LX200 RA tracking problems (are they the same for 14" LX200's)

I've begun CCD imaging with a pier mounted 10" F/10 LX200 Classic.

After the anticipated (usual) problem elimination phase, one
fundamental issue remains. The RA tracking (error graph) shows random
spikes of +/- 1-4 arcsec at frequencies of 1 second or less. This
"noise" is random and happens throughout the 8 minute worm cycle, not
intermittently. I can successfully train out periodic error (manually
or with CCD), but after training, auto-guiding is worse due to the
random spikes. Even with fast exposures (0.1 sec) the guider sees the
error, but by the time correction is applied, the RA error has changed
so overcorrection often results. PEC adjustment compounds it (if PEC
is on). So far, my best images were made by stacking 1 minute unguided
frames with PEC training erased! But RA spikes still manifest (too
often) as elongated or doubled stars. Sigh!

Since I really have exhausted all other possibilities, it MUST be the
RA drive/gears of the LX200. It can't be seeing as it doesn't happen
in the Y direction. I've tried loading to east and west, and perfect
balance. I've measured error with guiding active and off (spikes in
both cases). I have perfect polar alignment and I tried all variations
of aggressiveness and calibration settings. It looks like I've got to
disassemble and clean the RA mechanism as it is the only viable cause
remaining (and this worked for others from what I've read).

I'd hoped to avoid this altogether and I'm minded to make do as I
intend(ed) to buy a 14" LX200 at the end of this year (observatory and
mount were sized for a 14" SCT – not the 10" SCT I currently own.
How's that for aperture fever "built in" :-)

So my question is – does the 14" LX200 have exactly the same
RA/guiding issues as the earlier (8", 10" and 12") models – or is the
quality better these days? I'm not so sure that I want to spend £5,500
for a bigger scope if it's likely to have exactly the same (guiding)
limitations – even if it does have twice the light grasp. Or perhaps
I've just got the wrong impression from using a second-hand (old?)
Classic LX200.

Cheers
Beats

PS. I don't want a GEM and I DO want more aperture and resolution.

So my question is - does the 14" LX200 have exactly the same
RA/guiding issues as the earlier (8", 10" and 12") models - or is the
quality better these days? I'm not so sure that I want to spend £5,500
for a bigger scope if it's likely to have exactly the same (guiding)
limitations - even if it does have twice the light grasp. Or perhaps
I've just got the wrong impression from using a second-hand (old?)
Classic LX200.

I'ma member of a local astronomical society. quite a few of our members have
LX200s both classic and GPS. None of them has spoken of the error you are
having. It sounds as if you have grit in between the worm an wheel... In
your situation I would open up the LX200 and clean the worm and wheel as
well as possible, before re-greasing and reassembling...

From what I have seen of my friends' 'scopes, the LX200GPS does track much
better than the LX200Classic...

Rarius

"justbeats" wrote in message
m...
I've begun CCD imaging with a pier mounted 10" F/10 LX200 Classic.

After the anticipated (usual) problem elimination phase, one
fundamental issue remains. The RA tracking (error graph) shows random
spikes of +/- 1-4 arcsec at frequencies of 1 second or less. This
"noise" is random and happens throughout the 8 minute worm cycle, not
intermittently. I can successfully train out periodic error (manually
or with CCD), but after training, auto-guiding is worse due to the
random spikes. Even with fast exposures (0.1 sec) the guider sees the
error, but by the time correction is applied, the RA error has changed
so overcorrection often results. PEC adjustment compounds it (if PEC
is on). So far, my best images were made by stacking 1 minute unguided
frames with PEC training erased! But RA spikes still manifest (too
often) as elongated or doubled stars. Sigh!

Since I really have exhausted all other possibilities, it MUST be the
RA drive/gears of the LX200. It can't be seeing as it doesn't happen
in the Y direction. I've tried loading to east and west, and perfect
balance. I've measured error with guiding active and off (spikes in
both cases). I have perfect polar alignment and I tried all variations
of aggressiveness and calibration settings. It looks like I've got to
disassemble and clean the RA mechanism as it is the only viable cause
remaining (and this worked for others from what I've read).

I'd hoped to avoid this altogether and I'm minded to make do as I
intend(ed) to buy a 14" LX200 at the end of this year (observatory and
mount were sized for a 14" SCT - not the 10" SCT I currently own.
How's that for aperture fever "built in" :-)

So my question is - does the 14" LX200 have exactly the same
RA/guiding issues as the earlier (8", 10" and 12") models - or is the
quality better these days? I'm not so sure that I want to spend £5,500
for a bigger scope if it's likely to have exactly the same (guiding)
limitations - even if it does have twice the light grasp. Or perhaps
I've just got the wrong impression from using a second-hand (old?)
Classic LX200.

