3833 replies to this topic

[nm1213]

Well, that was my thinking, but the mount going nuts last night might have proved me wrong.  Maybe the goto++ function did do that after all.  Maybe it executed a sync at the very end.

 

Well, no chance to try again tonight, it's clouded over.  Maybe I get lucky tomorrow night.

Drop an email to app@skywatchertelescope.net about the issue.  The dev guys are great and will respond.  At the very least we can clarify what is going on.  Best case, they fix it.

[dciobota]

Thanks my man.  I meant to open a customer support case but haven't gotten off my butt to do it.  Your email sound like a better way to do it, directly to the devs.

[daw316]

Is there confusion between "sync" and "reslew".  Sync uses the offsets resulting from the plate solve in future go-to's.  Reslew does a sync, then moves the scope to the originally requested coordinates. (Centers your object.)

[dciobota]

I think maybe we're talking about two different applications.  In my case, I use AstroPhotographyTools (APT), and my reference is the Pointcraft section:

https://ideiki.com/a...g==&mw=MjQw#top

 

The way sync is explained is that once you have plate solved an image taken at the current mount position, pressing the sync button will update the telescope with the current position, in effect doing a one star alignment.  I know other telescopes like the celestron series also have a similar sync button function, where you slew to a nearby star (to the target object), press sync, then do a goto from there, which should be more accurate.  Both essentially update the telescope position.

 

In APT, the other function is goto++ which is an iterative process.  As explained in their user guide, it takes an image, platesolves, calculates the ra/dec error, then slews to the newly calculated position, then reiterates the steps until it gets to within a use defined acceptable error.  I not that in the manual it says nothing about doing a sync (update the telescope position), it only keeps track of it in the application itself while it iterates.

 

So, as far as APT, sync does update the telescope position for future slews as you said, but goto++ (which uses its own slews) does not.  At least that's the indication I get.  I may ask the question in Ivo's forum and see what he says.

[dciobota]

So, for you that use APT and eqmod (and maybe it applies to the synscan app as well), here's an interesting discussion on syncs:

http://aptforum.com/...lit=sync#p12546

 

Apparently I need to upgrade to the latest version to be able to turn sync on/off when issuing a goto++, since apparently my older version does not have that feature and applies a sync automatically after each solve during goto++.  This would explain the weird behavior I get after my first goto++ session.

 

So, for all you that use APT, I'd recommend getting the latest version and turning on PointCraft->Settings->No Auto Sync and  also PointCraft->Settings->Make Relative GoTo++ moves.  That will prevent goto++ from doing syncs, which currently do not work properly (imo) in the synscan app.

 

Hope this helps.

[dciobota]

So, to wake up this thread a little bit with some more observations and maybe even some eye candy (ok maybe not exactly eye candy lol).

 

So, I've had a chance to use the mount for a few nights this past couple weeks and play around with guiding.

 

First observation relates to APT and plate solving.  As mentioned in my previous post, APT allows you to avoid sending a sync command to the mount (which apparently has some issues) after it plate solves and does gotos.  One correction to my previous post however, the setting for Make Relative Goto++ Moves needs to be checked, not unchecked.  If you don't check it, APT (or synscan, don't know which) has trouble using absolute gotos to zero in on targets close to the meridian.

 

I have also been fiddling with the guide speed.  I had originally set it to 1x sidereal, which worked ok but I noticed occasional RA spikes.  Once I dropped the guidespeed to 0.75x, the RA graph smoothed out.  I'm guessing that either stiction or backlash was causing the RA spikes, since at 1x the motor actually stops when given east commands.

 

However, the slower guide speed exacerbated the issue with DEC backlash.  As I had mentioned before, I had some issues with DEC calibration which I attributed to a tensioner nut that was too tight.  But even though it did calibrate better, I noticed quite a bit of backlash in dec, causing occasional guiding jumps.  Switching the guide speed to 0.75x made the corrections even slower, which made the backlash effects worse.

 

So, I'm going to try and see if I can reduce that.  Tightening the tension nut didn't seem to have much effect.  I noticed that the reduction gears seem to have some play in them, but I don't see a way to adjust them.  So I'm going to try some heavy grease (an old Chinese mount trick) to see if it helps. 

