South Celestial Pole and drift correction

[Dennis G]

The drive and control to my Equatorial platform holds the object stationary in the horisontal, but occasionaly I experience a slow northerly drift which is sufficient to destroy the recording. Unable to sight the SCP I'm forced to set up using a compass. It isn't something I treat lightly and have read numerous articles, which require sighting stars at different angles. Is there a more simple solution to correct northerly drift? I must point out my recording time is short, around 30 seconds.

[AlexN]

You could try drift alignment...

Article here:
http://www.iceinspace.com.au/index.php?id=63,405,0,0,1,0

From what I understand, (and I may be wrong... I havent got mine aligned properly yet) If the star is drifting north, you have your altitude set too low..

As I said I may be wrong... the article has the answers!

Hope you have more luck with it than I've had..
Alex.

[vash]

well it depends one the scope and position, If your aiming at zenith and you have north drift it would mean that the mount is aiming east of the SCP and would need o be corrected to the west. If your aiming to the western sky then north drift would mean that the mount isn't set high enough and need to be moved up.

[Dennis G]

Thanks Ashley and Alex. That's the style of information I was looking for. Now its try it and see.
To add to this I have had occassions where the image barely drifted and having set it up accurately it leaves one confused. Although my compass is top quality I realise there are many factors that can produce an error and apparently the smallest error is sufficient to produce drift.

[AlexN]

yeah... depending on how long you are viewing/photographing an object, ANY misalignment no matter how small will eventually produce drift

[vash]

I put my mount in the same spot every time I set up and even though it almost exactly where it was from the last outing it still requires a few cranks to get it aligned, it is all just practice, once you get it done a couple of times you'll wonder how you couldn't do it before.

[AlexN]

I've got bricks set into the lawn out the back, which I've marked the exact spots of the tripod legs... I get it as close as I can to being on the marks then I have a quick look to see how the alignment is... Its taking time, but its better every time I do it, so im confident that it will come good soon.

[Blue Skies]

Have you taken the local amount of magnetic variation into consideration? In the sw land division of WA the average magnetic variation is 4 degrees west - this means if you are using a compass you should point your mount 4 degrees to the east of the magnetic south to get true south. However if you use drift alignment you should correct for this anyway.