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Miguel1983

Sky-Watcher AZ GTI tracking

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Posted (edited)

Hi,

Yesterday i went to the monthly gathering of our local astronomy club, did some observing there, and afterwords when i got home, i did some more playing around with my recently bought AZ GTI.

So some thoughts/remarks  on the mount.

  1. The alignment procedure via app is fairly easy but you really need this to be pin point right, since i don't yet own an eyepiece with illuminated crosshairs (on its way) i guess i start of a little off-set. So i notice that, after alignment, my target sometimes isn't in my field of view.
  2. The tracking,  yesterday i took a look at the Orion Nebula starting with a aspheric 62° 23mm eyepiece and the target was dead centre of my view, then i put in the 10mm Aspheric and it was at the lower part of my field of view...
  3. Back at home i started again with the alignment on Sirius an Dubhe, then i went for a control to Rigel and it was way of, corrected it, went to Orion Nebula, spot on, went to Betelgeuse, way off.... and so on.
  4. After that  "GoTo" - "adjust" - "Got To" "adjust".... i slew to the moon, and it was a mile off !!

So i don't now what happend, i did start off with the 8 AA-bateries inside, and i kinda heard on the slewing sound it was loosing power, so i connected my powerpack.

Some questions for those who own this mount:

  • Is it normal that when tracking you hear a "tack...tack.."-sound ?
  • Anyone adjusted the backlash settings ? How does it work ?
  • Altitude limit, how do you set it so it has no restrictions ? (tube can't hit the tripod anyway)

More tips and tricks are very welcome !

Thanks

Edited by Miguel1983
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I have found the gotos to be pretty accurate with my mount, although sometimes a little off if going to an opposite part of the sky for instance. Making sure the mount is level might help this aspect. I generally do use a cross hair eyepiece but have still managed good accuracy by centering in a high power eyepiece.

I have adjusted the backlash on my mount and it was very worthwhile. I found that there was a lot of movement on both axes i.e. I could move the scope a certain amount manually (even with clutches locked).

I followed the instructions given and it is quite straight forward. On my mount the screws which hold the gears in place were lose which is what allowed so much movement. I adjusted them, making sure I tested it throughout the range of movement as there are tighter and looser parts. I got it as tight as possible without binding on the tight parts and then clamped it down hard. I suspect your inaccurate gotos may be a result of movement for this reason so it is well worth investigating, it is very easy to do.

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On your point two the weight of any eyepiece can have an effect. For example, when using the 12 Meade SC, a big beefy scope, after using the 41mm Panoptic then changing to say a 24mm, maybe 1/3 of the weight, the object move a great deal.

Alan

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Using a cross hair eyepiece sounds a very good idea - I’ve been using an ethos 21mm and guessing the centre which has given good results but maybe I should try to get the centrering much more accurate for goto.

Has anyone got a recommendations for a good cross hair eyepiece - Is this one any good?

https://www.firstlightoptics.com/specialist/skywatcher-125mm-illuminated-reticle-eyepiece.html

 

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2 minutes ago, GavStar said:

Using a cross hair eyepiece sounds a very good idea - I’ve been using an ethos 21mm and guessing the centre which has given good results but maybe I should try to get the centrering much more accurate for goto.

Has anyone got a recommendations for a good cross hair eyepiece - Is this one any good?

https://www.firstlightoptics.com/specialist/skywatcher-125mm-illuminated-reticle-eyepiece.html

 

Pretty sure that's the one I've got Gavin. There are much more expensive ones for doing measurements of star separation etc, but this is all you need to get accurate centering.

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"Tak tak" during slew immediately tells me a clutch/gear is slipping.  So quite possibly a power supply (low voltage) issue.

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1 hour ago, Owmuchonomy said:

"Tak tak" during slew immediately tells me a clutch/gear is slipping.  So quite possibly a power supply (low voltage) issue.

Hi,

 

the tak tak is after slewing when the mount is tracking

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3 hours ago, Stu said:

I have adjusted the backlash on my mount and it was very worthwhile. I found that there was a lot of movement on both axes i.e. I could move the scope a certain amount manually (even with clutches locked).

I followed the instructions given and it is quite straight forward. On my mount the screws which hold the gears in place were lose which is what allowed so much movement. I adjusted them, making sure I tested it throughout the range of movement as there are tighter and looser parts. I got it as tight as possible without binding on the tight parts and then clamped it down hard. I suspect your inaccurate gotos may be a result of movement for this reason so it is well worth investigating, it is very easy to do.

Hi,

these instructions you speak of, those are the instructions in the Synscan app ?

I'm starting to think i had a different idea of what backlash actually is, i thought it had something to do with fine tuning the tracking speed.

But as i am reading the context it is correcting the return on overshoot when te scope is going to a new target. Correct ?