Cheers
Beats

PS. I don't want a GEM and I DO want more aperture and resolution.
This sounds like dust.
If you think about it, the error you are talking about, is in the same
order as the size of pollen grains/particles of smoke etc.. If the gear is
about 6" in radius, then the jump corresponds to about 30 micron particle
sizes, when smoke particles are normally quoted as around 40 micron. You
need to scrupulously clean the main gear, and worm, and relubricate with a
really good lubricant. This is probably just 'muck' that has got stuck in
the grease with time.
It is actually a lot smaller in size than the sort of jump that is often
seen from LX200's when new (where metal shavings have got left in the
mechanism...). The metal surfaces usually improve with use, developing a
polish that is not there on the new scopes.
Hence your thoughts to clean the mechanism are the way to go.

Best Wishes

justbeats wrote:
I've begun CCD imaging with a pier mounted 10" F/10 LX200 Classic.

After the anticipated (usual) problem elimination phase, one
fundamental issue remains. The RA tracking (error graph) shows random
spikes of +/- 1-4 arcsec at frequencies of 1 second or less. This
"noise" is random and happens throughout the 8 minute worm cycle, not
intermittently. I can successfully train out periodic error (manually
or with CCD), but after training, auto-guiding is worse due to the
random spikes. Even with fast exposures (0.1 sec) the guider sees the
error, but by the time correction is applied, the RA error has changed
so overcorrection often results. PEC adjustment compounds it (if PEC
is on). So far, my best images were made by stacking 1 minute unguided
frames with PEC training erased! But RA spikes still manifest (too
often) as elongated or doubled stars. Sigh!

I'm not familiar with the gears on the LX200, but if it has a series of
spur gears somewhere they may be too tight and "cogging". A few LXD55
owners had this problem due to over tight gear mesh.

-tom

If you plan on keeping the scope for a long time...just spend the $ if
needed and get a set of custom gears made if you want it next to perfect.
Our club has a 16" LX200 and the RA drift is all over the place...back and
forth..within 5 minutes of guiding. It has been sent to Meade twice and
each time they say its within spec. I don't see how anybody or anything can
photograph @ 4000mm. I took a 15 min exposure through a piggybacked scope
and guided through the 16" with a 9mm crosshair eyepiece...I couldn't hardly
look away for a second or two before quickly having to look back to see the
star running out of the cross hair..toward the first bullseye ring...either
one way or the other...say half the diameter of the Trapezium...if you draw
a circle through the 4 stars. I'm using this as a guide because this is
what I was guiding on at the time. I didn't have the PEC on ...just guiding
in regular mode or whatever. Maybe play around with the drive system of
the 10" first and see what works and what doesn't as far as adjustments and
grease and what not before buying the 14". You could become the SCT
motordrive GURU!!!!

Good Luck!

Joe

"J McBride" wrote in message ...

Our club has a 16" LX200 and the RA drift is all over the place...
I didn't have the PEC on ...just guiding in regular mode or whatever.


That would account for the major wobbles you were getting then. PEC
must be on!

My scope has a couple of points that behave as you describe if PEC is
off. Training the drive removes this altogether (I'm just left with
the random noise though). Actually, it's better for you 16" folks as I
read somewhere that PEC training is set at the factory. Bloody luxury
:-)

Cheers
Beats

"Rarius" wrote in message ...

From what I have seen of my friends' 'scopes, the LX200GPS does track much
better than the LX200Classic...


Thanks Rarius, exactly the kind of anecdotal observation I was looking
for (and all the better because it's a positive one :-)

There's surprisingly little comparitive info around for the 14", so
keep 'em coming folks. I'll summarise if enough "sample points" turn
up. Thanks.

Cheers
Beats

Lucky??? It has screwed up twice and We had to ship it back at our
cost...plus being without a scope for a month or so.

Joe

(justbeats) wrote in message om...
I've begun CCD imaging with a pier mounted 10" F/10 LX200 Classic.

After the anticipated (usual) problem elimination phase, one
fundamental issue remains. The RA tracking (error graph) shows random
spikes of +/- 1-4 arcsec at frequencies of 1 second or less. This
"noise" is random and happens throughout the 8 minute worm cycle, not
intermittently. I can successfully train out periodic error (manually
or with CCD), but after training, auto-guiding is worse due to the
random spikes. Even with fast exposures (0.1 sec) the guider sees the
error, but by the time correction is applied, the RA error has changed
[...]

Just musing: are your dew heater(s) running off the same power supply?
If so, don't do that.

"J McBride" wrote in message ...
Lucky??? It has screwed up twice and We had to ship it back at our
cost...plus being without a scope for a month or so.


"Lucky" he snorts - slamming down his coffee in righteous indignation!

Tee hee. Sorry! Your response conjured up that mental image. Raised a
bit of a chuckle here :-)

Does sound like you've had a bit of a runaround. I know what you mean
about being without the scope though. That's why I'm not keen to get
into serious disassembly of mine, just in case I break something
terminally and then have to wait for someone else (e.g. Meade) to fix
it for me.

I'd have thought that you could expect much better service and
performance at the price point of a 16" though. Weren't they about
£27K not that long ago? They seem to have dropped in price
dramatically lately (though still a big leap in cost from 14" to 16").
Are they the same scope at the new price point (if I'm not imagining
the new price point). When did your club get theirs?

Cheers
Beats