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Meade 14" LX200GPS - successfully updated from v2.0i

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#1 t-ara-fan

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Posted 30 July 2022 - 10:38 PM

My club has the above mentioned scope. In good shape, but with old firmware and definitely the GPS rollover bug.

 

Last year I put a new CR2032 battery in it.  Since this big boy was already on a wedge on a pier, I took off the front control panel and managed to jiggle the PCB out to swap the battery.  I have heard access is easier though the base, but no go with it on a pier.

 

The GPS would not get a fix ... tried many times. From my understanding, the GPS rollover bug only effects the date from the GPS, not the location.  But the GPS never got a location fix.

 

With the helpful people here (thank you OzAndrewJ) , I figured out I should use Starpatch and move up to v4.2G.  That was actually very easy to do, even with my scope being off the Internet so downloads of the patch etc. were done at home first.  Easy upgrade, but I still never got a fix. In the menus, I checked it was set up to get a "Fix on start" but still no go.  It would try getting a fix for a few minutes, then give up.   I cycled the power about 10x over a couple hours, the scope always gave up and used the location in memory which was Irvine CA ... I guess that was the location in the patch. 

 

What was weird and driving me nuts was the fact that I could look at the scope settings using Myscope 4.9.6.0 and see the handbox location data (Irvine) and the GPS location and time. The GPS location and time were correct to a few arc-minutes of lat/long.  But the handbox wasn't using the GPS data. What the heck?!?!?!?

 

I played around with a few things, set a new park position, parked the scope, and (sort of accidentally) left it powered on but parked and exposed to the sky (roll off roof open) from 4pm until 2am. That was pretty late when I packed it in, so I closed things up, powered down, and left it until morning.

 

Well surprise! In the morning, I opened the roof, powered up the scope and got a location fix and correct time in under a minute.  Yay!!!!!!!

 

What happened?  My guess is that the GPS unit needed lots of time to download a complete new almanac (rough satellite locations just to know what is in the sky) from one satellite, then the detailed ephemerides (exact up to date orbital elements) for each of the GPS satellites.  Once it had this data, the GPS was up to date and could quickly get a location fix and time it trusted. So the handbox could now use that GPS info and all is well.

 

This full download took hours.  When the scope is on a wedge the GPS antenna on the top of the fork doesn't point up like when the scope is in Alt-Az mode, it points 50° above the horizon. And the gable on the open roof to the north where the antenna is pointed blocks a bit of the sky too. The Meade finder scope beside the GPS blocks more of the sky.  All conspiring to slow the download and update of the GPS.

 

Great success

 

Next up: 3 star align, and put a Moonlite focuser I am not using on the scope.  Because holy cow does the image ever shift when focusing.  And there is brutal hysteresis with the manual focus knob.

 



#2 nitegeezer

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Posted 30 July 2022 - 11:39 PM

Turn the focus knob all the way one way and then reverse all the way several times to redistribute the grease, and that should help the focus. Then always focus ending in CCW turns so the focus is pushing on the mirror rather than pulling on it. Between the two the focus should be smoother and with less mirror flop.

I always park my scope with the GPS fork on the top and configure the GPS on at power up. I get a fix faster and every time that way.

#3 t-ara-fan

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Posted 03 August 2022 - 09:45 AM

Thanks for the tips.

#4 OzAndrewJ

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Posted 03 August 2022 - 04:47 PM

Gday t-ara-fan

Another way to do this ( but much faster ) is

release the focus lock and use the focusser to push the sled as far forward as you can.

Unscrew the 3 bolts holding the focusser to the rear casting.

You can now use the focusser as a pushrod to push the sled forwards and backwards quite fast

and as such detect when the stickiness drops to a smooth action.

Re screw the focusser in position and refocus.

 

Andrew Johansen Melbourne Australia


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