Thanks

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Posted (edited)
3 hours ago, alan potts said:

On your point two the weight of any eyepiece can have an effect. For example, when using the 12 Meade SC, a big beefy scope, after using the 41mm Panoptic then changing to say a 24mm, maybe 1/3 of the weight, the object move a great deal.

Alan

I can imagine, a co-stargazer from our group yesterday had a 2" beast on his scope !

But i'm not that equipped yet, so only small 1,25" eyepieces here :icon_biggrin:

Edited by Miguel1983
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38 minutes ago, Miguel1983 said:

Hi,

these instructions you speak of, those are the instructions in the Synscan app ?

I'm starting to think i had a different idea of what backlash actually is, i thought it had something to do with fine tuning the tracking speed.

But as i am reading the context it is correcting the return on overshoot when te scope is going to a new target. Correct ?

Thanks

I think of it as how quickly the gearing responds to a change of direction. Zero backlash would mean it would start reversing direction instantly, lots of backlash means it would take quite a few seconds for the slack in the gearing to be taken up. You can make adjustments to the software so that the mount quickly takes up the slack which reduces how much this problem is visible. The better option is to adjust the gears to get rid of backlash as far as possible without causing binding.

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Posted (edited)
9 minutes ago, Stu said:

I think of it as how quickly the gearing responds to a change of direction. Zero backlash would mean it would start reversing direction instantly, lots of backlash means it would take quite a few seconds for the slack in the gearing to be taken up. You can make adjustments to the software so that the mount quickly takes up the slack which reduces how much this problem is visible. The better option is to adjust the gears to get rid of backlash as far as possible without causing binding.

Oh Ok, so adjusting the backlash really is a trial and error thing.

Every new "go to" comand you do, one would have to take notice of how long from pressing the command it takes for the mount to react in both ALT & AZ direction and adjust accordingly.

Seems almost guesswork to me :help:

Edited by Miguel1983

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4 minutes ago, Miguel1983 said:

Oh Ok, so adjusting the backlash really is a trial and error thing.

Every new "go to" comand you do, one would have to take notice of how long from pressing the command it takes for the mount to react in both ALT & AZ direction and adjust accordingly.

Seems almost guesswork to me :help:

Well, to be clear there are two separate actions.

First is the mechanical adjustment, which involves opening the mount and adjusting the gearing to reduce the amount of backlash. Do you have the instructions for this?

Second is the software parameter which you can adjust to reduce the impact of the remaining backlash. This just speeds up the motor a little when the button is first pressed to reduce the time before the axis starts to move. The adjustment affect how long this quicker turning lasts.

It does seem to be largely trial and error. No need to do a goto, just move the axis in one direction, stop and the move it in the other. See how much of a pause before it actually moves (best to be looking through the scope at a star at this point I think), then adjust the backlash parameter and recheck. There is an optimum point, after which the motion will jerk quickly before settling down, this means you have put too much correction in so should reduce it back again. Repeat for the other axis.

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Posted (edited)
29 minutes ago, Stu said:

 

First is the mechanical adjustment, which involves opening the mount and adjusting the gearing to reduce the amount of backlash. Do you have the instructions for this?

 

Nope, don't have those

I guess opening the mount also makes warranty claims invalid ?

Edited by Miguel1983

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Here are the instructions. They were provided by Skywatcher so I would assume they don't invalidate the warranty but it is worth checking. I have adjusted my mount and believe it is still covered by warranty (I certainly hope so!)

 

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3 minutes ago, Stu said:

Here are the instructions. They were provided by Skywatcher so I would assume they don't invalidate the warranty but it is worth checking. I have adjusted my mount and believe it is still covered by warranty (I certainly hope so!)

 

Where are those instructions ? 

I've just checked the mount, with clutches locked, there's no moving it.

Then i pointed it at the top of an electric pylon and tested in the 5 speed, there's bit of a delay when i change direction, but not al that much i must say.

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Just now, Miguel1983 said:

Where are those instructions ? 

I've just checked the mount, with clutches locked, there's no moving it.

Then i pointed it at the top of an electric pylon and tested in the 5 speed, there's bit of a delay when i change direction, but not al that much i must say.

Sorry, I couldn't find them in a postable format. It sounds like you do not have a problem so should leave well alone. Good news.

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4 minutes ago, Stu said:

Sorry, I couldn't find them in a postable format. It sounds like you do not have a problem so should leave well alone. Good news.

I guess so, it's  just a lack of experience ;-)

There also aren't a lot of people with this mount yet and not much how-to / reviews on YouTube so if something isn't going as it should, there's no refference.

Thanks for the help Stu, much appreciated !

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Hi,

i thought about following up on this post, so i now have used the AZ GTI a number of times, and i must say, i find that the GoTo isn't all that great in my experience.

Since last posts here i've used a cross-haired ocular (12,5mm) so alignment should be better, all tough, i must say, it doesn't make it easier, you really have to hunt the alignment stars with that kind of magnification.