 

One thing I did to improve dec calibration was specify larger calibration steps (>1000 ms) in PHD.  It seems that PHD automatically sets its own calibration steps based on entered guidescope fl and pixel size.  So I cheated by changing the scope fl to a smaller value to achieve the calibration step size.  But this messed up my arcsec display values in the PHD graph  If anyone knows how to make PHD override its automated calibration step size, let me know.

 

Anyway, other than those minor annoyances, the mount guides well enough (somewhere around 1.5-2 arcsec rms).  So, without further ado, here's the two images I took over those nights (click on each pic for the info and stats):

https://photos.app.g...N1GpPexH24H42n6

https://photos.app.g...JGBT9MDXc8EyVY6

 

All in all, a pretty decent mount for the money still.

 

Hope this helps.

Edited by dciobota, 30 October 2018 - 04:24 PM.

[split]

I just purchased an AZ GTI and I notice with the alt clutch and azimuth adjustment knob both fully undone both axis movements are quite stiff. Is this what other are experiencing?

[Edwin]

I just purchased an AZ GTI and I notice with the alt clutch and azimuth adjustment knob both fully undone both axis movements are quite stiff. Is this what other are experiencing?

The same over here, but it doesn't effect its performance on mine.

[DIMITRIS K.]

I just purchased an AZ GTI and I notice with the alt clutch and azimuth adjustment knob both fully undone both axis movements are quite stiff. Is this what other are experiencing?

Yes it's pretty normal. The other isuue you must check is the stiffness of the motors. Do a full alt and az rotation and see if there is a significant motor stress in some directions. If no, you are ok. If yes you must readjust the gear tension spring that is inside the mount.  

Edited by DIMITRIS K., 31 October 2018 - 03:24 AM.

[Edwin]

Although the performance on mine is OK (good goto's), on lower speeds (2-4) it moves a little shaky, is that caused by too much stifness of the motors?

[dciobota]

That could well be the motors intermittently stalling Edwin.  In that case either loosening the tension nut yourself or sending it back for readjustment is your best bet.

[nm1213]

Dciobota, great pictures! I’ll have to try APT soon!

Edited by nm1213, 31 October 2018 - 06:47 PM.

[DIMITRIS K.]

Although the performance on mine is OK (good goto's), on lower speeds (2-4) it moves a little shaky, is that caused by too much stifness of the motors?

Yes! And with my first mount the problem was so intense that my mount had a serious problem on tracking objects and i was unable to fix it on my own. So i send it back for a replacement. The second one is much better, but the tension nut needs to be adjusted too. Now i'm very satisfied with the mount. As i understand there always a little bit "asymmetry" of the gear that turns the mount and that cause those problems. That's why Skywatcher made this spring tension "patent". If you want to adjust it, fist of all find the maximum friction point between the gear and the worm. This is the point that the motor struggles the most. Remove mount cover (it's easy, but be careful not to cut a wire as you remove it) and find the screw that holds the spring (look photo). Loose that screw and retighten. Now make a 360 turn to see if the tension was gone. Keep in mind that you must accept a slight amount of backlash in some points. You must find a balance between backlash and tension.  

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Edited by DIMITRIS K., 01 November 2018 - 12:08 AM.

[Edwin]

Thanks for the tips, guys! 

[dciobota]

Oh, another thing I remembered, and forgot to post.  I didn't notice it the first time I opened mine, but the second time, I noticed that during assembly, the RA gray ribbon cable that you see in Dimitris' pic (above where he points out the adjustment screw) was routed under the circuit board (not shown in his pic), potentially touching the big RA gear disk.  That may have explained why I was getting intermittent spikes in RA during guiding.  I rerouted the cable to go over the circuit board as I think it should have been.

 

Another thing.  That spring tensioner is adjusted by loosening the lock nut first like Dimitris said.  While holding the lock nut use a small flat head screwdriver to rotate the slotted bolt that the lock nut goes around. (you can see the slot in the pic).  That bolt rotates a cam underneath (you can't see it in the pic).  I think rotating clockwise increases tension, counterclockwise reduces tension.  I may have to fiddle with my dec tension and see if that helps with the backlash I have there.  Maybe it's too tight and what I think is backlash may actually be the motor stalling.

 

The more I fiddle with this mount the more I realize how fiddly it is.  ;-)  I do believe the mount can be made to perform very well, but I fear the factory assembly and adjustments don't give consistently good results out of the box.

