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OK3Z slipping?


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#1 lukepower

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Posted 20 February 2017 - 08:18 PM

Hi guys,

 

finally I got my new 12" astrograph from ASA, where my old OK3Z has been mounted. I never really used that focuser, and am now facing an odd problem: There is some slippage when I reverse directions, to a point that the positions are not repeatable.

I mean: if I focus perfectly at, say, 13.0, then go out of focus to, for example, 12.0, and then run back to 13.0 the image is still way out of focus.

 

I guess that there are some screws that might need to be tightened, but I found absolutely zero documentation for the focuser (hell, even for the driver it's nowhere to be found). Any hint would be very appreciated :)

 

Best regards

Lukas


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#2 RamaSpaceShip

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Posted 20 February 2017 - 09:17 PM

Hi Lukas,

 

I have the OK3-Z hardware manual (of course, ASA level doc). I should also have its software manual, but I have to do some ASA doc mining to get it.

 

Please send me your email adress by PM and I will send them to you.

 

Best regards.

 

Bernard

 

PS: I confirm I have both manuals.


Edited by RamaSpaceShip, 20 February 2017 - 09:26 PM.


#3 lukepower

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Posted 20 February 2017 - 09:43 PM

Hi Bernard,

 

thank you, I really appreciate your help. I just sent you a PM with my mail adress.

 

Best regards

Lukas


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#4 MarkS

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Posted 20 February 2017 - 10:25 PM

Hi Lukas,

 

If it is like the OK3, there is a single allen head screw for adjusting the holding friction. I set this by placing the OTA on a bench with the focuser facing up, loading the camera etc on the focuser (or an equivalent weight) and tightening the screw GENTLY until the focuser can drive the camera and return to the original focus point. The OK3 readout of focus position may not represent the actual focus position unless the friction screw is properly tensioned! Maybe the OK3Z is different???

 

Mark



#5 lukepower

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Posted 21 February 2017 - 07:18 AM

Odd thing...
Do you know where the ACC software can be downloaded?


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#6 RamaSpaceShip

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Posted 21 February 2017 - 09:27 PM

Hi Lukas,

 

I just sent you what I have by email.

 

Good luck.

 

Bernard



#7 lukepower

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Posted 21 February 2017 - 09:29 PM

Hi Bernard,

 

thank you very much. I already tested it and yes, the holding screws were quite loose. I tightenend them a bit and it became better, but not perfect. Still needs some work it seems...


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#8 RamaSpaceShip

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Posted 21 February 2017 - 09:38 PM

Hi Lukas,

 

My email with the ACC software was rejected: "because its content presents a potential security issue".

 

I will try to send it inside an archive.

 

Stay tuned.

 

Bernard



#9 lukepower

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Posted 22 February 2017 - 05:48 PM

Hi Bernard,

 

I got your last mail with the ACC software, thank you for that.

The system is now working - not perfectly, as there is still quite some slipping, but good enough to do some testing.

 

I truly like the performance of the KAF-16200 so far.  :)


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#10 maxmirot

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Posted 24 February 2017 - 02:48 PM

What manufacture for the 16200 camera ?

 

Max



#11 lukepower

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Posted 24 February 2017 - 03:51 PM

Its the Moravian G3-16200 :)


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#12 maxmirot

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Posted 25 February 2017 - 05:14 AM

That's one I looking to get. What filters are you using?

 

Thanks

 

Max



#13 lukepower

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Posted 25 February 2017 - 07:34 AM

I use the Baader Filters. The camera is working fine, however the slow readout is a bit of a downside


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#14 lukepower

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Posted 12 April 2017 - 05:50 PM

Update from my side:
I tightened the two screws as depicted in the ASA manuals, but am still experiencing heavy backlash - like, going into focus at 10.00, continuing to 10.20, then moving backwards I need to get to 9.40 to get into focus again - so backlash of about 0.60. Is this normal?

 

Thanks

Lukas


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#15 RamaSpaceShip

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Posted 12 April 2017 - 11:19 PM

Hi Lukas,

 

I don't have such huge backlash. Mine is not measurable as it seems less than 0.01. So no, I don't think this is normal.

 

Best regards.

 

Bernard



#16 lukepower

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Posted 14 April 2017 - 02:31 PM

I really have to grip what is going on here. I am able to get decent focus, but Autofocus is out of the question right now...


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#17 MarkS

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Posted 15 April 2017 - 07:03 AM

Lukas,

 

When I had this problem with the OK3 I found that the bolt needed much more tightening than I expected. I continued to tighten the bolt until the same position was reached from either side - as measured by a digital caliper.

 

Mark



#18 lukepower

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Posted 15 April 2017 - 07:51 AM

Hi Mark,

 

how much did you need to tighten it? I went now as much as I  could tighten it by hand with a small screw-bit - so not a screwdriver - and still experience the problem...


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL


#19 MarkS

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Posted 15 April 2017 - 02:06 PM

Hi Lukas,

 

On the OK3 the bolt has an Allen key head. I didn't measure torque, but the key has good purchase. So I would think I got the bolt a lot tighter than you could with a small screw-bit.

The best test is whether the focuser can actually hold the camera without slipping. I am using the same camera as you so the weight should certainly be no problem for the OK3Z.

 

Mark



#20 lukepower

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Posted 17 April 2017 - 08:50 AM

Hi Mark,

 

I will have to check this as soon as weather permits some testing under the stars. There is no visible slippage on visual inspection, so I assume it is little enough to only be seen during a focusing run...


Lukas Demetz
------------
www.skygemsobservatories.com
Astro Dolomites Observatory, Skygems Network
Santa Cristina Valgardena, Italy
20" Cassegrain-Newton on ASA DDM85XL





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