LX90 polar alignment driving me crazy.

[michael8554]

I've changed the post, see below

 

Edited April 12, 2020 by michael8554

[michael8554]

Here's the EQ PA setup from the LX90 manual, it's pretty clear it's the same procedure as the LX200  etc :

Begin polar aligning the telescope by locating Polaris. 

 

(They forget to mention to set the mount and wedge pointing true north as best you can, with the control panel facing north, see image below - MIchael)

 

1.

Select "Setup: Telescope" from the AutoStar menus. Press ENTER. Scroll to "Telescope:
Mount" and press ENTER. Scroll to "Scope Mounting: Polar" and press ENTER. The tele-
scope mount is now set to the polar mode.

2.

Press MODE until "Select Item: Setup" displays. Press ENTER. "Setup: Align" displays.
Press ENTER. Scroll to "Align: One-Star" and  press ENTER. AutoStar now prompts you
to set the telescope in the polar home position.

a. Using the bubble level of the wedge, adjust the tripod legs so that the bubble is level.

b. Set the wedge to your observing latitude.

c. Using the Up and Down Arrow keys, rotate the telescope tube in Declination so that

the telescope’s Declination reads 90°, that is the moulded Dec pointer (11, Fig. 1) is

pointed to 90° on the Dec. setting circle.

 

(Dec 90 on the Dec scale means you're pointing at Polaris, NOT south Dec 0 - Michael)al:

 

d. Loosen the R.A. lock, and rotate the fork arms to the 00 position H. A. on the R.A. setting circle.

 

(This means align the marks just below the RA lock with the mark on the base above the control panel. I'm not sure that's right, because the home position is definitely upside down, see image. 

So rotate 180 degrees in RA until the index mark is at the back and diametrically opposite the front marks - so that the scope is upside down - Michael)

 

H

  Ho

 

Home Position, pointing at the NCP

 

e. Press ENTER. The telescope slews to Polaris.

 

(As Polaris is only about 2 degrees from NCP, the mount will rotate a lot in RA to Polaris's hour angle, and a tiny bit in Dec 2 degrees. The Autostar now has a known position for Star Alignment, the next bit is setting PA  - Michael)

 

f. Use the azimuth and latitude controls on the wedge to center Polaris in the field of view. 

 

(The mount has moved to where Polaris should be at that time of night, so you centre it with the wedge controls. Only you can't see Polaris unless you have a Star Diagonal, or a camera that clears the base when pointing north , so just press ENTER and do a Drift Align - Michael)

 

Do not use the AutoStar handbox during this process. When Polaris is centered,
press ENTER. The telescope is now polar aligned.

 

Michael

 

 

[tooth_dr]

I spent a frustrating two hours trying to do an alignment. I’ve just searched and found this thread.

Im having the exact same problem as the opening poster.

I align/centred with Polaris as described in the manual but when it slews to the first star after that eg vega it was pointing to the wrong side of the sky.

It’s an LX600 with GPS.

Any pointers appreciated

[michael8554]

All the above assumes you have the scope on a wedge, the mount set to POLAR in the Setup/Telescope/Mount menu, with the control panel on the north side.

That's the opposite of the control panel position for AltAz operation.

Check that the GPS has got Date, Time, Lat, Long correct.

Meade show the date as eg 29 Aug 2020 so it's easy to check.

Long should be (-) for NI.

But you could try slewing with the handset to Vega, ENTER,  and then see if the next star is closer.

Michael

[tooth_dr]

31 minutes ago, michael8554 said:

All the above assumes you have the scope on a wedge, the mount set to POLAR in the Setup/Telescope/Mount menu, with the control panel on the north side.

That's the opposite of the control panel position for AltAz operation.

Check that the GPS has got Date, Time, Lat, Long correct.

Meade show the date as eg 29 Aug 2020 so it's easy to check.

Long should be (-) for NI.

But you could try slewing with the handset to Vega, ENTER,  and then see if the next star is closer.

