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Baffling Autostar behavior

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#1 hlritter

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Posted 16 May 2019 - 01:05 AM

HELP!

 

I have two LX200 GPSs, a 16" and a 7", both tripod-mounted in Alt-Az. I just moved both scopes to Ohio. Both scopes as of last night still had their original 2032 cells, 15-20 years old. I had not been aware of this cell until researching this problem online today. I had not checked or set the time or date on either scope, naïvely thinking that they got this information from GPS.

 

The 16 has long been having problems with azimuth pointing and with tracking, but at least when it headed for a star on alignment or did a GOTO, it pointed to the near vicinity of where it was supposed to. The 7 had been working satisfactorily when last used a year or so ago.

 

Until first Ohio light last night. Each scope, on two-star alignment after aligning on home, got a prompt GPS fix, noted that it was in a new location – then headed not for the chosen star, Vega, but to a spot some 120° of az away from Vega. I thought at this point to check the date, which on both scopes showed 29 Sep 2099, and the time, which was inaccurate. However, the new location was displayed accurately. I set the date and time and now got accurate pointing on Align and GOTO.

 

Today I replaced the 2032 cells. I took out the 16", set the time and date and did Align On Home. No improvement. When I turn the scope on, it's back to the default date (my wife's 150th birthday, as a matter of fact), and time is off. Worse, when I move away from Time or Date in the Autostar menu and come back, the date may have changed by a day or two and the time by an hour or two. If the time and date hold once set and the scope is not turned off, it will align, GOTO, and track well for the most part. I say "most part" because GOTO can be wacky: On GOTO Jupiter, the handbox says "Rises 2250", which is correct, but the time is 2350 and I'm looking at Jupiter low over the neighbor's house! I manually slew to Jupiter, center it, hold the Enter button to sync, then move the scope a few degrees away from Jupiter and tell it again to GOTO Jupiter..."Rises 2250". GOTO Moon gets me "Rises 1730", again correct but irrelevant since the Moon is practically overhead now. Same thing with Spica. The scope – despite (as I verified) having the time, date, and location correct – seems to think, somehow, that these visible objects have not yet risen. But GOTO Vega? GOTO Mizar? The scope swings into action and lands right on target!

 

I also note during two-star alignment that many bright stars that are in view and would be suitable targets do not appear in the list of stars that can be selected for this procedure, perhaps also because the scope thinks they're below the horizon, despite verifiably having the date, time, and location correct.

 

(Parenthetically, the scope's pointing accuracy for the first star during alignment, and on GOTO, is vastly improved from before, and tracking accuracy has been recovered, presumably because I'd never thought to check and correct the time and date.)

 

I did not have the 7" out tonight, but after replacing its C cells and the 2032 today, I did verify that it too still will not remember time and date after being turned off, and may accumulate errors in the same way as the 16 while being left turned on. Next clear night I'll see what mischief it gets into in actual use.

 

Again, neither scope behaved like this when last used, and neither behaves better with new 2032s. And, of course, getting new cells did not improve the suddenly – in BOTH scopes simultaneously – nonfunctional memory, which doesn't retain time or date reliably even when the scope is left on!

 

Are both scopes the victim of identical memory failures – simultaneously? And what about the error in the visibility of some objects but not others, which can't be accounted for by a failure to remember the time and date, because the handbox shows the CORRECT time and date and location? Any suggestions for correction?

 

And maybe this is known only to Meade, but why doesn't the scope take its time and date information from the GPS signal? It would avoid a lot of heartache if it did, because I'm surely not the only user who wasn't aware of the pitfalls of the loss of date and time from memory and is suffering a loss of pointing and tracking accuracy.

 

Sorry for the length, but I think the details are important. Thanks for reading.

 

--howard



#2 sg6

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Posted 16 May 2019 - 03:18 AM

The GPS had a problem in a way for the second time.

The GPS count Weeks (no idea why. And in April the ten digit value rolled over from 2048 back to 0

So your GPS is getting told that it is week 10 (say) and the firmware says week 0 or 10 or whatever it is is some years either in the past or the future.

 

This has occurred twice, the first time not many GPS around, this time lots.

 

Check the Meade specific area and I think you will find somewhere in it a link to new formware, you need to update the system with that. It basically knows where to start counting from.

 

I need to find it for 2 Meades that I also suspect will need it.

 

Alternative is to enter the menu and turn the GPS bit Off and then set Date+Time+Location yourself.



#3 EdIII

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Posted 16 May 2019 - 06:57 AM

See “Meade GPS rollover patches”,  this forum. Everything you need to know is there.

 

Ed


Edited by EdIII, 16 May 2019 - 06:57 AM.


#4 hlritter

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Posted 16 May 2019 - 10:42 AM

Thanks, sg6 and Ed. I'll see if I can install the update. I had no idea that there's a GPS rollover problem, or that GPS can be deactivated. The scope is scheduled to be optimized by Dr Clay this summer, but I'll see if I can do this myself. Failing that, I'll just turn it off.

 

--howard



#5 EdIII

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Posted 16 May 2019 - 01:24 PM

Thanks, sg6 and Ed. I'll see if I can install the update. I had no idea that there's a GPS rollover problem, or that GPS can be deactivated. The scope is scheduled to be optimized by Dr Clay this summer, but I'll see if I can do this myself. Failing that, I'll just turn it off.

 

--howard

 

As long as you have the correct cables and follow the instructions, it is a piece of cake. 

 

Ed



#6 SkipW

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Posted 27 May 2019 - 08:03 PM

The GPS count Weeks (no idea why...

I think it's because a week is the longest unit of time that has a constant length (but only if you ignore fortnights, which are two weeks).




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