Jump to content

Sketches

Skywatcher AZ Gti - Accuracy


Recommended Posts

As well as the 250px dob’, I also bought a Skywatcher AZ Gti 127 Mak as a more portable option. Apart from pointing it at the moon, last night was the first chance I got to play with it, as the weather gave a small window of opportunity.  Although optically, I’m very impressed with it, I was underwhelmed, to say the least, at it’s tracking capabilities. 

I initially tried the North/Level alignment process, and am confident that I was as accurate as I could be with my orientation. The results were very poor, even after I had aligned and confirmed many more stars beyond the initial two.  I was using a 32mm eyepiece, and had expected each star to enter my view, giving me the option to go with a more powerful eyepiece if I wanted.  Using the Telrad as a gauge, the target star could be missed by as much as 8 degrees.  I then tried Brightest Star Alignment, and the results seemed to improve, but not by much.  The only time the mount was able to get the target in the fov was when the destination  was within about 50 degrees of it’s departure star.  I was frequently having to check Stellarium to work out which star it had settled on as it often seemed to park itself between 2 stars of similar magnitude.

Needless to say, it was a complete waste of time trying to get anything other than bright stars in the eyepiece as the accuracy was so far off. I would have been hunting all night for anything faint.  I had read other people’s accounts of using this setup, and everyone seems delighted that targets are placed right in the eyepiece time after time.  Am I unlucky, or inept?  The tripod was spirit-levelled, alt-az securely tightened, and the motor mount moving freely.  I also double-checked the app to see that my location was correctly recorded. It was set to use the internal gps coordinates, and seemed fine, as I also ran it off the iPad as well as the phone, both showing the same results.  Not sure what, if anything, I’m doing wrong? Any suggestions?

Edited by Ande
Link to comment
Share on other sites

I suggest checking your inputs. Correct latitude/longitude, correct timezone, correct time/date.

As I understand it, the Skywatcher system has you point the telescope North so that it can 'help' you by pointing the telescope in the general direction of the guide star. You then have to manually slew onto the guide star and accept the precise position. With the tripod leveled, two guide stars should be enough.

For some reason, we get far more complaints here about the Skywatcher Goto sytems than about the Celestron Nexstar. Which means either that the SKywatcher sell far more units or the Celestron is easier to learn and operate. 

  • Thanks 1
Link to comment
Share on other sites

Thanks Geoff. When I next use it, I shall enter all location/time data manually, and see how that pans out.  Although I have checked the automatically generated data on both iPhone and iPad, and it is consistent, and seems accurate.  But, and please correct me if I’m wrong, I was under the impression that even if the longitude and latitude was only roughly accurate, it wouldn’t equate to an 8 degree discrepancy in the sky.  I also thought that with each star confirmed as being centred, the accuracy would improve throughout the evening as the mount became evermore certain of it’s whereabouts and orientation. 

Edited by Ande
Link to comment
Share on other sites

I was using my az gti last night and it worked fine. I don’t bother with the north alignment bit. I just make sure it’s level and then use the 2 bright stars alignment process. It brought all the targets from all sections of the sky straight in close to the centre of the fov of the scope. However I  did have a wide 1.5 degrees tfov so that also helped.

One silly mistake I have done once with the scope was to mount the scope the wrong way on the mount (ie with the scope on the right rather than the left side and as stand behind it). That really messed the tracking and finding up ?. I know I’m not the only one that’s done that as well!

Edited by GavStar
  • Thanks 1
  • Haha 1
Link to comment
Share on other sites

Haha ?.  No, I didn’t mount it on the wrong side.  I’m pretty sure that I’ve got a Friday afternoon special.  I can’t see anything more that I could be doing.  Think I just need to accept that it does it’s own thing, so I’ll have to forget the goto side of things.  Bit of a shame as it wasn’t exactly cheap.  Thanks all ?

Link to comment
Share on other sites

3 minutes ago, Ande said:

Haha ?.  No, I didn’t mount it on the wrong side.  I’m pretty sure that I’ve got a Friday afternoon special.  I can’t see anything more that I could be doing.  Think I just need to accept that it does it’s own thing, so I’ll have to forget the goto side of things.  Bit of a shame as it wasn’t exactly cheap.  Thanks all ?

Can’t you return it? If you can’t use the goto, imo it makes the mount unusable.

Link to comment
Share on other sites

Don't give up on the mount. I've seen a number of similar requests for help on the forum and as often as not, it's down to the operator getting confused by how the Chinese software is supposed to work, or problems with the power supply confusing the electronics.  You only need to align on two stars or, at a pinch, one, for these systems to work with adequate accuracy.

I anticipate that you really need someone who is familiar with this particular system to talk you through how it is supposed to work, till you have a lightbulb moment.  It's understandable if you have never encountered one of these GoTo systems before.

  • Like 1
Link to comment
Share on other sites

1 hour ago, Cosmic Geoff said:

Don't give up on the mount. I've seen a number of similar requests for help on the forum and as often as not, it's down to the operator getting confused by how the Chinese software is supposed to work, or problems with the power supply confusing the electronics.  You only need to align on two stars or, at a pinch, one, for these systems to work with adequate accuracy.

I anticipate that you really need someone who is familiar with this particular system to talk you through how it is supposed to work, till you have a lightbulb moment.  It's understandable if you have never encountered one of these GoTo systems before.

