GPS Alignment Issue

[dpskala]

I had been having problems auto-aligning my LX200GPS, and thought I had figured it out, but apparently I was wrong. After doing all the automatic stuff - leveling, finding home, mag. north, etc. the scope would slew to the first alignment star, and be about 10 degrees off in azimuth. Same with the second alignment star. My location, DST, time, and all other data check out OK when I display them. So last week someone suggested doing a calibrate sensors procedure. I thought I had already done this, and in any event wasn’t too concerned because I happen to be located in NE Indiana where magnetic and true north are almost the same anyway. So I do the calibrate sensors, and sure enough, Polaris is also 10 degrees off (the scope slews to the west of it). After lining up Polaris, I do an auto-align, and it works pretty much like I expect. Then it dawns on me that the scope probably thought it was still in Irvine CA where it was born, and which has a magnetic correction about 10 degrees different from mine.

So fast forward to last night. I naively attempt to auto-align right away, and the problem remains. The alignment stars are still 10 degrees off and difficult to find. So I do the calibrate sensors again, and Polaris is again 10 degrees off. What gives??? Is not the magnetic correction stored in memory after I do it for a given location? Do I have to calibrate sensors every time I move or power up the scope? If so, then what is the purpose of having a separate procedure to measure magnetic declination correction? It could just be incorporated into the auto-align. What am I missing here? Do I somehow have to explicitly tell it to store the correction to magnetic declination?

I guess I could do the calibrate sensors procedure first, manually move the scope to home co-ordinates (to take advantage of the GPS leveling and time setting), then do a two star alignment. But I shouldn’t have to if I read the manual correctly.

[DaltonSkyGazer]

You only should have to calibrate sensors once every few months at most. Be sure you setup get good level. Also be sure you train your drives.

The initial stars wont always be right on, double check your location setting be sure to use accurate time(GPS should do this for you), and check your daylight savings settings. Do use a high power EP when centering and do follow the up and right rule to remove backlash from gears as you do final push of directional buttons.

I found when I first bought my LX-200 GPS, that it became more accurate over time, after a few training sessions. It will put objects quite easily into 16mm EP all night long without issue, this is more than adequate, with high precision goto's it bangs them in my ccd all night long.

When I setup in Field I do the GPS routine and do the two stars. If I moved to new site, I also do the calibrate sensors once or sometimes even twice. Be sure after placing scope on tripod, that you lift tripod legs one at time and fully shake them out also...you will find that you will have more room to tighten the center bolt after doing this. Then place plumbers level back on to verify level once again.

[MadCrawdad]

How are you positioning the scope prior to alignment? My manual doesn't mention this, but I find that I get better accuracy in finding alignment stars during auto-align when the electronics panel faces North (and the tube points South).

As I can't find it anywhere in the manual, I recently tried facing the panel South and OTA North for auto alignment. Even calibrated the sensors again. I found the scope needed much more movement during alignment to even get the star into the finder scope. Switched back to my previous orientation the next night, and alignment went swimmingly.

[dpskala]

Tripod is level after bumping to set the clamp screw; drives have been trained over and over; panel is facing south, OTA north to start.

MadCrawdad - on p. 38, item #3, it says to set home position manually, face the panel south and the OTA north. Granted, it doesn't say to start there with auto-align, but it does seem to imply that. I will try your suggestion to reverse this and see how it does.

Does anyone know if the correction from mag to real north is stored in memory?

[DaltonSkyGazer]

The panel orientation is important as suggested. When I orient the ota for the recommended setup I place the plumbers level across OTA and lock clutch manually to begin with. The method mount uses to establish level, is via a ball bearing which rolls in a slot with sensor, not totally accurate but suffices. This level procedure or dance as I call it takes place on the 3 planes, which is more reason to ensure good level of tripod legs and ota to begin with.

The previous calibrate sensors is stored in memory. The smartmount routine continues to improve goto performance.

The calibrate sensors routine can be interefered with from local electrical disturbances also. Be sure to also check your default viewing site location in the menu for accuracy.

