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» Online Classroom   » Emergency Navigation   » Public Discussion of Emergency Navigation   » Pointer stars, sky patterns, and Mintaka

Author Topic: Pointer stars, sky patterns, and Mintaka

 - posted December 19, 2005 09:24 PM      Profile for FloridaAdventuring           Edit/Delete Post 
After a few days of unusual continued cloudiness here in north Florida, the sky cleared somewhat tonight. It was a great night for pointer stars because Polaris was in and out of view. Cassiopeia was over Polaris, making a level M in the sky. It occurred to me that while she was in this position, her first and last stars would make a good east-west pointer, at least for a while, until she moved on in her path across the sky. Then, for the first time in my life, I identified Capella and the Charioteer. I was able for a moment to use its pointer to find Polaris while Cassiopeia was still visible, which of course provided a double check. Then, farther to the east and south I saw Orion, Taurus, and, I believe, the Seven Sisters.

Thanks to EN, the directional patterns of all these star groups are becoming more familiar. Although I have long known about the Big Dipper and Cassiopeia as Polaris pointers, it's exciting to learn new ones in case the sky is cloudy. Also, just becoming more familiar with the overall arrangement of the night sky is a big help in direction finding.

I wondered if there are pointers which point to any of the six Polaris pointers, sort of a two-step method for finding north on those mostly cloudy nights when only isolated patches of sky are visible. Since the stars are fixed in relationship to one another, can you just find these secondary pointers for yourself? I assume so, but several times now my assumptions have been wrong due to the complex workings of the heavens.

And these questions:

1) If Mintaka rises due east and sets due west and passes straight overhead at the equator, is the maximum height of Mintaka (here in the northern hemispheres) equal to 90 degrees minus your latitude?

2) If so, above 45 degrees north latitude, could you use Mintaka to find direction in a way similar to the solar time method since its maximum atltitude would not exceed 45 degrees?

It seems that a low-altitude star that rises due east and sets due west would be very handy, especially if you could count on it moving across the sky at around 15 degrees per hour.

From: Melrose, Florida
David Burch

 - posted December 23, 2005 12:25 AM      Profile for David Burch           Edit/Delete Post 
0) I have not thought of pointers to pointers, but generally learn the locations of star groups relative to each other. Like learning that WA is two rectangular states up from the top of CA... or water from the big dipper falls into the little dipper, etc.

1) Yes, if dec = 0, latitude = zenith distance = 90 - H.

2) Yes that method would work, but it is not so easy to predict when Mintaka crosses the meridian. You can read this from a graph in the Nautical Almanac (relative to LAN), or compute it, which is a bit beyond the subject of emergency navigation covered here.

From: Starpath, Seattle, WA

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