Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Need help - LX600 12" - cannot find home

  • Please log in to reply
12 replies to this topic

#1 TomasKocanda

TomasKocanda

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 16 Sep 2020

Posted 25 September 2021 - 04:14 PM

Hi friends

swapped my old (well working) 8" LX200 for 12" LX600

And .... today tried new scope outside and got problem - during sensor calibration and alignment I get home sensor error. 

I can skip it by 2 star alignment and everything else works fine - but sometimes when it slew somewhere it hit hard stop and motor is trying to push it over hard stop. This should not happen.

What to try?



#2 OzAndrewJ

OzAndrewJ

    Fly Me to the Moon

  • *****
  • Posts: 5,358
  • Joined: 30 Nov 2010

Posted 25 September 2021 - 04:37 PM

Gday Tomas

The home sensors are in the base and are simple LED/Receiver pairs on a set of alloy plates.

The base should rotate freely for about 680degrees

and the centre of the swing should put the EP over the control panel.

Sooo, can you swing it "freely" for 680deg

If so, to check the sensors ( which really arent needed ) you need to open the base

 

Re hitting hardstop, which one, Altitude or Azimuth???

If the base, then the hardstop detection is based on where the OTA was pointing

at the time you started the align. You must be in the correct home position

for the system to know which way to go.

 

Andrew Johansen Melbourne Australia


Edited by OzAndrewJ, 25 September 2021 - 08:08 PM.


#3 TomasKocanda

TomasKocanda

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 16 Sep 2020

Posted 25 September 2021 - 05:11 PM

OK. I should clarify it bit more. 

I talk only about base rotation. Inclination works fine. 

So when it hit hardstop, it¨s when it rotate base and sometimes it keeps rotationg to find the correct position and it hit the hadstop.

Maybe I do it wrong from beginning. I´ve been told that the initial position of the unit is with panel facing north. Is it correct?

So my base is oriented north-south with panel facing north. And I release the lock and setup fork to be in the middle parralel to the panel and base and I see the top of the OTA (when is in vertical position with mirror up). Then I lock it and turn on scope etc. 

Maybe it should be oriented other side. Does it have influence?

Anyway, when performing sensors calibration it sooner or later hit the hardstop as like if the unit does not know its hard stop and motor is trying to push over the hard stop - it does not stop. 

 

And yes - I can get the free rotation about 680 degrees  almost two full rotations. Then I feel the hardstop. 

When I hit the hardstop, then I should go back in the middle - like one full rotation? Or just bit to find the position parallel to the panel? 


Edited by TomasKocanda, 25 September 2021 - 05:13 PM.


#4 OzAndrewJ

OzAndrewJ

    Fly Me to the Moon

  • *****
  • Posts: 5,358
  • Joined: 30 Nov 2010

Posted 25 September 2021 - 05:54 PM

Gday Tomas

 

So my base is oriented north-south with panel facing north.

That explains everything, as it is 180deg out.

For AltAz, the home position is with the RA axis mid hardstops ( ie EP over control panel )

with the OTA level and pointing North ( ie OTA is pointing to Alt=Az=0 )

In this position, the panel is always on the south side

On starting the align, the mount makes a note of this position and then prevents the base from

slewing more than say 270deg either way. It does this by dead reckoning.

If you start with the base out by 180deg, then you effectively have 320 +180 deg to one hardstop

and 320-180 deg to the other,

but the mount doesnt know that, so it can slew into the short side.

 

Re it failing during "sensor detection", that indicates the sensors have a problem

and it could be a loose cable, a corroded contact, a displaced sensor,

grease on the sensor, a dead sensor etc etc etc

You need to open and look, but again, you dont need the sensors for normal operation

 

Andrew Johansen Melbourne Australia

 

 

 

 

 

Andrew Johansen Melbourne Australia


Edited by OzAndrewJ, 25 September 2021 - 05:54 PM.

  • MikeBY likes this

#5 MikeBY

MikeBY

    Mariner 2

  • *****
  • Posts: 228
  • Joined: 28 Aug 2019
  • Loc: Huntington Beach, CA

Posted 25 September 2021 - 07:13 PM

Hi,
Are you operating in Alt-AZ mode or EQ mode?

 

Also

And yes - I can get the free rotation about 680 degrees  almost two full rotations. Then I feel the hardstop.

When I hit the hardstop, then I should go back in the middle - like one full rotation? Or just bit to find the position parallel to the panel?

 

Rotate the fork arms to be approximately midway between the hard stops.. about 1 full rotation.
 



#6 TomasKocanda

TomasKocanda

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 16 Sep 2020

Posted 26 September 2021 - 03:37 AM

I work in ALT-AZ right now. I have wedge but wanted to test the scope without it first...