Michael

Thanks Michael.  I have it on a wedge and as soon as its is turned on it, when I press 0, it tells me to put the mount in polar home position.  I have never used the scope in AltAz, and this is only the second time I've actually powered up the scope since it was bought.  The first time I had it on a tripod and when I turned it on, it went through a whole rigmarole of measuring how level the base was etc, it seemed to be doing a lot of calculations.  This time I have it pier mounted and it hasnt done that. The control panel points north and I have moved it manually to the polar home position by undoing the clutches.  I have followed the instructions for getting it aligned to polaris, and it does rotate in RA, then I recheck the position of polaris by adjusting the wedge and confirm this.  It is next that it doesnt go to the first star.

I manually entered the date and time last night as a final resort in case the GPS was wrong, and still it did not work.

It doesnt seem to behave like my older LXD75/autostar.  It would have slewed to a star, then beeped and asked to confirm if it was centred.  In this hand controller, autostar II, it says CTR. VEGA slewing..... and that screen doesnt disappear on the hand controller.  It's like it wants to keep slewing but it isnt moving.

 

Edited August 29, 2020 by tooth_dr

[tooth_dr]

2 hours ago, michael8554 said:

All the above assumes you have the scope on a wedge, the mount set to POLAR in the Setup/Telescope/Mount menu, with the control panel on the north side.

That's the opposite of the control panel position for AltAz operation.

Check that the GPS has got Date, Time, Lat, Long correct.

Meade show the date as eg 29 Aug 2020 so it's easy to check.

Long should be (-) for NI.

But you could try slewing with the handset to Vega, ENTER,  and then see if the next star is closer.

Michael

Michael.

Ive re-read your previous post and watched the video on the previous page and it’s clear I messed up on step c. This would explain why it didn’t slew to vega.  I MANUALLY moved it in Dec.  I did wonder how I was supposed to get it exactly on 90degrees.

Im going to try later and will let you know. 
 

Thanks again

Adam.

 

[Davey-T]

Mines permanently set up on  pier and parked in default up south position after using, this is important as it will know where it is next time you start it up and avoid all the setup rigmarole.

Long time since I set it up but IIRC I just had it upside down aiming at Polaris with something like a 26mm eyepiece, used the finder to get Polaris in the main scope and spun it back and forth in RA adjusting bolts to keep Polaris in the FOV, this gets it pretty close to being polar aligned.

I then drift aligned it but you can use PHD or DARV to get it spot on.

Then using handset park scope aiming up south, ie 0 RA 0 DEC, don't worry where it stops, switch it off then loosen clutches and manually put it in the parked position, next time you switch on it will know where it is so I just do a GoTo on a convenient bright star, something beginning with A to save scrolling down the list, using the handset and if necessary the finder scope centre it then hold down the enter key for a couple of seconds and you should get a message saying " to sync on Altair press enter " press enter to get a beep and success message, it should  then be good enough for imaging but if not the same thing can be repeated by syncing on something near your imaging target.

Dave

[tooth_dr]

4 minutes ago, Davey-T said:

Mines permanently set up on  pier and parked in default up south position after using, this is important as it will know where it is next time you start it up and avoid all the setup rigmarole.

Long time since I set it up but IIRC I just had it upside down aiming at Polaris with something like a 26mm eyepiece, used the finder to get Polaris in the main scope and spun it back and forth in RA adjusting bolts to keep Polaris in the FOV, this gets it pretty close to being polar aligned.

I then drift aligned it but you can use PHD or DARV to get it spot on.

Then using handset park scope aiming up south, ie 0 RA 0 DEC, don't worry where it stops, switch it off then loosen clutches and manually put it in the parked position, next time you switch on it will know where it is so I just do a GoTo on a convenient bright star, something beginning with A to save scrolling down the list, using the handset and if necessary the finder scope centre it then hold down the enter key for a couple of seconds and you should get a message saying " to sync on Altair press enter " press enter to get a beep and success message, it should  then be good enough for imaging but if not the same thing can be repeated by syncing on something near your imaging target.

Dave

Thanks Dave.  Also can I select it in ASCOM, to use the mount with eg SGPro or APT?  Is there a driver to download?

