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    Re: Yet another modified 2102-D star finder
    From: John Forrest
    Date: 2013 Jan 8, 04:40 -0800

    It would take me a while to go through that;-) Will try to.
    My initial impression, at least, is that my approach is quite simplistic and could I suspect be used by almost anyone. Also it only needs one modified disk to work with all the northern hemisphere. Perhaps a second for the south. Perhaps just the numbers going back. Yours seems a lot more complex to me, although I assume is more fully featured - unless I've missed a trick.

    I like your approach of putting the hours onto the horizion disk and pointing the time at the appropriate place on the base. However one still needs to allow for the longitude, unless working in LMT, so surely need to mark where you are pointing to? As such I think using a separate disk is preferable because the 00 mark remains fixed and thus forms the mark.

    The one thing I did discover is that the biggest set of errors I see seem to derive from the horizion disk not being appropriate - e.g. I'm around 51N so will locally use the disk for 55. This throws out the zenith point, so any high altitude bodies are likely to have the wrong bearing. However even lower down the bearings and altitudes of virtually all bodies is likely to be out - those further south have altitudes I think about five degrees out, and east or west have bearings similarly affected.

    Byron Franklin partly fixes this by using the (say) 55 disk but putting the Zenith at the correct point. I did wonder about putting extra holes through the 2102-D horizon disks, say at 3 degrees above and below. However the pin is relatively big and I think you'd end up with a slot rather than a set of holes, which would not really help anybody!

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