Alt-az corrections in doing so aren't helping because the mount can do some strange jumps when youre manualy fine aligning the alignment star, don't now if this is something backlash correction can correct ?

After alignment, the GoTo can sometimes be way off target...

 

Anyone who has similar experience ?

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13 minutes ago, Miguel1983 said:

Hi,

i thought about following up on this post, so i now have used the AZ GTI a number of times, and i must say, i find that the GoTo isn't all that great in my experience.

Since last posts here i've used a cross-haired ocular (12,5mm) so alignment should be better, all tough, i must say, it doesn't make it easier, you really have to hunt the alignment stars with that kind of magnification.

Alt-az corrections in doing so aren't helping because the mount can do some strange jumps when youre manualy fine aligning the alignment star, don't now if this is something backlash correction can correct ?

After alignment, the GoTo can sometimes be way off target...

 

Anyone who has similar experience ?

I can see that a 12.5mm eyepiece makes finding the alignment stars tricky. 

I bought a 26mm 70 degree crosshair eyepiece for this reason and it’s makes the alignment procedure easy and accurate in my experience.

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18 minutes ago, Miguel1983 said:

Hi,

i thought about following up on this post, so i now have used the AZ GTI a number of times, and i must say, i find that the GoTo isn't all that great in my experience.

Since last posts here i've used a cross-haired ocular (12,5mm) so alignment should be better, all tough, i must say, it doesn't make it easier, you really have to hunt the alignment stars with that kind of magnification.

Alt-az corrections in doing so aren't helping because the mount can do some strange jumps when youre manualy fine aligning the alignment star, don't now if this is something backlash correction can correct ?

After alignment, the GoTo can sometimes be way off target...

 

Anyone who has similar experience ?

Just a couple of pointers or observations which may help...

I use a 24mm 68 degree eyepiece when finding the alignment stars, and then switch to the cross hair once it is centred. Makes life much easier, as does an accurately aligned finder.

Do you use the Rate adjustment when centreing the star? Usually down at 3 or 2 you have very smooth adjustment. One thing to be sure of is that your scope is balanced front to back, if it is out then things can get a bit jerky or it just won't move!

Finally, always make sure you approach both alignment stars from the same direction, e.g. By moving up and to the right say. To a degree it doesn't matter which direction but keeping it consistent ensures that the backlash is being taken up in the same direction and this keeps things more accurate.

I do find that the gotos can get inaccurate when moving to the opposite side of the sky so realigning on stars in that area may be the best option.

Let us know how you get on.

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I spent a few hours out with mine last night and I was very impressed. I used a crosshair eyepiece and also made sure I was pointing due north by lining up with Polaris before I began alignment; I know it says you only need to do this roughly, but it was easy for me to be accurate. I then spent an evening getting everything in the eyepiece, no matter where in the sky it was, but I was only using a 24mm eyepiece on a 700mm scope, so I wasn't testing it too much! I also centred each object using the method Stu suggests.

One thing that did happen during the evening was the azimuth movement appeared to become very loose, but it turns out the bolt holding the mount to the extension pier had come loose, so that was easily rectified. I'd make sure that's done up tightly and that the three bolts on the top of the pier are too. 

Freedom Find doesn't seem to work on mine at all. Not sure why, but when I release the clamps and move about manually, the alignment's lost. 

Other than that, I love it!

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After having the mount loose and moved by hand then when you engage the clutch again what are you doing next?

Talking of alignment star choice the altitude and separation of chosen stars is key on the previous altaz goto mounts it's in the manual so I wonder if the azgti mount is any different?

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Last night I simply moved it about by hand and watched the coordinates on the app (and on Sky Safari) change....or not change as it happens. When I then tightened the clamps up again, and tried goto, the alignment had obviously gone. I know the manual says you can turn off freedom find if you're never going to use it, to increase goto accuracy, so I suspect that might be what's happened here. I just can't find the setting anywhere to turn it back on!

As for alignment stars, the app gives you a choice of stars to use, and once you've picked your first star, the choice of second stars changes a bit, so I guess it's trying to get us to use ones that are a certain distance apart. Last night, for example, I selected Rigel and it then put Regulus near the top of the list for 2nd stars...a bit away but not the opposite side of the sky it seems. 

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Thanks for all the replies !

I do first use a 21mm Hyperion to center the first alignment star, then slide in the 12,5mm cross-haired to fine tune, the scope then slews automatically to the second alignment star and i repeat the proces, so this is you all pointed out.

Maybe the balancing is a bit off, since the cross-haired EP weighs 100 grams or so, and a Hyperion 300-400 grams ? I also like to swap out the star-diagonal and EP and put in my camera, at that time i cant move the scope or alignment is gone.

 

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Anyone has seen the “fast solar tracking” feature on the SynScan App ? I could not longer find it this morning !

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