Help with LX90 alignment problems

lineout · #1 13-10-2007, 11:25 PM

I need some help...the frustration is killing me. I have a LX90 LNT GPS. Lately I've had trouble with the alignment stars when doing an auto-align. The problem is that after slewing to an alignment star it is never in the eye piece. It's always way off and I have to go hunting for it which can take up to 5 mins. When I first go the scope (Jan this year) the alignment was good but it's gotten progressively worse. I've heard that I need to calibrate the sensors every time I use the scope and train the drives every 6-8 months (something I should do as I've had it for 10 months).

The Meade manual says that when calibrating the scope slews to Polaris. What do we do in the southern hemisphere where we can't see Polaris?

Please, please help. I'm about to chuck the whole thing in!!!!!

Thanx in advance.

citivolus (Ric) · #2 14-10-2007, 12:16 AM

Is your clock accurately set? Is your time zone? Daylight savings time? The LX90 is clock dependent for doing automatic alignment and guessing where the alignment stars will be. If doing a GPS based alignment, the time should be accurate (while time zone/DST may not be), but if you are doing a two star or some other alignment, the scope will just use the current clock setting, which can result in initial pointing errors.

Additionally, is the mount level? Is the finder scope aligned with the OTA? Finding an alignment star should take no more than 20-30 seconds typically, so if it is taking longer, maybe there are some other issues that are getting in the way. What focal length of eyepiece are you using for your initial search while aligning? A short focal length (say, 6mm) would make for very difficult initial alignment. Try using a 26-32mm eyepiece while tracking down the star, and then switch to a shorter focal length or reticle eyepiece for the actual alignment.

Don't chuck it in, the LX90 is a very good scope once you master the initial set up. As for the calibration, I believe the mount will use Sigma Octans, although I've never actually calibrated an LX90 in the southern hemisphere.

Regards,
Eric

nightsky · #3 14-10-2007, 05:12 AM

G'Day,
Also check this Video out,it will give you a better idea what to do,even though it's for the ETX 125 it will still help.And make sure you have your coordinates for your area,check the setting.
http://www.meade.com/educational/etx%20videos/index.html
Cheers
Arthur

acropolite (Phil) · #4 14-10-2007, 07:44 AM

I suggest you give up on the LNT and manually level &find north then 2 star align. I gave up using the LNT to find level and set north, I do that manually, then a 2 star align. Like you, I found the initial alignment pointing to be wanting. The LNT is often affected by nearby metal, for example a metal shed, pipes in the ground, anything metallic nearby. It should only necessary to recalibrate the sensors after a reset, or battery change in the LNT module. Part of the calibration routine for the LNT is to point to Sigma Octans (if you can find it). Once trained it shouldn't be necessary to retrain unless the handbox has been reset for some reason.

xstream (John) · #5 14-10-2007, 10:52 AM

I have to agree with Phil. Even though Anna's LX90 is pre LNT it's probably quicker to manually set-up and align anyway , I can usually have her scope up and running in less than 5 miutes.

So long as the alignment star is in the field of view of your finder before centring it is fine.
The only time I've ever needed to train or calibrate her scope has been after a firmware update.
Anyone that has ever used Anna's scope will tell you it works beautifully and that's a few of them on this forum.

Hope this is of some help to you.

lineout · #6 14-10-2007, 01:24 PM

Thanks for all the advice guys. Still learning.

I found that I the date was wrong (out by a day) and the time was not set. I also manually set a site. Hopefully tonight when I take the scope out all will be ok.

acropolite (Phil) · #7 14-10-2007, 01:32 PM

Quote:

found that I the date was wrong (out by a day) and the time was not set

If it happens more than once, that can be a sign that the LNT battery is getting low. The date and time are accessed from the LNT module. It can also be a bug, I found recently my LX simply didn't like working with the APM plugged in, I'm not sure why and as I don't use the APM at the moment I haven't been bothered finding why.

lineout · #8 14-10-2007, 07:42 PM

Quote:

Originally Posted by acropolite

If it happens more than once, that can be a sign that the LNT battery is getting low. The date and time are accessed from the LNT module. It can also be a bug, I found recently my LX simply didn't like working with the APM plugged in, I'm not sure why and as I don't use the APM at the moment I haven't been bothered finding why.

