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Nexstar Evo Tracking Issues


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Hi all,

I've been struggling with my Nexstar Evo 8 for a while now. I'm using the 3 star align and can get the telescope to align pretty well after reading some very useful posts on here. The problem I now have is that although the scope aligns it doesn't track very well at all. Stars will just drift out of view quite quickly. 

I've got the scope set to sidereal tracking but wondering if the backlash settings could have anything to do with this? TBH, I don't really understand what backlash settings are for. If anyone could offer a simple explanation it would be very much appreciated!

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Backlash doesn't effect tracking. Backlash is the play in the gears, this comes into effect when changing direction and is manifested by a time delay between the motors changing direction and the mount moving.

When tracking the motors should mostly be going one way only.

Is the lat long set correctly on the handset? If these are wrong the tracking will be really bad.

Just to check, you're not using a wedge are you? If you are this will complicate things somewhat!

/Dan

Sent from my iPad using Tapatalk

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Hi Dan, 

Thanks for the reply. I believe it's correct. I typically would use the co-ords from my iPhone but I've got them from Google Maps and cross checked so they should be ok I think. I will however double/triple check! One aspect that I'm not sure of is how high up I am. I tend to try an use the scope from my apartment but my iphone jumps around on how high I actually am in the building. I'm guessing this would make a large difference too.

Not using a wedge at this stage - as much as I want one, I need to get this setup working first!

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Yes - backlash usually manifests itself as over or under shooting an object acquired using "goto" and sometime using the arrow keys. I wouldn't trust iphone co-ords - I prefer to trust the mount co-ords. It should track very well with little or no drift once the mount is successfully star aligned - objects shouldn't drift at all - even over an hour the object should still be dead center of the eyepiece. Check the date and time settings plus lat/long, and if required you can re-align on any star during the session in order to correct any drift and improve goto. Hth :)

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Well after a couple of hours, I've given up for the night. Go to was almost perfect, however I did get drift tracking.

I've double checked my co-ordinates and everything "seems" to be fine. I'm not sure about my altitude though as I'm in an apartment block. I was experimenting with it. I managed to get the drift to be slower but not gone. Stars tend to drift straight up rather than sideways.

I've also checked the balance, which I believe to be ok and the levelling.

One point is that I'm not using the hand controller but the Star Portal app on an iPhone and using "current location" which gets the co-ordinates ok (I've cross checked them on a map) but the atitude does bounce a round a lot if I refresh the screen - could it be the altitude rather than the co-ords? I'm willing to test each meter if I have to!

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Altitude shouldn't mess up the tracking that badly, just use whatever your phone averages.

More likely are errors in the time settings, some mounts are a real pain to understand the time system on, I just use GMT on mine to avoid confusion.

Another possibility is if the handset battery has died, this can cause odd behaviour in the mount.

/Dan

Sent from my iPad using Tapatalk

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If you are using the in-built wi-fi with your smart phone you shouldn't need to worry about coordinates. The scope works that out for you. If you are using the handset, though, it operates like a normal go to scope. But it's the wifi feature that the Evolution range has pioneered.

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Could you expand on what you mean by altitude and where you are finding that setting? Does this happen using the HC as well? I would check functionality using the HC which if fine points the finger at the app or phone. Use the HC and once you are aligned hit the menu button and scroll down to tracking and ensure this is set to alt-az with the second option set to sidereal. Ensure coordinates and time settings are accurate and monitor what the scope does.

Also under version from the menu what firmware versions do you have ? The latest public release is HC 5.28.5184 and MC 7.11.5100 which has corrected many anomalies. Once you get past version HC5.26 you can update your firmware for the handset and the motor controller by WiFi. Goodbye serial cable and this really works. Lots of niggles can be ironed out by reflashing firmware.

I must admit I have sky portal but do not use it preffering the better established Sky Safari 4, but don't recall altitude being asked for in any alignment or settings.

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Hi JG777, I'm using the Sky Portal App on my iPhone and not the handset. When you click on "location" it gives you the option to enter in your elevation. As Highburymark pointed out it's auto populated but in my case it bounces around quite a lot.

I'm hoping to get out tonight away from the apartment so will try again and also with the handset and see if there is a difference. I will certainly check the firmware later on when I'm home!

Thanks for taking time to respond!

Hopefully will be able to report back positively!!

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Got it! Senior moment here the setting is "Elevation" of course the same thing as altitude but didn't immediately twig this. Does your phone populate the Elevation setting? My tablet populates coordinates but has my elevation at 190 metres when it is actually 20 metres above sea level. I guess you know the Elevation your are observing at and add it to ground level. If it was wildy out then it may cause issues but it sounds like you have this part of it resolved.

So assuming all data in the app is correct and your tracking is off then a firmware update to the motor controller might correct this. One other thing and easy to miss, are the clutches tight? Any slippage in the mount?

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The phone will likely give altitude above the WGS84 datum that the NAVSTAR GPS satellites use, this is not always the same as height above sea level as it is a best fit spheroid on a rather lumpy planet. It is likely that your mount will expect this datum though so feeding it something else could confuse it.

It is not always possible to know what datum the manufacturers have gone for but WGS84 is the norm for GPS positions.

When used near buildings the GPS position can be unreliable due to masking (buildings blocking your view of the satellites) and multipath (signals bouncing off of buildings giving erroneous readings).

/Dan

Sent from my iPad using Tapatalk

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Hi all, thanks again for taking time to help me out with this. I've been trying again tonight and after nearly having a melt down, I deleted the app from my phone then reinstalled and did a reset on the mount. Not sure why this would make any difference but afterwards I did an alignment, then did a go to and tracked a star for about 30 mins before the mount batteries ran out! :) 30 mins was about 29 mins better than it has been, so I think we can call it success!

I've not refreshed the firmware as I don't have the right cable or laptop for that matter but I'll look into seeing how I could achieve this.

Thanks again - now I just need to get to some dark skies!

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Hi all, thanks again for taking time to help me out with this. I've been trying again tonight and after nearly having a melt down, I deleted the app from my phone then reinstalled and did a reset on the mount. Not sure why this would make any difference but afterwards I did an alignment, then did a go to and tracked a star for about 30 mins before the mount batteries ran out! :) 30 mins was about 29 mins better than it has been, so I think we can call it success!

I've not refreshed the firmware as I don't have the right cable or laptop for that matter but I'll look into seeing how I could achieve this.

Thanks again - now I just need to get to some dark skies!

Good to hear. A low battery may have been part of the issue as well. Let's hope its OK from here on. You might not need a cable to update the firmware, can be done over WiFi and takes about 5 minutes.
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