NavList:

Just received mine from FedEx yesterday and bought the ebook by David Burch as well. Contrary to some opinions I've read here on the list, I like the way the 2102-D is laid out.

I haven't finished the book, but there's one thing I don't understand: In the book, and in a YouTube video based on the book, it is mentioned that the scale around the edge of the red template is essentially useless and to ignore it. I thought that was odd. Why print it on there at all, then? So, I placed it on the star base and upon inspection, realized that when the pointer (0°) is set to GHA Aries, the red scale corresponds to longitude on Earth. Knowing this, you can rapidly find the LHA of Aries by simply looking up your assumed longitude on the red scale. Set the pointer of the appropriate blue template to this position and you can read the LHA off of the scale on the star base. And, you already have your sky for the time in question displayed.

You can also reverse the procedure to find the time when a chosen body will be at a particular azimuth/altitude: Simply set the appropriate blue template on the star base and rotate it until the chosen body is at the desired location. Then, set the red template on top and rotate it until the pointer on the blue template is indicating your assumed longitude. Next, locate the pointer on the red template and note the GHA of Aries. And finally, Look up the closest GHA Aries in the N.A. to find the approximate time. (The exact time can be interpolated, if desired.)

There may be more uses for the red scale; these are just the ones I've figured out so far. Apologies if this is common knowledge, or has been mentioned before.

~Sean C.
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