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Subject: Re: LX200 clock
From: Martin Tom Brown
Reply To: mapug@shore.net
Date: Tue May 21 01:12:20 1996

In message <v01510100adc663631abf@[136.142.137.137]> Robert Preston writes:
>
> Jeff Price wrote, quoting an automobile service situation,
> >'just how good is this thing if they can't get the stupid clock right?'

Sorry to have restarted this apparently perrenial thread...

Looking through the Mapug archive as you suggested I note that
TinyHost@aol.com claims to have seen an older motherboard with
a trimmer capacitor near the RTC Xtal which is replaced with a
fixed value on the modern boards. The raw accuracy of an untrimmed
Xtal is typically +-200ppm or 20s/day (in line with the range seen).
If this is really the case they had the design right, but chose to save
a few minutes unit test time by changing to a fixed load capacitor.

> When that question comes up with the lx200 at your local star party, you
> hit "M","5","7", "ENTER", and "GOTO", and while it's slewing say, "You
> wanna see the Ring Nebula? Take a look." Then, when they're looking
> at a smoke ring essentially in the center of your 30 arcmin field, you
> say, "This scope is SO good it runs on time even when its clock is wrong."

Do you work for Meade marketting? :-)

> Of course, as you hit the "GOTO", remember to silently pray that a drive
> doesn't blow.

OTOH perhaps not.

Anyway why point out that the clock is wrong at all?
I was only worried because it seemed that if I didn't reset the clock
(ie. setup in a hurry) then the pointing was not so good (v2.515 ROMs),
and in retrospect looked like it was roughly proportional to clock error.
I'll freely admit this could also be due to poor levelling on my part,
since I only have one star allignment. On a good day pointing is perfect.

Regards,

-- 
Martin Brown  <martin@nezumi.demon.co.uk>     __                CIS: 71651,470
Scientific Software Consultancy             /^,,)__/