope to always know which way to slew so it never hits this end point?

As noted by Chuck, the mount has an internal hardstop system.

When you start an align, the mount has to be put in a certain position and this is recorded "in software"

when the first slew starts. After that, the distance from this point is what determines what way the base will go in order to get to the target without hitting the stops.

There are "home sensors" in there, but they dont relate to the end stops, just the home position.

 

As noted by Don, you "may" have an encoder problem.

Very quick test.

Manually put the mount in the home position and boot it up.

Press and hold mode for 4-5 secs and release

Scroll to the Alt/Az screen

Note the Az, then slew at high speed for about 90deg ( as measured by the setting circles )

Drop speed near the end to get as close to 90 as you can

Note the reported Az

If it reports moving less than 90deg, then you might have an encoder problem.

 

Andrew Johansen Melbourne Australia




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