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my right ascension setting circle keeps moving?
http://www.boltonastro.co.uk/forums/viewtopic.php?f=6&t=768
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Author:  JHalliday [ Sun May 03, 2015 11:20 am ]
Post subject:  my right ascension setting circle keeps moving?

Hi

On my cheapo wobbly eq mount, the right ascension setting circle moves when i adjust the scope.

I dont yet understand the setting of it once ive polar aligned anyway, but when i move the scopes right ascension from then on the circle keeps slipping.

This cant be right can it?


Sorry if this is a daft question.

J

Author:  rwilkinson [ Sun May 03, 2015 2:11 pm ]
Post subject:  Re: my right ascension setting circle keeps moving?

Hello John.
First you need to polar-align your mount by adjusting its azimuth and elevation so that its polar axis aims at the star Polaris:
http://www.opticalvision.co.uk/documents/170.pdf

Then if you want to use your setting-circles, proceed as follows:
  1. Adjust the RA & declination axes to point the 'scope at at known bright star (e.g. Arcturus or Regulus)
  2. Look up the RA co-ordinates of this star (e.g. Arcturus is 14h13m RA)
  3. With the 'scope locked in position, turn your RA setting-circle by hand so that it indicates this co-ordinate:
    http://www.opticalvision.co.uk/documents/177.pdf

Now once you've done this calibration, you should be able to read off the current RA from the setting-circle as you unlock the clutch and rotate the 'scope's RA axis.

From the picture in the document above, it looks like the EQ1 has a fixed pointer and an RA scale which rotates along with the 'scope, so you'll need to re-calibrate it whenever you've been tracking an object using the RA slow-motion gear.
However on the EQ2 it looks like the pointer moves along with the 'scope, whilst the scale rotates with the slow-motion drive - this is a much better design, since once it's calibrated you shouldn't need to adjust it again during that session.

Author:  JHalliday [ Mon May 04, 2015 8:26 am ]
Post subject:  Re: my right ascension setting circle keeps moving?

Thanks Ross,

A bit easier now ta.

No clear skies at moment, but will be trying this next opportunity.

Some have said, use dob or goto, but i want to struggle, like those had to before me.

Author:  cstone [ Mon May 04, 2015 5:44 pm ]
Post subject:  Re: my right ascension setting circle keeps moving?

JHalliday wrote:
but i want to struggle, like those had to before me.


Gets my vote!! :D

Author:  JHalliday [ Fri May 29, 2015 9:18 pm ]
Post subject:  Re: my right ascension setting circle keeps moving?

Well.....

Update....

Managed to get myself a second hand SW EQ5 mount and just waiting for a dovetail bar delivery.

The mount and much less wobbly tripod was won on ebay for £100 which i thought was a good deal. The seller also included a tracking motor but its damaged and im not sure whats missing from it but i have the dual axis controller, so imagine i can get this repaired?

Even if i cannot repair the tracking motor, really pleased with the mount.... real solid.

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