So does that mean you don't set the date and time when you first set up the scope?

tempestwizz (Brian) · #9 15-10-2007, 09:06 AM

The LNT battery lasts for a couple of years. When you first acquire the scope, you need to set the time and date, but after that, it should remember (via the LNT module) until the battery goes low. When you power on, after the Autostar Message, it should show something like 'getting time and date' and then proceed to ask about setup/align. If it asks you to enter time and date, then the battery is flat.
To my understanding LNT does not remember the drive training information. This is held in the Autostar handpiece.
I had all sorts of trouble with mine when I started a couple of years back, but it was all pretty much operator error. Initially I had set my longitude in the wrong hemisphere! There is a need to train it where North (or South is) since this is what calibrates the internal chip to allow for magnetic variation. I think I did mine in daylight by working out magnetic deviation fo my location, then using a compass with the appropriate offset and a long piece of string radially away from the scope mount in that direction. When it asks to point at Sigma Octans, ignore the declination part, and adjust for the correct southerly direction along the stingline.
That got things pretty close. Rarely did the first alignment star end up in the eyepiece, but always in the finder scope.
Note: 1 minute of error in your clock time relates to an error in pointing angle of 15 minutes.
Since then I have not had any problems. Occasionally I retrain the drives to stop rubber-banding, but not often.

Hope this helps. Just practice and experience will build confidence.

Cheers Brian

lineout · #10 15-10-2007, 09:23 AM

I don't think I set the date and time when I first got the scope. Excitement got the better of me and I just set it up and (naiively) expected it to work. I suspect most of my problems are operator error. It's a steep learning curve. If it's clear tonight I 'll go out and give it a go.

Cheers for the help.

lineout · #11 15-10-2007, 09:11 PM

Well I tried again tonight with no luck. I entered in the date, time etc and even trained the drives. When I did the align, the scope went to the 'general' part of the sky but was way off. Every star I tried was to the right and above the scope (so the scope was down and to the left of the star). And it wasn't just a bit off. It was quite a way.

Even when I got the scope aligned the stars that I tracked to were off to the side of the FOV, not in the centre.

I'm not sure what to do. The only thing I can think of that may have put the scope out of alignment is that a while back I had a 2" diagonal on the scope was slewing near the zenith, the diagonal pushed against the bottomof the fork assembly..........not very hard but I'm wondering if I've somehow mucked up the fork alignment.

Is there a site that gives step-by-step instructions on how to train the drives, calibrate the sensors and do a proper 2-star alignment?

If I can't fix it soon I'm going to take the scope back to the store as a faulty unit and get a new one. Maybe pay the extra for an LX200.

Any help would be greatly appreciated.

One thing I did learn was to not do a 2 star alignment with a 13mm eyepiece.

Cheers.

faramir · #12 15-10-2007, 09:46 PM

I have recently purchased a LX90 GPS and have never found that with auto align it finds the alignment star very accurately. It simply points to that region of the sky the alignment star is in. It then takes me a minute or two to find the star in the reversed image finderscope. Once I have centred the two alingment stars I find that its goto is very accurate. I initially thought this was a problem with the scope but reading around it seems this is the usual accuracy for alignment. Therefore not sure why yours scope was working so accurately initially. Is the goto OK once you have aligned the scope?

lineout · #13 16-10-2007, 06:05 AM

Quote:

Originally Posted by faramir

I have recently purchased a LX90 GPS and have never found that with auto align it finds the alignment star very accurately. It simply points to that region of the sky the alignment star is in. It then takes me a minute or two to find the star in the reversed image finderscope. Once I have centred the two alingment stars I find that its goto is very accurate. I initially thought this was a problem with the scope but reading around it seems this is the usual accuracy for alignment. Therefore not sure why yours scope was working so accurately initially. Is the goto OK once you have aligned the scope?

