5 replies to this topic

[Buddy71]

Need some Guidance.  I have a 2018 8" LX90 ACF.  It has performed fantastic over all these years.  However, during the last 2 months, after "successful alignment", going to subsequent objects, the scope is slewing "past" or "short of the object.  Sometimes it is at least in the viewfinder and I can slew to it and sometimes it is not.  If it is a deep sky object, I can't see to even try to slew to it.  Last night, it picked Sirius and Rigel as the alignment stars.  I did slew to both and enter sync on both (as usual during all my initial alignments).  I then started experimenting.  I picked Almack for the next target.  It slewed to the area but not on the star but at least I could see it in the viewfinder and I slewed to it.  I pressed the "enter" button and then again to sync it.  Then I picked to go back to Sirius.  It did not go back to the exact location of Sirius (it even went past the viewfinder.  I slewed and "enter and sync".

 

The next experiment, I went from Sirius to Polaris.  This time at least Polaris was in the viewfinder and I slewed to put it in the EP.  However, this time I did not "enter and sync" it.  I then picked to go back to Sirius.  This time it went directly to a centered Sirius in the EP.

 

My question, I guess, is it the GPS?  Is it the AutoStar?  Is it the gears in the SCH?  Why has it started doing this over the past 2 months.  Appreciated any guidance... Buddy71

[OzAndrewJ]

Gday Buddy71

Polar or AltAz?

Slewing a big distance "past" a target is normally a result of the encoder losing a few pulses

Can yo try doing the spin tests to see if the encoders are reading properly

ref https://www.cloudyni.../#entry13493036

for the method but use say 180deg for an LX90 RA as you have no stops

See what you get for the mechanical vs encoder moves

Andrew Johansen Melbourne Australia

[Buddy71]

Hello Andrew.

 

I use only the AltAz

Next, I must admit that I don't know what the encoder does, where it is located and and if there is a read out, I would not know if it was even reading correctly.   I shall go to the "www. site you provided above.   Maybe I can figureout/understand what you mean by See what you get for the mechanical vs encoder moves.

 

As it will be cloudy here in Austin Texas for the next few days, it might be awhile before I repost with my results.  Thanks

 

Buddy

[OzAndrewJ]

Gday Buddy

The link i gave is to a thread in Cloudy nights that describes the test

It can be done indoors

Basically, you use the alternate menus in the handset to read out the current Alt/Az.

You note the "reported" values,

then move the mount at high speed by a "known" distance ( using the setting circles )

You then re note the "reported" positions

If they doint match, you need to investigate

A bad encoder will under report the distance moved

Andrew Johansen Melbourne Australia

[michael8554]

The Star Alignment refines the starmap in the controller to match reality.

 

AFAIK, If you press SYNCH at every alignment star you are shifting the whole map each time, not refining it.

 

So when you go back to the first Alignment Star it will be shifted.

 

Centre each Alignment Star and press ENTER, not SYNCH.

 

Andrew will correct me if I'm wrong :->

 

In any case the quickest way to find an "invisible" target is to centre and SYNCH on a star near the target.

 

Then a GoTo the target should be spot on.

 

But a GoTo a Target much further away may be inaccurate, so repeat  the technique.

Edited by michael8554, 03 March 2025 - 05:49 AM.

[Buddy71]

Good Day to Andrew and Michael...

   As it turns out, I discovered that I had not "trained" the telescope drives in over two years.  I used to train the drives once a year when I was out at McDonald Observatory.  Therefore, I took it out during the day in a flat area.  I found a transmission tower about 2 miles away.  I did the train drive procedure.  That night I set up the telescope and did my usual two star alignment.  I proceeded to "goto" various stars all around and even return some that I had had already seen.  The scope returned to the objects again and not only were they in the EP, but really very close to centered in the EP.    I did it again two nights later just to make sure that it wasn't just a fluke.   This coming weekend I will be using it four nights in a row.  I am hoping that the drive training was all that was the problem.

   Thanks guys!!!!!