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polar alignment am i mising the point ?

Started by MarkH, Dec 02, 2013, 19:19:50

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MarkH

Having been to my first dsc last weekend and my first attempt at solar alignment, (assisted). My understanding before was that the meade wedge had to be pre-set to replicate ones latitude , which I did. Levelled the tripod and then alligned. But then altered the alt to get correct alt to polaris. Soooooooo am I correct in thinking that as long as the wedge is level in the axis perpendicular to the polar alignment , that the purpose of the wedge is to alter the alt to polaris regardless of the level of the tripods level in the axis parallel to the pole.  :oops: :roll:

The Thing

Aha. Yes. The tripod doesn't have to be exactly level as you are aligning the face of the wedge to the pole which as long as it is within the range of adjustment of the wedge is independent of the tripod level - but it's more intuitive if its level. You adjust alt and azimuth until its right. End of story. BTW The scale for altitude on the wedge is not exactly accurate! Only use it as a starting point. But if you are way off you are pointing at the wrong star. Make a wedge mount for your finderscope as I suggested and it becomes a lot easier :)

MarkH

Thanks Duncan, I was sitting looking at the wedge and It suddenly dawned on me what I was supposed to be achieving with it. Knowing that now and based on Julians polar reticle I think I should easily be able to rig up a custom adjucstable and lockable system. How accurate is recommended to be for 30 sec exposures?

The Thing

Polar alignment is critical if you are doing unguided exposures, you should aim for the best possible accuracy or you will get stars more elongated than they would otherwise be with your focal length (about 1250mm with the f6.3 reducer). If you are piggybacking the camera and using a lens then it's not so critical as the image scale is so much smaller.

If you were guiding the scope then a little inaccuracy is actually though to be beneficial