[Davey-T]

Just now, tooth_dr said:

Thanks Dave.  Also can I select it in ASCOM, to use the mount with eg SGPro or APT?  Is there a driver to download?

Guess there must be, had it set up so long I can't remember it came with a CD and I've been using it with Maxim and WinXP Pro ever since.

Dave

[tooth_dr]

Just now, Davey-T said:

Guess there must be, had it set up so long I can't remember it came with a CD and I've been using it with Maxim and WinXP Pro ever since.

Dave

I have the CD and have just downloaded the most recent Autostar suite, hopefully it includes all the relevant drivers.

[Davey-T]

6 minutes ago, tooth_dr said:

I have the CD and have just downloaded the most recent Autostar suite, hopefully it includes all the relevant drivers.

Should do fingers crossed 🤞

Dave

[tooth_dr]

@michael8554 @Davey-T

I took a look at this today.  The mount wouldn’t move in Dec but worked in RA (via the controller).

I looked and one of the connectors was bent. I unplugged it and straightened it up and it started working. Photos if connector below. Following the instructions above the scope moved 100% as detailed above. I couldn’t see the stars as it was daytime but I moved to where I would expect eg Arcturus to be.

Patchy cloud forecast for later so will try again later.

Thanks for both your help.  This is an awesome setup 😍

 

[MeadeLover]

I’ve watched these posts for a while and I understand the pain of those struggling with LX90 accurate Polar Alignment. Here is my method. It assumes a few things. The fact is that Meade mounts (not optics) are not that well engineered, particularly the dreaded wedge!  Alt/Az adjustments are crude to say the least. Pay attention to making these as smooth as possible.  WD40 used sparingly is a wonderful ingredient.  My LX90 has GPS.  All the data gathered from GPS can be entered manually.  Just takes longer.

The thing that totally screws up PA is cone error ie the OTA is not aligned with forks. This done accurately eliminates 50% of your problems. Then do as follows:-

3 things to do after balance, BALANCE:-

a) Align OTA with fork mount

b) Align fork mount with celestial pole

c) Align computer database with sky.

1. Make sure sidereal tracking is turned off. 

2. Except for step 7 use only alt and az adjusters.

3. Align Polaris at 0hr R.A. with cross hairs.

4. Rotate forks to 18hr HA (90 deg anti clockwise)

5. Adjust altitude to alt cross hair

6. Rotate back to 0hr

7. Slew with handset in dec only to cross hairs

8. Repeat for additional accuracy.

9. Turn off handset.

OTA is now aligned with forks.

Spirit level alignment of tube and forks does not work. Optics not necessarily in line with tube.

1. Turn on handset

2. Select one star alignment after GPS initialisation. 

3. Adjust Polaris position with alt and az adjusters.

4. Confirm with Enter. 

5. Adjust alignment of star with handset. 

Telescope should now be polar aligned.

Select easy alignment .

Suitable stars will be selected.

Alignment error will show at end of alignment.

If errors are large >5’ start again!

Computer is now aligned with scope. 

NB - always finish slew manoeuvres with right button and up button to avoid backlash problems.

Hope this helps - once done you can expect 5 min subs without a guider.

 

Edited September 19, 2020 by MeadeLover
Incomplete

[Hicks]

Quote

1 star align with Polaris seems fine, then slews to several stars below the horizon.

Bit of a bump so apologies, but in case you're still having problems with the LX90 on a wedge in polar mode, try setting it to polar home such that the finder scope is on top. Like the person who took this photo does http://roger.blogs.exetel.com.au/uploads/AstroGeneral/IMG_8645.jpg

Then use the Alt/Az controls on your wedge to center polaris before doing a one star alignment and again using the alt/az controls on the wedge to center polaris.

Fork handles upwards/finder on top when in polar home is how I've always setup my LX90 from 2002. If LX90 models have changed since then and require a different alignment then ignore this, but if you're still having issues, that's how I setup mine.

Edited July 20, 2021 by Hicks

[michael8554]

It does seem that the LX90 and LX200GPS have different Polar Home Positions.

LX200GPS - upside down, with the finder under the scope.

LX90 - right way up.

Michael