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Homefind jump problem

DDM60 Homefind

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#1 asgr

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Posted 29 April 2016 - 11:03 AM

Hi,

 

I’ve just got back to work today to find a newly repaired DDM60 (I had an issue with the bearings which ASA have fixed- I hope). This afternoon I had a quick check of how things were looking, but unfortunately I’ve hit an immediate issue- when I run homefind as soon as it finds the location on the RA axis the mount rapidly slews round a huge amount (about 90 degrees) and the RA axis becomes unusable until I fully restart AutoSlew. The log displays an RA/AZ configuration error.

 

If I don’t run a homefind then things seem to be working fairly well once the mount is tuned and balanced, but no matter what I do I seem to be getting this error with the homefind. I’ve even done a factory reset and removed all files related to Autoslew in the ProgramData folder, but this didn’t help either. I’m assuming this is some sort of software issue to do with the old configuration settings and the repaired mount clashing, since sidereal tracking and normal slewing are generally working okay. Are there other hidden files that I need to find and delete?

 

Could anybody please give me some advice on what to try? Have you encountered a similar problem? I've also contacted ASA, but thought the forum might have some experience of this specific problem.

 

Thanks,


Aaron
 



#2 Waldemar

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Posted 29 April 2016 - 10:12 PM

Hi Aaron,

Did you get a new registration number with the repaired mount?

If so, did you use it, or did you try the old one?

If you tried to use the old registration number that might be the problem.

Part of the registration number is the code for the magnetic angle as I understand.

 

Regards,

Waldemar


Waldemar
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#3 asgr

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Posted 30 April 2016 - 02:33 AM

Thanks! I can't find a new registration code in the returned box or documents though. I'll have to get in touch with ASA.

#4 robertp

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Posted 30 April 2016 - 12:37 PM

Hi Aaron,

 

I also suspect that a wrong magnetic angle is the problem. I experienced a similar behaviour (a very sudden slew with a speed way faster than the maximum slewing speed) when the magnetic angle was off.

Besides using the licence-code to set the magnetic angle, there's still the option to determine it from scratch.

 

Best regards and I hope you resolve that issue soon,

 

Robert



#5 asgr

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Posted 30 April 2016 - 04:05 PM

Hi Robert,

Thanks for information. Where can I find instructions on how to do this? The mount is back at work, so I can't check the manual and software right now, but hopefully it is quite straight forward to do if ASA don't get in touch with a new code soon (it is the weekend though).

A

#6 GeorgeCarey

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Posted 30 April 2016 - 06:04 PM

I haven't done the magnetic angle find for many months. If I remember correctly you click on the 'turn motors on' button.
Autoslew will then send pulses of current to the motors and work out the angle.
I used to put the scope facing North or South with the counter weight arm horizontal.

When it has done the magnetic angle you do a Homefind as normal.

Be ready to catch the scope incase it starts slewing. There may be some other parameters that are incorrectly set.

ASA DDM60Pro, homemade 8" and 10" reflectors, QSI 683 camera, Astrodon 5nm filters, Pulsar dome observatory. Website: http://www.geoastro.co.uk


#7 asgr

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Posted 30 April 2016 - 09:23 PM

Thanks, but perhaps I am misunderstanding something here. I am turning the motors on (using autoslew 5.2.1.9) and it does the usual checks on each axis. It is only after it has made a Homefind on RA that it suddenly and violently slews a huge amount. Whatever checks the auto start is making obviously isn't finding the magnetic angle correctly (if that is the issue). My question is how do you find it and set it from scratch? What are the other possible parameters that could be incorrectly specified with the wrong registration code for a repaired mount?

Hopefully the solution is is simply to get the new registration code from ASA, so I'll probably wait for them to contact me before trying anything too radical.

A

#8 robertp

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Posted 01 May 2016 - 04:26 PM

Hi Aaron,

 

I guess that somehow even after the initial autofind the magnetic angle is not correct.

Please make sure, that when you do the initial autofind, that the scope is balanced as good as possible in both axis.

Wnen the autofind takes place, you get the window described at the bottom of page 9 in the manual (sorry, I couldn't find the english manual)

http://www.astrosyst...ng/?wpdmdl=3017

During the autofind, you will see these "bubbles" appear (the yellow lines). You should aim for two things:

 

1) The bubbles should be as symetrical as possible (meaning that the left half of the bubble should be very symetrical to the right half). If that's not the case, then you either have inbalance in your axis or you might try a different position of the counterweight and the telescope. I would start with e.g. the counterweigth pointing down and the telescope pointing towards the polar star.

2) At the end of the autofind a red line appears that to my understanding indicates the position of the magnetic angle that was measured. This red line should be very close to the maximum of the bubble. If that's not the case, then you might not have found the optimum magnetic angle which at least limits the perfomance of the mount or might lead to the unexpected behaviour you see.

 

If you have problems to get a good shape of the "bubble" then you might want to increase the test current or decrease the step size.

Only once you have a decent magnetic angle, you should be in the state to set a new homefind.

 

With my mount, I had problems to get a good autofind result, therefore I measured the magnetic angle once and now use the procedure where you don't do an autofind when starting the mount but instead manually turn the axis during homefind. I never had a problem with sub-optimal magnetic angle since.

 

Hope this helps,

 

Best regards,

 

Robert

 P.S.: I think you can't really mess something up doing some tests, but it might be a good idea to do a copy of all the ini-files so that you can easily switch back to the current parameters.



#9 GeorgeCarey

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Posted 01 May 2016 - 08:53 PM

You could also try turning on the log files. At the beginning of the log file it tells you what the magnetic angles are, as set by the licence key.
You can then try the manual Homefind and when you then check the log it will tell you by how much it has corrected the magnetic angle.

ASA DDM60Pro, homemade 8" and 10" reflectors, QSI 683 camera, Astrodon 5nm filters, Pulsar dome observatory. Website: http://www.geoastro.co.uk


#10 asgr

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Posted 02 May 2016 - 04:26 PM

All appears to be fixed. ASA sent me a new registration number, and the big jump is no more. The initial magnetic angle find for the RA axis doesn't look that great when it does the initial autostart stepping, but this doesn't seem to have a big impact on the operation. The optimise function seems to get a better setting, but the initial start refuses to use this. Does this matter? And can I force different autostart options?

Thanks for everybody's input so far- I'd say things are 99% fixed now!

#11 GeorgeCarey

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Posted 02 May 2016 - 05:47 PM

Good news that it appears to be fixed now.
I found that the magnetic angle find seldom gave a smooth curve. I always go straight to the Homefind operation and turn the mount slowly by hand. That method seems to give very reliable operation.

ASA DDM60Pro, homemade 8" and 10" reflectors, QSI 683 camera, Astrodon 5nm filters, Pulsar dome observatory. Website: http://www.geoastro.co.uk






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