Maybe I was just lucky the first few times I did it. The GOTO is sort of accurate. The star I slew to is also off centre. What eyepiece do you use when aligning? Also have you calibrated you sensors? How do you find Sigma Octans?

acropolite (Phil) · #14 16-10-2007, 07:18 AM

Quote:

Is there a site that gives step-by-step instructions on how to train the drives, calibrate the sensors and do a proper 2-star alignment?

The manual sets out the calibration procedure. As long as the time and date are correct and you have the correct Lat/Long and time offset (from UTC) it should be correct. The operating procedure is much the same on the LX200. One other thing that may be a problem is the addition of sites, in some versions of handbox software additional sites cause problems and it's necessary to pick a site closest to your location then modify the coords to suit. Failing all else a reset, retrain and recalibrate may fix your problems. The calibration of the LNT module is not important if you do a manual 2 star align.

noelo · #15 16-10-2007, 01:18 PM

Micheal at Bintel showed me a trick to align the scope that may help.

First of all declutch the OTA (loosen the gear knobs) so that the scope can move in any direction.
Select 2 star align and press enter to go to the first star.The motors should start whirring but as the gears are disabled the OTA shouldn't move anywhere.
Wait until the motors stop and the handset beeps to inform you so confirm the first alignment star.
Then physically move the OTA until the first star is aligned in the finder scope.
Once this is done lock the gears by tightening the knobs and fine grain align using the keypad.
Next select the second star and align that withtthe gears enabled.

I usually use very bright and easily identifiable stars to do this with and it works well..

However if this doens't work you may have a broken sensor which will need replacement. Once again the guys at Bintel will be able to help.

I bought a LX90 8" over 12 months ago and initially everything worked well but after a while the alignment was way off and in the end the scope was bunny hopping as one of the sensors was blown. However once the sensor was replaced everything returned to normal.

lineout · #16 16-10-2007, 01:33 PM

four questions:
1. Which sensor
2. How do I confirm it needs replacing
3. How much
4. How long to fix

Also I a bit confused now as some people say it's working as epxected whilst others say it may be broken.

But cheers for the help anyway. I might pop into Bintel on the weekend.

AndrewJ · #17 16-10-2007, 01:33 PM

Gday Noel
Re

Quote:

Micheal at Bintel showed me a trick to align the scope that may help.

First of all declutch the OTA (loosen the gear knobs) so that the scope can move in any direction.

This trick actually works well with all Meade scopes.
One caveat though.
If you have a scope with RA hardstops, you MUST start from approx home position ( with RA clutch locked ) and let it slew near to the first star,
THEN release the clutches and manually centre.
The scope only knows where it is "relative to the stops", by counting how many encoder ticks it has moved each way,
In DEC this doesnt matter, but in Az/RA, there are some situations where you could choose two ways to get to the align star if fully manual
Pick the wrong way and you may hit the stops later in the night

Andrew

noelo · #18 17-10-2007, 10:39 PM

Quote:

Originally Posted by AndrewJ

If you have a scope with RA hardstops, you MUST start from approx home position ( with RA clutch locked ) and let it slew near to the first star,
THEN release the clutches and manually centre.
The scope only knows where it is "relative to the stops", by counting how many encoder ticks it has moved each way,
In DEC this doesnt matter, but in Az/RA, there are some situations where you could choose two ways to get to the align star if fully manual
Pick the wrong way and you may hit the stops later in the night

Andrew

Thanks Andrew, I didn't know this and it didn't have any impact at the time but I can see how it would. I have learned something new...

regards
Noel

MarkN · #19 17-10-2007, 11:25 PM

lineout

Did you get the 'scope new? If you got it in January it should still have warranty. Why don't you contact the retailer and save yourself a lot of trouble?

Mark

lineout · #20 18-10-2007, 08:34 AM

Quote:

Originally Posted by MarkN

lineout

Did you get the 'scope new? If you got it in January it should still have warranty. Why don't you contact the retailer and save yourself a lot of trouble?

Mark

Yeah I did get it new. I have considered contacting the retailer.