[Joe Lalumia]

Good info above-- none of us can fix a mechanical problem-- however software issues are usually caused by:

1. Corrupted firmware data--- fix is to RESET the hand controller and reload the latest firmware.

2. Many strange issues can be fixed by doing a RESET in the hand controller and then a Calibrate motors -- and then a train drives (and sensors if you have a GPS/LNT module).

3. You only need to train drives about 1-2 times per year; calibrate sensors should be also be done about twice per year.

How does the scope perform once you have centered both alignment stars? Normally the first star will be off and the second star might also be a little bit off. This is normal.

So what happens after you center both stars??

Clear skies.

[dpskala]

1. Corrupted firmware data--- fix is to RESET the hand controller and reload the latest firmware.

Done that.

2. Many strange issues can be fixed by doing a RESET in the hand controller and then a Calibrate motors -- and then a train drives (and sensors if you have a GPS/LNT module).

Done that.

3. You only need to train drives about 1-2 times per year; calibrate sensors should be also be done about twice per year.

How does the scope perform once you have centered both alignment stars? Normally the first star will be off and the second star might also be a little bit off. This is normal.

So what happens after you center both stars??

After stars are centered properly, performance is fine. It's just a pain to find them when they are so far off.

I don't use smart drive - have never done the PEC corrections.

But I just now noticed something suspicious. The "home sensors" flag was set to off. If I read the manual correctly, that means that I'm on my own and it's ignoring the sensors. If so, it sounds like that could be my problem.

Thanks for the helpful suggestions.

[pdaderko]

I've also come across the same problem, on both of my LX200-ACF scopes (both bought brand new in the last couple years). I want to say after doing Calibrate Sensors quite a few times that it got better, but I can't say that with any certainty.

I did a bunch of searching last year for a fix, but never really got a solution for myself. One solution for someone was that their GPS was an hour off for some reason (one hour is 15 degrees). I checked that on mine, and it was fine. Others have said local metallic objects have messed with their sensor, and moving it fixed their problem. I've moved it all over the place (different part of the yard, different city, different state), no change for me. Both scopes are consistently wrong.

One thing I've wondered is if something is screwed up with the auto-align, where it ignores the magnetic declination (since it's kinda a fresh start, and thinks it's being smart w/ all the sensors). It's been a while, but I seem to remember auto-align working properly if I do "Calibrate Sensors" immediately before it. Polaris was still 10 or so degrees off for the calibration, but that's easy to find and center.

Both scopes perform great for me once they're aligned, but aligning is a tough. The best advice for a certain alignment is to press the '?' key so it tells you the name of the star that it chose, then find it in the sky and point there. Unfortunately for me, mine are remotely controlled... so to ensure I could do it, I mounted a wide angle camera on the scope so I can see a large chunk of the sky where I'm pointed.

Pat

[KeithBC]

I wonder sometimes if the 15 degree errors that various people report for various mounts is due to incorrect entry of DST / time zone information. Let me explain...

I live in the Pacific Time Zone. During the winter, on Standard Time, I am UTC-08:00. In the summer, on Daylight Saving Time, I am UTC-07:00. It would be tempting, in the summer, to enter my time zone as UTC-07:00, wouldn't it?

Yet (on my mount at least, and I suspect on most), that would be incorrect. The correct setting is UTC-08:00, Daylight Saving=YES, even though my clock is UTC-07:00.

[pdaderko]

I wonder sometimes if the 15 degree errors that various people report for various mounts is due to incorrect entry of DST / time zone information. Let me explain...

I live in the Pacific Time Zone. During the winter, on Standard Time, I am UTC-08:00. In the summer, on Daylight Saving Time, I am UTC-07:00. It would be tempting, in the summer, to enter my time zone as UTC-07:00, wouldn't it?

Yet (on my mount at least, and I suspect on most), that would be incorrect. The correct setting is UTC-08:00, Daylight Saving=YES, even though my clock is UTC-07:00.

From what I understand, DST and Timezone shouldn't matter for the scopes with GPS (unless there's a software bug). In my case I turn DST off and Timezone to +0, and work from UTC time.

Pat