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Gary writes:

I know the formula becomes ambiguous near 90� but it is a very short 
formula, quick and easy to use and can be used for most sights while 
keeping this possible complication in  mind.

gl

George Huxtable wrote:

>Gary LaPook wrote-
>
>| I have no idea how it could take ten minues to calculate Hc and  Zn on a
>| pocket digital calculator, I just did a sample test and it took me 58
>| seconds. I use the standard formula for Hc rearranged to the form:
>|
>| Hc = arcsin (cos LHA x cos dec x cos lat + sin lat x sin dec)
>|
>| and  Z = arcsin (sec Hc x sin LHA x cos dec) since implementing it this
>| way saves a few keystrokes.
>
>Well, using that formula for Z doesn't necessarily give Gary an unambiguous 
>result, seeing that the sine of 80� is identical to the sine of 100� (for 
>example). How would Gary distinguish between them, without some additional 
>keystrokes? Observing the azimuth isn't easy if the altitude is high.
>
>He would be better off using a formula that gives Z from its cosine, (or 
>better still, from its tan, in which case it isn't even necessary to 
>precompute Hc).
>
>George.
>
>contact George Huxtable at george@huxtable.u-net.com
>or at +44 1865 820222 (from UK, 01865 820222)
>or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. 
>
>
>>
>
>  
>


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