Thanks for the reply. To be honest, the software couldn’t be more intuitive. It is absolutely clear what stage it is at, and exactly what it is expecting of me, the user.  The alignment process itself could not be easier.  The mount is doing everything it should, albeit with very poor accuracy.   I think that because it is able to locate a target star successfully if it is fairly close to it’s current position proves that it is calibrated.  That the accuracy deteriorates the further you ask it to travel suggests to me that maybe the gearing inside the mount is poorly meshed. I’ve manually adjusted, and confirmed every target in the centre of the scope.  As I said earlier, I shall input startup data manually next time I use it (if the clouds ever part again), just to see if it makes any difference.

Regarding power supply, I ran it off batteries last night.  I do have a psu, so shall try that next time too ?

Edited by Ande
Link to comment
Share on other sites

1 hour ago, GavStar said:

Can’t you return it? If you can’t use the goto, imo it makes the mount unusable.

I’ll see how the next session goes first. Not really a fan of returning things when Its not exactly a fault of the seller.

Edited by Ande
Link to comment
Share on other sites

I would stick with using the information delivered by the phone, it makes it impossible to get it wrong.

I have found mine to be pretty accurate too, not perfect and when slewing to the opposite side of the sky it can get further out.

One thing to check, is there any excess backlash in the gearing? I found that first one axis and then the other got quite loose on mine, and had to adjust and tighten the worm gears. It is a simple process, if you have this problem then I can post up the instructions.

Link to comment
Share on other sites

Thanks Stu. That’s most kind. I’ll give you a shout if it remains a problem, which is quite likely, because it does seem to be a gearing problem. 

  • Like 1
Link to comment
Share on other sites

  • 2 months later...

I have just seen that new firmware version 3.12 is available for Skywatcher AZ GTI mounts. It does show as they are not so new but when you downloaded and unzipped the files it says Jun-22nd-2018 as the update date of the file" I didn’t installed it yet but just sharing for info.
Cheers

skywatcher az gti.png

Link to comment
Share on other sites

  • 2 months later...

Hello,

I´ve tried a first light this last weekend with my recently purchased AZ-Gti. To get it short I was unsuccessfull. I couldn´t point to where I wanted it to be.
I did not tried the North alignment. Just tried Two Bright stars method. I was using a Canon 7D Mark II seated on a L Bracket with my trusty Canon EF 300mm IS L lens.
I did connected the camera to the notebook running Astrophotography Tools software. Every thing looked right and I did use planets Saturn and Jupiter, Saturn and Mars, and couple of tries with a planet and a star such as Saturn and Vega or Saturn and Arcturus. 

In APT I had double crosshairs on screen and zoom +10 to get a very precise centering on screen. On all occasions I got confirmation that alignement was successfull. And I´ve tried M8 and M20 and did not get any closer. It was pointing way high than the objects I have selected.

I checked GPS on my IPAD (where I was running Synscan APP) and it was showing a different reading in longitude than the Compass app, or Google maps on my smartphone. I couldn´t figure out the reason for that. But next time I´ll try to input coordinates by hand too.

Let´s see if tracking improve from there.

 

Regards,

Henrique
Itapevi, SP
Brazil.

Link to comment
Share on other sites

  • 1 year later...

Hi all. I know this thread is a little old but just bought the AZ-GTI. I'm having issues not with the goto (not tried that yet) but just with tracking. I'm running the mount in AZ mode. My coordinates are accurate. I can centre on a star & the drift is crazy. I'm using sidereal but within 10 seconds, the star has drifted out of view, the drift (star) is to the left & up. I've tried sidereal, 0.75, 0.5, 0.25, all the way down but I can't keep the star centred for anything other than a 2nd or 2. I've also tried with the encoders on & off - same issue. Should I be able to  just manually point at a star, engage sidereal tracking & then stay centred - even for 20-30 seconds?

Granted, I haven't done North/level but thought that would only be needed for Goto?

Any help greatly appreciated.

Link to comment
Share on other sites

17 hours ago, Geordieboy46 said:

Hi all. I know this thread is a little old but just bought the AZ-GTI. I'm having issues not with the goto (not tried that yet) but just with tracking. I'm running the mount in AZ mode. My coordinates are accurate. I can centre on a star & the drift is crazy. I'm using sidereal but within 10 seconds, the star has drifted out of view, the drift (star) is to the left & up. I've tried sidereal, 0.75, 0.5, 0.25, all the way down but I can't keep the star centred for anything other than a 2nd or 2. I've also tried with the encoders on & off - same issue. Should I be able to  just manually point at a star, engage sidereal tracking & then stay centred - even for 20-30 seconds?

Granted, I haven't done North/level but thought that would only be needed for Goto?

Any help greatly appreciated.

Have you done your 2 star alignment? If you haven't I don't think the mount will be able to track properly as it won't know where in the sky it is pointing

Link to comment
Share on other sites

  • 9 months later...

I've found the tracking accuracy is sometimes good and sometimes not. I think it may have to do with pointing direction. If you're pointing at high elevation, I can only go about 10 sec without star trails. But if I'm flatter, i can go 30 sec. I've set the balance, so I don't know what else it could be. Anyone else see this? 

thanks

Link to comment
Share on other sites

last night, was looking at bode galaxy, and could only get 10 sec before I got star trails (with about 50x mag). Tonight, looking at M101, pinwheel galaxy, and can get 30 sec perfectly clear. Maybe the closer you are to polaris, the worse it gets?

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.