  • MikeBY likes this

#7 MikeBY

MikeBY

    Mariner 2

  • *****
  • Posts: 228
  • Joined: 28 Aug 2019
  • Loc: Huntington Beach, CA

Posted 26 September 2021 - 04:46 AM

I work in ALT-AZ right now. I have wedge but wanted to test the scope without it first...

Good idea.

Be sure the Telescope electronics setup is also in Alt-Az mode.



#8 jaymcgil19

jaymcgil19

    Vendor-LX200 CLASSIC ELECTRONICS EXCHANGE

  • *****
  • Vendors
  • Posts: 305
  • Joined: 01 Apr 2013
  • Loc: S/E Michigan

Posted 26 September 2021 - 10:41 AM

This procedure works for me every time:

  1. Panel on the south so you're looking north when standing in front of the panel.
  2. Slowly rotate the OTA counter clock wise until you hit hard stop...note the position of the OTA.
  3. Rotate clock wise 1 and 1/4 turns so basically the OTA is facing east.
  4. Turn the scope on.

The scope should start by rotating ccw a little past north then it will rotate cw for the rest of the dance.

 

John M



#9 TomasKocanda

TomasKocanda

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 16 Sep 2020

Posted 26 September 2021 - 12:35 PM

Tried that - no help. It start rotation to find home until it hard stop.. how do scope reall find home? I presume home is when is base oriented on north.
Interesting is, sensor calibration works ( without the home finding step). it find north and level OTA.
I had optic sensors dirty (grease), but even cleaning did not help.

#10 TomasKocanda

TomasKocanda

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 16 Sep 2020

Posted 26 September 2021 - 01:59 PM

I think I will need new home sensor board

#11 OzAndrewJ

OzAndrewJ

    Fly Me to the Moon

  • *****
  • Posts: 5,358
  • Joined: 30 Nov 2010

Posted 26 September 2021 - 04:44 PM

Gday Tomas

 

It start rotation to find home until it hard stop..

Based on the rest, its time to open the base

 

how do scope reall find home?

There are 2 semi circular plates in the base, one fixed to the fork assy

and one floats free ( it can move about 340 deg freely )

These plates block/clear a pair of LEDs as the base rotates

( ref piccy )

Knowing what is blocked and what is clear, the code can determine

when the mount is "near" the end of its travel.

 

I presume home is when is base oriented on north.

NO

As per before, the physical home position for the base is EP over the control panel.

This puts the base midway between the hardstops, and there is only one position

in the full 680deg of motion where you can do this.

In that position, you pick up the whole scope and rotate it so the OTA points North

ie control panel on south side.

 

Andrew Johansen Melbourne Australia

HomeSensors and HardStops.jpg

 

 

 

 



#12 MikeBY

MikeBY

    Mariner 2

  • *****
  • Posts: 228
  • Joined: 28 Aug 2019
  • Loc: Huntington Beach, CA

Posted 27 September 2021 - 10:29 PM

Hello Tomas,

North and Level sensors (tip and tilt during sensor calibration) are all in the left fork arm. 
If you can bypass the 'finding home' function to test the other calibrations, then you should be able to align the telescope without the 'home' function.  It really doesn't mean much if you start with the OTA rotated to the approximately correct position when powering on. In some versions of firmware there is a "disable home sensor" setting.

 

There are two detailed YouTube video from MeadeMods that shows the installation and discusses the location adjustment of this sensor on a LX200GPS. I believe this sensor should be very similar to what's found in your LX600 mount

Position adjustment can be tricky. If it rubs during adjustment you can end up with lubricant on the LED or the sensor.  It has a very close tolerance to the moving plates. You have to make sure the large block attached to the floating plate clears the sensors, not just the thin part of the plate and that the sensor is otherwise as deep as possible while still clearing. Here's a link starting at 4:15 where the sensor is discussed and the 2nd at 11:30 where it is installed.

 

https://youtu.be/w-wU41_c7w4?t=255


Installation

https://youtu.be/2wGHuUnb2Rk?t=690

 

 

 

Regards,

 

Michael


Edited by MikeBY, 27 September 2021 - 10:42 PM.


#13 TomasKocanda

TomasKocanda

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 16 Sep 2020

Posted 10 October 2021 - 02:24 PM

Just update:

- fixed issue with missing "home sensor off" in the menu. Reloaded back to 1.1g and then 1.1G and it´s there.

- I switched off home sensor in the menu

- when I now do alignment, it perform some kind of home check even when sensor is disabled, but scope turn just little bit from initial position and very slowly back and is OK 

 

So for me it´s fixed...


  • David Mercury likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics