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LX90 GPS Slew Times

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#1 epenna

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Posted 06 October 2019 - 08:07 PM

I have a LX 90 GPS. I recently calibrated the motors and trained the drives, but it has not helped me with this problem: 

 

During Goto, once the scope decelerates from fast-slew, it takes roughly 70 second to find the object and beep. 

 

Is this normal? Is that just how long it takes, or is there something wrong?

 

Thanks, 

E
 



#2 sg6

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Posted 07 October 2019 - 11:27 AM

Seems a bit long, I assume you have timed it as you give a value.

Is 70 from the start of the fast slew or from when? Just to get an idea of the detail.

Whichever it seems long.

 

If from start of slew then check the Max Slew Rate, may be lowish to reduce noise. Just thinking it could be at say 5 or 6 and 8 could improve.

 

Unsure of the detail of the centering action. But the Meades I have met usually take around 15-20 seconds - 70mm to 14" Meades. The fine end bit being quite small say 5-8 seconds.

 

There is a crazy option: Slew rate is set low, scope predicts how long to slew for at full speed, slews for that time but as slew is set to slow is say half way there, then completes at the slow fine rate hence taking a long time.

As said crazy but ???



#3 Piet Le Roux

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Posted 07 October 2019 - 12:52 PM

I have a LX 90 GPS. I recently calibrated the motors and trained the drives, but it has not helped me with this problem: 

 

During Goto, once the scope decelerates from fast-slew, it takes roughly 70 second to find the object and beep. 

 

Is this normal? Is that just how long it takes, or is there something wrong?

 

Thanks, 

E

 

Check if you have "Quite Slew" selected : this would prevent it from slewing at max speed. 
 



#4 OzAndrewJ

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Posted 07 October 2019 - 02:23 PM

Gday SG6

 

Slew rate is set low, scope predicts how long to slew for at full speed, slews for that time but as slew is set to slow is say half way there, then completes at the slow fine rate hence taking a long time.

Nor quite true, it has no concept of time

It slews at full speed til a set distance from home, then starts to ramp down as it gets closer.

Once within a set radius of target, it stops, recalcs position and does a second slew to get even closer.

 

Andrew Johansen Melbourne Australia


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#5 sg6

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Posted 08 October 2019 - 03:53 AM

Gday SG6

Nor quite true, it has no concept of time

It slews at full speed til a set distance from home, then starts to ramp down as it gets closer.

Once within a set radius of target, it stops, recalcs position and does a second slew to get even closer.

 

Andrew Johansen Melbourne Australia

It was just a thought, met so much software in my time that it occurred as a possibility. Would not make sense but sense and software do not always go hand in hand.

 

The thought process was that it could  "Slew for 10 seconds, then slew at fine (slow)."

If 10 sec was still a long way off then the slow bit took longer.



#6 Piet Le Roux

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Posted 08 October 2019 - 03:56 AM

Gday SG6

Nor quite true, it has no concept of time

It slews at full speed til a set distance from home, then starts to ramp down as it gets closer.

Once within a set radius of target, it stops, recalcs position and does a second slew to get even closer.

 

Andrew Johansen Melbourne Australia

 

Unless "Quite Slew" is selected, then it would newer slew at full speed.



#7 OzAndrewJ

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Posted 08 October 2019 - 04:00 AM

Gday SG6

Its all a game, as at full speed, the slew speed is based on the supply voltage, it is not "controlled"

At the end of the day, the basic firmware simply uses hardcoded distance from target values  to set speed, it has no concept of "time"

 

Andrew Johansen Melbourne Australia



#8 epenna

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Posted 08 October 2019 - 11:43 PM

Thanks for the feedback... for clarification:

 

I have the LX90 plugged into an outlet, so the voltage is steady and high. 

 

I do not have it on quiet slew. I hit the goto button, and it gotos fast enough to make make noise for as along as it takes to get close to the object... then it slews too slowly to make noise for about 60-70 seconds before it beeps. 

 



#9 Levant

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Posted 03 December 2019 - 04:28 PM

Hi Ranger 4, 

Please make sure that you have you tightened the both two axis screws because it will take excessive time to move the scope to desired point if those 2 screws are left loose.

Levent



#10 M57Guy

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Posted 10 December 2019 - 09:58 PM

70 seconds sounds like a lot of thumb twiddling to me, but my LX-90 is pre-GPS, and I've never measured slew times. 

I know my dad's LX-200 GPS takes what seems like forever to complete a slew, so maybe that's the nature of having GPS in control.

 

How is the accuracy after the slew?

 

As others have suggested, "quiet slew" mode sounds like obvious culprit but you've confirmed that's not the issue.

And, I'm guessing this isn't a "high precision" issue either?

 

How were the slew time before you calibrated motors and trained the drives?

 

My last though would be your power supply, but you said you're plugged into an outlet.

Is is powered by a long (say 100') extension cord?



#11 Piet Le Roux

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Posted 11 December 2019 - 01:46 AM

I did a mock two star alignment with my LX90ACF GPS and it picked Arcturus and Rigel Kent. After it had stopped at Rigel Kent I let it slew to Arcturus and timed it : about 35 seconds. I when let it slew back to Rigel Kent and it was about 35 seconds again. The GPS plays no part in the slew process, and it does not control anything it just enters your coordinates and time. The only things that I think could make a difference is your supply voltage and firmware version. saying that " I have the LX90 plugged into an outlet, so the voltage is steady and high." is not a good assumption : It should not be higher than 13.8V and should not drop bellow 12V under load, so it should be well regulated like a good lead-acid battery or voltage controlled lithium 12V power pack. The latest firmware that you could use on the LX90 is A4S4, I am using patched firmware A4s4. 

 

PS: If you have selected "cord Wrap"  it may in some instances "take the long way" to a object to prevent cord wrap. 

 

PPS: with "Quiet Slew" selected my Arcturus to Rigel Kent time was coincidentally 74 seconds !?   


Edited by Piet Le Roux, 11 December 2019 - 09:52 AM.



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