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Author
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Topic: Altitude of a star at MT using Star Finder
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Rchappus
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posted December 03, 2015 10:36 AM
How does one determine the altitude of a star at meridian transit using the Star Finder?
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David Burch
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posted December 03, 2015 01:59 PM
The method of computing the height at upper or lower transit is posted at
http://davidburchnavigation.blogspot.com/2015/11/latitude-by-meridian-transit-ex.html
This is just a matter of add or subtract lat and (90 - dec), so not sure how much the approximation of the star finder helps — it does add the approximate time of the sight.
To get the answer that way you start by putting nearest lat template on, the white disk, then figure the LHA of Aries for say the time of twilight.
example
Celestial Navigation Data for 2015 Dec 3 at 3:00:00 UT
For Assumed Position: Latitude N 45 00.0
Longitude W 125 00.0
Almanac Data | Altitude Corrections
Object GHA Dec Hc Zn | Refr SD PA Sum
o ' o ' o ' o | ' ' ' '
A
VEGA 197 16.0 N38 48.2 +37 39.5 290.3 | -1.3 0.0 0.0 -1.3
POLARIS 73 11.1 N89 19.9 +45 24.6 0.7 | -1.0 0.0 0.0 -1.0
ARIES 116 37.8
LHA aries = 116 37.8 - 125 + 360 = 351 37.7 = 351.6º. so set the arrow of the blue template to 351.6 and mark that 03 UTC tomorrow or 17 PST today. You will see Fomalhaut just past mer transit.
Then rotating the dial (1º = 4m) you will see Rigel cross at 78º at a height of about 37º. this would occur at 78+ 360-351.6)x4m + 03 UTC = 345.6m +03h = 8.76 = 08h 45m 36s.
the more exact values are slightly lower Ho and slightly later time.
elestial Navigation Data for 2015 Dec 3 at 8:45:36 UT
For Assumed Position: Latitude N 45 00.0
Longitude W 125 00.0
Almanac Data | Altitude Corrections
Object GHA Dec Hc Zn | Refr SD PA Sum
o ' o ' o ' o | ' ' ' '
MOON 41 02.0 N 5 57.3 + 8 28.2 90.0 | -7.1 14.9 54.1 62.0
REGULUS 50 57.7 N11 53.2 +19 37.8 92.7 | -2.7 0.0 0.0 -2.7
RIGEL 124 26.1 S 8 11.2 +36 48.7 179.3 | -1.3 0.0 0.0 -1.3
From: Starpath, Seattle, WA
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Rchappus
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posted December 09, 2015 07:00 AM
Thanks for your help on this David.
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