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Hi Davo3960 and Deimos
Solved the apparent 'PAS issue'. I went out tonight and was able to match the LXD PAS recticle pattern exactly to the sky view pattern of Octantis, and thus obtain precise polar alignment.
I should have thought of this earlier, the explanation is basic lens optics '101'. The PAS polar scope will turn (ie. rotate) the view upside down (as typical lenses do), but it does NOT mirror invert it left to right. This is why the recticle pattern of Octantis is still valid to relate to any star map/atlas (as Dennis shows above). Because of this, although the sky view of Octantis through the PAS will look upside down (compared to say the naked eye or binoculars) you still align to this pattern via rotation of the PAS around the RA axis.
Try this for yourself, draw a diagram of Octantis on a sheet of paper, and say write a word as well in large capitals (using thick texta will help), and stick it on the wall about 10 feet away. Now look at your diagram and word through the PAS, you will see it is only rotated 180 deg upside down, but not mirror inverted (the image will 'appear' to be backwards, but it is not truely mirror-inverted, only backwards because it has been rotated 180 deg!).
So all up, the PAS is 100% accurate. A tip for finding Octantis using the PAS, find the pattern via 7x50 binoculars first, then you will know how to pre-rotate the PAS first and how it will look when you try searching for it through the PAS - this will help greatly because the pattern is faint if light pollution is a bug bear.
47 Tucana was glorious tonight through the Genesis and 6mm Radian...!
Cheers
Fox
Last edited by Fox; 23-09-2006 at 10:41 AM.
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