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ETX-125 Autostar/alignment problem


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#1 Roadracer2002

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Posted 12 April 2007 - 01:31 PM

Over the past month my telescope doesn’t seem able to find any stars in the right place!  Each time I set up in the Alt/Az home position and set time and date the telescope will slew to alarming angles when using either one or two star alignment.  For example, tonight Betelgeuse is at about 32 degrees attitude from my location and the telescope repeatedly slews to almost vertical but in roughly the right azimuth direction for the star.  If I then adjust the scope to align the star (which involves slewing the telescope almost 40 degrees downwards) and getting a successful alignment the next object I select is also way out (for example Autostar says Venus is below the horizon).

It seems to make no difference which alignment process I use and whether I bother to correct the alignment or not.  The telescope frequently hits the base when slewing downwards.  The same also happens in polar mode and the problem seems to have started when I tried to use this position for photography.  I am certain I am setting the telescope in the correct home position, facing North.

I have updated the handset to the latest version of Autostar, and I am on external power (as battery power refuses to work, so I’m also assuming a power circuit board problem, but this is longstanding).

Does any of this sound familiar and can anyone suggest any remedies?

Thanks, Hadrian

#2 Guest_rtanton_*

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Posted 12 April 2007 - 01:41 PM

Hi Hadrian,

Is your ETX still set in polar in the AutoStar handbox when setting up in alt-az?

Russ

#3 Roadracer2002

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Posted 12 April 2007 - 10:17 PM

Hi, No I have changed it.  I have also trained the drives and calibrated the motors since upgrading the handset software.

#4 Clear Skies

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Posted 15 April 2007 - 09:09 PM

Have you tried a complete reset of the controller? If not I suggest you do so: Reset, calibrate drives, train, re-enter the az/dec-percentages...
Is the scope working correctly without attempting an alignment?

Regards,


Victor

Victor van Wulfen

 

author of the Clear Skies Observing Guides - A Modern Day Celestial Handbook
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#5 Guest_rtanton_*

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Posted 16 April 2007 - 06:52 AM

Hadrian, if you tried Victor's suggestion and still have no success, it may be time (assuming your scope is not stll under warranty) to take a look inside.  You can open the base bottom by removing the screws under the rubber feet.  Several connectors are slip on (and unfortunately slip off) and you may find that one is only partially in position.  Use either a silicone RTV or hot melt glue to more securely attach those connectors.  As a bonus you will probably see and repair broken wire which is disabling your battery pack.

Russ 

#6 Roadracer2002

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Posted 16 April 2007 - 09:18 AM

Thanks for all the advice guys.  I had a look inside and I think I've solved the problem.

There was a blob of grease on the declination encoder LED.  I've cleeaned it up, and done the RA drive encoder as well and after a reset, calibrate motor and train drive all seems to be OK again.

Thanks for all your help, Hadrian

#7 Clear Skies

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Posted 16 April 2007 - 11:24 AM

Great! Glad to hear you got it fixed! Excess grease was the cause for many a runaway slew on my ETX...

Victor van Wulfen

 

author of the Clear Skies Observing Guides - A Modern Day Celestial Handbook
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