 

I would consider this mount an excellent mount for a tinkerer.  ;-)

[DIMITRIS K.]

Something I forgot to mention. My new mount doesn't have a nut and screw on spring tension adjuster. Just a screw with a washer. Upgrade or old design? I'll never know!!

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[Edwin]

Has anyone already downloaded and used the 'right-arm' firmware update, which enables you to mount the telescope with the dovetail pointed to the left (instead of standard right) ?

 

On the SW service website is mentioned that ' It is for testing purpose only, not a formal version'. Is it a stable version?

[Cometeer]

Has anyone already downloaded and used the 'right-arm' firmware update, which enables you to mount the telescope with the dovetail pointed to the left (instead of standard right) ?

 

On the SW service website is mentioned that ' It is for testing purpose only, not a formal version'. Is it a stable version?

 

Many of us have been using it for quite some time with zero issues. 

[dciobota]

+1 on what Cometeer said, the right-arm firmware update works just fine (it enables eq mode also btw).  The synscan app still has some very minor bugs (mostly related to sync) but otherwise works great as well.

[echobeach]

If anyone is considering using this mount in EQ mode, there is a cheaper and more stable alternative than the Skywatcher latitude base.I bought an old EQ2 mount with counterweight and bar with the M12 thread for $20AUD. I then removed  the RA axis and replaced it with an aluminium plate. I then screwed on  a dovetail clamp and a dovetail to the base of the AZGTi. The wingnut screw assists in getting the correct polar angle.

 

Total cost around $50AUD. I used it last night with my ED72 and ASI385mc camera for EAA and was really impressed by the performance of this mount , GOTOs and tracking were spot on

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[Tamworth_John]

The same over here, but it doesn't effect its performance on mine.

The Same here. I am going to use mine in EQ mode with the wedge. I have posted on here regarding how do you balance it with this stiffness ?

 

John

[dciobota]

Balance doesn't have to be perfect, so the way I do it (mine has some RA stiffness too), I release the clutch all the way then rotate the mount left and right by hand, right at where the counterweight shaft is parallel with the ground (means counterweight is on one side, scope//lens on the other).  You get a feeling of which side is heavier that way by how easy it is to rotate one way vs the other.  Like I said, it's not perfect, but close enough.

[Maxchess]

Very impressed with this mount. Bought this as my travel kit, tried a test run last night and was amazed by the results. See this image of M31 60 secs unguided using a Canon 1100d with a Canon 300m F4 lens.

I control the whole thing using Indi - Ekos which gives me all the usual stuff plus plate solving. Runs on a Raspberry Pi so I sit inside and connect via VNC.  Also have Orion SSAG guide scope connected but just used that for polar alignment, plan to try guiding when clouds go away.

Got this image under 75% moon M31 . Advice on this sight proved invaluable.  Thanks Max

Edited by Maxchess, 19 November 2018 - 03:33 PM.

[riverpoet]

I tried autoguiding AZ-GTI with PHD2 + Synscan Mobile Telescope ASCOM driver. RA works fine, but DEC is just weird. It would only move north, not south. So I think to myself, backlash or axis stiffness... and try to help it by manually nudging the mount by pushing the appropriate button in Synscan Windows APP - and whoa, the PHD2 graph jumped in RA??? Now, align procedure using the Synscan app works, gotos work, left-right is definitely RA and up-down definitely DEC - in the Synscan app.... I was doing imaging in southern hemisphere (for the first time ever) if that could be the issue...

 

So, those of you who are successfully autoguiding this mount with EQ firmware:

- are you using hand controller + EQMOD pulse guiding or the SyncanApp/Mobile ASCOM driver?

- is anyone in southern hemisphere?

 

Thanks,

Peter

[dciobota]

Peter, I guide the same as you, phd2-> synscan mobile driver-> synscan app and have seen the similar behaviour at first, the dec wouldn't even calibrate.  A few pages back you can read my posts, I ended up opening the unit and messing with the dec assembly.  It's better now, but I still have to use a large calibration step and 1x guiding rate to make dec calibrate and guide.  Even then, it has pretty large backlash.  I opened it back up and looked, and it seems that the motor reduction gears have some play.  I haven't yet figured out how to fix that, but as the stars seem to come out nice and round anyway, I'm not messing with it anymore.